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Dec. 31, 1946.
w. H. COLBERT ETAL _
‘2,413,605
PROCESS OF EVAPORATING METALS
Filed May 27, 1944
_
.
.
INVENTORS
Wylham H. Colbert
By
.
I
Arthur RWeinrich.
MI”W*%
'
ATTORNEXS
2.413.605
Patented "Dec. 31, 1-946...
'
William H. Colbert and Arthur R.. Weinrich,
_
Brackenridge, 'Pa., assignors to Libbey-Owens
Ford Glass Company, '1‘oledo, Ohio, a corpora
tion of Ohio
Application May 27, 1944, Serial No. 537,676
9 Claims. , (CL'll'l-IM)
1
Our present invention relates to a novel
method or process of evaporating metals.
It has
to do, more particularly, with the coating or wet
ting, by capillary attraction, of a ?lament which,
for example, may be formed from a .coil of al
loyed tungsten wire, tantalum, molybdenum or
However, with a large ‘number of metals which
it is desirable to be able to thermally evaporate
and which from their vapor ‘pressure at elevated
temperatures should readily. evaporate,.it has '
been ‘found di?icult, if not impossible, to carry
out satisfactory deposition of such coatings by'
thermal evaporation. Thus, ,for example, silver
while readily lending itself to thermal evapora
columbium wire, by ‘various metals which it is
preferred to evaporate and which normally do
tion from a crucible cannot be evaporated readily
not wet similar pure metallic ?laments, and the
from a coil of tungsten, tantalum, molybdenum.
ll)
application of said metal or metals by deposition
or columbium when applied to a ?lament of these
resulting from thermal evaporation, to the face
metals and. heated by electrical resistance. The .
or surface of an article, such as a piece of glass, >
porcelain, plaster, metal, plastic, Cellophane,
paper, or the like, to provide a re?ective or metal
‘lized surface coating for said article.
- ,
Methods and apparatus have previously been
employed to apply coatings of metals by thermal
v evaporation to the faces or surfaces of such
articles to produce mirrors, re?ectors, or metal
lized materials for other purposes. In these
methods it is desirable to effect the thermal
evaporation of the metal, such as silver or alu
minum, by applying the metal directly to an
, electrically energized and thus heated tungsten
or other metallic ?lament which is preferably
located within a vacuumized chamber. The
metals which may be used as' ?laments for such
evaporations must obviously be of high melting
point and also of low vapor pressure at the ele
vated temperatures at which the metalsapplied
to the ?laments evaporate. Thus, tungsten,
tantalum, molybdenum and columbium have
represented the. only practical materials 'for such
use.
Platinum also has been used to a small
degree but its high cost is generally prohibitive.
While iron and nickel are of relatively low vapor
silver on melting shows no a?lnity for the metallic
?laments and almost immediately after melting
15 collects into a drop and falls off the ?lament.
This lack of ability to wet tungsten, tantalum,
’molybdenum and columbium occurs alsowith the
metals copper, gold, zinc, tin, antimony, cad
mium, bismuth, lead, thallium and indium.
With each of these metals the use of the four
available coil ?laments as a means of evapo
rating these metals has not been possible, and
less desirable means of heating have been neces
sary where it became necessary to evaporate
these under practical conditions repeatedly in
the commercial production of mirrors and metal
lic coated articles. As each of these metals, after
melting, pulls together into 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 failures 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 al
ways been uncertain and without control.
pressure they are of'such relatively low melting
point that ?laments made from them rapidly
We have found that we may use tungsten,
and spread over the ?lament by capillary attrac
tion and satisfactory evaporation of these metals
mally non-wetting metals to wet the alloyed
tantalum, molybdenum or columbian as ?laments
for the evaporation of metals which do not wet
burn out.
With these ?laments many of the metals can 40 these ?laments and cause them to wet the ?la
ments by ?rst alloying such ?laments with an
be readily evaporated. Thus, for example, alu
other metal which is characterized in that it will
minum, beryllium, magnesium, vanadium, bar
not only form an alloy with tungsten, tantalum,
ium, strontium, iron, nickel, cobalt, manganese,
molybdenum and columbium but will also alloy
thorium, chromium. and titanium, when applied
with the metal we desire to evaporate. As metals
45
to ?laments of tungsten, tantalum, molybdenum
which we have found which may‘ be used in a
or columbium, will on heating in a vacuum, melt
relatively small quantity which cause the nor
then occurs from the large amount of surface
which the molten metal covers.
‘
metallic ?laments we may use ,iron, nickel, cobalt,
50 platinum or palladium, ,or several of these to
2,413,005
.
3
,
4
»
gether. ‘Thus, for example, we may add. small
columbium ?lament a metal such as copper, sil
amounts of nickel to a tungsten ?lament and
ver, gold, zinc, tin, antimony, cadmium, bismuth,
when silver is melted on such an alloyed tungsten
lead,‘ indium or thallium, to bring about a desir
"?lament the silver will be found to wet the tung
able wetting or coating of, the ?lament metal by
sten ?lament and to spread itself by capillary Cl capillary attraction under the in?uence of heat
attraction over the surface of the tungsten wires.‘
applied to the ?lament and‘thus permit thermal
evaporation of the metals.
