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Патент USA US3072485

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Uite
ttes
tent .;
fm
3,972,475
Patented Jan. 8, 1963
1
2
3,072,475
use of the oxide has not appeared feasible. Attempts
have been made to produce an alloy of uranium and
molybdenum from the oxides by the alumino-thermic
process, but the product produced by this method is badly
METHOD OF MAKING ALLOYS OF SECOND
RARE EARTH SERIES METALS
Richard D. Baker, Los Alamos, N. Mex., and Benjamin
segregated and highly porous. A non-homogeneous alloy
poses problems relating to fabricating, heat-treating, and
R. Hayward, Whittier, Cali?, assignors to the United
States of America as represented by the United States
Atomic Energy Commission
N0 Drawing. Filed Mar. 7, 1951, Ser. No. 214,442
7 Claims. (Cl. 75-1225)
working in general, in addition to the obvious and serious
defect of non-uniformity.
It is therefore an object of this invention to provide
10 a method for the production of homogeneous, high purity
alloys having desirable nuclear and structural properties,
This invention relates to a method of making alloys
of the second rare earth series metals; more particularly
it relates to a method for making alloys of the second rare
earth series with molybdenum, niobium or zirconium.
namely, alloys of metals of the second rare earth series
with molybdenum, niobium or zirconium.
It is another object of this invention to provide a method
In the ?eld of reactor design the necessity for high 15 for producing the above alloys using the oxide- of the
metal which is to be alloyed with the second rare earth
strength materials having the required nuclear properties
series metal.
is well known. Substantially pure uranium is often the
It is a further object of this invention to provide a
optimum metal for use in neutron reactors and neutron
method for producing the above alloys which provides a
multiplying systems, but the metal itself is di?icult to
work and to fabricate because of its low mechanical 20 high percentage yield.
It has been found that the above and other objects are
strength. Alloys containing a large proportion by weight
accomplished by thoroughly mixing a halide of a second
of uranium and a minor proportion by weight of other
rare earth series metal with an oxide of Zirconium, ni
elements may be used in neutron reactors as long as the
obium or molybdenum, a reducing agent consisting of an
modifying element does not cause a material increase in
the neutron capture cross section for the uranium alloy. 25 alkali metal or an alkaline earth metal, such as calcium,
and a booster such as iodine, and heating the mixture in
Of particular interest in this ?eld are the alloys of uranium
an inert atmosphere until reaction is initiated. In the re
with nobiurn, molybdenum and zirconium.
action, the oxide and halide are co-reduced by the reduc
Alloys of uranium containing from 1 to 10 atomic
ing agent to produce the metals, which are lique?ed and
percent of zirconium, niobium or molybdenum possess
desirable nuclear and other properties. The capture cross 30 alloyed by the high local internal heat resulting from the
exothermal character of the reaction. Although it has
sections of these metals for neutrons at thermal energies
proved impossible to measure the maximum temperature
are below that of natural uranium, i.e., about 3 barns,
accurately because of its short duration, a temperature of
or 3 X10‘24 square centimeters; uranium alloys containing
1700“ C. has been noted and it appears that temperatures
the above percentages of these elements also have low
capture cross sections. Any of these alloys may thus be 35 in excess of 2620° C., the melting point of molybdenum,
are obtained at least locally. Heat to initiate the reducing
conveniently used in a nuclear reactor without requiring
reaction is furnished in part by the reaction between
an appreciably greater amount of the alloy than of pure
calcium and iodine, the preferred combination of reduc
uranium. In addition to the above properties these alloys
ing agent and booster, to form calcium iodide. By virtue
possess increased strength over unalloyed uranium. How
of its low melting point, this material increases the ?uidity
ever, for satisfactory results, it is highly important that
of the slag and thus aids in the collection of the metal
they be homogeneous and possess a high degree of purity,
formed into a unitary mass, in which condition the alloy
and further, there must be available a suitable process for
may be recovered from the cooled reaction mixture.
their production.
