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Dec. 31, 1946.
w. H. COLBERT ETAL
2,413,604
METHOD on PROCESS OF EVAPORATING METALS
'
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Filed May 2'7. 1944
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Fiji. 5.
INVENTORS
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William H. Colbelft
Arfhur R. Wei‘nnch.
[WW6 d-m
‘2,413,604
Patented Dec. 31, 1946
UNITED STATES PATENT OFFICE‘
,
2,413,604
METHOD 0R PROCESS OF EVAPORATING'
METALS
'
William H. Colbert and Arthur R. Weinrich,
Brackenridgc, Pa., assignors to Libbey-Owens
Ford Glass Company, Toledo, Ohio, a corpora
tion of Ohio
Application May 27, 1944, Serial No. 537,675
6 Claims. (Cl. 117-107)
1
,
2
Our present invention relates to a novel method
or process of evaporating metals. It has to do,
more particularly, with the coating or wetting,
by capillary attraction, of a ?lament which, for
example, may be formed from a coil of ordi
nary tungsten wire, tantalum, molybdenum or
columbium wire, by various metals in the form
minum, beryllium, magnesium, vanadium, bar
ium, strontium, iron, nickel, cobalt, manganese,
thorium, chromium and titanium, when applied
to ?laments of tungsten, tantalum, molybdenum
evaporation, to the face .or surface of an ar
temperatures should readily evaporate, it has
or columbium, will on heating in a vacuum, melt
and spread over the ?lament by capillary at
traction and satisfactory evaporation of these
metals then occurs from the large amount of
of an alloy or different alloys, which metal or
surface which the molten metal covers.
metals it is desired to evaporate and which in
However, with a large number of metals which
pure form normally ‘do not wet these metallic 10
it is desirable to be able to thermally evaporate
?laments, and the application of said metals or
and which from their vapor pressure at elevated
metal alloys by deposition resulting from thermal
been found ‘di?lcult, if not impossible, to carry
out satisfactory deposition of such coatings by
metal, plastic, Cellophane, paper, or the like, to
thermal evaporation. Thus, for example, silver
provide a re?ective or metallized surface coat
while readily lending itself to thermal evapora
ing for said article. The invention also has to do
tion from a. crucible, cannot be evaporated read
with securing wetting and with thermal'evapo
ily from a coil of tungsten, tantalum, molyb
ration of such metals from pure tungsten, tanta
lum, molybdenum, or columbium ?laments by 20 denum or columbium when applied to a ?lament
of these metals and heated by electrical resist
alloying such ?laments by the application to the
ance. The silver on melting shows no ai?nity
?laments of the metals desired to be evaporated
alloyed with and carrying the elements which " for the metallic filaments and almost immedi
ately after melting collects into a drop and falls
we have found it desirable that the ?laments be
25 off the ?lament. This lack of ability to wet
alloyed with. tungsten, tantalum, molybdenum and colum
Methods and apparatus have previously been
bium occurs also with the metals copper, gold,
employed to apply coatings of metals by thermal
ticle, such as a piece of glass, porcelain, plaster,
zinc, tin, antimony, cadmium, bismuth, lead,
evaporation to the faces or surfaces of such ar
thallium and indium. With each of these metals
ticles to produce mirrors, re?ectors or metallized
materials for other purposes. In these methods 30 the use of the four available coil ?laments as a
means of evaporating these metals has not been
it is desirable to effect the thermal evaporation
possible, and less desirable means of heating
of the metal, such as silver or aluminum, by ap
have been necessary where it became necessary
plying the metal directly to an electrically en
to evaporate these under practical conditions re
ergized and thus heated tungsten or other me
tallic ?lament which is preferably located within
a vacuumized chamber.
The metals which may
be used as ?laments for such evaporations must
peatedly in the commercial production of mir
rors and metallic coated articles.