In the absence of the nickel, or upon a pure
Generally speaking, and in accordance with our
tungsten ?lament, the silver melts, drawsitself
into a droplet and falls off the ?lament wire
present invention, the metal to be evaporated '
because it does not wet the same. Not all metals, 10 which normally does not wet .a pure metal heater
when pre-alloyed into the tungsten, et cetera,
?lament is applied to the coils ‘of an alloyed ?la
?lament, have been found to act in this manner.
ment which may be formed from tungsten, tan
talum, molybdenum or columbium and another
In each case it is found that the metals of the
iron group, namely, iron, nickel and cobalt and
metal or metals, the latter having an affinity for
the metals of the platinum group, namely, pal
the metal to be evaporated and providing wetting
ladium, platinum, rhodium and iridium, readily
characteristics. Thus, in order to thermally
evaporate copper, zinc, gallium, or arsenic, which
form alloys with tungsten, tantalum, molybde-_
num and'columbium and also form alloys with
are metals of the chemical periodic table ar
rangement found in series 5 or the'metals silver,
copper, silver, gold, zine, tin, antimony, cadmium,’
bismuth, lead, indium and thallium. Thus, the 20 cadmium, indium, tin and antimony, which in
metals of the iron and platinum groups which'
we have enumerated readily bring about the de
sired wetting'and it appears clearly that this is
accomplished through the mutual alloying ten
dency which these metals possess.
a
clude the metals of series 7, or the metals gold,
' thallium, lead and bismuth which in the periodic
arrangement include series 11, all of which metals
do not wet ?laments made of pure tungsten, tan- .
25 talum, molybdenum or columbium, we ?rst bring
about a satisfactory wetting ‘ and adhesion of
One of tne objects of our invention is to pro
vide an improved and satisfactory method or
process of evaporating metals‘ which normally
do not wet heater ?lament coils of tungsten, tan
talum, molybdenum, or columbium, by alloying 30
the ?lament so as to cause the metals to wet the
coils of such ?laments and to coat the coils by
capillary attraction so that thermal evaporation
can then be carried out.
' -
Another object of our invention is to apply to
these metals to the ?laments by pro-alloying the
?laments with another metal either selected from
the iron group such as iron, nickel or cobalt, or
selected from the platinum group. metals such
as platinum, palladium, rhodium or iridium, and
then by energizing the alloy ?lament and thus
heating it we cause a melting of the“ pure metals
applied. When the applied metals are thus
35 melted they apparently alloy to some degree with
an alloyed or coated tungsten,- tantalum, molyb-'
. denum or columbium ?lament a pure metal to be
_ the metal used to alloy the heater ?lament wire
and by reason of such tendency the molten metals
evaporated which does- not wet ordinary ?la
wet the ?lament wires and by capillary attrac
ment coils of the same pure ?lament metals to
bring about a proper wetting or coating of the
tion are drawn out over the surface of the coils.
The molten metal which has thus covered con
?lament wires by capillary attraction under the ',
siderable surface of the heated coil and is held
thereto by capillary adhesion is thereafter evap
orated uniformly from the heater coils to apply
in?uence of heat applied to the ?lament.
,
As another object of our invention there is
provided an improved method or process whereby
a metal which is to be evaporated and which does
not normally wet heater ?laments of tungsten,
a surface coating of a metallic or reflective nature
to an article such as a piece of glass, porcelain,
' silica, mica, plastic, metal, Cellophane, resin, or
tantalum, molybdenum, or columbium is applied
other support materiahby deposition resulting
to a ?lament which has previously been alloyed
from the thermal evaporation of the metal from
with another metal, such as platinum, palladium,
the alloy ?lament. The operations of thermal
nickel, cobalt, or iron, which ?laments readily be 50 evaporation may with some of the metals'be car
come wetted and coated by capillary attraction
ried out. at normal pressure but generally are pref with the metal desired to be evaporated by ther-_
erably carried out in vacuum chambers known
mal evaporation, to provide an article with a
to the art and within a high_vacuum, which may
reflective or metallized surface coating.