It is a feature of the process of this invention that
In the past, attempts have been made to produce these
alloys by direct fusion with the aid of external heat and 45 the alloys produced thereby are in the form of buttons
or unitary masses, and may therefore be recovered readily,
by the aluminothermic process. However, neither of
simply and completely from the reaction mixture without
these methods has proved entirely satisfactory as the
the necessity for leaching processes or other troublesome
alloys when produced on a large scale by these and other
or possibly deleterious treatments required for the re
prior methods are porous and the constituents are segre
gated.
Further, the high temperatures required make
50
covery of ?nely-divided products, with consequent danger
these methods impractical. Zirconium melts at 1900° C.,
and the melting points of niobium and molybdenum are
2500° C. and 26200 C., respectively. Efforts to place
these metals in solution in uranium using conventional
vacuum melting techniques have met With only limited 55
of damage to the alloy or of incomplete recovery there
be easily obtained by present direct melting techniques.
rwith the general practice in the uranium reduction art,
success when production is attempted on a large scale. It
appears that a higher temperature is necessary than can
of. It is to be noted, however, that thorough mixing of
the charge has been found important to the production
of such a button. If the charge is not completely blended,
the button will be poorly formed and the alloy may be
inhomogeneous.
The success of the present process is not in accord
where it has been found important to provide a uranium
Most of the prior processes which have been attempted
for the production of the above alloys require that the 60 halide completely free from oxygen in order to obtain
high yields in a reduction process such as the present
metals themselves be used, thus necessitating the pro
process. While no complete understanding of the mecha
duction of the metal from the oxide or other compound
nisms here involved has yet been achieved, it has been
before the alloying process. In attempts to make alloys
found that satisfactory results are obtained by the process
using the oxides of the metals so much di?iculty has been
encounterd because of the presence of oxygen that the 65 of this invention in preparing alloys containing up to the
3,072,475
a
4
order of about 20 atomic percent ‘of the alloying ele
data regarding improvements in grain size of the alloys,
ment. Thus, the process of this invention covers the
range of from 1 to about 20 atomic percent of the alloy
ing element. The upper limit is not a ?xed one, and will
pyramid hardness tests.
and in hardness as shown by both Rockwell and diamond
Table I
vary according to variations in standards, procedures,
techniques and materials. For example, operation on the
URANIUM-NIOBIUM ALLOYS
[a. Corcduced alloys]
relatively small scale of a charge of only a few grams will
not permit the attainment of acceptable alloys of such
high percentage of alloying element as will operation on
Niobium Content
a larger scale. The proportions of reducing agent and 10
booster used may be varied to modify the behavior ‘of the
reaction mixture and the nature ‘of the ?nal product.
Many other variations will be obvious to those skilled in
the art, and the detailed nature and limits of the process
can be affected thereby.
Sample No.
Charged
At.
Percent
preferred embodiments of this invention. It is to be under
stood that halides of other elements of the second rare
earth series such as thorium, plutonium and neptunium 20
Wt.
Percent
5. 01
5. 01
5. 01
5. 01
5. 01
The following information regarding preparation and
properties of uranium alloys is given to illustrate typical
Found (Wt. Percent)
2. 01
2. 01
2. 01
2. 01
2. 01
Average _____________________ ._
may be alloyed in a comparable manner, and that no
limitation to uranium or to a ?uoride is intended. The
A
B
0
2. 21-2. 26
1. 98-2. 00
2. 02-2. 09
2. 02-2. 04
2. 07-2. 08
2. 10-2. 10
1. 96-2. 02
2. 03-2. 08
1. 98-2. 01
1. 99-2. 00
2.07
2.03
2. 05-2 15
1. 97-2 01
1. 95-2 04
1. 96-1 99
1. 99-2. 01
2.01
[b. Direct fusion alloys]
other halides, that is, chloride, bromide and iodide, may
be satisfactorily employed and the metals may be in
Niobium Content
(Wt. Percent)
‘Sample No.
either the trivalent or tetravalent state.
A well-blended charge of the following ?nely divided
Charged
Found
components is used as the base charge in a series of ex
periments, selected amounts of the oxide of the alloy
ing element being blended therewith as desired.
