ORNL-1816 - the Molten Salt Energy Technologies Web Site

ANP QUARTERLY PROGRESS REPORT
TABLE 5.8. PHASES FOUND IN MF-UF3 BINARY MIXTURES
Lattice
Molar Compositiona Phases Structure Type
Zb
Dimensions (A)
2NaF-lUF3 Hexagonal phase ond p2- N aU F4 a = 6.17
3NaF-2U F3 also NaF c = 3.78
1KF-1UF3 Hexagonal phase and P,-KUF4 a = 6.51
cubic phaseC c = 3.76
F I uorite type a. = 5.9
1 K F - 1 Na F-2U F3 Two hexagonal phases @2%Na)UF4 a = 6.27
c = 7.71
3
3
4
3
4
P,-KUF4 a = 6.51 %
c = 3.76
aSomples prepored by V. S. Coleman and W. C. Whitley and examined petrographically by T. N. McVay.
bThe number of molecules per unit cell.
CThis phase may be the cubic phase of KUF4 or the compound UOF with the fluorite structure.
and So = 29.90 e.u., of which 0.53 e.u. was obtained
by extrapolation below 20°K.
The heat capacity of a sample of pure MoS,
was measured from about 15OK to room temperature.
The heat capacity and the derived thermodynamic
functions mentioned above were tabulated at 10-deg
intervals up to 300OK. At 298.15'K, C, = 15.62
cal/mole*°K, and So = 15.34 e.u. The heat capacity
of MoS, follows a T2 dependence between
15 and about 70°K of the sort previously reported3'
for MOO,. This behavior of MoS, is consistent
with its layer structure, which is so pronounced
that MoS, actually is a good high-temperature
I ubri cant (L iqu i-Mol y).
Density and electrical conductance measurements
were made of molten mixtures of KCI and KI across
the entire composition face. The molar volume, as
calculated from the density, is nearly additive
for this system, although it shows deviations close
to the KI side. In contrast, the equivalent conuctance
shows pronounced negative deviations
additivity for all mixtures, with maximum
ation at high KCI concentration. These data
in show that it is inadvisable to interpret
maximums and minimums in electrical conductance
as the consequence of formation of compounds in
34E. R. Van Artsdalen, ANP Quay. Prog. Rep. Sept.
10, 1954, ORNL-1771, p 72.
* r
*
the melts. The specific conductivity of molten -
KI is expressed by the equation r "
K = -1.7100 + 6,408 x 10-3t
- 2.965 x 10-6t2 mho/cm
between 725 and 925OC, and the density is given
by the equation
p = 3.0985 - 0.9557 x 10-3t g/sm3
between 680 and 91OOC. The temperature, t, is
in OC.
The density and electrical conductance were
determined for pure molten NaBr and are given
below for the range 750 to 960OC:
K = -0.4392 + 5.632 x 1013t
- 1.572 x 10-6t2 mho/cm
and
p = 2.9518 - 0.8169 x 10-3t g/cm3.
The self-diffusion coefficient of sodium ion in
molten NaNO, has been determined by a radiochemical
tracer technique. The heat of activation
for self-diffusion is approximately 6 kcal/mole and,
-
therefore, higher than the heat of activation for
electrical conductance. Similar work with thallous
chloride35 has shown that the heat of activation
7 ,
.
35E. Berne and A. Klernm, Z. Naturforsch. 8a, 400
(1953).
c
-