‘
L be of the order of one millimeter down to 10 to
As a further object of our invention there is 55 the minus 5 millimeters‘ or ‘better. It is very
provided an improved method or process where
necessary that the metal to be evaporated wet
by a metal desired to be evaporated to form a
and coat the coil surfaces in order that the metal
reflective surface coating is applied to a tungsten,
will evaporate uniformly in all directions. By
tantalum, molybdenum or columbium ?lament
securing such wetting action the thermal deposi
which has been alloyed with another metal, whose 60 tion of these metals, in addition to being made
vaporizing temperature is higher and which met
possible, has been found by our process to give
al brings about a wetting and coating of the
uniform coatings.
alloyed ?lament by capillary attraction, thus per
We may proceed to secure the objects within
mitting the deposition of the desired metal upon
the scope of this invention in various ways.
the face or surface of an article by thermal evap 65 Thus, we may start with a ?lament of tungsten,
oration without appreciable evaporation of the
tantalum, molybdenum, or columbium which has
been pre-alloyed with one of the metals of the
alloying metal so as to give a re?ective surface
coating showing the characteristic properties of
iron or platinum group and apply the pure metal
the desired metal only. Alternatively, the metal ' to be evaporated to the pre-alloyed ?lament as
to wet the ?lament and to, be evaporated may 70 pieces, or otherwise. The ?laments in such case
be alloyed with another metal which has an
are drawn, into wire form and shaped from the
a?inity for a pure metal'?lament, as set forth in
our copending application, Serial No. 537,675.
Afurther object of our invention is to apply to
an alloyed tungsten, tantalum, molybdenum or
preformed alloy. We vmay also previously alloy
an
our ?laments bylapplying a coating of the de
sired alloying element of the platinum or iron
group and heating the filament to cause melting
2,418,605
,
5
'
of‘ the coating and allowing with the wire in its
is-capable of other embodiments and of being
surface. Such surface-alloyed ?laments have
been found to wet satisfactorily with all of the
practiced or carried out in various ways. It is to
be understood ‘also’ that the phraseology or ter
metals which otherwise do not wet'the pure a
minology employed herein is for the purpose of
tungsten, tantalum, molybdenum, or columbium
description and not of limitation,and it isnot
?laments. Such surface~alloying may be carried
out during actual use during a thermal evapo~
ration by merely starting with a ?lament which
has a coating of the desired alloying element ap
intended to limit the invention herein claimed
beyond the requirements of the prior art.
,
Referring now particularly to Figure 1 of .the
drawing, we have shown a suitable apparatus for
carrying out our improved method or process, as
well as one suitable alloyed or coated ?lament.
plied thereto. - The ?laments may also be pre
alloyed on the surface by making a preliminary
evaporation from a pure tungsten, tantalum,
Such suitable apparatus employed by us com
prises, as shown, a supporting base I0 upon which
is mounted a housing, shown as awhole at | I.
The housing H may be in the form of a bell-jar
molybdenum 0r columbium ?lament, of a small
amount of our desired alloying element, such as
a platinum metal or a small amount of the de
sired platinum or iron group metals may be‘ left
as a residue of an evaporation of an alloy of_
these with a more volatile metal. Such residues
left upon the hot ?laments alloy with- the same
or the like having a dome-like or semi-spherical
top portion or enclosed end andv a bottom open
end having a surrounding ?ange or projection
I! which is adapted to rest upon the .top face or
and- readily are wet by normally non-wetting 20 surface of the supporting base I0.
Within the chamber provided by the housing
metals thereafter. Thus, a silver alloy carrying
a small amount of platinum, such as 5% to 15%, ' H, we have shown a suitable work-piece support
I3 for supporting a work piece, such as a plate or
or iron to the extent of 1% to 10%, will wet a ‘
piece of glass, plastic, plaster, paper, porcelain,
pure ?lament, as shown in our copending appli
metal, or the like M, in upright position.
Located within the chamber and mounted upon
the supporting base in, is a pair of upright ‘sup
porting posts 15 between which is carried or sup
ported, in substantially horizontal position, an
cation. , The platinum or iron remain alloyed
with the ?lament after such an evaporation and
pure silver, et cetera, may then be evaporated
directly from this ?lament as it will thereafter
wet directly with molten silver, gold, copper, et
cetera.
-
‘
V
30 alloyed or coated electric ?lament, shown as a
The foregoing and other objects. and advan
tages of the present invention will appear from
the following description and appended claims
when considered in connection with the accom
panying drawing forming a part of this speci?
cation wherein similar reference characters des
ignate corresponding parts in the several views.
In said drawing:
whole at IS. The ?lament, as "shown, is in the
form of a coiled wire made of tungsten, molyb- I
denum, columbium or tantalum alloyed or coated
with another metal, whose opposite ends are at
tached to brackets ll mounted upon the support
ing posts I5 and adjustable thereon so as to vary
the position or location of the ?lament It with
relation to the supporting base I 0.
e
.
The chamber provided by the housing Il may,
Figure 1 is a perspective view,- partly broken
away, showing a suitable apparatus for carrying 40 if desired, be completely evacuated of air through
outlet pipe or conduit Ito and have a high vac
out the improved method or‘ process embodying
\ Figure 2 is an enlarged cross-sectional view,
uum created therein by means of suitable air
evacuating and vacuum creating means, such as a
taken substantially along the line 2-2 of Figure
pump (not shown) .
our invention.
