Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
Field of the Invention
. .
The present invention relates to a continuous electro-
deposition process wherein solid particles are dispersed in a
fused-salt electrolyte to obtain an electrodeposited metal or
alloy which is e~tremely flat and free of flaws on the surface of
a cathode immersed in the electrolyte.
Description of the Prior Art
In the prior art, when a desired metal or alloy is to be
electrodeposited as a solid by fused-salt electrolysis, the
electrodeposited metal is often in the form of a powder,
aggregate crystal, dendrite or sponge. When the desired metal or
alloy electTodeposited in the above form is recovered, a great
amount of electrolyte is inevitably lost during separating the
-1- ~
- - - : ;................... . ............ :
- . .. .
:. ;: :.,,
1073400
metal or alloy from the electrolyte. Further, when the desired
metal or alloy has high reactivity with oxygen, nitrogen and
the like, the high surface area caused by the aforesaid form of
the electrodeposited metal is subject to contamination by
reaction with such different elements. Thus, after treatments
of the deposited metal are usually accompanied by many diffi-
culties.
Further, even when the metal or alloy can be electro-
deposited as a relatively homogeneous film, conditions which
permit such to be obtained are very narrow, e.g., a small
allowable limit for the cathode current density and so on.
Accordingly, lmdesirable restrictions have been imposed on pro-
cesses for producing such film materials.
U.S. Patent 3,662,047 issued May 9, 1972, in the name ;-
of Tokumoto et al discloses a method for the electrodeposition
of titanium or a titanium alloy. A fused salt electrolytic
bath containing a mixture of chloride salts of barium, magne- --
sium, sodium and calcium having a freezing point of less than -~
600C and titanium dichloride, and, if desired, a source of a
suitable metal alloy, is electrolyzed. The electrolytic bath
is maintained at a temperature of 400C to 580C and under such
conditions as will maintain the molar ratio of titanium tri-
chloride to titanium dichloride at less than 0.5 in the vicinity
of the electrode to be electrodeposited.
SUMMARY OF THE INVENTION
Accordingly, a main object of this invention is to pro-
vide an electrodeposition process which improves upon the above-
identified processes and/or is free from the above drawbacks.
Another object of this invention is to provide an
electrodeposition process wherein a fused electrolyte is used,
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even with a metal whose electrodeposition as a relatively homo-
geneous, dense film is considered difficult, whereby a desired
metal or alloy can be electrodeposited with its surface being
kept flat on an electrode under operating conditions which are
industrially useful, whereby a relatively homogeneous, dense
film of electrodeposited metal or alloy having a predetermined
thickness and high flatness can be obtained.
The above and other objects of the present invention are
obtained by the presence of dispersed particles in the electro-
deposition bath during the electrodeposition. While the parti-
cles may be added per se to the electrodeposition bath or
formed in situ, in both instances the agitation effect of the
dispersed particles permits one to obtain an electrodeposited
metal or alloy layer which is extremely flat and free of flaws
at the surface of the cathode in the electrodeposition bath.
More particularly, there is provided:-
an electrodeposition process in which a fused-salt electro-
lyte is used to deposit metal or alloy on a cathode disposed in
said electrolyte, wherein solid particles are maintained dis-
persed in the electrolyte at least in the immediate region ofthe cathode, and continuous relative movement is caused to occur
between the cathode and said solid particles whereby said solid -
~particles agitate the electrolyte in the immediate region of the
cathode and a homogeneous, smooth electrodeposit is obtained.
In the foregoing process, the said electrolyte may com-
prise halide salts including salts of said metal or of the con-
stituent metals of said alloy, and wherein the electrodeposition
is effected at a predetermined temperature of said electrolyte;
and comprising the steps of providing at least one of said
halide salts in said electrolyte in an amount substantially in
excess of the solubility level thereof at said predetermined
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electrodeposition temperature, so as to crystallize a portion
of each of said halide salts provided in said excess amount and
form said solid particles thereof.
The above and other objects and features of the inven- -
tion will appear more fully hereinafter from a consideration of
the following description accompanied with preferred embodiments.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Before the description of the present invention, a fused
electrolyte as is normally used in a fused salt electrolysis - -
10 will be described. -
A fused electrolyte or electrolytic bath capable of dis-
solving a desired metal or alloy deposited by electrolysis com-
prises a higher valent compound of the desired metal in the -- -
fused electrolyte which reacts with electrodeposited metal to
produce a lower valent compound of the desired metal, thus pro- -
viding the deposited metal corroded and dissolved therein. One
example thereof is a fused electrolyte where an electro-
deposited metal is corroded and dissolved in the electrolyte by
a disproportional reaction or disproportionation. A dispropor-
20 tionation of this kind will be described with reference to the ~ -
electrodeposition of titanium, by way of example. As will be -~
appreciated by one skilled in the art, in the electrodeposition `
of titanium from a fused-salt electrolyte, the starting material -~ -
actually used is TiC14, which is reduced into TiC13 and TiC12 in
a conventional manner. Since in the electrodeposition of titan-
ium using a fused-salt electrolyte this step inherently occurs, -
in the following examples the starting portions of TiC12 and
TiC13 are given for purposes of convenience, as such terminology
is more conventionally used in the art.
Between a higher valent compound of titanium such as
TiC13, K2TiC16, BaTiC16 or the like contained in a fused elec-
-` 10'73400
trolyte and metallic titanium deposited by electrolysis, the
following disproportionation exists at least in the temperature
range of about 400C to 600C.
Ti + 2TiC13 3TiC12 ...................... (1)
Ti + K2TiC16 >2KC1 1 2TiC12 ............. (2)
Ti ~ BaTiC16- ~BaC12 + 2TiC12 ........... (3)
When a trivalent complex of titanium such as Cs2TiC15 is pre-
sent in the electrolyte, a similar disproportionation is also
seen. In either case, however, the metallic titanium deposited
by the electrolysis reacts with a higher valent titanium com-
pound, such as a trivalent or tetravalent compound, in the
electrolyte to produce a lower valent titanium compound, such
as a divalent compound, which is dissolved in the electrolyte.
Another example of a fused electrolyte capable of dis-
solving a desired metal or alloy deposited by electrolysis is
one where the metal or alloy can be subjected to anodic dissolu-
tion in the fused electrolyte.
Another example of a fused electrolyte capable of dis-
solving a desired metal or alloy deposited by electrolysis is
one where the desired metal is locally dissolved in the electro-
lyte by the electromotive force of a concentration cell based
upon the concentration difference of desired metal ions locally
produced on the surface of the electrodeposit (hereinafter
referred to as a deposit surface).
A description will now be given of a fused electrolyte
used in the electrodeposition process of this invention in which
a highly viscous material is produced on the deposit surface of
a metal or alloy during electrodeposition of the desired metal
or alloy as described above.
