The diffusion and solubility of oxygen in Ag in the temperature range between 412 and 862 C was determined. The following interpolation formula was found for the solubility: L = 8.19.1/100.exp(-11 860/RT)Mol O2/g.At.Ag.at 1/.5. The process obeys the Sieverts square root law within the limits of error. The dissolution of oxygen in Ag may be accompanied by the dissociation of the oxygen molecules into atoms. The tests on Ag-foils reveal that below a temperature of about 500 C a higher solubility is simulated by the adsorption of oxygen. The diffusion coefficient of oxygen in silver obeys the following equation: D = 2.72.1/100.exp(-11 000/RT)sq cm/s. The relatively low activation energy of 11 kcal/g.At suggests that the diffusion of oxygen takes places over interstitial sites

Eichenauer, W.

Miller, G.

English

NASA Technical Reports Server

%NASA TECHNICAL MEMORANDUM NASA TM-77938
DIFFUSION AND SOLUBILITY OF OXYGEN IN SILVER
W. Eichenauer and G. M_ller
NASA-TM-77938 19860012184
Translation of "Diffusion und Loeslichkeit von Sauerstoff
in Silber," Zeitschrift fuer Metallkunde (Journal of
Metallurgy), Vol. 53, 1962, Stuttgart, West Germany,
pp. 321-324.
I bl' /
Lii: [)' ' ['7_ " '"
!"10v"':;,:....... "
L;_:,.'.,;.:,", L.'..-._
H " • i v.'_'" _,_',_
\
\
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON, D.C. 20546 OCTOBER 1985
https://ntrs.nasa.gov/search.jsp?R=19860012184 2020-03-20T14:59:15+00:00Z
DiAPi_V ¢,9/2/i
o,-_,_,,.-=_:_ i.SF;!JFio PAF4F.is.o-, pV',TC.---r_n',/2q, nE'T_" FJa'e'_-T_''l--_Vasg: 'uAr
i -I _. _r,.-:,o ........ \ ........ £'_-,7i iA_I I ? F'AAF'=, _"-' "'_'_ FTff) E!C:I',.":tIMFNT--', f [-.L]O i l'll_l ld<.,--,;l_z_t ,L,., i U,:,:, Hc,c,i• . : '_.:_ _ _ .!_..'r_..-. - :A,' --[ ,.J :j ._., ............ _ _ . _ _- _ ................
UTTL;Diffusionand sc;]ubi!i t':i of ox'vgenir,, s1lver
,,. _.-.:- ...... . ...... -.. E,_iMTI t EE__tjTH:A/FTC!qFF, dAi!FQ, hi :. , ,.,,:,......_,_,,., .__.
,"_'.;._-,RP:H_tir;r,_i _,-r,r-,:'r_i,-:.-qarid Space _rimir;iq+.r_tinn, Wssinir.,c!.ior.,,r:!.C.
AVAIL.NTIS
S An` i4,7 A,?,,T-'iM7 A-',:ii
f-ln: _Fr'":-''='''' FFF)FRA! RFPIIA! lq C:'.FTrar:,_!. m..' '.4_r,n_r fi _r-,'.: Aqqr.,"i__t_A. F.t_di'ir,r_d '._. _ .;. "__ _.i: i t- L _._.,'f ;_.., = :_._. _. _- : = _ _ = . __ ._ _-_-._ _- _.
L-it':'.-.C_:alifo __._gir..,a! doC. ;).les prep, b'-' !_e:i-.,r,i,-_:a]L,'ni,d.- [)arm.=.,..-.':.:,.-West
t__..H_:.+ Tr_.nml. '..n+.:.,.-.,Fi'-.4GIlfiU frc.,m U!tt'J.S'.,.or,..and Loeslich!/,.eit ',.iOn
.'--;_.um:stoff in S_i _^"-.!_.'._I fqfll_,trJ_i-'i, h.l._RtS._rrn_nv;'.., t# F-,R..I%.:,.7' ,,->-o-_._:..-o,_
.......1"I_ it"-- Ig-'F'_TE_i!C'T_'tM":'7_TMTTE P_[ F_-r_O_':i-'_ TUE[iD"' i';:"-I";$"'C'-MCT_I :"I'-:'T &I-FFmk,,"T1-_-..RHL- ! [ -_Ji"::il_i":{,:. ,i',. i " tJ.'.'. : ',Q.Ji:_l:l: : .i.:: / l,_. :.--'=: ! r="-.Llli._L !.'-I-'_.'-...!"-. !-" .'-__r1=_: I"L_=::.. _ ....
