Silver oxide electrode study and transport parameters of zincate ion through polyethlene separato

Nanis, L.

English

NASA Technical Reports Server

RE-ORDER NO. .= 
QUARTERLY REPORT 
FEBRUARY 1970 
J E T  PROPULSION LABORATORY 
CONTRACT # 952 - 543 
STUDY O F  THE ZINC-SILVER OXIDE 
BATTERY SYSTEM 
PRINCIPAL INVESTIGATOR 
DR. LEONARD NANIS 
ASSOCIATE PROFESSOR 
SCHOOL O F  CHEMICAL ENGINEERING 
UNIVERSITY O F  PENNSYLVANIA 
This work was performed for the Jet  Propulsion Laboratory, 
California Institute of Technology, sponsored by the 
National Aeronautics and Space Administration under 
Contract NAS7-100. 
https://ntrs.nasa.gov/search.jsp?R=19700013960 2020-03-12T02:48:57+00:00Z
SUMMARY 
1. Electrode Studies 
The product of leaching of si lver peroxynitrate (Ag708 NO3) in distilled 
water a t  room temperature has been shown by X-ray diffraction to be Ago. 
2. Transport  Parameters  
Use of the rotating disk method for permeation studies of zincate 
through polyethylene separator mater ia l  i s  justified because of solution 
side mass  t ransfer  res is tance in the viscous electrolyte. 
7 .7  x 
Diffusivity of zincate ion, measured by the capillary method, i s  independent 
of concentration ( 0 . 0 2  to 0 . 4 M )  and i s  3 . 0 3  x 10 
3 . 2 4  x 10 cm sec  a t  25OC. 
Permeability of 
- 1  cm sec a t  25OC in 0 . 4  M ZnO -. 4070 KOH has been found. 
-6 2 -1 c m  sec at  2OoC, and 
-6 2 - 1  
TABLE O F  CONTENTS 
1. Electrode Studies ( Dr. Leonard Nanis, Jongmin Kim) 
1.1. 1 Equilibrium Electrode Potential 
1.1. 2 X-Ray Diffraction Studies 
1.1 Silver Oxide Electrode 
TABLE 1 
1 
1 
3 
2. Transport  Pa rame te r s  ( Dr .  Mitchell Litt, Dr. G. Madan) 
2. 1 Battery Separator Permeabili ty 
2. 1. 1 Permeation Apparatus 4 
2. 1. 2 Permeation Results 4 
2. 2.1 Capillary Method 6 
2. 2. 2 Diffusion of KC1 6 
2. 2 Electrolyte Diffusivity 
2. 2 . 3  Diffusivity of Zinc Oxide - 4070 KOH solution 7 
1. Electrode Studies 
1. 1 Silver Oxide Electrode 
1.1.1 Equilibrium Electrode Potential 
In order  to obtain la rge  a r e a  si lver oxide surfaces  for  electrode 
studies, electrolytically grown si lver  peroxynitrate crystals  have been 
converted to Ago through leaching in water. As a general  index of the 
chemical nature of the surface of the treated crystal  the open circuit  
potential (with respect  to Hg - HgO reference electrode in 1M KOH) has 
been followed a s  a function of time. 
distilled water,  a crystal  with area 3 ~ 1 0 - ~ c r n ~  exhibited a potential 
of t580 mV (Hg - HgO). 
20 minutes, the potential was 496 mV, and drifted slowly down to 484 m V  
over a 45 day period at 25O C. 
478 m V  for  the reaction 
After leaching for 3 hours in boiling 
After cathodic treatment at 1mAfor  a total of 
The expected equilibrium potential i s  
2Ag0 t 2 e t H20 = Ag20 t ZOH- Eqn. 1 
F r o m  the potential measurements,  it is concluded that Ago is prepared 
a s  a resul t  of leaching and that AgZO is produced by the subsequent 
reduction step. 