It will be apparent that in the case where, for example,
an intermittent DC current (cut on and off at predetermined
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;periods and at predetermined rates) is used as an electrolytic
current during electrodeposition of a desired metal, if the
electrolytic current is cut off the afore-mentioned dispropor-
tionation will occur on the deposit surface without interference.
Referring to the above described reaction formulas (1),
(2) and (3) relating to titanium, by way of example, as is
obvious from these reaction formulas, the amount of TiC12, KCl,
BaC12 or the like increases to more than the starting composi-
tion ratio of the electrolyte itself at the reacting areas on
the deposit surface of the metal. Accordingly, when the compo- ~ -
sition of the fused electrolyte is selected to be substantially
at or near the liquidus line or face of the fused-salt phase
diagram (but in the liquid region) at the electrolyte tempera-
ture with respect to the components whose concentration is
increased at the metal deposit surface by the reaction, it will
be seen that at least a portion of the by-products produced by
the electrodeposition will be in the form of a highly viscous
material which will cover the reacting area of the deposit
surface.
Further, another example of a fused electrolyte used in
this invention will be described with reference to the electro-
deposition of titanium. In the case that a fused electrolyte
composed of alkali and/or alkaline earth chloride and titanium
chloride has magnesium chloride added thereto to deposit mag-
nesium metal preferentially next to the titanium in accordance
with their decomposition voltages, the thus deposited metallic
magnesium is substituted for by titanium which is present in the
fused electrolyte to form magnesium chloride (Mg ~ TiC12 >
MgC12 ~ Ti) which returns to the fused electrolyte by a rehalo-
genization reaction. If the composition of the fused electro-
lyte is selected to be substantially at or near the liquidus
--6--
-` 1073400
line or face of the electrolyte phase diagram at the electrolyte
temperature with respect to magnesium chloride, at least a part
of the magnesium chloride will form a highly viscous material.
Of course, in this case, the electrolyte must flow and move
relative to the deposit surface.
The above described electrolytes are only examples of
fused electrolytes which can be used in this invention, and it
is needless to say that the present invention is not limited to
the above illustrative materials.
As will be obvious from the above description, in a fused
electrolyte for use in the electrodeposition process of this
invention, an electrolyte having a different composition from -
that of the original fused electrolyte is produced at areas
adjacent to the deposit surface of metal or alloy. The electro- -
lyte at this portion will hereinafter be referred to as-"a
deviated electrolyte portion" meaning a portion of the electro-
lyte having a compositional deviation from the original fused
electrolyte. As will be appreciated by one skilled in the art,
the "deviated electrolyte" differs from the main portion or
balance of the fused electrolyte primarily in having a higher
viscosity than the main portion or balance of the fused electro-
lyte and in having a higher percentage of electrolytic by-
products, mostly anions released from the metal electrodeposited
and, for example, MgC12 due to rehalogenation when an electro-
lytic system comprising MgC12 as described, for example, in U.S.
Patent 3,662,047 Tokumoto et al, is utilized. The "deviated
electrolyte" can be considered equivalent to the highIy viscous
material produced during the electrodeposition.
Furthermore, in the following description, so far as it
is not necessary to distinguish an alloy from a single metal for
purposes of understanding the disclosure, the term "alloy" will
be omitted from the explanation.
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: '
While the process of the present invention finds wide
application, it finds particular use as an improvement of the
method described in U.S. Patent 3,662,047 Tokumoto et al, where
solid particles are added per se to the electrodeposition bath
of the Tokumoto et al patent or formed in situ therein, there-
after the particles being agitated in the electrodeposition bath
to provide the effects now to be described and to permit one to
obtain an electrodeposited metal or alloy layer which is ex-
tremely flat and free of flaws at the surface of the cathode
upon which electrodeposition is proceeding.
As indicated, the primary feature of the present inven-
tion involves dispersing solid particles in a fused-salt electro-
lyte electrodeposition bath so as to utilize the agitation
effect of the dispersed solid particles to obtain a metal or
alloy layer which is extremely flat and free of flaws. The
following discussion deals with such particles in detail.
The solid particles of the present invention may be
added per se to the electrodeposition bath or may be formed
therein by an in situ crystallization procedure as will later be
described. Of these two embodiments, the in situ crystalliza-
tion of solid particles is preferred.
There is no particular limitation on the identity of the
solid particles, but, as will be apparent, when the solid par-
ticles are formed of components which are different from the
components of the reaction system and are undesired in the re-
action system, the solid particles should not melt, degrade or
be abraded at the electrodeposition conditions. Particularly
preferred crystallized salt particles are the particles of com-
ponents used as the raw material of the desired metal, though as
will be apparent to one skilled in the art from the later offered
examples, the crystallized salt particles need not necessarily
- --8--
` 1073400`
comprise the raw material of the desired metal, and can comprise
other components of the fused electrolyte, either alone or as
various admixtures thereof. However, most preferred solid par-
ticles which are in situ crystallized are TiC12 solid particles.
As other solid particles which can be dispersed, there can be
employed compound particles such as oxide particles, nitride
particles, boride particles, carbide particles, sulfide parti-
cles, bromide particles, chloride particles, fluoride particles
or the like, and /or carbon particles or metallic particles.
It is generally preferred that the solid particles dis-
persed in the fused electrolyte during the electrodeposition of - -
the present invention have a size less than about 1 mm. At the
same time, it is preferred that the solid particles dispersed in
the fused electrolyte have a size greater than about 1 micron. -
Most preferably, the solid particles dispersed in the fused elec- -
trolyte have a size greater than about 20 microns but less than -
about 200 microns. If the solid particles dispersed in the
fused electrolyte are too fine, the effect of the present inven-
tion is not achieved. On the other hand, if the solid particles
dispersed in the fused electrolyte are too large, uneconomical
amounts of power are required to maintain the solid particles
dispersed in the fused electrolyte.
It should be understood by one skilled in the art, of
course, that all solid particles need not be exactly the same -
size, and particles of a varying size distribution can be dis- ~-
persed in the fused electrolyte to achieve the unique effect of
the present invention.
Further, it should be apparent to one skilled in the art
that not all of the solid particles dispersed in the fused
electrolyte need have a size in the above range. However,
practically speaking, particles much finer than the above range
. . . .. . . . . .
10734~0
do not lend any substantial beneficial effect to the electro-
deposition, nor do solid particles substantially outside the
above range, and hence it is preferred that such not be present
at all.
It should further be apparent to one skilled in the art
that, if desired, solid particles can be added to the system in
combination with the formation of solid particles formed by in
situ crystallization. Generally speaking, however, no substan-
tial benefits are obtained by utilizing such a more complicated
system, and on an industrial scale the general rule will be that
particles will be exteriorly added to the fused-salt eIectrolyte
or the solid particles will be formed therein by an in--situ
crystallization, with the latter procedure being preferred. In
this regard, it should be noted that while nothing would prevent
solid particles which are identical to those formed by an in situ -
crystallization from being added exteriorly from the fused
electrolyte, little is to be gained by such a procedure.
