Correlation Between an Electrochemical and a Chemical Approach to the Constitution of Glasses Containing Heavy Metal Ions

127 Pages·04.815 MB·English

by  Subrahmanyam, Sanga Venkata

THE PENNSYLVANIA. STATE COLLEGE
THE GRADUATE SCHOOL
DEPARTMENT OF MINERAL TECHNOLOGY
CCRREIATION BETWEEN AN ELECTROCHEMICAL AND
A CHEMICAL APPROACH TO TEE CONS JTITUTIQN OF
GLASSES CONTAINING HEAVY METAL IONS
A Thesis
by
Sanga Venkata Subrahmanyam
Submitted in partial fulfillment
of the requirements
for the degree of
Doctor of Philosophy
January 19!? 1
APPROVED
2.)^ ___________
/ 7^ Department %/Mpaeral Technology
* Chief, Division offe'resramics
ACKNOWLEDGMENT
Most sincere appreciation is extended to Dr* 1Y. A. Weyl, for
suggesting the problem and for continued guidance throughout the
investigation, Dr. G. E. Rindone for infinite patience, help and
constant advice. Thanks are due to Mr. N. R. Thielke, Dr. E. C.
Henry for many editorial comments and corrections and to Prof.
F. A. Hummel for many hours spent in discussing the results.
Finally grateful acknowledgment is made to Mr. P. K. Chu for his
permission to use the hydrogen reduction apparatus.
i
TABLE OF CONTENTS
Page
I. INTRODUCTION
Origin of the Problem. ......... 1
Survey of Literature............................................... 3
Theoretical Basis of the Problem.............................. 6
II. CONSTRUCTION AND DESCRIPTION OF APPARATUS
Equipment for Measuring Peak Potentials
Polaro-Analyzer ....... 11
The amplifier............................................. 13
Construction and details of the furnace....... lU
The glass cell............. 16
Hydrogen Reduction Apparatus
Air displacement type..................................... 17
Enclosed system............ 19
III. EXPi-RIMENTriL PROCEDURE
Preparation of the Glasses................................... 23
Peak Potential Measurements
Preparation of the cell.....................................2U
Making a run on the Polaro-Analyzer........................ 25
Reading of current-voltage curves.......................... 25
Reduction Temperature Measurements
Air displacement method.....................................26
Procedure for hydrogen reduction....................... 27
Introducing hydrogen into the system.........................28
Reduction of glass powder ............................ 28
ii
Table of Contents (continued) F&ge
IV. ffiELIRINARY KXPERB-EENTS
Reducibility of Silver in Certain Salts Using Air Displacement
Method............................................... 30
deducibility of Silver in Some Alkali Salts and Kaolin, Silica Gel
and Alumina Utilizing the Enclosed System............... 3k
Effect of Variable Factors on the Accuracy and Reproducibility of
the Results
Peak Potential Measurements.................................35
Effect of the ar© of the top electrode..................36
Effect of the total time of applying e.m.f....... 36
Effect of temperature on the peak potential.............Uo
Effect of the distance between the electrodes........... lj.2
Effect of silver concentration on the peakp otential U2
Effect of base glass free of silver on the peak potential UU
Reproducibility of peak potential.........................U8
Reduction temperature measurements............. U9
Tightness of the enclosed system................... 51
Effect of temperature on the absorption of hydrogen
by the empty boat............... ............51
Absorption of hydrogen by the silver free glass 53
Effect on the reduction temperature of preheating
the glass sample -under vacuum................. 55
Effect of temperature on the absorption of hydrogen
by glass containing silver....................55
Effect of using a water trap on the reduction
temperature.......................... 57
Effect of silver concentration on the reduction
temperature..................... 57
Effect of heat treatment on the reduction
temperature.............................. 60
Reproducibility of reduction temperature........... 62
iii
Table of Contents (continued) ' Page
V. PRESENTATION OF DATA.......................................... 65
Effect of Minor Additions on the Peak Potential and Reducibility
of Silver in Na20. 3 Si02. 0.002 Ag2C........................ 66
Effect of Substituting Divalent Ions of Both Noble and Non-noble
Gas Types for Mg............................................ 67
Effect of Introducing Various Heavy Metal Ions into Glasses of
Increasing Silica Content.................................. 70
Effect of Substituting B203 for Si02................... 78
Effect of Increasing Ka20 to B203 ratio......................... 79
Effect of Substituting A1203 for SiC2............................83
Effect of Substituting Ka0 for IJa20..............................8U
Effect of Substituting Ti02 and Zr02 for SiC2..................... 88
Effect of Substituting **or ^i02.............................
VI. DISCUSSION
Role of Silver in Glass...... 9k
Mechanism Producing Potentials in Galvanic Cells................. 95
Mechanism Producing Peak Potentials......... ................... 96
Discussion of the Results........................................99
Stability of silver in the presence of divalent noble and