1 .1 .2  X-Ray Diffraction Studies 
The potential measurements discussed in Sec 1.1.1 can, of course,  
indicate only the nature of the surface. The degree of conversion and 
nature of product was studied by X-ray diffraction (Debye - Scherrer )  
techniques. 
crystals  to a temperature  slightly greater  than the l l O o  C transition deter-  
mined f rom thermogravimetric studies (Sec. 1.1.3, Oct. 1969 Quarterly 
Report) and of the mater ia l  produced by leaching initial crystals  in distilled 
water. 
final thermal  decomposition product (si lver) were  also studied. 
a r e  summarized in Table 1 in which the 16  principal latt ice spacings have 
X-ray studies were  made of the product of slow heating of initial 
F o r  comparison, the initial crystals  (si lver peroxynitrate) and 
The resul ts  
1 
been listed. All studies were  made on powders in standard Debye - 
Scherrer  cameras  (114.6mm)l with Ni filtered CuKa radiation (8 hr. 
exposure, 45 KV, 15 mA). 
matches the standard pattern for Ago (ASTM file 14-646) and also 
The data in the column headed "Leached" 
agrees  with the data of Scatturin, Bellon and Salkind 
SOC. 108 (1961) p. 819 . The medium strength l ine at 2.86 A is not 
par t  of the Ago pattern and corresponds closely to the strongest line 
(2. 84 A) of the Ag708 NO3 starting material .  It seems probable that 
the reaction 
1 -
0 
is not complete even after one week in distilled water a t  25O C. 
presence of other strong lines of the Ag708 NO3 structure  is masked by 
nearby lines of the Ago latt ice i. e. the strong Ag7O8 NO3 lines 2.47 and 
1.74 A appear possibly as the weak 2.46 and 1.741 lines of the leached 
product although an unambiguous assignment is not possible because of the 
s imilar  medium intensity lines of the Ago s t ructure  a t  2.421 and 1.743 .k 
A further strong Ag70 line at 1.49 A f rom residual start ing crystals  
may be reinforcing the weak Ago line at 1.477 A to produce the line at 
1.477 A in the leached product with anIpmalous medium intensity. 
line a t  2. 03 
for Ago listed in Table 1 bracket this region of latt ice spacings with no l ine 
appearing between 2.287 and 1.743 A. Thus, the occurrence of the s t ray  2.08x 
line is not accounted for  in the Ago s t ructure  and is also not in the Ag708 NO3 
structure. 
The 
0 
0 
NO 8 3  
0 
0 
A: weak 
is found in crystals heated to 115O C. The standard lines 
0 
The heated product also h a s  a weak line at 2.36 Awhich is not in 
the A.gO structure. 
principal lines of si lver (2. 359, 2. 044 A) .  
is unexpected, according to Eqn. 2, and may be an impurity produced by de- 
composition of Ago caused by local heating during grinding for powder pre- 
paration. 
The 2.36 and 2. 08 i l i n e s  are, however, close to the two 
The occurrence.of metallic si lver 
0 
2 
TABLE 1 
# 
Ag7°8 N03 
5.66 W 
4.90 W 
3.48 W 
2.84 VS 
2.47 s 
1.74 S 
1.65 M 
1.49 s 
1.13 S 
1.10 s 
1.01 s 
0.952 S 
0.874 M 
0.837 S 
0.825 S 
0.783 M 
Principal X-Ray Diffraction Data 
(lattice spacing, Angstrom Units) 
(S = strong, M = medium, W = weak) 
Leached" 
2.95 W 
2. 86 M 
2.79 s 
2.77 vs 
2.74 W 
2.62 M 
2.51 W 
2.46 W 
2.41 S 
2.28 M 
2.03 W 
1.741 W 
1.699 M 
.I Jr 
He at e d 'r 
4.49 W 
4.08 W 
3.63 W 
3.00 W 
2.74 vs' 
2.71 S 
2.62 M 
2.52 W 
2.41 S 
2.36 W 
2.28 W 
2.08 W 
1.74 W 
J - J - J .  
AgoTTT 
2.95 W 
2.797 vs 
2.776 S 
2.626 M 
2.421 M 
2.287 M 
1.743 M 
1.703 M 
1.676 M 
1.622 M 
1.477 W 
1.460 M 
1.435 W 
1.533 W 1 .69  W 1.409 W 
1.477 M 1.67 W 1.397 M 
1.395 M 1.62 W 1.386 W 
+ Leaching treatment: 1 week, 25' C ,  distilled water. 
