US1777371A - Feathery copper powder and process of producing the same - Google Patents

Description

2 thas been Patented on. '1, 1930 ED A S i PATENT? OFFICE mm: roman-or CLEVELAND, omo, Assumes. '10 THE xonm nn onmxcan comm, or AKRON, ozno, acoaroaa'non or omo FEATHEBY corms. rownna min, rnocnss or raon'crcnse THE W 1V0 Drawing.

- This invention relates to copperpowder having new and improved properties and'to uline metal and the sludge or mushy metal has been discarded as useless and the conditions corrected as uickly as possible to produce a re line meta agaim 1 V roposed heretofore to varythe a conditions in't e plating bath-t0 deposit metal on the cathode in finely divided form as cona trastedwith the usual reguline form for oer an purposes,'for example, where the finely divided material is later to be fiatten'edor' stamped out into sheet-like particles for making metallic paint. The prior art metalpowable largely, Ibelieve, to the fact that m parders are characterized by-being composed of amix'ture of particles of various andradically difiere'nt sizes and shapes, a large proportion of these particles being in the form of slender rods having rounded nodules thereon or-dense, compact bodies. These prior powders when compressed under several thousand pounds pressure per square inch pro duce an article of relatively low tensile strength, elongation and hardness.

- So far as I am aware, however,- it has never been proposed prior to my present invention to carry out an electroplating rocess under either of the foregoing productswill be pro ducedbut that ,metalwill be de sited in' I 3 ties. "The" copper powder" produced-by my 'present' invention" is of an entirely new. charactor orformiaiid new an'dn'mch compression, heat treatment and the like but scribed in brief language I have empf oyed such conditions that but very l ttleif any of Application filed January 22, mo. semi 28o. 422,670.

improved properties. This powder is composed of particles substantially all being of the same shape and size and with 'an almost entire absence of small particles of'other shapes and compact bodies. This powder is soft and feather or fiocculent, that is, each particle has a b y of irregular or fixed or characteristic shape with rou h ed es and sharp pointed extremities and whie these shapes vary somewhat they are all generally similar. or example, when copper particles of this invention are yiewed in profile under the microscope; they are'jagged and ma be said to resemble the edges of a Killarney fzarn. These feathery particles possess the property of matting to other underpressure and may be compress or worked into various shapes and articlesby known processes involving without requiring an binder and when so'7 compressed or shape the resulting article is dense, 'relatively non-porous and has a" much higher tensile strength, elongation and hardnessithan similar articles made of the prior powder and containingthe slender -rod particles or the dense compact bodies.

' This property of matting together is traceticles are in a flocculent condition whic permits a close interlocking and interweavin of the particles as contrastedwith the lac of such action where the rounded compact particles of the prior art'are used. Thiscontrast may be visualized by thinking of compressing felt on the one hand an sand on the other hand. p

My new owder is distinctive and readily recognized ut since it is not so easil dsthe termsKoehler metal powder or oath ery powder-to describe the powdered metal.

of my invention jand'wish 115170 be understood'that powder of myi invention is re-' ferred to herein whenever either of these ex pressions are employed.

electrolyte iselectrolized under certain con so I - W I have discovered that when 'a suitable v on the cathode without any reguline metal or any appreciable amount of the prior art powder being deposited. The conditions which must be observed in attaining my results involve several factors including (1) the amount of metal in solution in the electrolyte (2) the acidity of the bath (3) the voltage and amperage of the current (a) the temperature of the bath (5) the distance between electrodes and (6) the nature .and amount of any additional metal or metals present in solution in the electrolyte.

While these various factors may vary widely it is important that the conditions be such in all cases to cause the evolution of gases over the active face of the cathode.

Various copper salts may be used in producing feathery metal according to my pres ent invention, for example, sulphates or chlorides or acetates of copper. Obviously many other salts may be employed but in all instances I prefer that the solution should be an acidulated solution.

The amount of the metal which should be in solution in the electrolyte for the production of the feathery powder may vary between about percent by weight and upward to an amount at which-under the same current conditions the evolution of gas over the cathode practically ceases. Thismaximum is usually only a few percent.- If the solution contains more than the maximum amount of the metal salt the excess salt will polarize the anode and seriously interfere with the economical operation of the process. The weight of powder per unit volume increases as the metal in solution increases. The acidity of the bath may vary from about of 1 percent by weight and upward therefrom but for the higher efficiencies the acid content should not exceed about 10 percent. In general the increase in the acid content above the minimum is accompanied by a drop in voltage and amperage efficiency without any attendant and compensating results.