l,_1-T Ir" z'-,l-"_ i
..... i:!L-_L._LLO.-""'k._i_y LIEI_i "'.-it; ?Ei":.; "'OLSLLIBZL_ it'
,,,T_,_r.. .--'-.r_r.Ar,rc _r;_,t.- CMFNTrAi F'Fm-Tlf;kic;i NISSOCt_TI_mll ,._--m._-,-._,_-'L_,..,-,_,,_ -..r-: ., ---,,l'!!l_O, I ML.,Z.,,..,E .I [Ls..,. ; ...... ., ..,,.,.-.- __ "" i_,",'- -" r'£'d IF'_ I_ ITFF F ",¢'BPi
!!,]Tm:rL,LH. it_t!,:,, i.,,,'-T,",i r,<--_,,--,ou',:n',,.'- ! ._._.'.=.'Ut_._-.F_.-" H ]
_RA: _- "' ""
ABS: The diffusion ar.,.dsol_.-bi!it<i of ox,/gen i.r.,.Aq_in the.temperature ran-_qe
h_fi',!_ '__q .... "_ R,-:_- r t"as determined° The foi'.........r,_:---d::,-:.... _ot.t.'.inginterpolationf0rm-!la
ill_q #(%tlT'.'d for th_ ,mqllihiii+v • 1 = F: lq i ,"_Ci,-:,_";_;-1i _.oT--,,,:-_
02!g:_t,,-, -* 4 - r Tk_ prc:c._.qs ni--,_vq tb..._Si._'._rt.__qtj_!:._ ro,.":t l_!ll ,-',ithir,..... H_: dt --' .... , ................. . ... ......... ....... -, .,.........
_!_,-_ ]irrilt_ r;+ ei.-Fr,.<-, Tk,-.. di,.-q.qq:,lilti,qr., r.,{ e,,.z,..lG_r_ in Aq rri_"..."b# a':cc:,rr!par.,.iedhv
_h_ d,.._.q,.'.,ci_tic:,n, c,f the c,x':.;genmolecules into atorr..,s;-.Thetests or. Am4.-foi!s
ENTER:
_. .......... . .... • ......... , .............................................. . ........ ,................................................ -_.....
I. R.g •• 1 tho
NASA TM-7.7 938
2. C••• l'1'\nlenf Ace •• '.0'"' H ••
DIFFUSION AND SOLUBILITY OF OXYGEN
IN SILVER
1. A.,o..(.,
W. Eichenauer and G. MUller
,. 'l.pa;' 0,1,
October 1985
10. Wet\ U..U He.
1I. Co..l'tct •• C..... Nt.
NASW-4005
'. P •• I.....:"g O.,...,.....a" 14 ...... ...,4 .A t!t!. 4 It
Leo Kanner Associates
Redwood City CA 94063 11. T f ~ 4 P 4 C
t---------------------------1 Tr~:~la·~:~: ••i. "·'·~·Il .'.
12. ~..,.a .."~ .Ag."er H_. _4 .Actd,•••
National Aeronautics and Space Adminis
tration, \'Jashington D.C. 20546 1(. ~a....',.. ~ ...:."e'Co~. I
IS. S,·;;lu,."lc'r HoI ..
Translation of "Diffusion und Loeslichkeit von Sauerstoff
in Silber," Zeitschrift fuer Metallk~nde (Journal of
Metallurgy), Vol. 53, 1962, Stuttgart, West Germany, pp.