9&:kHeat treatment: slow heating to 115O C. 
***Ago: 16 principal l ines f r o m  ASTM File 14-646. 
#Ag708 NO3: 16  principal lines f r o m  ASTM File 6-0434. 
3 
The lines l isted for the heated product indicate the presence of a latt ice 
in addition to Ago, particularly a t  l a rge  latt ice spacings. From Eqn. 2, it 
is  suspected that AgNO3 is present in the heated product. 
ment would dissolve any silver ni t ra te  which formed. 
mechanisms associated with Eqn. 2 a r e  of general interest  but a r e  being 
deferred in favor of electrode studies of battery reactions using the Ago surfaces 
produced by leaching of Ag70g NO3. 
The leaching t reat-  
Details of the reaction 
2. Transport  Parameters  (Dr.  Mitchell Litt, Dr.  G. Madan) 
2. 1 Battery Separator Permeability 
2. 1. 1 Permeation Apparatus 
The rotating permeation disk apparatus described in the previous 
report  Oct. 1969 has been used to make a number of preliminary studies 
of the battery separator permeability using JPL provided samples of poly- 
ethylene grafted with acrylic acid and cross-linked with divinyl benzene in 
the K sal t  form. 
in 4070 KOH solution. 
[ 1 
t 
The initial studies used a solution of 0.4 molar zinc oxide 
The resul ts  a r e  reported in Sec. 2.1.2. 
As reported previously, the "0" rings had been replaced by special 
alkali impervious mater ia ls  for  these studies. However, after making the 
preliminary runs, it was discovered that solution had leaked into the main 
aluminum gear drive, causing excessive corrosion. A new gear has been 
fabricated and i s  being treated with an alkali impervious plastic coating 
(Kynar) before reassembly. 
2. 1. 2 Permeation Results 
Runs were made using the grafted polyethylene membrane under the 
following conditions: wet thickness of membrane, 0.003in; temperature,  
2 5 O  C; a r e a  of membrane, 5 square centimeters. The driving force for 
permeation was provided by a differential concentration of zincate ion with 
0.4M ZnO in 4070 KOH on the input side and 4070 KOH in the exit compartment. 
4 
The overall permeability through the apparatus, including resis tances  
due to the membrane and the boundary layers  on both sides of the membrane 
gave a resul t  of 3. 8 x lo-’ centimeters/sec.  
the solution, i t  was expected that the boundary layer  resistance would be a 
significant factor. 
Because of the high viscosity of 
The boundary layer  mass  t ransfer  coefficient was estimated 
using the method of litt and Smith Science 160 (1968) p. 201 using the 1 -
relations hip 
1 / 2  s c l / 3  Sh = 0.62 Re Eqn. 3 
Calculation of the membrane permeability f rom the Sherwood number (Sh) 
requires that the viscosity be known for computation of the rotational Reynolds 
number (Re) and also the Schmidt number (Sc). 
estimated that the viscosity of the solution was 90 centipoise and the density 
1.4 grams per  cc. 
experiment resul ts  (to be discussed in Sec. 2.2.3) was 3. 2 x 10 
For  these conditions, the Reynolds number i s  calculated to be 10. 5 and the Schmidt 
number 2 x 1 0  
per  second. 
membrane resistance,  the permeabilities all add reciprocally so that the 
estimated permeability for the membrane itself is calculated to be 7.7 x 10 
centimeters per second. 
For  this system it  was 
Diffusivity, which was estimated f rom the diffusion 
-6 2 -1 
cm sec  . 
5 -4 
giving a mass  t ransfer  coefficient of 1.53 x 10 centimeter 
Since the two boundary layer res is tances  a r e  in se r i e s  with the 
-5 
F o r  the measured film thickness and diffusivity, a permeability of 
42.5 x centimeters per second would be expected if the complete 
surface a r e a  of the membrane were  available for diffusion. 
