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Патент USA US2411524

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2,411,52
Patented Nov. 26,1946
UNITED STTES PATNT OFFICE.
2,411,524
PROCESS FOR THE PRODUCTION OF
ZIRCONIUM
RIDE
Lewis W. Davis, Peabody, Mass, assignor to
Metal Hydrides Incorporated, Beverly, Mass, a
corporation of Massachusetts
'
No Drawing. Application October 4, 1943,
Serial No. 504,908
6 Claims. (Cl. 23——-204)
1
It is known in the art that zirconium oxide can
be readily reduced to metal with calcium, yet on
account of the high cost of calcium metal at
tempts have been made in the past to reduce Zir
conium oxide with magnesium. And under cer
tain conditions such a reduction was partly suc
cessful. However, in all cases the resulting metal
was contaminated with magnesium which readily >
alloys with zirconium metal at the temperature of
reduction.
Attempts to produce pure zirconium metal by
reduction with magnesium whether in vacuum,
hydrogen, or in inert gas such as helium, never
gave material free from magnesium and therefore
at present magnesium, in spite of numerous at
tempts, is not used as a reducing reagent for the
production of pure zirconium.
I have found, however, that if instead of at
tempting to produce zirconium metal, the condi
tions are regulated so that the ?rst product of
reduction will be zirconium hydride, di?erent re
sults can be obtained if a proper sequence of
different operations is observed.
My preferred method of operation consists in
mixing dried zirconium oxide with freshly cut
chips or ?lings of pure magnesium metal in sub
stantially molal proportions with an excess of
magnesium in the order of ten per cent. The
2
the sublimed magnesium vapor tends to remain
longer in the charge, thus facilitating the desired
reaction, and the equipment is subjected to less
wear and tear, not to mention the economy in
fuel used to provide the heat.
Zirconium hydride, as with many other metallic
hydrides, is a chemical compound with properties
very different'from the zirconium metal. The
chemical a?inity of the metal is partly satis?ed
by alloying or'combining with hydrogen. So that
the resulting compound (ZrI-Li) has little affinity
left for other elements with which it may come
in contact.
If at this stage the ‘operation is interrupted, the
zirconium oxide will appear not as a white oxide
but as a black powder which on heating will give
up a certain amount of hydrogen, demonstrating
the fact that the surface of every grain has been
transformed into zirconium hydride.
However, if the heating is continued with a
gradual elevation of temperature from 600° C.
to 800° C., an additional amount of sublimed
magnesium vapor will come in contact with zir
conium hydride without alloying with it and will
di?use through it to the deeper layers of unre
duced zirconium oxide. The temperature is ‘still
below the dissociation of zirconium hydride at
that pressure of hydrogen so that the incoming
sublimed magnesium vapor will not alloy with
charge of these powdered materials thoroughly
mixed together is placed in a retort, provided with 30 that material. Heating to a still higher temper
ature will bring the remaining amount of sub
a gas-tight cover and the necessary pipings con
limed magnesium vapor necessary for the ?nal
reduction vof zirconium oxide to the center of
each grain after which the hydrogen reacts with
After evacuating all the air from the retort
the
reduced zirconium to convert it to zirconium
35
and the interstices in the powdered charge, the
hydride.
retort is then ?lled with pure dry hydrogen to a
The dissociation of zirconium hydride into zir
pressure of about ?fteen pounds per square inch
conium metal and hydrogen is a function of tem
and slowly heated to bring the charge gradually
perature and hydrogen pressure. For instance, if
to a temperature of 660° C., for example. At
that temperature magnesium sublimes or evap 40 zirconium hydride is heated to a temperature of
900° C. in a retort connected with a vacuum pump,
orates in a hydrogen atmosphere. Both magne
it is dissociated almost entirely into metallic zir
sium vapor in sublimed form and hydrogen then
conium and hydrogen since the evolving hydrogen
come in contact with the particles of zirconium
will be continually withdrawn by the pump and
oxide. Magnesium vapor in sublimed form re
the pressure of that gas above the zirconium hy
45
duces the particles on the surface and since the
dride will be very low indeed. If hydrogen is
temperature is su?iciently low, zirconium hydride
merely passed over or maintained at normal pres
is instantly formed covering the whole grain
sure the dissociation will also be Very pronouncedv
with a layer of zirconium hydride.