30
BASE CHARGE
Grams
0. 7
0. 75
1.3
0.28-0.29
4 ____________________________________________ __
1. 25
0. 73-0. 98
URANIUM-NIOBIUM ALLOYS
106.6
After being thoroughly mixed, the complete charge, 35
consisting of the base charge together with the desired
_
Nb Content (Atomic Percent)
Rockwell
Grain Size
Hardness
(Mean Diam.
amount of oxide of zirconium, molybdenum or niobium,
is placed in a steel bomb with a refractory liner, typically
with an inert atmosphere such as argon, and heated in
an induction furnace to an external temperature of about
550° C. This external temperature corresponds to an
internal temperature, as shown by a previously calibrated
150
100 R13
100 BB
150
120
45 R o
90
Table III
URANIUM-MOLYBDEN UM ALLOYS
sufficient to initiate reaction between the calcium and
the iodine. The booster reaction sets off the main re
duction reaction, and a peak temperature is reached in
Molybdenum Content
about 15 minutes after ‘the beginning of the heating cycle.
contents are removed, and the slag and the refractory
500
100 R n
50
thermocouple, of between 350° C. and 400° C., which is
After the bomb has cooled to room temperature, the
Microns)
80 RB
vitri?ed magnesium oxide. The bomb is sealed, provided
liner are broken away from the metal button.
0. 03-0. 10
0. 03-0. 20
Table II
Uranium tetra-?uoride _____________________ __ 1319.2
Calcium metal __________________________ __
439.4
Iodine __________________________________ __
1 ____________________________________________ __
2 ____________________________________________ __
3;-
Sample No.
Charged
Found (Wt. Percent)
50
At.
Percent
The but
Wt.
Percent
A
B
ton is cleaned by immersion in dilute acetic acid, and is
then weighed and sectioned for examination.
Typical amounts of molybdenum oxide, zirconium
0. 61
0.61
oxide or niobium oxide added to a base charge are:
________ ._
ADD-ED OX[DE
Oxide
V7eight
(g.)
9. 0
29. 5
27. 2
percent
1 5
5 0
6. 0
.67
2-2. 18
2.08
2.23-2.33
2. 29
2. 29
Average .............................. . _
. 68-. 68
. 64-. 65
.67
2.08
________ __
Atomic,
. 68-. 71
. 63-. 64
2. 16
2. 17-2. 21
2. 28-2. 19
2. 21
'
2. 14
2. 09
2.12
2. 38-2. 39
2. 26-2. 27
2. 33
Table IV
Results of a program of tests on the above alloys and 65
other similar alloys are given below.
Tables I and III
show data regarding the homogeneity of alloys prepared
by the process of this invention.
The yields of metal
recovered based on materials charged were uniformly
greater than 99 percent. The data on alloying element 70
content, both as charged and as found by analysis of
various portions of the button, indicated in the tables
as A, B, or C, show clearly the homogeneous nature of
the product.
Data on so-me direct-fusion alloys are in—
cluded for comparison.
URANIUM-MOLYBDENUM ALLOYS
In Tables II and. IV are given 75
_
Mo Content (Atomic Percent)
Diamond
Grain Size
Rockwell
Pyramid
(Mean
Hardness
Hardness
Diam.
Microns)
80 RB
29 Re
33 Re
90 BB
27 Re
150
293
325
185
278
500
500
300
150
50
3,072,475
5
The above alloys are heat-treatable: such properties as
tensile strength, corrosion resistance and resistance to com
pression are controllable by heat treatment. The alloys
show an increased tensile strength over unalloyed ura
nium. The alloy containing 5 atomic percent of molyb
denum after heat treatment has an ultimate strength in
excess of 200,000 pounds per square inch as compared to
6
the second class with a halide of at least one metal from
the ?rst class, iodine and a reducing agent from the class
consisting of alkali metals and alkaline earth metals and
heating the mixture in an inert atmosphere to a tempera
ture of about 350° C. whereby a reduction reaction is
initiated.