The shape of the particles in the present application is ~-
not overly important, and the particles can be circular, irregu-
lar, accicular, etc., and mixtures thereof can be used, if
desired. Generally speaking, however, it is preferred to utilize
; particles of approximately the same shape since this makes
process reproducibility easier. -
For an easy understanding of the fact that the electro-
deposition process according to this invention is superior to
the prior art, a description will now be given on the operation
and effect of crystallized-salt particles produced from the ~ -
aforesaid electroIyte and of other solid particles added ex- -~
teriorly of the fused electrolyte.
In the electrodeposition process of this invention,
the deviated electrolyte portion is produced adjacent the deposit
surface as described above.
--10--
10~34l)0
When the fused electrolyte is flowed and moved relative
to the deposit surface, an electrolyte portion showing a parti-
cular fluid condition called a boundary layer in the fluid
dynamics art is produced along the deposit surface. Within this
boundary layer, the further away from the deposit surface a por-
tion of the boundary layer is, the greater the relative velocity
of the electrolyte to the deposit surface in that portion.
Accordingly, the portion within this boundary layer immediately
adjacent the deposit surface can be substantially considered a
diffusion-dominated area with respect to mass transfer. The
thickness of this boundary layer is determined with regard to -
the relative velocity of electrolyte to the deposit surface, the
viscosity of electrolyte and the like, but it becomes thin as
the viscosity of the electrolyte becomes small and as the rela- -
tive speed to the deposit surface becomes high. In a turbulent
flow area of the electrolyte produced by a further increase of
this relative velocity, there remains only a very thin layer
which is a laminar sublayer. Accordingly, in the case of
turbulent flow, when the electrolyte flows and moves relative to
the deposit surface, the projections on the deposit surface are
in greater contact with the original electrolyte than the reces-
sions therein. In such a case, if solid particles exist in the
electrolyte, and their sizes are the same as or greater than the
thickness of the boundary layer and are large enough for them to
be affected by the relative velocity distribution in the boundary
layer, the solid particles are swept along the deposit surface
or rotated, depending on their relative velocity distribution,
so that the solid particles are moved relative to the deposit
surface with the effect of agitating the electrolyte near the
deposit surface. Consequently, as will be obvious from fluidized
bed engineering, there will be achieved a reduction in the thick-
-` 1073400
ness of the portion considered a substantially diffusion-
dominant area. Accordingly, it will be apparent that when solid
particles of a size large enough to achieve the effect of re-
ducing the thickness of the portion considered substantially
diffusion-dominant as mentioned above is dispersed in the
electrolyte for the electrodeposition and the electrolyte flows
and moves relative to the deposit surface, the result is to
increase its limit density with respect to the cathode current
density. While U.S. Patent 3,662,047 Tokumoto et al generally
discloses the formation of a highly viscous layer at projections
and depressions during electrodeposition, there is no disclosure -
whatsoever therein of the utilization of dispersed solid par-
ticles as in the present invention to achieve the unique effect
of the present invention.
Therefore, the electrodeposition process of this inven-
tion is designed to achieve a novel effect due to the above
mentioned dispersed solid particles utilizing the special condi-
tions of fused salt electrolysis in which operation is carried
out at a relatively higher temperature than is normally used in
a fused salt electrolysis, wherein a fused salt consisting of a
plurality of component salts is used as the electrolyte. Electro-
deposition is carried out at a temperature above the melting
point of the fused-salt electrolyte and at a temperature below
the temperature at which substantial volitilization of the
fused-salt electrolyte occurs. Electrodeposition is most pre-
ferably carried out at a temperature of from about 400 to about
550C, most preferably, at a temperature from 4Q0 to 500C,
though with certain fused-salt electrolytes it is possible to
perform electrodeposition at somewhat lower and somewhat higher
temperatures.
..
10~3~00
Generally, in such an electrodeposition, the raw material
of the desired metal is reduced into its metal from the electro-
lyte adjacent the deposit surface due to electrolytic current
and successively extracted therefrom. When a comparison is made
between the concentrations of the raw materials of the reducible
desired metals contained in the portions of electrolyte adjacent
to the projections and recessions of the deposit surface, the
concentration of the raw material in the electrolyte adjacent to
the recessions is apt to be smaller than that adjacent the pro-
10 jections and this tendency becomes notable as the cathode current ~ -
density becomes higher. In order to avoid the above defect, -~-
violent agitation of electrolyte is normally carried out during
the electrodeposition.
In an electrodeposition process carried out at a fused
electrolyte temperature near the liquidus line or face, the
fluidity of the electrolyte is relatively small, so that even
with violent agitation it is difficult to supply a sufficient
amount of raw material to the electrolyte portion adjacent the --~
deposit surface from which the raw material of desired metal can -
be gradually extracted due to the reduction to the desired metal
by the electrolytic current.
In one embodiment of the electrodeposition process of
this invention, the original or starting electrolyte contains
the raw material (which provides the desired metal) in an amount
greater than its solubility at the electrolysis temperature, so
that the amount of the component exceeding the solubility there- -
of at the electrolysis temperature is dispersed in the electro-
lyte as solid particles. When such an electrolyte flows and
moves relative to the deposit surface, as previously described
above, the following effects are achieved: the thickness of the
.. - ~ ........................... .. .
.
10'~3400
portion adjacent the deposit surface considered substantially a
diffusion-dominant area can be made very thin. However, when
the solution concentration of the raw material of the desired
metal becomes low in this area as a result of deposition of the
desired metal according to electrolytic current, the solid par-
ticles of the raw material present by dispersion in this portion
dissolve to compensate for the shortage of the solution concen-
tration. Therefore, the shortage of the raw material of the
desired metal in the recessions of the deposit surface, that is,
concentration polarization of the component, can be remarkably
prevented, though it is normally apt to occur. This is the
reason why in the electrodeposition process of this invention
solid particles particularly suitable as particles dispersed in
the fused electrolyte are the compound particles of the raw
material of desired electrodeposition metal among the crystal-
lized salt particles.
As previously mentioned, in the fused electrolyte the
thickness of the portion adjacent the deposit surface which can
be considered a substantially diffusion-dominant area becomes .
very thick when the solid particles are not present. ~owever,
when the difference between contact rate of the original electro-
lyte at the projections and recessions of the deposit surface is
utilized to increase the dissolution of the metal at the pro-
jections much more than that at the recessions to flatten the
deposit surface according to the disproportionation previously
described in detail with reference to the electrolyte used in the :
electrodeposition process of this invention, the small height
difference between the recessions and the projections of the
deposit surface provides a remarkable difference in the amount
of disproportionation as the boundary layer produced on the
-14-
.. . .
10~3'100
deposit surface is thinned due to the existence of the solid
particle, so that the effect of flattening the deposit surface
is achieved.