1, looking in the direction of the arrows, of, a 45
tungsten, molybdenum, tantalum or columbium
It is known that silver, copper and gold con
. stitute a closely related family in the periodic ta
ble and lend themselves admirably to thermal
evaporation but they have no wetting a?inity for
tungsten, tantalum, molybdenum or columbium
ment metal when the coating is applied to the ~50 surfaces and thereforesilver, copper or gold alone
is unsatisfactory for coating a pure metal ?la
?lament by a method involving the use of heat.
ment formed from either of these metals by a
Figure 3 is a perspective view of the precoated
wetting action effected by capillary attraction.
?lament shown in Figures 1 and 2 and upon
Wetting of the ?lament wire is essential to se
which pieces of the pure metal to be evaporated
55 cure a. maximum of evaporating surfaces to pro- ‘
have been hung.
vide evaporation uniformly in all directions, to
Figure 4 is a perspective view after the ?lament
the securing of vuniform deposits, and also to
and piecesof metal of Figure 3 have been heated
avoid the dropping of the molten metal off the
to effect a wetting of the ?lament.
heater wires. We have found that platinum,
Figure 5 is an enlarged cross-sectional view of
a ?lament formed from tungsten, molybdenum, 60 while having a higher melting point than gold,
copper or silverrreadily alloys with silver, gold
tantalum, or columbium which is alloyed
electric resistance ?lament precoated with a thin
layer of a platinum or iron group metal and in
which there is a surface alloying with the ?la
throughout withan iron or platinum group metal .
_ and copper and the alloys have a wetting a?inity
for the four above-mentioned metals. Also, plat- '
and upon which the pure metals, on melting, will
inum alloyed with the ?laments lends itself par- _
directly show a good wetting action; and
Figure 6 is another enlarged cross-sectional 65 ticularly well to securing the wetting of a ?la
ment by capillary attraction with the ordinary
view showing a ?lament of tungsten, molyb
non-wetting metals, such as silver, gold and cop
denum, tantalum or columbium which is alloyed
per.
only in the surface of the ‘?lament and which
Heretofore, when attempts were made to wet‘ a
may be used directly as is the ?lament of Fig
70 pure metallic ?lament by the use of silver, cop
vure5.
.
per or gold alone, only small portions of the
Before explaining in detail the present inven
molten metal would cling to the ?lament as drop
tion it is to be understood that the invention is
lets hanging from the lower ends of the coils of
not limited in its application to the details of
the ?lament, with the major portion of the molten
construction and arrangement of parts illustrated
in the accompanying drawing, since the invention 75 metaldropping’or falling off the coils. This was
v
'
r
[2,418,005
7
-
crease the cheat therein whereby the metal or .
. particularly undesirable since it was practically
impossible to produce, by thermal evaporation, an
‘metals in‘the molten coating upon the alloyed
even surface‘ coating by deposition, or to control
the deposition to desired coating deposit thick
evaporated and transferred by-deposition to the
or surface-alloyed ?lament will be thermally
face or’surface of the work piece It which, as
shown, see Figure 1, is disposed in a position op
posite the ?lament l6. It will be understood that
‘any platinum metals forming the alloy ?lament
do not evaporate at the temperatures required to
but had a tendency to drop of! said ?lament, the 10 evaporate the applied metal or metals and that
the re?ective deposits produced in such cases are
_ process of coating'with these metals by deposi
of re?ective values and otherwise similar to gold,
tion was unsatisfactory, slow and painstaking be
cause only a small portion or percentage of the ' ' silver and copper mirrors made by evaporating
these metals from crucibles within a high vacuum.
?lament received the metal coating. ConsiderAs stated above, the ?lament shown in Figures
able shutting down and starting over again was 15
1, 2 audit of the drawing is in the form of a wire
required when most or the gold, silver or copper
or coil which is formed from tungsten or the like
on ?rst melting dropped o? thecoils and no evap
and is provided with a surface coating which may
oration was secured. Thus, great waste occurred,’
be an alloyed coating, formed from platinum or
the process was considerably slowed down, and r
the coating produced by deposition, if any, was 20 palladium, et cetera, or an iron group'metal such
as iron, nickel or cobalt, or of several of these
uneven or spotty and unsatisfactory because of
metals.
such uneven character thereof on the surface of
As shown in Figure 3, the heater wire or coil _l 6
the article coated. Commercial production un-,
has hung onto its loops lGc, a plurality of the
der such uncertain conditions was impossible.
strips or pieces i8 which are formed from silver or
We have found that if, for example, the loops
other suitable pure metal. By hanging the strips
of a pure metallic electric ?lament were to have
or pieces l8 of the pure metal to be evaporated
- applied thereto pieces of pure silver, or of pure
onto the coil and then heating‘the coil or ?la
copper, and relatively smaller pieces of some suit
ment su?gziently to melt the silver, copper or other
able wetting or carrier metals, such as platinum
or nickel, that when the coil or ?lament is en 30 metal pieces Is, there is a. rapid wetting of the
ergized and thus heated, whereby to cause a melt
?lament by the silver, copper, or the like, as shown
at 19 in Figure 4 and an alloying with the ?la
ing of the metals, the molten metals generally
drop off the loops before su?lcient alloying of
ment alloy on the ?lament surface appears to
these, and alloying and a wetting of the surfaces
occur. .