As each of
these metals, after melting, pulls together into
is generally prohibitive. While iron and nickel
droplets and falls off the ?laments, there has
resulted a wastage of the metal‘whenever it has
been attempted to evaporate them from these
?laments and there have been continuous fall
ures of the apparatus to function due to the loss
of the metals from the heated wires; and where
any metal has been evaporated the amounts so
evaporated have always been uncertain and
are of relatively low vapor pressure, they are
without control.
of such relatively low melting point that ?la
ments made from them rapidly burn out.
We have found that we may use tungsten,
tantalum, molybdenum‘ or columbium as ?la
obviously be of high melting point and also of
low vapor pressure at the elevated temperatures
at which the metals applied to the ?laments
evaporate.
Thus, tungsten, tantalum, molyb
denum and columbium have represented the only
practical materials for such use. Platinum also
has been used to a small degree but its high cost
With these ?laments many of the metals can
,
ments for the evaporation of metals which do
be readily evaporated. Thus, for example, alu 50 not wet these ?laments by causing them to wet
2,413,604
3
4
such ?laments by the application of such ?la
ments, or the forming thereon, of alloys of these
provided an improved method or process whereby
molybdenum and columbium in the presence of
temperature is higher and which metal brings
about a wetting and coating of the ?lament by
a metal desired to be evaporated to form a re~
metals which we desire to evaporate with an
?ective surface coating is applied to a tungsten,
other metal which is characterized in that it
tantalum, molybdenum or columbium ?lament as
will also form an alloy with tungsten, tantalum, 5 an alloy with another metal whose vaporizing
the metal we desire to evaporate.
As metals
which we have found which may be used in a
capillary attraction, thus permitting the deposi
relatively small quantity which cause the nor
tion of the desired metal upon the face- or sur
mally non-wetting metals to wet the metallic 10 face of an article by thermal evaporation without
?laments we may use iron, nickel, cobalt, plat
appreciable evaporation of the added metal so
inum or palladium, or several of these together.
as to give a re?ective surface coating showing
Thus, for example, we may add small amounts
the characteristic properties of the desired metal
of nickel to silver and when such alloys are melt
only. The alloy element may also be alterna
ed on a tungsten ?lament the silver will be 15 tively used in the ?lament to secure the same
found to wet the tungsten ?lament and to Spread
objectives, as set forth in our copendlng appli
itself by capillary attraction over the surface
cation, Serial No. 537,676.
of the tungsten wires. In the absence of the
A further object of our invention is to apply
nickel the silver melts, draws itself into a drop
to a tungsten, tantalum, molybdenum or colum
let and falls oif the ?lament wire because it 20 bium ?lament, a metal such as copper, silver,
does not wet the same. Not all metals have been
gold, zinc, tin, antimony, cadmium, bismuth, lead,
found to act in this manner. Alloying the nor
indium or thallium, alloyed with a suitable pro
mally non-wetting metals among themselves,
portion of another metal which brings about a
such as adding lead to silver, does not seem to
desirable wetting or coating of the ?lament metal
bring about any desirable improvement in the 25 by capillary attraction under the in?uence of
wetting characteristic. In each case it is found
heat applied to the ?lament and thus permits
that the metals of the iron group, namely, iron,
thermal evaporation of the metals.
nickel and cobalt and the metals of the plat
Generally speaking, and in accordance with
inum group, namely, palladium, platinum, rho
our present invention, the metal to be evaporated
dium and iridium readily form alloys with tung 30 which normally does not wet the heater ?lament
'sten, tantalum, molybdenum and columbium
is applied alloyed with another suitable metal
and also form alloys with copper, silver, gold,
providing wetting characteristics to the coils of
zinc, tin, antimony, cadmium, bismuth, lead, in
a ?lament which may be formed from tungsten,
dium and thallium. Thus, the metals of the iron
tantalum, molybdenum or columbium. Thus, in
and platinum groups which we have enumerated 35 order to thermally evaporate copper, zinc, gallium,
readily bring about the desired wetting and it
appears clearly that this is accomplished through
the mutual alloying tendency which these metals
or arsenic, which are metals of the chemical
periodic table arrangement found in series 5
or the metals silver, cadmium, indium, tin and
possess.