Even when a continuous electrodeposition is carried out
with the deposit surface rendered flat by using both the electro- '
lytic current with a periodic reversal of the electrolytic
current as disclosed in U.S. Patent 3,662,047 Tokumoto et al to
dissolve the deposit surface for a predetermined period during
electrolysis, continuous electrodeposition is performed with the
deposit surface being flattened utilizing the concentration
difference between the raw materials of the desired metal con-
tained in the electrolytes adjacent the recessions and projec-
tions of the deposit surface, if the boundary layer produced on
the deposit surface is made thin by the solid particles. The ~-
flattening effect will be remarkably achieved due to a slight
difference between recessions and projections of the deposit
surface in a manner similar to that described in the case of the
flattening effect utilizing disproportionation.
Further, in the case of electrodeposition of a metal as
previously described, when the electrodeposition is carried out
using a fused electrolyte which produces a highly viscous
material on the surface of electrodeposited metal, the highly
viscous material produced on the deposit surface may not be suf-
ficiently removed even though the relative velocity of the elec-
trolyte consisting only of solution is greatly increased with
respect to the deposit surface unless the solid particles are
dispersed in the electrolyte. In a practical case, if such an
electrode position operation is carried out, a non-metallic
coloring called "burnt marks" is apt to appear on the deposit
surface, or crater-shaped dents or pits are apt to appear
. ~
- ; ', - ~ ~ .: . - -
10734t)0
accidentally. If solid particles are dispersed in the electro-
lyte when the above mentioned problems are noticed, the afore-
said dents or pits disappear or their rate of appearance is
decreased. It is believed that the agitating effect of the
dispersed solid particles moving along the flow of electrolyte
and their mechanical polishing operation serves to remove the
above-mentioned highly viscous material.
In the case when the above-mentioned highly viscous
material is produced due to the increase of raw material of the
desired metal on the deposit surface as in the case of, for
example, titanium dichloride in the electrodeposition of titanium,
the balance between the amount of the above increased raw material -
and the amount of the electrodeposited metal is kept in the
proper range by properly controlling, for example, the dispro-
portionation speed and electrolytic current density and, further,
the dispersed solid particles are present in the electrolyte,
whereby good electrodeposition is achieved. However, when an -
electrolytic component such as KCl, BaC12, MgC12, or the like,
other than the raw material of the desired metal is involved in -
the production of the highly viscous material of the electrolyte
produced on the deposit surface as described above, it is dif- -
ficult to completely and positively remove the solid or highly
viscous material of the electrolyte relying only on physical
operations such as agitating and mechanical polishing of the
solid particles. In such a case, if the composition of a fused-
salt electrolyte is selected so that the solubility of KCl at
the electrolyte temperature is increased by increasing the
amount of MgC12 as, for example, in the electrolyte shown in
Example 5 to be described later, and a fusion having a low
melting point is produced, the above mentioned drawbacks can be
completely and reliably prevented in cooperation with the afore-
-16-
`" 1073400
mentioned effective agitation effect by the solid particles,
though the amount of each salt which has been increased over its
solubility level may produce a highly viscous material on the
deposit surface, unless a plurality of salts intermingle with
each other.
For reliable formation and fusion of the above mentioned
nighly viscous material, it is advisable that electrolytic con-
ditions having different rates of increasing the amount of the
two or more components be alternately combined to continue the
electrodeposition as shown in Example 5. Similarly, solid
particles such as those of a barium salt, a sodium salt or the
like must also be taken into consideration with reference to the
electrolysis operating conditions, such as the electrolyte
temperature and the like, upon detPrmining the composition of the
original fused-salt electrolyte so that the viscosity of the
deviated electrolyte portion at the electrolytic temperature and
the solubility of the raw material of the desired metal at the
aforsaid deviated electrolyte portion, e.g., the titanium salt
in Example 5, may be maintained in the desirable condition.
In order to disperse solid particles in a fused electro-
lyte, the velocity of the electroly*e must be more than the
minimum fluidization velocity of the solid particles, which is
determined upon considering the size, shape and specific gravity
of the particles. In order to provide the velocity necessary to
achieve the above object to the fused electrolyte, a mechanical
agitating means is used such as a bubble tupe agitator, a pro-
peller type agitator, a fan turbine type agitator, a slanting-
blade fan turbine type agitator, an arrow fan turbine type
agitator, a helical shaft or helical ribbon agitator, or fluid
transport means such as one or more pumps. It is needless to -~
say that the aforesaid object can be sufficiently attained using
such and other means and the exact agitation method selected is
~ . .
- 17 -
- 1073400
not particularly limited. It is often preferred, however, to
rotate or vibrate the cathode, either at a constant rate or by
periodically varying the rate of rotation or vibration of the
cathode. For the case of rotation, a rotation rate in the range
of about 70 to about 2500 rpm is often conveniently used.
Further, particularly in order to disperse crystallized-
salt particles into a fused electrolyte, the following method
is preferred.
With respect to a component salt of the desired crystal-
lized salt particles to be dispersed into a fused electrolyte,the temperature of the fused electrolyte is decreased so as to
obtain the desired amount of crystallized-salt particles at the -
electrolytic temperature with reference to the liquidus line or ---
face of the phase diagram of the electrolyte and the solubility. ~
Generally, the desired amount of crystallized-salt particles at -~ -
the electrolytic temperature is decided, the electrolytic
temperature is selected, and thereafter a batch of materials
which will provide the desired fused-salt electrolyte and the
desired amount of crystallized-salt particles blended, where-
after the temperature of the electrolyte is raised to a tempera-
ture sufficient to substantially completely melt, most preferably
completely melt, the composition whereafter the composition is
cooled to the electrolytic temperature to thereby form the
crystallized-salt particles, the component salt in an amount
corresponding to the difference between the solution concentra-
tion of the component salt at the original high temperature and
that of the component salt at the electrolysis temperature is
precipitated into the electrolyte as solid particles. The shape
and size of the precipitated solid particles can be controlled
by the time required to lower the electrolyte temperature from
-18-
- : , :: . .,. . . -. : , , .. .,;: - : .
` ` 10734~0
the original high temperature to the electrolysis temperature,
the agitating condition of the electrolyte, and the type of
precipitated component salt using conventional techniques as are
common in the crystallization art. When the electrolysis
apparatus is provided with exterior cooling means, for example,
at least a portion of the walls of the electrolysis apparatus is
provided with a cooling jacket to perform the above described
cooling of fused electrolyte, the amount of crystallized com-
ponent deposited on its surface is affected by the type of pre-
cipitated component salt, the agitating condition of the electro-
lyte and the like, in a manner similar to the foregoing.
Further, it is most preferred that at least a portion of
the walls of the electrolysis apparatus be provided with heating
means so that the amount of electrolyte deposited on the walls
surface, which has no relation to the electrolysis, can be
reduced. However, when the electrolyte is kept at the electro-
lysis temperature for a long time, the solid particles gradually
precipitate and accumulate at the bottom of the electrolyzer.