321-324.
10. J.~ ... .;;. The rate of loss of oxygen from Ag samples led to the
determination of the diff~sion and solubility of oxygen in Ag
in the temperature range between 412 and 8620 C. The following
interpolation formula was found for the solubility:
L = 8.19·l0- 2 ·exp(-11 860/RT)Mol 02/g·At.Ag·at-l/2
The process obeys the "Sieverts" square root law within the
limits of err~r. The dissolution of oxygen in Ag is probably
accompanied by the dissociation of the oxygen mole~ules into
atoms. Our results do not agree with the data given by Steacie
and Johnson which show a minimum in the solubility at 400 0 C.
Tests on Ag-foils revealed that below a temperature of
about 500 0 C a higher solubility is simulated by the adsorption
of oxygen.
The diffusion coefficient of oxygen in silver obeys the
following equation: D = 2.72·l0-2 ·exp(-11 OOO/RT)cm2/s
The relatively low activation energy of 11 kcal/g'At suggests
that the diffusion of oxygen takes place over interstitial
co;+-oC'
' 17• (.r lI .. ct. (Selected tlJ' Author(,,) 11. Olol,lbvl"., Slal.co..,'
Unclassified - Unlimited
r.;-:-:--:-;:---::--:-:-~--:----,-:-__--l. --r -,...-__~lJ8h-;)1b/~5#
'f. ~.cw ... , CI .... ,. (e' ."•••;"••• , 20. ~.<'rf'" ~le44t'. (., .......,.1 JI. He•• f P.,.. J1. fJ-) S 5, 7t~3
Unclassified Unclassified
°
t
DIFFUSION AND SOLUBILITY OF OXYGEN IN SILVER
W. Eichenauer and G. M_ller
Eduard Zintl Institute, Technical University, Darmstadt
The temperature curve for the solubility L of a gas /321"
in a metal is given by the equation:
L=L ocxP'(- II '1 (l )R 7' .i
where L is the solubility coefficient (expressed in moles of gas
per gram-atom metal at a pressure of 1 atm), _ is an entropy
factor, R is the gas constant, T the absolute temperature and H
the heat of solutio_ referred to the standard state. Based
on thermodynamic considerations, a monotonic function of tempera-
ture is expected for the heat of solution in the range considered
here. Hence for the temperature-solubility curve one likewise
gets a monotonic function. Metal-gas systems examined to date
all fit this picture, with one exception: The system silver-
oxygen.
Measurements conducted by E.W.R. Steacie and F.M.G. "Johnson
[i] on silver foils found a clearly marked minimum solubility of
oxygen in silver at ca. 400°C. Later, an attempt was made to
explain this minimum by the formation of silver oxide Ag20
[2,3]. In our opinion the solubility minimum can be interpreted
at least partly as a consequence of an additional adsorption of
oxygen onto silver in the investigations of Steacie and Johnson
[i]. The deviations of solubility values from the square-root
law at low temperatures and lower pressures, as found by these
authors, suggest the same origin. The apparatus and test method
allowed no distinction between solubility and adsorption.
"Numbers in the margin indicate pagination in the foreign
text.
*Editor'sNote._ heatof solutionshouldbe solutionenthalpy
Our own orientation measurements with compact silver by our
method, which only detects reversibly dissolved oxygen, yielded
values as much as an order of magnitude below the data published
by Steacie and Johnson [i]. This finding led us to repeat the
determination of the solubility of oxygen in silver, while at the
same time obtaining data on the diffusion of oxygen in silver,
about which nothing was known but a single calculated value [4].
Experimental Method
The procedure we previously developed to determine the
diffusion and solubility of gases in metals, already described in
detail elsewhere [5,6], was also applied successfully to the
system silver-oxygen. The method is based on observing the
release of gas from a gas-charged metal body. The gas escaping
from the metal is transferred to a collector vessel and the
development over time is tracked with pressure measurements. The
diffusion and solubility coefficients can be calculated from the
resulting gas release curves.
