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Patented Sept. 17, 1946
2,407,874
UNITED STATES PATENT OFFICE
2,407,874
FLUORINE-CONTAINING CERAMICS AND
METHOD OF MAKING SAME
Walter A. Fraser, Irondequoit, N. Y., assignor to
Bausch & Lomb Optical Company, Rochester
N. Y., a corporation of New York
~ . ‘
_
N0 Drawing. Application August 31, 1943,v ‘
Serial No. 500,632
. .
..
2 Claims.’ (01. 106—52)
1
2
.
This invention relates 'to novel ?uorine-con
taining ceramic compositions and the method of
making the same.
The ceramic compositions of the present inven
tion are particularly adapted for use as optical
glasses where glasses having relatively high re
ciprocal dispersions and low indices, are desired.
Glass of this type has been produced by the in
troduction of ?uorine into the batch, the: ?uorine
the glass forming reactions are substantially com
plete.
‘
“
It has been noted by prior Workers in the art
that in ?uorine containing glasses, an excessive
loss of ?uorine in melting is caused by the pres
ence of water in the batch, that is, by the use
of compounds yielding Water on decomposition
such as boric acid and aluminum hydrate‘, or con~'
taining water of_crystallization, such as potas
?goride, silicoe?uoride, alumino-?uoride, and the
10 sium carbonate and similar compounds. It was
believed that when such materials are used, con
forming reactions were substantially complete.
In the optical glass compositions of the present
having been heretofore introduced as an alkali
siderable ?uorine is volatilized as hydro?uoric
acid during the melting process.
The ?uorine was added in the forms mentioned,
Furthermore, boric acid in decomposing reacts
as these ?uoride compositionshave a relatively
high melting temperature and it was believed 15 with the refractory ?uorides heretofore used to
form boron ?uoride which is extremely volatile
that the ?uorine was less apt to be lost if the
and lost during the melting operation.
?uorine compound did not melt until the glass
li e.
invention, although considerable boric acid is
Fluorine was continued to be‘ introduced in the
used
to insure the desired transparency in the
20
forms mentioned even after it was discovered
resulting glasses, a larger percentage of the ?uo
that the loss of ?uorine during the melting of
rine introduced into the batch in the form of an
alkali metal acid ?uoride is retained than where
‘I have discovered that the ?uorine content of
the previously proposed ?uorides were used. The
many ceramic compositions can be maintained
probable explanation of this phenomena is that‘
relatively high, that is, the loss is less, if the 25 the boric acid reacts ‘at intermediate tempera
?uorine is introduced in the ‘form of an alkali
tures with the ?uorides heretofore used, While the
metal acid ?uoride. It might appear that such
alkali metal acid ?uorides begin decomposing at
?uorine compounds would not be practical as a
much lower temperatures and enter into the
means of introducing ?uorine, for they have low
glassy matrix before the boric acid will react with
decomposition temperatures as compared with
the same.
those of the previously used ?uorides.
In addition to the fact that it is di?icult to
Although alkali metal acid ?uorides do de
retain the ?uorine when introduced as anhy~
compose at Very low temperatures, I have found
drous sodium ?uoride or potassium ?uoride, these
such glass batches was excessive.
‘
.
that they can be used as a source of ?uorine par
ticularly in many glasses without the excessive
?uorine loss as compared with previously proposed
glasses in which the ?uorine was introduced in
the forms heretofore discussed.
35 two compounds are hygroscopic and tend to re
As the ?uorine >
act With the Water absorbed and the carbon diox
ide usually present in the air. These ?uorine com
pounds are further objectionable as they both
tend to increase the amount of hydrogen ?uoride
. loss is less, ?uorine containing glasses produced 40 liberated, thereby increasing the ?uorine loss.
in accordance with the present invention have a
Another disadvantage which occurs when an
lower refractive index and a higher reciprocal
hydrous sodium ?uoride or potassium ?uoride is
dispersion than many of the previously proposed
used, is that it may not be desirable to add as
?uorine containing glasses.