2. The process of making alloys comprising one metal
from the class consisting of uranium and transuranic ele
65,000 pounds per square inch for uranium. Comparable
ments and from 1 to about 20 atomic percent of one
‘strength features are possessed by the uranium-niobium
alloys produced by the above process. As previously in 10 metal from the class consisting of zirconium, niobium
and molybdenum which comprises thoroughly mixing a
dicated, this strength factor is highly important in reactor
development.
Changes in composition of the alloys are accompanied
by corresponding changes in properties. The composition
halide of a metal from the ?rst class with a charge com
prising an oxide of a metal or" the second class, iodine,
and a reducing agent chosen from the class consisting of
of the alloy can be made highly ?exible below the afore 15 alkali and alkaline earth metals and heating said mixture
in an inert atmosphere to a temperature of about 350°
mentioned upper limit of the order of about 20 atomic
C. whereby a reduction reaction is initiated.
percent, as it is possible to produce with the above process
either an exact alloy of a predetermined composition or a
master alloy which can be diluted to the required percent
age. One of the major diti‘iculties connected with the di
rect fusion process is the fact, as indicated by the results
in Table 112, that it is di?icult to obtain an alloy ap
proaching the desired alloy composition. In contrast, the
3. The process of claim 1 in which the halide is ura
nium tetra?uoride, the oxide is niobium oxide and the re
ducing agent is calcium.
4. The process of claim 1 in which the halide is ura
nium trichloride, the oxide is molybdenum oxide and the
reducing agent is calcium.
5. The process of claim 1 in which the halide is ura
results in Tables Ia and 111 show that by the present proc
ess an alloy of the predicted composition is obtained with 25 nium tribromide, the oxide is zirconium oxide and the
reducing agent is calcium.
in analytical limits. The importance, especially in nuclear
6. The process of claim 1 in which the halide is plu
work, of having available a process which wili produce an
tonium tetra?uoride, the oxide is niobium oxide and the
alloy of a predicted composition is obvious.
reducing agent is calcium.
Photomicrographic examination of the above samples
7. The process of claim 1 in which the halide is nep
shows conclusively that a true alloy is formed. This study 30
tunium trichloride, the oxide is molybdenum oxide and
veri?es the presence of homogeneous alloys rather than
the reducing agent is calcium.
inhomogeneous mixtures. Analyses of these alloys reveal
a purity consistently greater than 99.9 percent. Unlike
References Cited in the ?le of this patent
analyses of alloys formed by direct fusion, the analyses of
the above alloys show no indication of insolubility in any
UNTTED STATES PATENTS
case: in contrast to direct fusion alloys, they are com
pletely soluble in hydrochloric acid.
While preferred embodiments of the invention have
been described, it will be apparent to those skilled in the
art that this invention is not necessarily limited to the par 40
ticular embodiments described herein, but that various
modi?cations may be made without departing from the
scope of the invention ‘as set forth in the appended claims.
We claim:
45
1. The process of making alloys comprising at least
one metal from the class consisting of metals of the second
875,345
1,019,394
1,306,568
1,648,954
1,728,940
1,728,941
1,814,721
Goldschmidt _________ _._. Dec. 31, 1907
Weintraub ___________ __
Weintraub ___________ _._
Marden _____________ __
Marden _____________ __
Marden _____________ __
Marden _____________ _._
Mar. 5,
June 10,
Nov. 15,
Sept. 24,
1912
1919
1927
1929
Sept. 24, 1929
July 14, 1931
OTHER REFERENCES
Lilliendahl: The Electrochemical Society, preprint 91
16, pages 237-246 (1947). (Copy in Div. 3.)
rare earth series and a total of from 1 to about 20 atomic
Mellor: Modern Inorganic Chemistry, 1939 edition,
percent of at least one metal from the class consisting of
zirconium, niobium and molybdenum which comprises 50 page 527, published by Longmans, Green and Company,
London. (Copy in Scienti?c Library.)
thoroughly mixing an oxide of at least one metal from
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