These accumulated solid particles may be sometimes used again
merely by a simple mechanical agitation even after the passage
of one day and night. A fused electrolyte shown in Example 6 is
an electrolyte of this kind. However, when the crystallized
particles accumulated at the bottom of the electrolysis apparatus
are gradually welded and one night passes at the same tempera-
ture, they frequently aggregate into the shape of a solid sheet.
In such a case, it is necessary that the aggregate be fused by
increasing its temperature and the above described operation for .
forming solid particles be repeated. In order to overcome this
problem, it is necessary to keep the conditions of the crystal-
lized particles near the electrodeposition electrode at the
--19--
~0~340O
desired constant conditions in such a manner that, as shown in
Example 5, the temperature of the portion within the electrolysis
apparatus where crystallized particles are liable to be pre-
cipitated (mainly, the bottom of the electrolysis apparatus) is
kept high, whereby the crystallized particles precipitated onto
the aforesaid portion are fused, and the resulting solution is
shifted to a low temperature portion of the electrolyte, thereby
continuously producing crystallized particles. Further, if a
separate high temperature bath compartment is provided, electro-
lyte and crystallized particles can be removed from the lowerpart of the low temperature portion of electrolyte to the afore-
said high temperature bath compartment through a passageway
which is slightly slanted so that a large amount of crystallized
particles cannot accumulate thereon, and the electrolyte again
circulated to the low temperature portion after fusion.
In the embodiment of the present invention wherein solid
particles are formed by in situ crystallization, it will be
apparent to one skilled in the art, that if desired, three -
separate vessels can be utilized, i.e., a high temperature vessel
wherein substantially all of the components of the fused-salt
electrolyte are melted into the liquid state, a cooling vessel
wherein-in s-itu crystallization is conducted and an electro-
deposition cell. However, as earlier indicated it is preferred
to utilize a single vessel divided into three regions, i.e., a
bottom high-temperature region wherein substantially all of the
components of the fused-salt electrolyte are melted, an upper
region which receives the product of the high-tempèrature bottom -
region wherein cooling is effected to perform in situ crystalli-
zation, and a middle region wherein electrodeposition is con-
ducted. In the above embodiment, of course, coagulated large
-20-
., . . ~
11~73~100
particles of crystallites which cannot be maintained in the flow
of the electrodeposition zone fall down into the bottom high-
temperature region and are remelted.
On a commercial scale, when solid particles are formed
by in situ crystallization, typically the high temperature
region wherein substantially all of the components of the fused
salt electrolyte are melted into the liquid form is in the area
j of about 500 to about 560C and the in- si-tu crystallization
region and the electrodeposition region are maintained at a
temperature of about 400 to about 490C, cooling tubes being
provided in the crystallization region. The temperature differ-
ential between the electrodeposition temperature and the tempera-
ture wherein substantially all of the components of the fused- ~ -
salt electrolyte are melted is not overly critical so long as -
the desired amount of the component or components to be crystal-
lized can be placed into solution and then crystallized there-
from by cooling. Usually, a temperature differential of from ~
about 30 to about 150C is used, and on an industrial scale a ~ -
temperature difference on the order of 100C is often used.
Next, in order to attain the afore-mentioned effect,
particularly by dispersing solid particles in the fused electro-
lyte, the electrolyte must have a sufficient relative velocity
at the deposit surface. It will be apparent that a sufficient
relative velocity can be produced near the deposit surface by
the above described mechanical fluid transport means with the
cathode electrode being motionless or slowly revolving or shift- r
ing, and/or the aforesaid sufficient relative velocity can be
produced by violently vibrating or rotating the cathode electrode
as shown in the Examples.
As earlier indicated, the process of the present inven-
tion is of broad application, i.e., it finds general utility in
.
``` 10~3~0
electrodeposition systems wherein a desired metal or alloy
electrodeposited by electrolysis can be dissolved in a fused-
salt electrolyte and/or wherein a fused-salt electrolyte forms
a highly viscous material on the surface of the electrodeposited
metal or alloy.
The present invention does, however, find particular
application in the electrodeposition of titanium or a titanium
alloy from a fused salt electrolyte comprising BaC12, KCl, MgC12,
NaC12, CaC12 and TiC12 and TiC13, most especially where the
molar ratio of TiC13 to TiC12 is less than 0.5 in the vicinity
of the cathode upon which electrodeposition is occurring.
If desired, the bromide form of the above materials may
be utilized in accordance with the present invention (bromide-
based system~, but such is generally non-preferred.
It will be appreciated by one skilled in the art, of -
course, that the present invention is not limited to the electro-
deposition of titanium or titanium alloys, but that other metals
can be electrodeposited in accordance with the process of the
present invention, for example, by utilizing the corresponding
chloride(s) of metals other than titanium in a system as
described above.
The average current density utilized during the electro-
deposition of the present invention can be substantially varied,
and to a large extent, is influenced by the size of the cathode
selected. While definitive values cannot be set due to the wide
variation in cathode sizes which can be utilized in the present
invention, the general rule to be followed is that the larger
the cathode the higher the current density used, and the smaller
the cathode the lower the current density used. Optimum current
density is generally determined in an empirical fashion, i.e.,
as is conventional in the art a few process runs are conducted -~
- -22-
- . ~ , . ~. .
- : . .
1073400
at varying average current densities until the current density
which provides the best product is determined. For example,
using a cathode with a diameter of 32 mm the maximum average
current density may be about 30 A/dm2, whereas using a vibrating
cathode of a larger size as would commonly be used on an
industrial scale an average current density of 80 A/dm2 or higher
is realistic for the electrodeposition of titanium metal by the
process of the present invention in an agitated bath, for example.
One particularly advantageous effect of the process of
the present invention is that the present invention can be
practiced at an extremely high current efficiency, for example,
70 to 80 % on a reproducible basis. This is a great improvement
over conventional prior art fused-salt electrodeposition pro-
cesses wherein substantially lower current efficiencies are
obtained.
The electrodeposition process of this invention will now
be described with reference to several Reference Examples and
Examples. -`
As will be obvious from the following, the present inven-
tion comprises not only the above characteristics but also othercharacteristics which are preferably simultaneously utilized
therewith.
Principle matters common in the Reference Examples and - -
Examples were as follows:
The analysis of the component salts of the electrolyte ~-
composition was performed when the electrolyte was produced.