The gas release from a metal follows the laws of volume
diffusion, when this is the process that governs rate. However,
in the many partial processes into which the escape of an
atomically dissolved gas from a solid can be broken down, there
is a risk that interface processes may govern or at least
influence the gas release rate and hence cause misinterpretation
of the results. If these processes are not known already from
the found time law, using specimens of different dimensions
and shapes makes it possible to find interference of this sort.
Therefore our studies employed cylinders and various sizes of
spheres.
Some experiments with refined silver (99.9 wt% Ag) did not
yield reproducible results. Subsequent microscopic examination
2
revealed pores in the edge zone of the refined silver specimen.
The test specimens for the final measurement were produced
as follows: Raw material was so-called crystallized silver,
99.995 wt% pure. It was melted in a vacuum (10.3tort) in a
quartz crucible, and poured into chills. Rolling and turning
produced the following specimens:
Cylinders 0.53 cm _ and 29.85 cm long
Small spheres 0.98 cm
Large spheres 2.99 cm 9
To remove surface impurities, all specimens were pickled for
1 hr in a 10% aqueous solution of hydrochloric and tartaric
acids. Precision determinations of density by the buoyancy
method [7] yielded the following mean results:
Density before measurements
. A
0(250C) =]O..lq20_f).O(_O_.'(.nl_
Density after measurements
_(25 °C) = 10. 1925 ± 0.0008 g!cm 3
Accordingly the dissolution of oxygen has no determinable
effect upon the density of the silver we employed. For /322
for comparison, here we give the results obtained by T. Heumann
and W. Wicke [8] with refined silver:
X-rays [.{zs"(;i_ 1|).3()7!()d)I_,/,,,):'
Buoyancy method "(23°C)-10_']96!()-(I1)3F'''ha
(Heumann and Wicke [8] give the specific volumes for 20°C.
Using the coefficient of thermal expansion of silver [9] we
converted this data to the above densities at 25°C.)
The oxygen used for our studies was produced at 300°C from
potassium permanganate (p.a.), condensed in a vessel chilled with
liquid nitrogen, and purified by repeated distillation, freezing
out all expectable impurities (water, carbon dioxide).
Results
In all, 38 measurements were performed in the range between
412 and 862°C at various pressures. The results are shown in the
usual manner in Figs. 1 and 2. Measurements at constant tempera-
ture and different pressures had shown, in agreement with Steacie
and Johnson [i], that the Sieverts square-root law also applies
to the solubility of oxygen in silver. Within the error limits,
the gas release curves of all specimens followed the law of
volume diffusion. The low solubility and very slow development
of diffusion below 400°C impede measurements in this range
exceedingly, and prohibit expanding the investigation the
temperature range where the compound Ag20 is stable [i0,ii].
For the temperature function of the diffusion coefficient,
from our measurements we get Do = 3.66 i0-3cm2/sec for the
frequency factor, and E = ii.00 kcal/I/2 mol 02 for the activa-
tion energy. For solubility one gets I_ = 3.34 10.2mol O2/gr-
at Ag • atm-I/2for the entropy term, and for heat of solution H
= 11.86 kcal/i/2 mol 02. This yields the amount of oxygen 1
(cmsNTP) dissolved in 100.g silver at temperature T (°K) and
equilibrium pressure p (torr) as
2593 ]b_gp (3)10gi=].403-T -I-2
Table 1 has the solubility values for an equilibrium pressure of
1 atm.
4
Fig. I. Solubility Fig. 2. Diffusion
coefficients for oxygen coefficients for oxygen
in silver in silver
a :_,0,_r,,_oc a l,_.;.o,o,_.,._.oc
_,0 200 500 ,300 6_,3 _O>
_-1-,- ,, -,_0 ,_--_ -r-_---- ]_ ........