non-noble gas type ions..... .100
Stability of various heavy metal ions in simple alkali
silicate glasses of increasings ilica content............ 101
Stability of silver in the presence of B203..................10U
Stability of silver in the presence of A1203........... 106
Effect of mixed alkalies on the stability of silver...........106
Stability of silver in the presence of Ti02 and Zr02......... 108
Stability of silver in the presence of F20^.............. ....108
iv
Table of Contents (continued) Page
Comparison of peak potentials and reduction temperatures with
galvanic potentials measured by Rindone.•••.............109
Peak potentials and reduction temperatures compared to low
temperature viscosity and dielectric loss...............Ill
VI. SUMMARY AND CONCLUSIONS i i ................................... 113
VII. SUGGESTIONS FOR FURTHER WORK.................... ll£
VIII. REFERENCES CITED........................................... 117
▼
TABLES AND FIGURES
Page
Table I 1* -
Table II 23
Table III 31
Table IV 32
Table V 33
Table VI 1*1*
Table VII 66
Table VIII 69 -
Table IX 71
Table X 72
Table XI 73
Table XII 79
Table XIII 81
Table XIV 81*
Table XV 86
Table XVI 88
Table XVII 89
Table XVIII 91
Table XIX 110
Figure 1 12
Figure 2 a & b l5a & b
Figure 3 17
Figure 1+ 18
Figure 5 20
Figure 6 21
Figure 7 36
Figure 8 38
Figure 9 39
Figure 10 la
Figure 11 1*3
Figure 12 1*6
Figure 13 1*7
Figure H* 50
Figure 15 52
Figure 16 5U
Figure 17 56
Figure 18 58
Figure 19 59
Figure 11 61
Figure 20 61*
Figure 21 68
Figure 22 71*
Figure 23 75
Figure 21* 76
Figure 25 77
figure 26 103
vi
Figure 27 80
Figure 28 105
Figure 29 82
Figure 30
Figure 31 87
Figure 32 9*
Figure 33 91
Figure 3h 61
I. INTRODUCTION
Origin of the problem
Although glass has been known to man for nearly 5000 years, the
science and development of glass technology passed through a relatively
quiet stage until the latter half of the past century* The dawn of the
twentieth century gave a great impetus to the sciencef various glasses
were developed to suit specific needs* The application of glass in
science, industry and home made it a versatile product. With such rapid
growth of the technology of glass one is rather surprised to note that
the knowledge of the constitution of glass was little but speculation.
Theories were limited to very narrow fields and proved satisfactory in
considering one particular property but failed to explain other proper­
ties. There was a clear need for a fuller elucidation of the complex
nature of glass. Physicists, chemists and glass technologists quite
independently viewed glass and very cleverly limited the definition of
glass to suit their special interests.
A skeleton theory of the atomic arrangement of glass was needed to
form a starting point so that refinements could be made if and when more
data were available. The groundwork was laid by Zacharisen^" who deduced
the constitution of glass by a brilliant piece of reasoning while working
under Goldschmidt in 1932. This marked a significant milestone in the
long approach to a theory of the constitution of glass. This theory was
accepted by scientists all over the world. X-ray diffraction was a
fully developed tool by that time and was immediately put to use by
2
Warren and his coworkers who substantiated the deductions of Zacharisen.
2
The theory was so firmly established and accepted by the leading
scientists that it was natural to expect that the fruits of labor were
close at hand. This was not the case, since the structure of glass was
found to be more complex than had been expected. The addition of modi­
fying ions to glass has a profound effect on the behavior and properties
of glass. Progress in understanding the constitution of glass was slow.
One contributing factor to this slow pace was that no systematic work
was done on simple glasses. Existing data, though enormous, would not
give sufficient information on the fundamental properties, hence the
need for studies such as the present investigation.
A fuller knowledge of the constitution of glass not only would aid
in the synthesis of glasses to suit particular needs but also would
probably throw greater light on the problem of concentrated solutions.•3
Tt would be impossible to conduct studies at elevated temperatures with
ordinary concentrated solutions but glasses readily submit to such
studies over a wide range of temperatures.
Rindone studied theb ehavior of glass as an electrolyte in a galvan­
ic cell. He developed a glass cell containing small amounts of silver
wherein it was possible to reduce silver at the vicinity of one electrode
with no reduction at the other electrode. This changed the nature of the
electrodes, thus setting up an e.m.f. The magnitude of this e.m.f.
depended on the nature of the forces acting on the silver in the glass
structure. Rindone came to the conclusion that silver was held more
tightly in an alkali phosphate glass than in an alkali borate glass and
more tightly in the latter than in an alkali silicate glass.
The work of Rindone stimulated the development of the present inves­
tigation. It was thought that this problem of the stability of heavy