The illustrated titanium salt was quantitatively ana-
lyzed as TiC12 and TiC13 after metallic titanium and TiC13 were
supplied to the electrolyte and caused to react with each other
at a bath temperature of 560C. The method of S. Mellgrem and
-23-
, , - ,; , -, , ;
`` lOq3400
W. Opie (refer to Journal of Metals, 266, 1957) was used as the
above analysis method. This analysis method is based on the
fact that TiC12 discharges hydrogen gas quantitatively upon
reaction with a dilute acid solution as follows:
Ti+2 + H+ > Ti 3 + 1 H2~
That is, a sampled electrolyte at the operating temperature was
suddenly cooled to produce a specimen which was placed in
aqueous hydrochloric acid (0.7 % HCl) to generate hydrogen gas
and the amount of the hydrogen gas measured to thereby determine
TiC12 in the electrolyte, considering the hydrogen gas was
generated from TiC12. TiC13 analysis was carried out in such
a manner that the specimen was dissolved in aqueous hydrochloric
acid (5% HCl), barium salt removed by adding aqueous sulfuric
acid (10%), whereafter titanium ions reducible by zinc amalgam
were all reduced to Ti+3 which was titrated with a standard
Fe~3 solution. The amount of the titanium salt produced by the
above titration as TiC13 was subtracted from the amount of TiC1
to thereby determine the amount of TiC13.
With the above described titanium salt, a complex salt
may be at least partially formed at the high temperature of the
electrolyte in its fused condition. Except for the case where
the electrolyte is added with solid particles which are indepen-
dent of the original electrolyte component, the existence or
absence of crystallized-salt particles in the electrolyte at the
electrolysis temperature in an amount sufficient to have a sub-
stantial effect on the electrodeposition process of this inven-
tion was judged in the following manner.
The electrolyte was agitated at a temperature higher
than the electrolysis, i.e., at a temperature high enough to
melt all components of the fused electrolyte, and electrolyte
-24-
1073~)0
immediately adjacent to the cathode position, which i8 3 to 5 cm
under the surface of the electrolyte was sampled for analysis.
Next, with the temperature of the electrolyte lowered to elec-
trolysis temperature and kept there without agitation for at
least 10 hours, the electrolyte near the cathode position was
sampled for analysis. Then, both of the above analyzed values
were compared to each other; if a significant difference could
be detected therebetween in view of the mechanism of the electro-
deposition process of this invention, it was judged that the
crystallized-salt particles were present in the electrolyte in
an amount sufficient to have a substantial effect on the electro-
deposition process of this invention.
As will be appreciated by one skilled in the fused-salt
electrodeposition art, it is difficult to sample a fused-salt
electrolyte at the elevated temperature or electrodeposition
with complete accuracy, and, as will be apparent, such sampling
is also difficult at the higher temperatures required for bring- ~ `
ing the excess component or components which is!are later to be
crystallized into solution. Considering the possibility of
analytical error, the general rule used on an industrial scale
is that if there iæ a difference of greater than 5 molar % in
the amount of any one component to be crystallized at the ele-
vated "solubilizing" temperature and at the crystallization
temperature (the temperature of the electrodeposition), this is
considered a "significant difference".
It is most preferred in accordance with the present
invention that more than about 10 molar ~ but less than about
30 molar ~, of at least one component in the fused electrolyte
be crystallized as solid particles, i.e., based upon the amount
of the component in the fused-salt electrolyte at the electro-
-25-
.
- , - : -
1073400
deposition conditions a 10 to 30 molar % excess of that component
is melted at the "solubilizing" temperature and then crystal-
lized. As reference to the later given Examples will make clear,
however, this range is not mandatory, merely preferred. Further,
in all electrolytes except an electrolyte which had added thereto
solid particles independent of the original electrolyte compo-
nent, when an electrolyte sampled therefrom by the afore-
mentioned method was dissolved in aqueous hydrochloric acid (5%)
and filtered on a filter paper to collect insoluble component(s),
the dissolved residue obtained by roasting the above insoluble
component was less than 2 weight %, i.e., the in situ formed
particles were substantially contaminant free.
Each electrolysis apparatus used except for that used in
Example 5 was a test tube type container made of glass with an
inner diameter of 75 mm and a depth of 500 mm provided with
external heating means (using an electric heating furnace).
The depth of the electrolyte in each tube was about 20
cm.
In addition, the surface of electrolyte within the
20 electrolysis apparatus was kept under an argon atmosphere at --
atmospheric pressure.
REFERENCE EXAMPLE 1
Electrodeposition in an electrolyte with no solid par-
t les dispersed therein at the electrolysis temperature.
(1) Composition of Electrolyte (In molar ratio):
BaC12 12.70, MgC12 23.80, CaC1210.52
NaCl 33.77, KCl 10.65, TiC127.84
TiC13 0.71
(2) Temperature of Electrolyte: 460C
-26-
10~3400
(3) Electrodes:
Cathode .... Stainless steel cylinder 15 mm in diameter
and 25 mm in length
Anode ...... Round carbon bar 8 mm in diameter, sub-
merged portion 150 mm in length.
Distance between electrodes ... about 30 mm
(4) Electrolytic Current:
Intermittent DC with cathode current density of 35
A/dm2
Intermitting period 0.6 sec
Current-On time 0.3 sec
Current-Off time 0.3 sec
(5) Agitation: Rotation of cathode electrode at 2000 revolu-
tions per minute (rpm)
(6) Electrolysis Time: 30 min
(7) Results (Appearance of Electrodeposit):
Black fine dendrites were grown in a shaggy state on the
surface of a silver gray thin foil.
EXAMPLE 1
Electrodeposition with SiO~ particles dispersed in the -
. _ _ _ . _
electrolyte of Referenc`e Example 1.
(1) Composition of Electrolyte:
An electrolyte composed of 2 kg of the electrolyte of
Reference Example 1 having added thereto 500 g of SiO2 particles
having an average diameter of 200~ (added exterior of the system).
(2) Temperature of Electrolyte, (3) Electrodes, (4) Electrolytic
Current and (5) Agitation were all as in Reference Example 1.
However, referring to the agitation, when the cathode electrode
was rotated at 2000 rpm, it was noticed that an electrolyte
vortex occurred under the cylindrical cathode electrode and a
~ -27-
lOq340(~
violent circulating flow of the electrolyte was generated to pull
up SiO2 particles dispersed thereinto.
(6) Electrolysis Time: 1 hour
(7) Results (Appearance of Electrodeposit):
Compact, thick plate having a glossy, smooth surface of
fine crystals.
EXAMPLE 2
Even when an electrolyte having dispersed therein ground
particles of sintered boron nitride having an average particle
10 diameter of 150 ~A (Tradename: DENKA BORONITRIDE HC-TYPE) was
used in place of the SiO2 particles contained in the electrolyte
of Example 1/ there was obtained an electrodeposit showing -
substantially the same appearance as in Example 1 above.
`~ REFERENCE EXAMPLE 2
Electrodepo ition using an elec*rolyte with no solid
particles dispersed therein at the-electrolysis-*emperature.
q (1) Composition of Electrolyte (In molar ratio)
~!: BaC12 9-09~ MgC12 28.85, CaC12 12.18 -- NaCl 27.00, KCl 14.63, TiC12 7.47
TiC13 0.77
~ (2) Temperature of Electrolyte: 460 C
9 ( 3) Electrodes: Same as those of Reference 1.
(4) Electrolytic Current: ~ -
Intermittent half-wave rectified current of single-phase
AC of 50 c/s having a cathode current density of 50 A/dm (peak
value).