The electrolyzing current employed may vary widely above certain readily determined'minimum limits. However, practical commercial considerations which involve power and equipment cost as well as the character of the deposit will determine the upper limits of the voltage and amperage. It will be understood that the current density re quired will increase as the amount of metal in solution in the electrolyte increases and the voltage will decrease with an increase in the acidity of the electrolyte until about 10 percent of acid is reached after which it will remain substantially constant. The voltage will also vary with the distance between electrodes, that is, the voltage will be lower the closer the electrodes are together and higher the'farther apart theyare placed. The voltage and ampere eificiency is perhaps highest when the acidity of the electrolyte is below about 6 percentr In general the amperage should not fall below'about 30 or exceed about 240 per square foot of cathode area.

Variations in current also result in variations in the weight per unit volume of the powder.

The temperature of the bath may vary up wardly from about 35 degrees F. to about 200 degrees F. and naturally tends to increase as the electrolysis proceeds unless steps are taken to cool the electrolyte. Asthe temperature increases the mobility of the ions increases and hence the current density-must be increased to prevent the formation of reguline metal or nodular powdered metal. Practical considerations make it advisable to mainf tain the bath temperature below about 150.

degrees F. and above about 70 degrees F. and exceptionally good results can be obtained between about 70 degrees F. and about 100 degrees F. The size of the particles varies with the temperature and the weight per unit volume-increases as the temperature rises.

The distance to be maintained between the electrodes will largely be controlled by praccal considerations such as current cost and the space available for and the cost of the equipment. A distance of about 3 between electrodes gives. good results but this distance may be increased or decreased if desired and is preferably decreased.

While I may practice my invention in a simple acidulated electrolyte containing in solution only the copper to be converted into feathery form, some respects desirable also to employ in the I find it advantageous and in solution a metal which is more positive in nature according to the electro-motive scale than the copper. Many different'metals may be employed. Merely as illustrative of such metals Imention sodium and zinc. These more electro-positive metals should be used in the form of salts of the same acid as is present with the copper.

These added salts may vary in amount through a considerable range which is limited beginning with about.% of 1 percent by weight and extending upwardly thereabove to the extent of a few percent.

'I cite the following as a specific example of the conditions under which my new and improved copper powder may be produced. An electrolyte is prepared containing in solution between about and about 3 percent by weight of copper, preferably aldout 2 percent, and between about and about 10 percent by weight of free acid, preferably about 6 percent. The temperature of the bath may range between about 35 degrees F. and about'20O degrees F. but preferably is kept between about 70 degrees 100 degrees'F. The electrodesare spaced apart about 3". The current may range be tween about 40 amperes and 240amperes per i square foot of cathode area with about' 70 amperes bein preferably-with the above referred con itions. The voltage may vary rom 7 to 2 depending on the acid content with about 2 volts being suitable under the above preferred conditions.

When operating under the above preferred conditions, Koehler metal powder will be deposited on the cathode. This powder should m be completely removed periodically from the cathode for otherwise the deposit changes rapidly and contains an increasingly large content of dense compact copper of the prior art. This change is apparently controlled by the current density and length of deposition period between the steps of removal of deposit from the cathode. In general these variables may be summarized by'the stateaccomplished by a severe operation, such. as

brushing, which dislodges any! particles which tend to adhere closely to the cathode. Jolting or jarring operations are not satisfactory-for they do not remove'all thedeposit and hence permit the formation'of'the dense compact prior art powder.

As an illustration of the use of an added, more highly positive metal in the electrolyte in producing Ko'ehler copper powder the electrolyte may contain in solution about 2 percent by weight of copper, and about 2 percent by weight of sodium or zinc and about 6 percent by weight of free acid. j With this illustration as in the preceding example, sulphuric acid is used and-the metals are in the form of sulphates. With the anodes and cathodes spaced apart about 3" and the'temperature of the bath maintained between the foregoing ranges Koehler copper powder will be produced when a current of am-.

peres per square foot of cathode area is used and when-the voltage is maintainedat about For the successful practice of my invention the composition of the bath must'remain substantially constant particularly-with reference to the concentration of the inetaltobe converted into feathery owder for, if on the one hand, the concentration of the copper increases and a preaches the saturation point of the liquid the anode will become polarized by crystallization thereon of the salt of that metal and will thus require that the voltage be largely increased with a consequent power loss, and, on the other hand, if the concen tration of acid i'rithe bath'increases materially the predominant efiect of'the electrolysis will be the liberation. of hydrogen and consequently a reduction in the yield of feathery metal.

Under the normal conditions of operation;

of my process which includes the continuous evolution of gases over substantially the entire active surface of the cathode, the cathode efficiency as measured by the amount of metal deposited is materially lower than the anode.

eficiency as measured by the amount of acid radical liberated. This difference in efiiciency may and often does amount to as much as 20 percent. Consequently in order to maintain a.balance between the amount of copper salt and the amount of acid in the bath some means must be provided to compensate for this difference in elliciencies.

One means for maintaining the said balance is to employ a combination of anodes, a part of which are inactive so far as their reaction with the free acid radical in the bath .3 o 1s concerned and others of which are active with such acid radicals. Such anodes are not claimed in this application, however, but this subject matter is being reserved for presentation in a separate application.