antimony, which include metals of series 7, or
One of the objects of our invention is to pro 40 the metals gold, thallium, lead and bismuth which
vide an improved and satisfactory method or
in the periodic arrangement include series 11, all
process of evaporating metals which normally do
of which metals do not wet ?laments made of
not wet heater ?lament coils of tungsten, tan
tungsten, tantalum, molybdenum or columbium,
talum, molybdenum, or columbium, by alloying
we ?rst bring about a satisfactorywetting and
the metal so as to cause the metals to wet the
adhesion of these metals to the ?laments by ap
coils of such ?laments and to coat the coils by
plying the metals to the ?laments as an alloy
capillary attraction so that thermal evaporation
with small amounts of another metal either se
can then be carried out.
lected from the iron group such as iron, nickel
Another object of our invention is to apply to
or cobalt, or selected from the platinum group
a tungsten, tantalum, molybdenum or colum 50 metals such as platinum, palladium, rhodium
bium ?lament a metal to be evaporated which
or iridium, and then by energizing the ?lament
does not wet such ?lament coils, alloyed with
and thus heating it we cause a melting of the
a suitable proportion of another metal of the iron
metals. It is, of course, well known that the
or platinum groups which alloys with the ?la
metals copper, silver and gold constitute a family
ment and brings about a proper wetting or coat 65 in the chemical periodic table arrangement.
ing of the ?lament wires by capillary attraction
When the applied metal alloys are thus melted
under the in?uence of heat applied to the ?la
they apparently alloy to some degree with the
ment.
metal comprising the heater ?lament wire and
As another object of our invention there is
by reason of such tendency the molten metals
provided an improved method or process whereby 60 wet the ?lament wires and by capillary attrac
a metal which is to be evaporated and which
tion are drawn out over the surface of the coils.
does not normally wet heater ?laments of tung
The molten metal which has thus covered con
sten, tantalum, molybdenum and columbium is
siderable surface of the heated coil and is held
alloyed with another metal such as platinum,
thereto by capillary adhesion is thereafter evap
palladium, nickel, cobalt or iron, and applied to 65 orated uniformly from the heater coils to apply
such a ?lament, or in which a suitable alloy
consisting of one or more of these metals'with
a surface coating of a metallic or reflective nature
to an article such as a piece of glass, porcelain,
the metal to be evaporated is applied to such ?la
silica, mica, plastic, metal, Cellophane, resin, or
ments, and by securing a wetting and coating of
other support material, by deposition resulting
the ?lament by capillary attraction of the metal 70 from the thermal evaporation of the metal from
desired to be evaporated may be deposited upon
the ?lament. The operations of thermal evap
the face or surface of an article, by thermal evap
oration may with some of the metals, be carried
oration, to provide such article with a re?ective or
out at normal pressure but generally are pref
metallized surface coating.
erably carried out in vacuum chambers known '
As a further object of our invention there is 75 to the art and within a high vacuum, which may
2,413,004.
'
.
be of the order of one millimeter down to 10 to
the minus 5 millimeters or better. It is very
necessary that themetal to be evaporated wet and
coat the coil surfaces in order that the metal will
evaporate uniformly in all directions. By secur
ing such wetting action the thermal deposition
of these metals, in addition to being made possible,
6
’
posite ends are attached to brackets 11 mounted
upon the supporting posts I! and adjustable
thereon so as to vary the position or location of ,
the ?lament IS with relation to the supporting
base Ill.
The chamber provided by the housing ll may.
if desired, be completely evacuated of air through
outlet pipe or conduit Illa-and have a high vacu
um created therein by means of suitable air
As will be shown more fully later, pieces of the 10 evacuating and vacuum creating means, such as
has been‘ found by our process to give uniform
coatings.
metal to be evaporated and which have been pre
Vious’ly alloyed with the metal which brings about
the alloying with and wetting of the ?lament,
may be hung onto the loops or coils of the ?la
ment.
The foregoing and other objects and advantages
of the present invention will appear from the fol
a pump (not shown) .
