chemical physics of discharges - Argonne National Laboratory

160
Group I11 compounds. No in estigations have been made on the compounds
of boron. Ywkovskii t& &.' reported in 1958 that BC1 was reduced to
elemental boron by H atoms, and the present work on alum?nium halides
supports this claim.
When inert csrrier gases were used there was a very limited
deposition of metal from Al and Sc halides amounting to onu a few
per cent of the vapour passed through the discharge, but when hydmgen
wee employed much higher yields of metals were obtained. It would
appear, therefore, that at least one step in the decomposition involves
a H atom reaction, and the process may well be, for AlCl :- initial
dissociation of UC~ to uc13 : H atom reduction of UC~, to UCI :
disproportionation 03 fic1 to U and fic13. A maas spectromet+c
examination of the species present in the discharge revealed AN1 In
readily detectable quantities but no AlCl was observed. Yields of up
to 55% Al metal have been obtained from Ab1 in a single pees through
3
a 2450 mC plasma, and if a second discharge was produced downstreem
more Al deposited. The rate at which AlCl decomposes, with
comparatively low power, and with ita intenae blue plama makes this
reaction one of the most spectacular of those studied. The relatively
involatile AlF3 also dissociated quite readily to glve the metal,
although it is not easily handled in the experimental 8pparatUe described.
The chloride and fluoride of ecandiun behaved in a similar manner to the
corresponding aluminium compounds.
NCl also dissociated readily in the lower frequency apparatus.
It should be Lntioned here that the chief difference between the wavesuide
and the coil-coupled apparatus appear8 to be that in the formar
the electrons are accelerated to higher energlea since the electrostatic
field is concentrated between the resonator walls where a high potential
gradient exists in a direction axial to the discharge tube. By
comparison the E field in a coil is much more randomly distributed.
Rare Earth Comounda. We have not as yet had an opportunity of studying
these halides systematically, but preliminary erperiments have shorn
that they behave in a menner similar to AlCl That is, there is only
limited dissociation to metal in an inert c&ier gas, but with hydroem
satlafactory yields of metals are obtained. Thae Ce and Le result
from &F3, CeC13, LaB and LaC13. If, for example, chlorides contsirr
ing appreciable quautjties of oxychloride are used for the dirsooiation
this inpurity is left in the sample boat and a highly pure metal is
deposited. Such reactions may therefore prove of use in the preparation
of certain metalm.
2. Markovakii, L. V., Lvova, V. I., Kondrashev, Y. D.,
PO Bora i Ego Sveedin, 36 (1958).
Ber. Tr. KO&.
1
i