US1936334A - Electrode - Google Patents

Description

Patented Nov. 21, 1933 ELECTRODE Richard E. Miesse, Chicago, Ill., assignor, by

mesne assignments, to General Scientific Corporation, Chicago, 111., a corporation No Drawing. Application January 31, 1929 Serial No. 336,658

2 Claims.

My invention relates to electrodes and more particularly to electrodes for use in connection with gaseous conduction devices in which a gas more or less rarefied is used as a conducting medium. It has been found in the operation of devices of this nature that electrodes when made of certain metals sputter during the operation thereof. I believe that the most tenable explanation at the present time in regard to this phenomena of sputtering is based upon the theory that the sputtering is caused by positive ion bonbardment. Various expedients have been tried to eliminate sputtering. The choice of metals is a factor which enters into this consideration and also the size of the electrode itself. The rate of sputtering also varies with the cathode fall at the electrode and is also dependent upon Whether or not the entire electrode is, or is not, covered by the glow.

I have found as set forth more in detail in my application Serial No. 305,122, filed September 10, 1928, that I can obtain a high electron emissive electrode by providing upon the active portion of a suitable base metal, such for instance as nickel, a coating of such a substance as barium carbide. This barium carbide is a substance of high resistance and may probably be called a dielectric and when in its finished form upon the electrode presents a glassy surface something on the order of a vitreous coating.

My present invention concerns itself with a simple and improved electrode of this type together with the method of producing it. I have found that I can very readily produce an electrode of this character if I obtain the ultimate product, barium carbide, through the initial use of such a substance as barium azide. Barium azide has, I believe, in its usual form the constituents as shown in the formula Ba(N3) 2.

In preparing an electrode, I use a base metal such as nickel which has a high melting point, and which also is easily alloyed with barium, thus forming barium nickel alloys and allowing for a closely bonded surface coating of either barium oxide or barium carbide.

I do not wish to limit myself by the use of the word alloy to any technical definition of alloy as such, although I believe that under a liberal definition of that term a barium nickel alloy is formed.

I might also say at this point that instead of the barium carbide coating which is dark in color, a lighter barium oxide coating may be obtained as will presently appear and this barium oxide coating may in itself permit of useful application although my preferred form herein has more particular reference to the barium carbide coating. The form of the electrode may preferably be a small cup and I may say that in actual use the discharge need go merely to the interior of the cup. This nickel base metal is then heated to a very low red heat in order to remove all oil, dirt, and other undesirable substances and also to cause an expansion between the crystals of the metal to reduce the bonding effect between them. 7

A solution of barium azide is then prepared by dissolving the barium azide in water. The heated electrode is then quickly plunged into the barium azide solution which immediately cools the electrode so that when it is withdrawn it has a covering thereon of barium azide solution. The electrode thus coated is then heated again in a bushy gas and oxygen flame and this heating is continued until substantially all of the barium azide has been dissociated. This point in the heating is preferably indicated by the fact that there is no more cracking or exploding of the azide covering. This process may preferably be repeated four or five times in order to insure a heavy and well defined coating of barium oxide. If the oxide coating is desired, then the process is discontinued at this stage, but if as is required in the production of my preferred electrode the carbon is desired, then the electrode at this stage is again heated to a very high yellow heat by being placed in the hotter part of the flame where it can be seen that the oxide is fused and starts to run. The process is stopped at this time and the result is a black glossy coating of which the chemical formula, I believe, is quite complex as there may be present a barium nickel alloy, also some barium oxide, but mostly barium carbide, the carbon having been absorbed from the excess'of carbon which was in the flame during the time of heating.

In order to be positive that the coating is satisfactory, the above process may be repeated if desired. In the above manner I am enabled to produce a barium carbide coating for the base metal so that the completed electrode is free from sputtering and has a very low cathode fall.

In specifically thus describing one form of the invention, I, of course, do not wish to' be understood as eliminting equivalents. Having, however, thus described one form which my invention may take, what I claim as new and desire to secure by Letters Patent is:

l. The method of producing an electrode for gaseous conduction devices which consists in 1 coating the active surface of a base metal with a; barium compound by dipping said base metal into a solution of barium azide, thereafter heating said base metal with its adhering covering of solution and thereafter heating said device in the presence of carbon to a higher temperature to change the nature of the barium compound to one in which barium carbide in glossy form predominates.

RICHARD E. MIESSE.