In accordance with one method embodying our
invention which is' to be performed or carried out
within the chambered housing II, we preferably
provide a metal alloy which may consist of silver,
copper or gold or other normally non-wetting
metal and approximately 5 to 15% or more of
platinum. Pieces of this preformed silver and
platinum alloy, or copper and platinum alloy, or
drawing forming a part of this speci?cation 20 gold and platinum alloy, several of which are
shown at I8, in Figures 1 and 2, are bent and
wherein similar reference characters designate
hung on the loops or convolutions lid of the ?la
corresponding parts in the several views.
ment IS in the manner shown.
_
In said drawing:
It is known that silver, copper and gold lend
Figure l is a perspective view, partly broken
themselves admirably to thermal ‘evaporation but
away, illustrating one suitable apparatus for ‘car
they have no wetting a?inity for tungsten, tan
rying out our improved method or process.
talum, molybdenumor columbium surfaces and
Figure 2 is a perspective view of a fragment of
lowing description and appended claims when
considered in connection with the accompanying
therefore silver, copper or gold alone is unsatis
an electric ?lament showing the application of a
factory for coating the ?lament i6 formed from
suitable metal alloy to several of the coils or con
volutions thereof, and illustrating one phase of 30 either of these metals by a wetting action effected
by capillary attraction. Wetting o! the ?lament
the method or process of wetting or coating the
wire is essential to secure a maximum of evap
?lament by said alloy; and
orating surfaces to provide evaporation uniform
Figure 3 is a view similar to Figure 2 showing
ly in all directions, to the securing of uniform
the ?lament after the completion of the wetting
deposits, and also to avoid the dropping of the
process by the alloy of Figure 2.
molten metal off the heater wires. We have
Before explaining in detail the present inven
found that platinum, while having a higher melt
tion it is to be understood that the invention is
ing point than gold, copper or silver, readily alloys
not limited in its application to the details of con
with silver, gold and copper and the alloys have
struction and arrangement of parts illustrated in
the accompanying drawing, since the invention is 40 a wetting affinity for the four above-mentioned
metals, any one of which may be used for making
capable of other embodiments and of being prac~
the ?lament I6, and thus platinum lends itself
ticed or carried out in various ways. It is to be
.particularly well to securing the wetting of the
understood also that the phraseology or terminol
?lament by capillary attraction. Therefore, by
ogy employed herein is for the purpose of descrip
including a certain percentage of platinum, pref
tion and not of limitation, and it is not intended
erably 5% or more, with the silver, copper or
to limit the invention herein claimed beyond the
gold to form the alloy IS, the platinum will serve
requirements of the prior art.
to bring about wetting or coating of said ?lament
Referring now to the drawing, we have shown
by the molten metal by capillary attraction when
a suitable apparatus for carrying out our im
proved method or process, as well as one suit 50 the ?lament is energized and thus heated and will
act to cause the silver, copper or gold to also cling
able metal alloy and the steps of applying the
to or wet the ?lament. An early stage or phase
alloy or a ?lament by a wetting action resulting
of the wetting action of the ?lament I6 by the
from capillary attraction.
alloy I8 is shown generally at l9, Figure 2. As
Suitable apparatus employed by us, and illus
trated in Figure 1, comprises, as shown, a sup 55 the wetting action by capillary attraction con
tinues, the two metals of the alloy will proceed
porting base Ill upon which is mounted a housing,
to wet the coils of the ?lament l6 and in fact,
shown as a whole at H. The housing Il may be
in the form of a bell-jar or the like having a
dome-like or semi-spherical top portion or en
closed end and a bottom open end having a sur
rounding ?ange or projection l2 which is adapted
to rest upon the top face or surface of the sup
porting base I0.
will substantially wet or coat and cover the sur
faces of the ?lament. In Figure 3, we have illus
trated several of the coils or loops i6a of the
?lament as being coated at 20 .by the alloy from
which the pieces l8 are formed.