nesses on the surface of an article, such as the
article I! to which it was desired to apply a re
?ective surface coating. By virtue of thefact '
' that the silver, copper or gold did not properly
wet the tungsten or other pure metal ?lament
of the ?lament, occurs, and the results are un
certain and losses of evaporations and materials
35
and time occur. This is always the case with the
low melting metals such as zinc, cadmium, tin,
lead and indium, which non-wetting metals melt
.As we have stated, we have found that where
we have used platinum or palladium to secure the
wetting action, these metals do not appreciably
evaporate and are left behind on the tungsten or
other metal heater wires after the silver, copper,
quickly at low temperatures and fall off the heater 40 et, cetera, evaporate. The same may be true of
wires or ?laments before any appreciable solu
the iron metals at some operational temperatures.
tion or alloying with the, higher melting iron or
Such a Platinum or palladium or iron, nickel or
platinum metals occurs. ‘Consequently, with all
cobalt coated wire is surface-alloyed due to the
of the metals we ?nd it necessary and desirable,
heat during such previous operation. Such ?la
in accordance with the present invention, to start
ments as shown inFigure 2 and in Figure 6 pre
with a pro-alloyed or coated ?lament. One such
sent an ideal means of applying the platinum. Dab
?lament is shown as a whole at IS in Figures 1,
ladium, iron, nickel or cobalt to the ?laments and
2 and 3 0f the drawing. The ?lament l5 has a
represent an ideal means to‘secure wetting when
core Ilia which is preferably formed from tung
the normally non-wetting metals are hung there
sten, tantalum, molybdenum or columbium and
on and melted. Thus by hanging strips I8 of the
which is platinum or palladium coated and sur
pure metal, such as silver or copper. to be evapo
face-alloyed, as shown at I612.
Such a ?lament '
rated thereon, as in Figure 3, and heating the coils
represents an ideal means of applying platinum
or palladium, or iron, nickel or cobalt, to cause
wetting by pieces of pure metal which are later
applied to the coils or loops lie of the ?lament I6. =
It is to be understood that in carrying out the
‘method or process as described above, in the
chamber of the housing I I, the chamber, depend
su?iciently to melt these, there is a rapid wetting
of the ?lament, as shown in Figure 4, and an al
loying with the ?lament alloy on the ?lament'sur
face appears to occur.
Speci?cally, a deposit of platinum was pro
duced upon a tungsten ?lament by applying to a
pure tungsten ?lament made or wire .040 inch in
ing upon the metal being evaporated, may be at
diameter upon each loop thereof 0.3 gram pieces '
atmospheric pressure, or .it may be evacuated 60 of a silver platinum alloy containing 15% plati
of air and a vacuum created therein. Thereafter,
after pieces of a suitable pure metal or metals,
shown at l8, Figure 3, have been applied to the
loops I6c of the alloyed 0r coated ?lament and‘
the work piece It mounted upon its support l3
within the chamber of the apparatus, a vacuum
of 10 to the minus 3 millimeters, or better, is cre
ated and the ?lament i6 is then energized and
therefore heated so as to melt the appliedmetal
pieces ‘l8 to start in motion the wetting action
of the ?lament by capillary'attraction, as ex
plalned above; After the wetting action has been
completedthe coil or ?lament IE will have the
appearance of the ?lament shown in Figure 4.’
num and then evaporating the silver oil of this by _
heating to a temperature in the neighborhood of
1700” C. in a high vacuum. With a ?lament coil
65 of 1"; inch in diameter and four turns to the inch,
the weight of platinum left on the surface of the
’ tungsten and alloyed therewith was 10% of the
weight of the tungsten. When pure silver pieces »
were then applied to this coil and the coil heated,
the silver wetted the coil perfectly and a good
thermal evaporation was secured.
In a similar way, a-tantalum ?lament was al
loyed in the surface by evaporating from each loop
of such a ?lament of .040 inch diameter wire 0.2
The ?lament is then further energized to in 76 gram. pieces of a copper alloy containing 5%
'
8,418,805
10
.
of nickel was evaporated from a tungsten or
platinum and 5% palladium. The platinum and
platinum ?lament onto other cold tungsten ?la
ments. By way of example, with tungsten ?la
palladium remained after the copper had evapo- _
rated as a surface alloy with the tantalum, each
ments of wire .035 inch diameter deposits of
being approximately 3% by weight upon the
nickel thereon ranging from .0005 to .0036 cen
weight of the tantalum. The alloyed tantalum
timeter thick comprising 1% to 7% by weight of
?lament then wetted readily with various non;
the tungsten ?lament were quickly wettedv and
wetting metals, such as copper, silver, gold and
coated by capillary action when tin, cadmium,
lead, when these were melted thereon and evapo
indium, lead, gold, silver or copper pieces were
ration could be readily and uniformly carried out.