However, if the hydrogen pressure is appreciably
It has been known for some time that mag
nesium sublimes at a temperature substantially 50 higher than normal, in the order of ten to ?f
teen pounds per square inch, the dissociation of
below its boiling point, 1110° C. Under ordinary
zirconium hydride is retarded. So that even at
conditions, magnesium in fact begins to sublime
a temperature of 900° C., the zirconium hydride
at a temperature below its melting point, 651° C.
is only partially dissociated, and the contamina
In the practice of the invention, I prefer to take
advantage of these lower temperatures because 55 tion with magnesium is low.
necting it with a vacuum system and a supply of
hydrogen.
2,411,524
After completion of the reduction in hydrogen
at increased pressure, the furnace is connected
with the vacuum pumps and all free hydrogen
is evacuated. During this operation the remain
ing amount of magnesium in the charge is quickly
evaporated and condensed in a cooler part of the
retort removed from the charge.
During this
vacuum treatment of the charge, any traces of
4
creasing the pressure of hydrogen appreciably
above the atmospheric pressure, gradually heat
ing the charge to a temperature in the order of
that of the melting point of magnesium, con
tinuing the heating until the temperature of the
charge is considerably above the melting point
of magnesium, withdrawing all the hydrogen
from the retort and establishing a vacuum, con
magnesium which might have alloyed with the
tinuing the heating until all the traces of free
partly dissociated zirconium hydride will be evap 10 magnesium are evaporated from the charge, re
orated.
admitting hydrogen in the retort and cooling the
If it is desired to obtain zirconium metal 'as a
?nal product the charge is cooled in vacuum.
However, if it is desired to obtain zirconium hy
dride, the hydrogen is readmitted in the retort
while the charge is still at red heat and the cool
ing is carried on in a hydrogen atmosphere. ,Dur
ing that period the hydrogen will be absorbed by
the Zirconium metal and transformed into zir
conium hydride. After cooling the charge is re
moved from the furnace, vbroken into pieces of
three to four inches in diameter which then are
crushed in a jaw crusher to ‘a mixture of powder
and small pieces of one quarter inch or less. This
charge in a hydrogen atmosphere which is con
tinually supplied to it until the charge is at room
temperature.
3. In the production of Zirconium hydride, the
improvement which comprises heating a charge
of .intimately admixed zirconium oxide and excess
metallic magnesium in a reaction zone in the
presence of hydrogen gas to a temperature su?i
ciently high to reduce the zirconium oxide and
to convert the resulting metallic zirconium to zir
conium hydride, the charge ‘being gradually ele
vated in temperature so that the zirconium oxide
particies are ?rst reduced'and hydrided at their
crushing o-perationis easily carried out since due 25 surface and then in their interior, evacuating
to the vacuum treatment all the vmagnesium is
evaporated from the charge which is then left
in the state or" spongy brittle matter.
Summarizing the description it can be stated
that my method depends on ,a sequence of de?
nite steps, neither of which by itself is ‘sui?cient
to produce thedesired results, but the combina
tion of these steps and the proper sequenceas
sures the results which otherwise could not be
the heated reaction zone and resulting reaction
mass to remove hydrogen gas therefrom, distil
ling the excess metallic magnesium-and condens
ing it in a zone removed from the reaction mass
While the reaction zone is still under vacuum to
keep the metallic magnesium out of contact with
the zirconium and hence to prevent it from al
loying with the zirconium, readmitting hydrogen
accomplished.
My method gives excellent results vin the pro~
gas to the heated reaction/zone and, reactionmass,
converting reduced zirconium present in the re
duction of zirconium. Yet it is limited in scope
and cannot be applied with the same success to
admitted hydrogen gas, and cooling the ?nal re
the production of other hydrides. The principal
reason for this is that >magnesium does not form
a stable compound with Zirconium oxide, which
is not the case when other oxides are used. In
the case of titanium
for instance, the mag
nesium vapor alloys with ‘the titanium oxide
action mass to zirconium hydride with the newly
action mass containing the zirconium hydride in
the presence of the hydrogen gas.
4. In the production of zirconium hydride, the
improvement which comprises evacuating a
charge of intimately admixed zirconium oxide
and excess metallic imagea
ium
a reaction zone
forming a stable salt (M'gTiOg) which prevents 45 to remove objectionable air, admitting hydrogen
gas to the reaction zone and charge, heating the
the further reduction of titanium oxidewithmag
charge
to a temperature su?iciently high to re
nesium.