Thus, by includingplatinum with the silver,
copper or gold, as an alloy, it is possible, to quickly
II, we have shown a suitable work-piece support 65 and e?ectively coat or wet the ?lament l6 by
capillary attraction. Since, therefore, the alloy
l3 for supporting a work piece, such as a plate or
builds up onto the surfaces of the ?lament in
piece of glass, plastic, plaster, paper, porcelain,
substantially the manner illustrated in Figure 3,
metal, or the like [4, in upright position.
there will be a relatively uniform coating or wet
Located within the chamber and mounted upon
the supporting base I0, is a pair of upright sup 70 ting of the ?lament and a uniform dependable
evaporation of the silver, copper or gold. Here
porting posts l5 between which is carried or sup
tofore, when attempts were made to wet the ?la
ported, in substantially horizontal position, .an
ment by the use of the silver, the copper or the
electric ?lament IS. The ?lament, as shown, is
gold alone, only small portions of the molten
in the form of a coiled wire made of tungsten,
molybdenum, columbium or tantalum whose op 75 metal would cling to the ?lament as droplets
Within the chamber provided by the~ housing
2,413,604
hanging from the lower ends of the coils of the
?lament, with the major portion of the molten
metal dropping or falling off the coils. This was
8
and palladium, such as 5% to‘ 10% of each in
alloy with either silver, copper or gold, gives
equally as good wetting action as is secured wit
particularly undesirable since it was practically
impossible to produce, by thermal evaporation, 5
either alone.
an even surface coating by deposition, or to con
for example, the loops lBa of an electric ?lament
or coil [6, such as that shown in Fig. 2, were to
trol the deposition to desired coating deposit
thicknesses on the surface of an article, such as
the article 14, to which it was desired to apply
a re?ective surface coating. By virtue of the
fact that the silver, copper or gold did not prop
erly wet the tungsten or other metal ?lament but
had a tendency to drop off said ?lament, the
process of coating with these metals by deposi
tion was unsatisfactory, slow and painstaking be
'
We have also found on the other hand, that if,
have applied thereto pieces of pure silver, or of
pure copper, and relatively smaller pieces of some
suitable wetting and carrier metals, such as plati
num or nickel, that when the coil or ?lament is
energized and thus heated, whereby to cause a
melting of the metals, the molten metals generally
drop off the loops before sufficient alloying of
these, and alloying and a wetting of the surfaces
cause only a small portion or percentage of the
of the ?lament occurs, and that the results are
?lament received the metal coating. Consider
uncertain and losses of evaporations and mate
able shutting down and starting over again was
rials and time occur. This is always the case with
required when most of the gold, silver or copper
the low melting metals such as zinc, cadmium,
on ?rst melting dropped off the coils and no 20 tin, lead and indium, which non-wetting metals
evaporation was secured. Thus, great waste oc
melt quickly at low temperatures and fall oi the
curred, the process was considerably slowed down,
heater wires or ?laments before any appreciable
and the coating produced by deposition, if any,
solution or alloying with the higher melting iron
was uneven or spotty and unsatisfactory because
or platinum metals occurs. Consequently, with
of such uneven character thereof on the surface 25 all of the metals we ?nd it necessary and desir
of the article coated. Commercial production
able to start with a preformed alloy.
under such uncertain conditions was impossible.
The iron metals are particularly active in al
It is to be understood that in carrying out our
loying with tungsten and tantalum and the alloys
method or process as described above, in the
produced are of much lower melting point than is
chamber of the housing H, the chamber, de 30 true of the pure tungsten or tantalum. Conse
pending upon the metal being evaporated, may
quently, we have found that where we apply pieces
be at atmospheric pressure, or it may be evacu
of iron, cobalt, or nickel to such ?laments along
ated of air and a vacuum created therein. Thus,
with the metals to be evaporated, or use these as
after the pieces iii of the silver and platinum
alloy or copper and platinum alloy or gold and
platinum alloy, as the case may be, have been
applied to the coils of the ?lament l6 and the
work piece M mounted upon its support l3 within
?ne wire windings around such metals, that upon
heating the ?laments, the iron metals cause rapid
melting through the ?laments and breakage of
the same which stops or interrupts the attempt to
carry out a thermal evaporation.