Intermitting period 0.6 sec
Current-On time 0.15 sec
Current-Off time 0.45 sec.
; 30 (5) Agitation: Rotation of cathode electrode at 2000 rpm.
: -28-
10734~0
(6) Electrolytic Time: 30 min
(7) Results (Appearance of Electrodeposit):
Black fine dendrites were grown in a shaggy state on the
surface of a silver-gray thin foil. The amount of dendrites was
much more than that of the electrodeposit of Reference 1.
EXAMPLE 3
Electrodeposition using an electrolyte in which crystal-
lization and dispersion of a TiCl compohent was observed at the2
electrolysis temperature
(1) Composition of Electrolyte (In molar ratio)
BaC12 8.77, MgC12 26.06, CaC12 11.50
NaCl 25.96, KCl 12.61, TiC12 14.61
TiC13 0.60 ~ -
(2) Temperature of Electrolyte, (3) Electrodes, (4) Electrolytic
Agitation and (6) Electrolytic Time were all the same as those
of Reference Example 2. Prior to the electrodeposition, the
above fused electrolyte was raised to a temperature sufficient
to melt the same and then cooled to the electrodeposition tempera-
ture, whereafter electrodeposition was conducted. The solid
particles of TiC12 were estimated to have a size on the order of
the solid particles as were added exterior of the system in
Example 1 and Example 2.
(7) Results (Appearance of Electrodeposit): -
Compact plate having a semi-glossy flat surface made of
fine crystals.
EXAMPLE 4
Electrodeposition in an electrolyte wherein crystalliza-
tion and dispersion of a BaC12 component wa-s observed at the
electrolysis temperature.
(1) Composition of Electrolyte (In molar ratio)
-29-
lOq3~00
BaC12 15.12, MgC12 28.44, CaC12 11.37
NaCl 25.42, KCl 11.28, TiC12 8.05
TiC13 0.34
(2) Temperature of Electrolyte and (3) Electrodes were the same
as those of Reference Example 2.
The above fused electrolyte was raised to a temperature
sufficient to melt the same, and thereafter cooled to the electro-
deposition temperature to crystallize solid particles of BaC12.
The solid particles were estimated to have a size on the order
of the solid particles added exterior of the system in Examples
1 and 2.
(4) Electrolytic Current:
Intermittent half-wave rectified current of single-phase
AC of 50 c/s having a cathode current density of 50 A/dm2 (peak ~-
value). :
Intermitting period 0.15 sec
Current-On time 0.11 sec
Current-Off time 0.04 sec
(5) Agitation and (6) Electrolytic Time were the same as those
of Reference 2.
(7) Results (Appearance of Electrodeposit):
Compact plate having a semi-glossy flat surface made of ~:
very fine crystals.
EXAMPLE 5 ~ -
Electrodeposition in an electrolyte wherein crystalliza-
tion and dispersion of BaC12, KCl, MgC12, NaCl and TiC12 com-
ponents was observed at the electrolytic temperature.
The electrolysis apparatus used in this example was as
follows:
A square electrolyzer of the internal heating type was
used and 180 liters of electrolyte filled therein so to provide
-30-
.. ..
.,
10734~0
an electrolyte 135 cm in depth. The electrolyte surface within
the electrolyzer was kept under an argon atmosphere. With the
temperature of the electrolyte being kept at more than 520C to
melt the components at the bottom of the electrolyzer, the
electrolyte was agitated by a stainless-steel propeller type
agitator, where the speed of the propeller type agitator was
controlled so that the electrolyte composition near the cathode
electrode was kept substantially constant.
. ~
A stainless steel pipe 100 mm in length, 32 mm in outer
diameter and 1.5 mm thick was employed as a rotating cathode
electrode. For this purpose, the pipe was attached to the top
end of a stainless steel rotary shaft 25 mm in outer diameter
via a copper conductive ring. The opening at the tip of the
cathode pipe was covered with a porcelain nut, and the cathode
elec*rode inserted into the electrolyte for rotation so that the
cathode electrode was positioned between 5 cm and 15 cm under
the electrolyte surface with the porcelain nut facing downward
'~ and the rotary shaft substantially vertical. The portion of the
rotary shaft located above the cathode electrode and submerged
, 20 in the electrolyte was covered with a porcelain cylinder whose
outer diameter was substantially the same as that of the cathode
pipe.
As the anode electrode there were used two 1.5 cm thick ~-
sheets of square carbon plate with each side 20 cm long. These
two carbon sheets were immersed in the fused electrolyte sym-
metrically disposed opposite to each other with the cathode
electrode being interposed therebetween, keeping each carbon
plate from the cathode a distance of 15 cm.
Further, a pouch-like partition membrane of twilled
quartz cloth was disposed around each anode so as to be wrapped
- . . : . , .
10'73400
around each anode at a distance of about 3 cm from the anode
surface. This membrane served to prevent the composition of the
electrolyte from being changed by the products produced by the
anode reaction during electrolysis. The following electrolyte
composition and temperature were obtained by sampling the
electrolyte at the portion where the cathode electrode was
insertedbetween 5 cm and 15 cm under the electrolyte surface.
(1) Composition of Electrolyte (In molar ratio)
BaC12 23.73, MgC12 22.65, -CaC12 13.06 - ~
;~ 10 NaCl 41.00, KCl 20.53, TiC12 27.38 -
! TiC13 3.88
Prior to electrodeposition, the temperature of the above
fused electrolyte was elevated so as to melt all components,
whereafter the fused electrolyte was cooled to the electrodeposi~
tion temperature, thereby crystallizing solid particles of BaC12,
KCl, MgC12, NaCl, TiC12 to serve as dispersed solid particles -
during the electrodeposition. The solid particles were - -
estimated to mostly have a size of on the order of the solid - -
particles added exterior of the system in Examples 1 and 2.
(2) Temperature of Electrolyte: 473C to 476 C
(3) Electrodes: ~ ~ -
Cathode A stainless steel cylinder having diameter
of 32 mm and length of 100 mm --
Anode ...... Two sheets of carbon plates each 20 cm x
20 cm 1.5 cm thick
Distance between the Electrodes ... 15 cm
(4) Electrolytic Current:
DC current of a cathode current density of 33 A/dm2 was
intermittently supplied at a rate of on-time 0.006 seconds and
off-time 0.004 seconds, this intermittent current periodically
-32-
.~ . . . .
1073400
being changed to an intermittent current with an intermitting
period of 2.4 seconds, on-time 2.1 seconds and off-time 0.3
seconds.
(5) Agitation:
The cathode electrode was alternately rotated for 16
seconds at 2350 rpm and 8 seconds at 300 rpm over the electro-
lysis time. It took about 2.5 to 3 seconds, respectively, from
the change-over time to the time when the number of each rota-
tion was stabilized at a constant speed.