7.7 therefore indicate that - 42. 5 
diffusion, i. e. the membrane re ta rds  the diffusion of zincate ion by a factor 
of 5 over what it would be in  water solution alone. 
under the condition used, the combined boundary layer  res is tances  were  about 
equal to the membrane resis tance so that the use  of the rotating disk apparatus 
i s  essential  in these viscous solutions to cor rec t  for  liquid boundary layer  effects. 
The resul ts  
o r  only 18% of the membrane a rea  i s  effective for  
It i s  interesting to note that 
5 
These runs will be repeated with the permeation cell fitted with the new 
coated driving gear,  and will be extended to different concentrations and 
temperatures to determine if diffusion through the membrane i s  purely 
passive, o r  i f  there  i s  some interaction between the zincate ion and the 
membrane material. 
2. 2 Electrolyte Diffusivity 
2.2. 1 Capillary Method 
The equipment for diffusion measurement using the capillary method 
described in the previous report  was completed. 
actual diffusion experiments, dye studies were  made to determine lo s s  of 
mater ia l  from the capillary as  a resul t  of initiating the diffusion process. 
Six capillaries were  filled with methylene blue solution and an extra drop 
of indicator put on the rectangular mouth of the plexiglass capillaries. 
capillaries were inserted into their slots in the diffusion apparatus and the 
water flow started. 
the intensity of color in each of the capillaries compared with the intensity 
of solution in a control capillary. 
lene blue were used. 
the experimental solutions and the control solutions was measurable. . The 
tes t  was repeated using potassium permanganate with s imilar  results.  We 
can conclude that the procedure used does not cause significant e r r o r  at the 
s t a r t  of the diffusion process,  i. e. no hydrodynamic removal of mater ia l  f r o m  
the mouth of the capillary occurs during start-up. 
Before running the 
The 
Five seconds l a t e r  the capillaries were  removed and 
Three different dilutions of the methy- 
No significant difference in the color intensity of 
. *  
2. 2. 2 Diffusion of KC1 
To check on the reliability of the method, inTtial studies were  made using 
potassium chloride in aqueous solution for which l i terature  values a r e  known. 
The system was kept at  temperature for three hours to insure total thermal  
equilibration before starting the diffusion. The diffusion process was allowed 
6 
to proceed for  a four to six hour interval and the change in concentration 
of the potassium chloride solution determined. 
using atomic absorption spectroscopy. The resul ts  for  the 0. 1 Normal 
potassium chloride solution gave a diffusivity of 1.79 x 10 cm sec . 
This resul t  compares very favorably with the well-known [Handbook of 
The solutions were  analyzed 
- 5  2 -1 
L -5 2 -1 
Chemistry and Physics] value at 25' C for  0.1N KC1 of 1.844 x 10 c m  sec . 
J 
Diffusivity for a 0.1 molar  zinc chloride solution was also determined 
-5  2 -1 giving a value of 1. 02 x 10 
comparison. 
cm sec . No l i terature  value is known for  
2. 2.3 Diffusivity of Zinc Oxide - 40% KOH solution 
Diffusivities of the zinc oxide - 40% KOH sys tem were  measured at 
and 20 C using concentrations of zinc oxide ranging f rom 0. 02 to 0.4 
The scat ter  in this data was greater  than that experienced with the 
0 0 25 
molar.  
potassium and zinc chloride solutions, presumably because of difficulties 
with the analysis of the highly alkaline solution. 
concentration could be determined f r o m  the data. 
based on about twenty-five measurements  each, are: for 25 C, zincate 
No significant variation with 
The average values obtained, 
0 
diffusivity equal to 3. 24 x 10 -6  c m  2 sec  - '; for 20 0 C, 3. 03 x 10 -6  c m  2 sec -1 . 
Further  work at other temperatures  is necessary to determine if  these 
resul ts  are  significantly different. 
needed to reduce the scatter.  
a l a rge r  concentration change which will reduce the influence of the analytical 
e r ro r .  
Better control of the analysis is a lso 
Also, future runs will be lengthened to give 
7 


Study of zinc-silver oxide battery system Quarterly report

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server