the chamber, a vacuum of 10 to the minus 3 mil
Thus we ?nd it necessary to utilize preformed
limeters or better, is created and the ?lament i6 40 alloys and with iron, cobalt or nickel, we use
is then energized and therefore heated so as to
preferably 5% or less, by weight, in the alloys with
melt the alloys and to start in motion the wetting
the metal to be evaporated as, for example, silver,
- action of the ?lament by capillary attraction, as
and a weight of such metals as low as 0.5% may
explained above. After the wetting action has
often effectively be used to bring about satisfac
been completed as illustrated generally at 20 in 45 tory wetting of the ?laments. Thus, in evapo
Figure 3, the ?lament I5 is further energized .to
rating silver or copper by the use of an alloy of
increase the heat therein, whereby silver, copper,
either with either nickel or iron, we have used
or gold in the coating 20 of the alloy will be
alloys very satisfactorily which wet the ?laments
thermally evaporated and transferred by depo
uniformly in which there was 1% to 2%, by
sition to the face or surface of the work piece 50 Weight, of iron or nickel present on the weight of
I4 which, as shown, is disposed in a position op
the silver or copper.
.posite the ?lament E6. The platinum does not
evaporate at the temperatures required to evap
. The use of our metals such as platinum, pal
ladium, iridium or rhodium to bring about a satis
orate the gold, silver or copper and the re?ective
factory wetting and evaporation has been par
deposits produced in such cases are of re?ective 55 ticularly attractive in that when used with the
values and otherwise similar to gold, silver and
metals which it has been desired to evaporate,
copper mirrors made by evaporating these metals
these metals, platinum, palladium, iridium and
alone from crucibles within a high vacuum.
rhodium have not appreciably evaporated so that
In a similar way pieces of a preformed alloy of
the deposits of silver, copper, tin, lead or other
silver with 5 to 15% or more of palladium may 60 metals have been secured essentially pure and as
have been applied to the heater ?lament coils of
tungsten, tantalum, molybdenum or columbium
and on heating sush coils the alloy melts, wets
mirrors they have shown the full normal re?ec
tivity and colors characteristic of pure mirror
deposits of these metals. Thus, with silver 95%
the ?laments, and thereafter in a vacuum the
re?ection value mirrors may be readily secured
silver evaporates off the ?lament onto the article 65 when using palladium or platinum with the silver.
to be coated and produces a silver mirror of 95 to
From the following table of temperatures at which
98% re?ection thereon. The palladium all re
the vapor pressure of the di?erent metals is 0.01
mains with the ?lament. Alloys of copper and 5
millimeter, it is apparent that, as these are also
to 15% or more palladium are similarly useful
the boiling or evaporating temperatures in a vac
in preparing copper mirrors and the copper de 70 uum of this pressure, there is negligible chance of
posits in their re?ectivity and color show that no
contamination of the metal deposits with the
palladium is carried over, Palladium alloys with
platinum metals since the vapor pressures of these
the other non-wetting metals cause these to wet
are negligible below 2000“ C. at which the various
the ?laments desirably.
elements under consideration would evaporate.
We have found that using a mixture of platinum 75 On the other hand the use of iron, nickel, or co
2,410,004
9
.
halt in the evaporation of gold, copper or tin might
be expected to give mirror deposits containing
some iron, nickel or cobalt. Moreover, iron, nickel,
or cobalt can be used in the thermal evaporation
of antimony, bismuth, zinc and cadmium without
their contaminating the mirror deposits secured.
l0
metals from which the coiled ?lament or element
l8 may be formed, other suitable metals may be
used for this purpose. We have mentioned these
metals particularly since their high melting
points and low vapor pressures at the boiling
temperatures of other metals as shown‘ in the
above table make these the practically desirable
- metals for use as such ?laments.
Temperatures at which
We have described our improved method or
_ metal boils
melting 1o process as preferably being carried out in a
Met?“
A, o m
At 760 mm.
‘
mu; '
norma‘iait
mosp er c
pressure
point
vacuumized chamber in which the step of wet
ting the ?lament takes place. ‘as does also the
step of thermal evaporation of the metal to e?ect
its deposition upon the workpiece to provide a
. °C.
re?ective coating thereupon.
pressure
°C'.