• _t$,ne*ugelrc _I
.,o,,....... oI )......i.,ifi
5c -
J o 6,.e_,Mo_'d (':NC ,
-g5 -_.01 ' i. _\L__
0.75 7.0 ;.25 Z5 ;.75 0.75 [o ;2L :_ )75
7000/7_n7,'_K IODE'?_':?/_K
Key to both figures:
a. temperature b. cylinders
c. small spheres d. large spheres
e. after E.W.R. Steacie and F.M.G. Johnson [i]
f. after R.A. Rapp [4], calculated with L values from [i]
g. after R.A. Rapp [4], calculated with our own data
Table i. Solubility of oxygen in silver at an
equilibrium pressure of 1 atm, calculated with equation (3)
- t,•
91141 ._ (l.llll]_
41111 |I.IIlql
.",€.J cL::,_::
V,(.J 1_7IT
_(i0 l.:,_
$'HIll 2.1,7
UIII) .I.:HI
Key: a. temperature
Our estimates indicate the error limit of the diffusion
coefficient above 500°C as ± 4%; at lower temperatures it rises
to ± 6%. The error limit of the solubility coefficient is ± 8
in the entire range.
At higher temperatures the solubility data of Steacie and
Johnson [i] coincide with our measurements (Fig. i). The
5
deviationsat lower temperatures,however, are clearly outside
the error limits of the two studies•
Adsorption of Oxygen on Silver
Several passages in the literature report adsorption of
oxygen on silver [12,13]. In the pressure and temperature range
of interest to us, according to W.W. Smeltzer, E.L. Tollefson and
A. Cambron [13], chemisorption of oxygen onto silver occurs.
These authors' investigations were conducted with silver powder
produced from a silver-calcium alloy. Since to us it seemed /323
questionable to draw direct conclusions about the behavior of
silver foil from the results from silver powder, we performed
some experiments of our own, initially only for a qualitative
determination of adsorption. The raw material was the same metal
used to produce our specimens.
The apparatus we used, intentionally kept simple in struc-
ture, corresponds in principle to the test setup used in [13].
At a pressure of ca. 450 torr, a total of 14 measurements
were performed between 240 and 400°C. Because of the broad
spread of the individual results (error limit: ± 50%) no definite
pronouncements arepossible about the temperature dependence of
adsorption. For the same reason we limit ourselves to reporting
a value averaged over the whole temperature range: On the
average, 0.085 cm3 NTP oxygen were adsorbed on a silver surface
measuring 2 103 cm3, equivalent to a coverage of 1.9 • 10.9mol
O_/cm2. This value practically corresponds to a monomolecular
layer, and given our rather coarse method is in satisfactory
accord with the results of Smeltzer et al. [13], who found a
coverage of 9.7 i0-I°mol 02/cmz under similar conditions
(270°C and 400 torr pressure). From this we conclude that
concerning oxygen adsorption, our silver foil behaves similarly
to the silver powder studied in detail by those authors.
6
Fig. 3. Oxygen uptake of :0,
silver foils (adsorption _ I I
and solubility) referred
to 1 atm. -_
Key: _" Ic_,_ ......_, .._ /
a. temperature __0.,_
b. after E.W.R. Steacie _[_and F M G Johnson [i]
c. our own studies ;_ a?0_ _o_ 5c_
(adsorption and _: .....°c
solubility)
Figure 3 shows the calculated temperature curve for oxygen
uptake (consisting of adsorption and solution) in our silver
foil, compared to the solubility values of Steacie and Johnson
[i]. The calculations were based on the data of Smeltzer et
el. [13] for adsorption up to 300°C, and our own interpolation
formula for solubility. The adsorption values above 300°C were
obtained by extrapolation. Because of this imprecise procedure,
naturally no quantitative agreement of the two curves can be
expected. However, in our opinion their similarity confirms our
initial view on the genesis of the solubility minimum found by
Steacie and Johnson [i]
Comparison with Diffusion of Hydrogen in Silver
Our earlier investigations [6] found the following for the
diffusion of hydrogen in silver between 388 and 600°C:
I) 2._:2"1(I :'_CXl,(-75(_cJ,'RT" )
. o
Using neutron deflection, it was found for the system palladium-
hydrogen that the hydrogen atoms occupy the octahedral inter-
stitial sites in the metal lattice [14]. We have no reason not
to assume the same mechanism for the pair silver-hydrogen. The
numerical values we found for the frequency factor and the
activation energy for hydrogen diffusion in silver support this
7
assumption.