What I claim as new and desire to secure by
Letters Patent oi the United States is:
1. A method of production of zirconium hy
dride consisting of the following steps; mixing
zirconium oxide with magnesium chips orjpowder
in molaliproportions ‘with only alimited, excess of
magnesium, placing the charge ina closed ‘retort,
duce the zirconium oxide and to convert the re
sulting metallic "zirconium to zirconium ‘hydride,
the charge being gradually elevated in tempera
50 ture so that the zirconium oxide particles are ?rst
reduced and hydrided at their ‘surface and then
in their interior, evacuating the heated reaction
zone and resulting reaction mass to remove-hy
drogen gas therefrom, distilling the excess me
evacuating all the air from the retort and the 55 tallic magnesium-and condensing it 111a zone re
charge and replacing it with hydrogen, increas
ing the pressure of hydrogen appreciably above
the atmospheric ‘pressure, gradually ‘heating the
moved i‘rom the reaction mass to keep the me
tallic magnesium out of contact with the zir
conium and hence to prevent it vfrom alloying with
charge to a temperature of 660° 'C., continuing
the heating until the ‘temperature of the charge
has reached at least 900° C., withdrawing all ‘the
hydrogen from the retort and establishing a vac
uum, continuing the ‘heating until all traces ‘of
free magnesium are evaporated from the charge,
the zirconium, readmitting hydrogen gas to the
room temperature.
2. A method of production of :ziroonium hy
charge of intimately admixed zirconium oxide
heated reaction zone and reaction mass, con
verting reduced zirconium present in the reaction
mass to zirconium hydride ‘with the newly ‘ad
mitted hydrogen gas, and cooling the ?nal reac
tion mass ‘containing the zirconium hydridein the
readmitting hydrogen in the retort and ‘cooling 65 presence of the hydrogen gas.
the charge in a hydrogen atmosphere which is
'5. In the production of zirconium hydride, the
continually supplied to it until the charge is at
improvement which comprises evacuating a
and excess metallic magnesium in a reaction zone
dride consisting of the following steps‘; mixing 70 to remove objectionable ‘air, admitting hydrogen
zirconium oxide with magnesium 'Chipsor powder
gas 'to the reaction zone and charge under sub
in molal proportions Withonly a'limite,dexcess of
stantia1 positive pressure, heating the charge to
magnesium, placing the charge in the closed re
‘a temperature su?iciently high to- reduce the zir
tort, evacuating all the air .from the retort and
conium oxide and to convert the resulting metal
the charge and replacing it iwith‘hydrogen, in 75 lic zirconium to zirconium hydride, the charge
2,411,524
5
S
being gradually elevated in temperature so that
stantial positive pressure, heating the charge to
the zirconium oxide particles are first reduced and
hydrided at their surface and then in their in
conium oxide and to convert the resulting me
a temperature sufficiently high to reduce the zir
tallic zirconium to zirconium hydride, the charge
resulting reaction mass to remove hydrogen gas (1 being gradually elevated in temperature so that
the zirconium oxide particles are ?rst reduced
therefrom, distilling the excess metallic mag
and .hydrided at their surface and then in their
nesium and condensing it in a zone removed from
interior, evacuating the heated reaction zone and
the reaction mass to keep the metallic magnesium
terior, evacuating the heated reaction zone and
out of contact with the zirconium and hence to
prevent it from alloying with the zirconium, re
admitting hydrogen gas to the heated reaction
zone and reaction mass, converting reduced zir
conium present in the reaction mass to zirconium
hydride with the newly admitted hydrogen gas,
and cooling the ?nal reaction mass containing
the zirconium hydride in the presence of the hy
drogen gas.
6. In the production of zirconium hydride, the
improvement which comprises evacuating a
charge of intimately admixed zirconium oxide
and excess metallic magnesium in a reaction zone
to remove objectionable air, admitting hydrogen
gas to the reaction zone and charge under sub
resulting reaction mass to remove hydrogen gas
therefrom, distilling the excess metallic mag
nesium and condensing it in a zone removed from
the reaction mass to keep the metallic magnesium
out of contact with the zirconium and hence to
prevent it from alloying with the zirconium, re
admitting hydrogen gas to the heated reaction
zone and reaction mass under substantial positive
pressure, converting reduced zirconium present
in the reaction mass to zirconium hydride with
the newly admitted hydrogen gas, and cooling
the ?nal reaction mass containing the zirconium
hydride in the presence of the hydrogen gas.
LEWIS W. DAVIS.
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