Molybdenum and columbium ?laments may be 10 melted thereon within a vacuum and thermal
evaporation of these metals could then be readily
pre-alloyed in their surface in such manner as carried out. Similarly, tungsten wire .035 inch‘
just described to secure ?laments showing good
diameter upon which nickel, cobalt or iron coat
wetting characteristics.
ings .0002 to .0003 inch were electroplated were
a ?lament comprising an alloy '
of tungsten, molybdenum‘, tantalum or 15 found to wet well and permit satisfactory evap- ,
Obviously,
throughout
columbium with palladium or platinum or iron,
nickel or cobalt as shown in Figure 5 can also be
similarly used, in which case the wire is drawn
from a preformed uniform alloy.
In Figure 5 of the drawing, we have shown an 20
‘ enlarged cross section of a heater wire, coil or
oration of all these various metals which normally
cannot be evaporated from tungsten coils. Using
a tungsten coil of this nickel, cobalt or iron elec
troplated wire wound four turns to the inch as
a 1% inch diameter coil and applying a load to
each loop thereof of silver of 0.2 gram the silver
?lament in which the wire is formed preferably
readily wetted the nickel, iron or cobalt electro
from tungsten alloyed with a suitable coating
plated tungsten wire, when the wire was heated
metal and which appears in cross section like that
by an electric current. Surface alloying occurred
shown at 20 in this ?gure. The ?lament or wire 20 25 and in these cases the nickel, iron or cobalt was
of this ?gure may comprise an alloy throughout
1.1% of the total weight of the tungsten and 1.9%
of tungsten, molybdenum, tantalum or columbium
of- the weight of the silver. Weights of the iron
with palladium or platinum or one of the iron
metals applied to either tungsten, molybdenum,
metals insmall amounts, or of a, mixture of these
columbium or tantalum ?laments of, 0.5% to 5%
30 of the ?lament weight have given readily wetted
various elements.
In Figure 6 we have shown another modi?ed
?laments.
form of heater wire, cOil or ?lament’in which the
Instead of applying pieces of the pure metal
core thereof may be formed from tungsten, as
to be evaporated to our surface-alloyed or sur
shown at 2|, and in which the core 2| is provided
face-coated ?laments, the metal to be evaporated
with an alloyed surface coating 22 formed with 35 may be coated upon our surface-alloyed or sur-.
any of the metals suitable for bringing about wet
face-coated ?laments. Thus the nickel-electro
plated tungsten or the platinum surface-alloyed
tungsten ?laments already described may have a
coating of lead electroplated thereon and when
ting.
In accordance with another form of our .inven
tion (not illustrated), we may precoat the tung
sten or other metal comprising the heater coil or
?lament with a thin platinum coating, or other
iron group or platinum group metal, either by
electroplating, by hot-dipping, by sputtering, by
heating and decomposing metallic compounds ap
plied thereto, or by any other suitable means.
Such precoated coil as that shown in Figure 2, for
example, readily wets with silver, copper or gold
since these-metals melt and alloy with the plati
num or other applied metal, and the coating on
melting also rapidly alloys with the ?lament due
to the heat.
'
.
a
'
,
Thus, from ?laments of tungsten which have
had a small amount of platinum or palladium or
a mixture of these deposited on their surface by
sputtering or by thermal evaporation or as a resi
due from a prior evaporation of a metal alloy from
40 these are placed in the vacuum chamber and the ‘
'
?lament energized the lead wets the ?lament
and thereafter good evaporation is secured,
The use of our metals such ‘as platinum,
palladium, iridium or rhodium to bring about a
45 satisfactory wetting and evaporation has been
particularly attractive in ‘that when used with
the metals which it has been desired to evap
50
orate, these metals, platinum, palladium, iridium
and rhodium have not appreciably evaporated
so that the deposits of silver, copper, tin, lead or
other metals have been secured essentially pure
and as mirrors they have shown the full normal
re?ectivity and colors ‘characteristic of pure
' mirror deposits of these metals. Thus, with silver
95% re?ection value mirrorsmay be readily se
cured when using palladium or platinum as the
alloying metal. From the following table of tem
peratures at which the vapor pressure of the dif
metals tin, cadium, indium, lead, zinc, thallium,
bismuth, antimony, copper, gold and silver. In 60 ferent metals is 0.01 millimeters, it is apparent
that, as these are also the boiling or evaporating
each case these metals‘which would not wet pure
temperatures in a vacuum of this pressure, there
uncoated tungsten wetted the tungsten, coated
is negligible chance of contamination of the metal
and surface-alloyed with the platinum or pal
deposits with the platinum metals since the vapor
ladium. The metals spread out over the heater .
pressures of these are negligible below 2000? C.