780
321 15
' 030
>
147
1,380
1,800
2,260
2.200
2.040
2,600
1,800
1,900
2. 300
419
271
Obviously also in the case of the most readily
volatile metals, such as cadmium and zinc, the
630
melting of the metals and the wetting of the
327
232
?laments,
as well as the evaporation of the readily
1,615
000 20 volatile metals, such as cadmium or zinc, may be
1,063
659
1,260
1,083
carried out under atmospheric conditions of pres
sure if desired, while employing a suitable inert
atmosphere.
Having thus described our invention, what_we
I
2,000
4,300
2,200
4.400
+2,500
+4,100
5.000
3,100
1,480 25 claim is:
1. The method of producing coatings by evap
1,756
1,555
oration
of silver from a ?lament selected from
2, 440
the group consisting of tungsten, tantalum,
1,985
molybdenum and columbium, wherein the silver
2,850
3,310 30 is alloyed with a metal selected‘ from the group
2,620
consisting of platinum and palladium and is
1, 950
I
heated on said ?lament, and wherein said plati
num or palladium causes the silver to wet, to
adhere to, and to spread out over the ?lament
tance in the thermal evaporation of the various 35 surfaces and by the continued application of
heat, to evaporate and to deposit upon an article
metals has been secured through our securing
good wetting of the ?laments in that the metals
to be coated.
2. The method of producing coatings by evap
being evaporated show very little explosive boil
oration of a metal of the silver chemical periodic
ing or spitting which by reason of small chunks
of metal blown over onto the article being coated 40 table family from a ?lament selected from the
group consisting of tungsten, tantalum. molyb
has caused spoilages, This appears to have been
denum and columbium, wherein the metal to be
accomplished by the decrease of surface tension
evaporated is alloyed with‘a metal selected from
forces accompanying the wetting and also in the
the group consisting of platinum and palladium
elimination of conditions leading to super-heat
ing by getting the metal to spread out in a thin 45 and is heated on said ?lament, and wherein said
A further advantage of very practical impor
coating over most of the ?lament surfaces.
platinum or palladium causes the metal desired
From the foregoing it will be seen that we have
provided an improved method or process for ap
plying certain metals to a ?lament of tungsten,
to be evaporated to wet, to adhere to, and to
spread out over the ?lament surfaces and by the
continued application of heat, to evaporate and
tantalum, molybdenum or columbium by causing 50 to deposit upon an article to be coated.
3. The method of producing coatings on
a wetting resulting from capillary attraction
articles by evaporation of silver from a ?lament
through the application of other metals and ap
selected from the group consisting of tungsten,
plying heat from the ?lament, and have thereby
been able to carry out evaporation of such metals
tantalum, molybdenum and columbium, wherein
we secure the desirable requisite of wetting of
to deposit upon the article to be coated. '
after the wetting action has been completed by 55 the silver is alloyed with platinum and is heated
on said ?lament, and wherein said platinum
thermally evaporating the metals and have
causes the silver to wet, to adhere to, and to
caused their deposition upon the face or surface
spread out over the ?lament surfaces and by the
of a work piece to provide metallized or re?ective
continued application of heat, to evaporate and
surface therefor. It will also be seen that while
the ?laments of tungsten, tantalum, molybdenum
or columbium, by metals which normally do not
4. A method according to claim 3, wherein
copper is substituted for the silver.
wet these, by the use of a platinum group or iron
group metal this may be accomplished in sev
is substituted for the silver.
eral ways. Thus, we may apply separate pieces
of a preformed alloy of such metals with one
of our platinum or iron group metals and these
will wet the pure metallic ?laments.
While we have referred to the use of tungsten,
tantalum, molybdenum, or columbian as suitable
5. A method according to claim 3, wherein gold
'
6. A method according to claim 3, wherein the
platinum present is of the order of approximately
5% to 15%.
WILLIAM H. COLBERT.
ARTHUR R. WEINRICH.
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