' Koehler metal powder or the feathery powder as described herein feels soft and smooth to the touch and the particles are highly oriented and highly voluminous in bulk.

. They arehomogeneous, highly compressible and exceptionally pure chemically and have an enormous expanse offiliform surface which provides, for the intimate mixture of i the particles with each other or with other substances which gives the material properties which collectively make the feathery powder susceptible to treatment of many and varied kinds and utilization to many useful purposes.

This 'applicationis a continuation in part of my copen'ding application, Serial No. 182,866 filed April 11, 1927, and 190,341, filed May 10, 1927 being restricted to copper powder' and its production. No claim is made herein to the remaining. subject-matter of these three applications.

' Having thus described my invention that those skilled in the art may be enabled to practice the same what I'desire to secure by Letters Patent is, defined 'in' what i is claimed, it being understood that the foregoing 'detaileddisclosure has been made by way of-illustration not by way of limitation on'the scope of the invention as defined inwhat'is claimed.

1'. 'Ehe prgoi producin the herein describedffeathery coppegipow er which comelectrolyzi'ngan': acidulated solution eontaning above about ,5 pencentby weight of copper, under bonditions as W111 substantially continuously over evolve gas surface of the cathode there the entire active by depositing the copper dered state on the cathode and formity is substantially maintained in the feathery form of the deposit.

' tive metal and also between about and about fi epercent by weight scribed so weight-of-co per I de'nsit ;toohi ghto I 2. The process as described in claim 1 in which the solution contains between about percent and about 6 percent by weight of copper. g 3. The process as described in claim 1 in which the solution contains a few percent by weight of a'metalcf a more highly positive nature than copper I 4. The process as described in claim 1 which between about /2 percent and about 10 percent by weight of free; acid is present. 5.- The process as described in claim 1 in which the solution containsbetween about percent and about 10 percent by weight: o acid and between about percent and about 6 percent by wei ht of a metal of a" s of producin copper, which 7. The-'ptroce 'feathry powder comprises 7 tion containing a ve about rcent by with a catho e current depositjreguline metal, and t-will produce a substantially con-.

timtous-evolution of gas over the ent1reac tive surface ofthe cathode, thereby depositing-the copper as a soft feathery 'wd'er'on the cathode, and removing all; e deposit fromthe eathode before the total current new hm-r-eachedaufamountsufiicient to produce hard non ieathery particles in the dea claim 7, in which removabof the depo sit from the cathode is accomplished periodically with guficient-jfrquency to prevent the formation ofiioh feathery particles after a current flow of be ween about 19 and about 20 ampere hours per squarefootof cathode area.

I 9'; Asanew erticleofmanufacture,cop'- per-powder of theherein described feathery 1 o theprope tics of featherypow er produced by electrormhavin'grties'and characterislging "an acidulated solution containing a ve about hpercent by weight ofcopper, under such conditions-including current voltage and density as evolve. 'assubstantially continuously over substantially the entire active surface of the cathode and removeamen e 'depbsit r the M1 in a feathery. powremoving the V deposit from the cathode at a rate that uniclu 'ng current volta about percent electrol zing an acidulated, soluode at such a rate that uniformity is substantially maintained in the feathery form of the deposits. 7 10. As a new article of manufacture, copper powder ofthe herein described feathery form having the properties and characteristics of feathery copper powder produced by: electrolyzing a solution containlng between about percent and wei ht of copper under such conditions inand density as will evolve gas substantia ly continuously over the cathode and removing substantially all deposit from the cathode at such a rate that uniformity is substantially maintained in the feathery form of the deposit.-

11. v As a new article of manufacture, copper powder of the herein described feathery orm' having the properties and characteristics of feathery copper powder produced by electrolyzing a solution containing between and about 6 percent by weight of copper, between about a percent and about 6 percentrby weight '0' sodium and between about percent and percent by weight of acid under such conditions including current volta' e and density as will evolve gas substantialcontinuously over substantially theentire active surface of the cathode, and removingthe material deposited on thecathode at such a rate that uniformity-is substantially: maintained in the feathery form'of'the deposit.

12. Asa new article of manufacture, cop per powder" having the properties of that produced bythe process of c aim ,7 13. As a new article of manufacture, copoduced by'electrolyzing an acidulated soutioncontainingabout percent by weight of copper, with a cathode current density too per powder having the properties of that,

' high to depos't reguline metal, and that will produce a substantially continuous evolution of the 'gas over the entire activesurr'ace of the ca ode, soft feathe removing a1 thereb depositing copper as a pow er. en the cathode, and t e; deposit from; the cathode about 6 percent by after a current flow of between about 10 and about 20 ampere hours persquare foot of cathode area, thereby preventing the formation of non-feathery particles. 7

In testimony whereof'I hereunto aflix my signature this 4th day of -J anuar 1930. 7

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