?lament wires and did not drop off. The same
a at which the various elements under considera
was found true for ?laments of tantalum, molyb
tion would evaporate. On the other hand the
denum and columbium, and‘iron, nickel or cobalt
use of iron, nickel or cobalt alloyed in the ?la
could be used inplace of the platinum or pal
ment in the evaporation of gold, copper or tin
-ladium.
' -,
.
We may similarly use ?laments of tungsten, 70 might be expected to give mirror deposits con
taining some iron, nickel or cobalt. Moreover,
tantalum, molybdenum orcolumbium, as in Fig
iron, nickel or cobalt alloyed in the ?lament can
ure 2,‘which have been precoated while cold with
be used in the thermal evaporationof antimony,
platinum, palladium, nickel, cobalt or iron by
bismuth, zinc and cadmium without their con
thermal evaporation of these metals from other
hot ?laments in a vacuum. Thus, a small amount 75 taminating the mirror deposits secured.
such ?lament which contained platinum or pal
ladium, we have successfully evaporated the
2,413,600‘ y; ,
.
g
,
12
.
boiling 'temperatures'oi' other metals as shown in
the above table make these the practically desir
able metals for-useas such ?laments.
Temperatures at which
metal boils
.
We have described our improved method or
process as preferably being carried out in a vacu
umized chamber in which the step of wetting the
melting
Met?“
Mom
At 760 mm.
mu!‘
'
pressure
point
normal
a_t- .
mosp enc
I
prwsam
?lament takes place, as does also the step of ther
mal evaporation of the metal to effect its deposi
° 0.
'
321
419
271
630
327
232
2, 200
2, 040
2, 600
l, 800
l, 900
2, 300
l, 615
960
l, 063
659
l. 260
1.083
3, 000
2, 900
2, 900
4, 300
2, 200
l, 535
l, 452
l, 480
l, 755
l, 555
4, 400,
2, 440
+4, 100
5, 900
2,850
3, 370
3, 700
2, 620
+2, 500
.
tion upon the work piece to provide a re?ective
° C.
780
930
147
l, 380
l, 800
2, 260
Columbium __________________________________________ __
10 coating thereupon.
It will be understood, how
ever, that if desired the alloyed ?laments, as de
, scribed above, may be produced in the manner
outlined, prior to being placed inthe vacuum, for
later use in the deposition by thermal evapora
15 tion of the metal coating thereon in a vacuum as
a re?ective surface coating for a work piece or
work pieces. Obviously also in the case of the
most readily volatile metals, such as cadmium and
zinc, the melting of the metals and the wetting of
20 the ?laments as well as the evaporation of the
readily volatile metals, such as cadmium Or zinc,
may be carried out under atmospheric conditions
of pressure if desired, while employing a suitable
1, 985
1,950
inert atmosphere.
25
Having thus described our invention, what wé
claim is:
a
,
1. The method of producing coatings by the
evaporation of a metal melting below 1900° C.
-A‘ further advantage of very practical im
portance in the thermal evaporation of the vari
from a ?lament selected from the group consist
ous metals has been secured tlrrough our securing 30 ing of tungsten, tantalum, molybdenum and co
good wetting of the ?laments in that the metals
lumbium which it normally does not wet or ad
being evaporated show very little explosive boil
here to, wherein pieces of the metal are applied
‘ing or spitting which by reason of small chunks
to the ?lament and heated ori- such ?lament, in
of metal blown over onto the article being coated
which said ?lament has been previously alloyed V
has caused spoilages. This appears to have been 35 with another metal selected from the group con
accomplished-by the decrease of surface tension
sisting of platinum, palladium, iron, nickel and
forces accompanying the wetting and also in the
‘cobalt, which’ alloyed ?lament causes the metal
'desired to be evaporated to wet, to adhere to, and
to spread out. over the ?lament surfaces, and by
' elimination of conditions leading to super-heata
ing by getting the metal to spread out in a thin
coating over most of the ?lament surfaces.
.40 the continued application of heat, to evaporate
From the foregoing it will be seen that we have
and to deposit upon an article to be coated.
2. The method of producing coatings by the
provided an improved method or process wherein
evaporation of copper from a ?lament selected
certain metals applied to an alloyed ?lament of
from the group consisting of tungsten, tantalum,
tungsten, tantalum, molybdenum or columbium
are caused to give a desirable wetting resulting 45 molybdenum and columbium which it normally
does not wet or adhere to, wherein pieces of the
from capillary attraction upon the application of
copper are applied ,to the ?lament and heated on
‘heat from the ?lament, and haye thereby been,
able to carry out evaporation of such metals after ‘ such ?lament, in which said ?lament has been
‘previously alloyed with another metal selected
the wetting action has been completed by ther
mally evaporating the metal or metals and have 50 from the group consisting of platinum, palladium,
iron, nickel and cobalt which alloyed ?lament
caused their deposition upon the face or surface
of a work piece to Provide metallized or re?ective
surface therefor.
