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ORNL-4191 - the Molten Salt Energy Technologies Web Site

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I000<br />

900<br />

800<br />

0<br />

?- ii:0<br />

W<br />

2: 3<br />

$ 600<br />

CT<br />

LII n.<br />

500<br />

t<br />

400<br />

500<br />

?00<br />

N& M 40 M, Ex2 N'3BF,*<br />

mole 9h NaBF,<br />

Fig. 13.1. The System NaF-NaBF4.<br />

GRNI: DNG 67-3474<br />

indicates that <strong>the</strong> high-temperature modifications<br />

of NaHF, and KBF,, believed to be cubic, form<br />

a complete series of solid solutions exhibiting a<br />

shallow minimum (392OC) near 15 mole % KBE,.<br />

Subsolidus relations are not clear at present. A<br />

<strong>the</strong>rmal effect at about 190°C is evident in all<br />

~<br />

mixtures in <strong>the</strong> system, while o<strong>the</strong>r subsolidus<br />

effects vary with composition. Because of <strong>the</strong><br />

previously mentioned difficulty in quenching in<br />

<strong>the</strong> high-temperature forms of <strong>the</strong> compounds and<br />

<strong>the</strong>ir mixes, resolution of <strong>the</strong> subsolidus relations<br />

in this system may require detailed investigation<br />

with a high-temperature x-ray dtffractometer.<br />

We have started to map <strong>the</strong> phase boundaries and<br />

iso<strong>the</strong>rms in <strong>the</strong> legion of <strong>the</strong> ternary system<br />

bounded by <strong>the</strong> compounds NaF-NaBF 4-KBF,-KF.<br />

'<br />

-<br />

u<br />

1000<br />

900<br />

800<br />

7G0<br />

w<br />

%<br />

2 600<br />

n!<br />

a<br />

W<br />

=" 500<br />

lil<br />

1.-<br />

400<br />

Fig. 13.4. The System NaBF4-KBF4<br />

Only a few compositions in addition to <strong>the</strong> two<br />

compound joins (Figs. 13.3 and 13.4) have been<br />

examined to date. Compositions in <strong>the</strong> ternary<br />

system containing more than 50 mole % BF,<br />

probably exist in equilibrium with very high pres-.<br />

sures of OF,.<br />

13.2 DlSSOClATlQN VAPOR PRESSURES<br />

IN THE NoBF,-NcIF SYSTEM<br />

Stanley Cantot<br />

To determine BF dissociation pressures from<br />

salt mixtures composed of sodium fluoride and<br />

sodium fluoroborate, a static method is being used<br />

in which <strong>the</strong> melt atid its vapor are essentially<br />

enclosed in a metal-glass system. The apparatus

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