Moreover, observations concerning the diffusion of oxygen in
this metal, particularly the relatively low activation energy for
diffusion, suggest oxygen also behaves similarly• The low
activation energy of oxygen diffusion rules out the assumption
of diffusion via flaws in the silver•
Our measurements allow no far-reaching conclusions about the
state of the oxygen or hydrogen dissolved in the metal. Hydrogen
may very likely assume a state between an atom and a proton.
There are no indications of the degree of ionization of oxygen
atoms in the silver lattice.
A similar study of the systems gold-hydrogen and gold-oxygen
only yielded conclusions about the diffusion of hydrogen in gold
[15]. The solubility of oxygen in gold was below the detection
limits of our equipment (under i0-;mol OJgr-at gold)•
Summary
From the course of oxygen release from silver specimens
over time between 412 and 862°C, the diffusion and solubility of
oxygen in this metal were determined. The following interpola-
tion formula was obtained for solubility:
L-&lgl()-_'exl,(- ll_(,(IRTIM,I()..,
_-AI_ ._g •al_ l'_
Within the error limits, this satisfies the Sieverts
square-root law. Hence oxygen dissolves in silver very probably
by splitting the molecule• We could not confirm the solubility
curve with a minimum of 400°C, as given by E.W.R. Steacie and
F.M.G. Johnson [I].
From some experiments with silver foils, we verified that
8
4below ca. 500°C the adsorptionof oxygen may simulatean increase
in solubility.
The diffusion coefficients for oxygen in silver obey the
following equation:
D _.72-](_ _-,.\1_(_]1 (_()(_]?T)+.m_/,_ _ :
The relatively low activation energy of ii kcal/gr-at
indicates a diffusion of oxygen via interstitial sites.
Our special thanks to Prof. H. Witte for discussions on this
work. Our thanks to the Degussa company, Hanau, for supporting
our investigations. The silver samples were kindiy produced,
finished and microscopically examined at the Metals Laboratory of
the same company.
9
REFERENCES
i. Steacie, E.W.R. and F.M.G. Johnson, Proc. Roy. Soc. A 112
542 (1926).
2. Simons, J.H., J. Phys. Chem. 36, 652 (1932).
3. Domanski, W., Arch. Ilutnictwa 3, 81 (1958).
4. Rapp, R.A., Acta Met. 9, 730 (1961).
5. Eichenauer, W. and A. Pebler, Z. Metallkde. 4_88,373 (1957).
6. Eichenauer, W., H. K_nzig and A. Pebler, Z. Metallkde. 49,
220 (1958).
7. Smakula, A. and V. Sils, Phys. Rev. 99, 1744 (1955).
8. Heumann, T. and W. Wicke, Z. Elektrochem. 6--0,'1154 (1956).
9. Saini, H., Helv. Phys. Acta 6, 597 (1933).
i0. Keyes, F.C. and H. Hara, J. Amer. Chem. Soc. 4__44,479 (1922).
ii. Garner, W.E. and L.W. Reeves, Trans. Farad. Soc. 50, 254
(1954).
12. Benton, A.F. and L.C. Drake, J. Amer. Chem. Soc. 56, 255
(1934).
13. Smeltzer, W.W.,_ E.L. Tollefson and A. Cambron, Canad. J.
Chem. 34, 1046 (1956). :_
14. Worsham, J.E., M.K. Wilkinson and C.G. Shull, Phys. Chem.
Solids 3, 303 (1957).
15. Eichenauer, W. and D. Liebscher, Z. Naturforschq. 17___aa,in
publication (1962).
i0
i 3 1176 00188 7935


Diffusion and solubility of oxygen in silver

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server