US1397008A - Method of preparing finely-divided metals - Google Patents

Description

UNITED STATES PATENT OFFICE.

ALBERT MCG'ALL, OF NEW YORK, N. Y.

No Drawing. Application filed September 16, 1918, Serial No. 254,346.

Specification of Letters Patent.

Patented Nov. 15, 1921.

Renewed February 2, 1921.

Serial No. 442,012.

To all whom it may concern Be it known that I, ALBERT MoGALL, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Methods of Preparing Finely-Divided Metals, of which the following is a specification.

This invention is an electrolytic method whereby oxidizable metals, such for example as zinc, copper, aluminum, etc., may be prepared in a state of minute subdivision but in non-oxidized condition. The metals so prepared are useful for a wide variety of purposes, among which may be mentioned the preparation of electrodes for primary or secondary batteries, and the manufacture of explosives of the known type comprising a metallic component and an oxidizing agent, such for example as ammonium nitrate.

I will describe my invention by reference to the preparation of non-oxidized zinc in minutely sudivided state, as a typical or illustrative example thereof. It will be understood, however, that the invention is not restricted to the particular manipulative details below described, since the composition and concentration of the electrolyte, as well as the current conditions, may be rather widely varied. Obviously also the conditions will be somewhat varied according to the particular metal which it is desired to obtain in subdivided form.

I prefer to proceed as follows:

Sheet zinc, which has preferably been amalgamated (although this is not essential) is coated by rubbing or otherwise with a thln layer of a suitable oleaginous substance, such for example as an organic or inorgan c (hydrocarbon) oil or grease, or material containing the same. The mineral grease known to the trade as sponge grease, and having the characteristics of a non-flowing grease or oil, is entirely satisfactory for my purposes.

The coated sheet is then connected as the anode in a suitable electrolyte, which is preferably acid, and may consist initially of a sulfuric acid solution having a specific gravity of about 1.3. A suitable cathode is provided which is preferably also of zinc: for although other metallic or conductive materials may be employed as cathode, there is less liability to loss of metal by local action when zinc is used. Also, I prefer to apply a like oleaginous coating to the cathode although this is not necessary for the practice of the invention. The coating of the cathode is, however, a distinct advantage for the reason that the cathode, if provided with an oleaginous coating, is not acted upon by the electrolyte when the flow of current is interrupted.

Unidirectional current from an outside source is then caused to flow from the coated sheet zinc as anode, whereupon, irrespective of the current density employed, a deposit of sponge or minutely subdivided zinc will be formed. This deposit is at most only loosely adherent to the cathode, and may be either continuously or intermittently removed from the electrolyte, washed and dried. A current density of about one ampere per square inch of cathode surface will be found satisfactory; and the anode and cathode areas may be substantially equal.

Contrary to what might be anticipated from the known insulating character of oleaginous materials, it will be found that the coated metal, although quite unafiected by the acid electrolyte so long as no current flows through the system, nevertheless passes freely into solution as soon as current is applied from an external source, and is simultaneously deposited in minutely subdivided or sponge form at the cathode. Instead, however, of forming a highly oxidizable, unstable, and often partially oxidized sponge, as is the case when the oleaginous coating is omitted, the deposit will be found to be substantially non-oxidized, and relatively very stable. This I now attribute to the presence upon the individual particles of the deposit of an oleaginous protective coating of extreme tenuity.

Finely subdivided copper is readily prepared under the above conditions. Metallic aluminum in minute subdivision may also be prepared in substantially the same manner. The aluminum deposit is however more liable to oxidation than zinc when removed from the solution, and especially when spread in contact with air. Consequently the aluminum deposit should preferably be shielded to a reasonable degree from oxidizing influences, as for example by storing in an inert atmosphere, or even by compressing in order to reduce the exposed surface.

Metals which have been treated with an oleaginous material and thereby rendered in active toward acid electrolytes so long as no current flows through an electric circuit in which they may be included as anode, are conveniently referred to as immunized metals The immunity from purely chemi cal as distinguished from electrochemical attack thus conferred is remarkably persistent; and, particularly in the case of electrodes which have been in use for some time, may persist after thorough wiping of the electrode, and even after washing it with such cleansing agents as gasolene, etc., until all apparent traces of the oleaginous coating have been removed. I employ the expression immunized metal anode in the claims to designate anodes possessing the above described characteristic due to the previous treatment with oil or equivalent material.

The term metal is used herein to include alloys, to which the method is likewise applicable.

I claim 1. Method of preparing oXidizable metals in minutely subdivided, non-oxidizedcondition, comprising electrodepositing the metal in sponge form by means of an electric current flowing from an immunized metal anode.

2. Method of preparing oXidizable metals in minutely subdivided, non-oxidized condition, comprising electrodepositing the metal in sponge form by means of an electric current flowing from an anode of the same metal, said anode presenting surfaces having an oleaginous coating.

3. Method of preparing oxidizable metals in minutely subdivided, non-oxidized condition, comprising electrodepositing the metal in sponge form by means of an electric current passing between an anode and cathode of the desired metal, said anode immunized by treatment with an oleaginous substance.

4. Method of preparing oXidizable metals in minutely sudivided, non-oxidized condition, comprising electrodepositing the metal in sponge form by means of an electric current passing between an anode and cathode of the desired metal, both of said electrodes immunized by treatment with an oleaginous substance.

In testimony whereof, I aflix my signature.

ALBERT MoGALL.