(6) Electrolysis Time: 2 hours
~7) Results (Appearance of Electrodeposit):
Compact thick plate having a semi-glossy and flat surface
made of very fine crystals.
REFERENCE EXAMPLE 3 -- -
(1) Composition of Electrolyte:
An electrolyte composed of 59 parts of LiCl and 41 parts
of KCl (in molar ratio) having added thereto a raw material for
titanium electrodeposition according to the method of adding the
titanium salt components as described in the earlier References ~
20 Examples and Examples. When this electrolyte was lowered in --
temperature to 400C and kept at that temperature without agita-J
tion, about 8 weight % of TiC12 and about 3 weight % of TiC13
were present near the cathode posLtion about 3 cm under the
surface of the electrolyte after the passage of about one day
and night after the temperature had been lowered. In Reference
Example 3, the supernatant solution from the maintenance in the ~ -
quiescent state for one day and night was used as the electro-
lyte. -
(2) Temperature of Electrolyte: 400C
(3) Electrodes:
-33-
10~3400
Cathode... Molybdenum plate with submerged portion of 27
mm in length; 13 mm in width and 0.2 mm in
thickness.
Anode..... Round carbon bar, submerged portion of 150 mm
in length and 8 mm in diameter.
Distance between electrodes... about 30 mm ~-
(4) Electrolytic Current:
DC current of a cathode current density of 100 A/dm2 --
supplied intermittently with an intermitting period of 0.15 sec. -
10 a current-on time of 0.04 sec and a current-off time of 0.11 sec.
(5) Agitation: ^-~
The cathode electrode was vibrated with a vibration
period of 400 cycles/min, amplitude 36 mm and vibration direction -~
45 to the cathode flat surface.
(6) Electrolytic Time: 30 min.
(7) Results (Appearance of Electrodeposit): - --
Sooty, black fine powder stuck onto a silver-gray very - -
thin foil. -~ ;
EXAMPLE 6
:
Electrodeposition using an electro-lyte in which-the ~~
... .
amount of the titanium salt component added to the electrolyte -- -
o Reference 3 was increased and crystallization and di-spersion
. - .~ "
thereof were observe-d at the~electroly-sis-temperature.
(1) Composition of Electrolyte: -
The electrolyte of Reference 3 had further added thereto
metallic titanium and TiC13 according to the previously described - -
method of adding the titanium salt component, and the tempera-
ture of this electrolyte was increased to a temperature suf-
ficient to melt all components of the fused electrolyte. There-
after, the temperature was lowered to 400C to obtain an electro-
lyte (containing cxystallized solid particles having a size ~~
-34- !
~. - , - ,~", ,,", , ~ ,- " , ,, - -
1073400
.."-
estimated to be on the order of the solid particles added
exterior of the system in Examples 1 and 2), comprising 19.2
weight % of TiC12 and 7.0 weight % of TiC13 near the cathode
position about 3 cm under the electrolyte surface. This electro-
lyte was used in this example and the same vibration of the
cathode electrode as in Reference Example 3 was carried out.
(2) Temperature of Electrolyte, (3) Electrodes, (4) Electrolytic
Current and (5) Agitation were all the same as those of Reference
3.
(6) Electrolytic Time: 3 hours.
(7) Results (Appearance of Electrodeposit):
Thick plate having a glossy, smooth surface with its
peripheral portion being raised into a round dike-like ridge.
EXAMPLE 7
An alloy deposition is illustrated in this Example.
(1) Composition of Electrolyte (in molar ratio): -
BaC12 26.48, MgC12 26.00, CaC12 13.77,
NaCl 41.00, KCl 17.63, TiC12 26.04,
TiC13 2.10 MnC12 0.87
The fused electrolyte was first raised to a temperature
sufficient to melt all components, whereafter the fused electro-
lyte was cooled to the electrodeposition temperature, thereby
crystallizing solid particles having a size estimated to be in
the order of that in the earlier examples, whereafter electro-
deposition was conducted.
(2) Temperature of Electrolyte: 470 C
(3) Electrodes:
Cathode... Molybdenum plate, submerged portion 25 mm in
length, 10 mm in width and 0.3 mm in thickness.
30 Anode..... Carbon plate with submerged portion 50 mm in
length, 30 mm in width and 5 mm in thickness.
-35-
1073400
(4) Electrolytic Current:
DC current of a cathode current density of 60 A/dm2 was
intermittently supplied at a rate of on-time 0.3 seconds and off-
time 1 2 seconds, i.e., 1.5 second intermitting period.
(5) Agitation:
The cathode electrode was vibrated with a vibration
period 400 cycle/min. (0.15 second) and a 30 mm amplitude.
Vibration direction: 45 toward the cathode surface.
(6) Electrolysis Time: 30 min.
(7) Results (Appearance of Electrodeposit):
Compact plate having a flat surface consisting of fine
crystals, its peripheral portion being raised into a round or
dike-like perimeter. As a result of X-rays diffraction analysis
the content of the electrodeposit was found to be 10.7% manganese - -
and 87.0% titanium by weight. These values were constant regard- ;~
less of the position of the flat surface, except for the peri- ~`
pheral portion of the electrodeposit.
- Further, it was also noted that according to X-ray
microanalysis the crystal construction was of the body-centered
cubic structure type.
Accordingly, from the composition and the crystal con-
struction, a Ti-Mn ~-type alloy was obtained.
As will be appreciated by one skilled in the art, in the
embodiments of the present invention where an in s-itu crystalli-
zation of solid particles is effected, it is not absolutely
necessary that the fused-salt electrolyte be completely melted
at the elevated temperature prior to crystallization, i.e., if
some minor amount of the fused-salt electrolyte is not melted
this does not excessively harm the electrodeposition process and,
in some instances, to achieve lower production times certain
small amounts of the components of the fused-salt electrolyte
-36-
` 1073400
would not be melted at the elevated temperature. Nonetheless,
the general rule will be that the melting of the components
should be as substantially completely performed as is possible
as this makes it much easier to obtain reproducible process runs.
As a practical matter, complete melting is easily achieved even
on an industrial scale.
The above examples are described with respect to the
electrodeposition of titanium. However, the electrodeposition
process of this invention can also be applied to zirconium,
aluminum, tantalum, niobium, uranium, manganese and other metals
or alloys. ~ ~
Further, with the electrodeposition process of this in-
vention, if a metal, such as titanium, having very strong reac-
tivity with negative elements is to be electrodeposited and a
negative element such as oxygen, nitrogen, boron or the like is
contained in the electrodeposited material as an alloying element,
the above objects are attainable by using an electrolyte which -~ -
has added thereto particles of a compound which has such a
negative element(s) and which provides the electrodeposited metal
with the element(s) and/or an electrolyte capable of having the
required amount of the compound(s) fused therein. --
While the invention has been described in detail and
with reference to specific embodiments thereof, it will be
apparent to one skilled in the art that various changes and
modifications can be made therein without departing from the
spirit and scope thereof.
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