It will also be seen that while '
. causes the copper to wet, to adhere to, and to
spread out over the ?lament surfaces, and by the '
continued application of heat, to evaporate and
alloyed ?laments of tungsten, tantalum, molyb 55 to deposit upon an article to be coated.
we'secure the desirable requisite of wetting of the
denum or columbium, by a metal or metals which
normally do not wet‘these, by the use of a plati
num group or iron group metal this may be ac
complished in several ways. We preferably start
3. The method of producing coatings by the
evaporation of silver from a ?lament selected
from vthe group consisting of tungsten, tantalum,
molybdenum and columbium which it normally
with a ?lament carrying‘ a surface alloy or coating 60 does not wet or adhere to, wherein pieces of the
silver are applied to the’?lament and heated on
of the ?lament metal and an iron group or plati
such ?lament, in which said ?lamenthas been
num group metal and the pure metals which will
not wet the pure ?lament are found when applied , ‘previously alloyed with another metal selected
from the group consisting of platinum, palladium,
as pure metals to wet our ?laments carrying the
preferred surface‘ coatings and alloy. We may 65 iron, nickel and cobalt which alloyed ‘?lament
causes the silver to wet, to adhere to, and tq
also in a similar way to the latter use a ?lament
spread out over the-?lament surfaces, and by
previously alloyed throughout with a metal of
the continued application of heat, to evaporate
the iron or platinum group.
and to deposit upon an article to be coated.
> While we have referred to'the use of tungsten,
4. The method of producing coatings by the
tantalum, molybdenum or columbium as suitable 70
evaporation of a metal melting below 1900° C.
metals from which the coiled alloyed ?lament or
element l6 may be formed, other suitable metals
may be used for this purpose. vWe have men
1 from a ?lament selected from the group consist
ing of tungsten, tantalum, molybdenum and
tioned these metals particularly since their high
‘columbium which it normally does not wet or
melting points and low vapor pressures at they 75 adhere to, wherein pieces of the metal are applied
2,418,605
~
13
.
to the ?lament and heated on such ?lament, in
which said ?lament has been previously alloyed
with platinum, which alloyed ?lament causes the
metal desired 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 to deposit upon an article to'be
coated.
‘
,
.
5. A method according to claim 1, wherein the
coating is a mirror coating and wherein the
evaporation of the metal occurs within a vacuum.
6. The method of producing coatings by the
evaporation of a metal melting below 1900° C.
from a ?lament selected from the group consist
- l4
.
alloy with the silver and cause said silver to wet.
to adhere to, and to spread out over the ?lament
surfaces, and by the continued application of
heat, to evaporate and to deposit upon an article
to be coated.
.~
j
8. The method of producing coatings by the
evaporation of copper from a ?lament selected
from the group consisting oi’ tungsten, tantalum,
molybdenum and columbiurn which it normally
does not wet or adhere to, wherein pieces or cop
per are applied to a ‘coated ?lament coated with
platinum,‘ heating‘ the ?lament to cause the
platinum coating to alloy with the filament and
to alloy with the copper and cause said copper
ing of tungsten, tantalum, molybdenum and 15 to wet, to adhere to, and to spread out over the
?lament surfaces, and by the continued applica
.columbium which it normally does not wet or
adhere to, wherein pieces of the metal are applied
tion of heat, to evaporate and to deposit upon
to a coated ?lament coated with another metal
an. article to be coated.
ment surfaces, and by the continued application
coated ?lament coated with platinum, heating
of heat, to evaporate and to ‘deposit upon an ar
ticle to be coated.
the ?lament to cause the platinum coating to al- ‘
'
9. The method of producing coatings by evapo
selected from the group consisting of platinum,
palladium, iron, nickel and cobalt, heating the 20 ration of a metal melting below 1900° C. from a
?lament selected from‘ the group consisting of
?lament to cause the metallic coating to alloy
tungsten, tantalum, molybdenum and columbium
‘with the ?lament and to alloy with the metal de
which it normally does not met or ‘adhere ‘to,
sired to be evaporated and cause said metal to
wherein pieces 01 the metal are applied to a'
wet, to adhere to, and to spread out over the ?la
'7. The method of producing coatings by the
loy with the ?lament and to alloy with the metal
desired to be evaporated and cause said metal to
wet, to adhere to, and to spread out over the ?la
evaporation oi.’ silver from a ?lament selected
from the group consisting of tungsten, tantalum, 30 ment surfaces and by the continued application _ ‘
of heat, to evaporate and to deposit upon an ar
molybdenum and columbium which it normally
ticle to be coated.
does not wet or adhere to, wherein pieces of the
I ‘WILLIAM H. COLBERT.
silver are applied to a coated ?lament coated
ARTHUR R. WEINRICH.
with platinum, heating the ?lament to cause the
platinum coating to alloy with the ?lament and to
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