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AhP PROJECT QUARTERLY PHOGRESS REPORT
particles 0.010 in. in diameter.
After receiving a 0.005-in. protective
nickel plate, the particles would be
packed in beds in the reactor core,
and cooling water would flow through
the interparticle channels.
Several methods for preparing the
spheres, with the use of both high-
and low-me1 ting-point alloys, were
given a preliminary examination. The
high-me1 ting-point alloy contained
5% uranium in molybdenum, and the
low-melting-point alloy contained 5%
uranium in nickel or copper. The
results ohtainedby using the following
methods of preparation were only
partly successful: (2) suspension in
refract,ory powder and heating above
the solidus, (2) momentary melting by
passing through a high-temperature
arc, and (3) spraying from a metal-
lizing gun.
Suspension in Refractory Powder.
The U-Ni and U-Cu alloys were swaged
and drawn to 0.010 in. in diameter and
then cut into short segments. The
U-Ni particles were mixed with A1,0,
and heated to 1450°C; one sample was
heated in hydrogen and another in a
vacuum of 3 microns. The U-Cu parti-
cles were spread on a refractory plate
and heated to 1100°C for 5 min in
hydrogen. A surface film formed in
all three cases and prevented spheroid-
ization, even though a liquid phase
was present.
Momentary Melting in a Nigh-
Temperature Arc. A rig for housing
two water-cooled electrodes and
supplying an argon atmosphere was
assembled. Both carbon and tungsten
electrodes have heen used. The U-Ni
alloy particles, similar to those used
in the first method, were dropped
through an arc struck between the
electrodes. Alignment proved to be
very critical, hut the particles that
passed through the arc zone did melt.
The yield was quite low, however.
Particles that passed through the
carbon arc were porous, whereas those
156
that passed through the tungsten arc
were not.
Similar U-Ni alloy particles were
a1 so dropped through an atomic-hydrogen
arc, and a small number of essentially
spherical, but porous, particles were
f o rm e d .
Spraying from a Metallizing G M ~ .
A length of 0.057-in. -dia U-Ni alloy
wire was fed through a metallizing
gun, and the resulting particles were
collected in water. ‘4s with the other
methods, a porous product resulted.
Substitution of argon for the normal
air blast produced what appeared to
he a sound product, with only a
superfici a1 surf ace film.
During the process of dropping
segmcnts of wi rc: through the tungsten
arc, it was noted that small particles
were ejected from the electrode at
current densities high enough to melt
the electrode tip. The bulk of the
particles ranged in size from 0.010
to 0.020 inch. These results were
duplicated when U-Mo electrodes were
substituted for the tungsten elec-
trodes, The U-Mo electrodes were
prepared by pressing a mixture of the
elemental powders and sintering at
1200°C for 5 hr in a vacuum of 0.5 to
1 micron. The spheroidized particles
did not give a response on exposure
to an alpha counter as did the parent
e1ecLrode.s and U-Ni particles from an
earlier spraying experiment.
SOLID PHASE BONDING OF METALS
E. S. Romar J. €1. Coobs
Met a1 lu rgy Divi sion
The initial tests on the solid-
phase bonding of metals, performed
essentially as a screening operation,
have been completed. These tests were
undertaken to determine which materials
are easy to hond and which are diffi-
cult to bond. The tests were run on
both sheet stock and sintered-powder
compacts and were performed by stacking
wafers in a molybdenum-lined graphite
die. The laminates were hot pressed