much alkali to the batch" as would be required
The explanation of this apparent anomaly is 45 when these alkali ?uorides are used to insure that
believed to be that the alkali metal acid ?uorides
the desired amount of ?uorine would be present
start to decompose at a relatively low temper
in the batch. Thus, it is possible to reduce the
ature and enter into the glass forming reactions
at an early stage of the melting and that the
?uorine is captured and retained in the glassy
matrix. Where the ?uorine is introduced in the
forms of ?uorides having higher melting temper
atures than the alkali metal acid ?uorides, it ap
pears that, as these previously used compounds
are very refractory, they do not decompose until 55
alkali and yet maintain the percentage of ?uorine
desired when the latter is introduced into the
batch as an alkali metal acid ?uoride. This per
mits more of the alkali to be introduced as a ni
trate or a carbonate which, as is Well known, aids
in the ?ning operation.
Although any of the alkali metal acid ?uorides
can be used as a source of ?uorine, I prefer to
2,407,874:
3
4
use either potassium acid ?uoride or sodium acid
?uoride as these two compounds are easily pro
positions in which it is desired to have ?uorine
present in the ?nished body. I have produced
. cured on the open market free from impurities
excellent opal glasses by introducing ?uorine as
and at a cost substantially less than that of the
an alkali metal acid ?uoride, and the following
are examples of two of the batch compositions
other alkali-acid ?uorides.
.
The amount of ?uorineto be present in the glass
will, of course; depend upon the use to which the
glass is put. The compositions of ?uorine con
taining glasses vary considerably and the follow
ing tables will illustrate typical batches which 10
can be produced by the method of the present
invention:
used.
‘
'
'
"FLUORINE OPAL GLASSES '
TABLE I
Batch compositions
I
OPTICAL FLUOR-CROWN GLASSES
TABLE I
300
77.7
62.3
"
Batch compositions
I
S101 ___________________________ __
K1003
KN
__
1
________ ._
300
19.75
KHF,“
’
300
.
14. 2
NazCOa
.2_
A1(OH)z _ . _ _ _ _ _ _ _ _ _ .
..
_
._
.
7s. 4
0. ea‘-
0 5
.8
45.4
. ..
AS103 __________________________ __
...... ._
0. 5
TABILE II
Percentage compositions
_
-~ 45.6
179.6
.
.
20
______ __
43
NaNOa
NaHFz_
11303
43.9
75.8
III
300
.
18 9
300
21.0
16.8
150.0
40.8
64.6
II
300
___________________ _.
II
.
' 0. 51
o. 57
.
I
111
168.4
.158. 1
0. e9
_19.52
7.7
,
18.39
18.11
4.80 a. ,1 4.52
.
TABLE II
9.62
0.1
0.10
. Percentage compositions
It will be at once apparent that various mod;
i?cations of the nature of the several constituents
in a particular batch and the percentage com.
position thereof are possible without ‘departing
from the spirit of ‘the invention or'the‘scope‘ of t
the appended claims.
I'claim:
‘
‘
*
'
‘
‘
"
'
1
'
l. A glass batch containing thefollowin'g ma‘
terials in approximately the following parts-by
TABLE III '
Optical properties
i
Np?lv_________________ ._
1.4900,
V—N,_NG------------ --
“70:1.
40
4
""11
I
i
*
.55-9.
;..§"_~.?i._;-i..62r2
‘
~
‘
-
1
‘
S101! __________________ __'___;_'_____V_‘__._; ‘300
KzCOs
‘111’ "CIVIL
11.4622 "1.4774 "T155016
weight:
45
'_
‘
H____- 25.8
KNO3 _V__:_ __________ _'____.‘_;:__.;_'____' ____ __l"18.9
KHFz ______________ __'___; ______ _;___‘_'____ 168.4
H3303 ________ __'_____ _____ _l__‘____t___'_'____- 212.2
AS203
’
'
__‘_
'
'
'
0.63
> 2; A glass batchyifor a ?uorecrown'opticaliglass
Although the compositions set out in the above
a refractive index of about 1_.490':—1.501 and 1
tables havebeen limited’ to batch compositions 50' having
a reciprocal relative dispersionof about 62.2-70.1
producing optical glasses, the invention
not
comprising about the following vparts by ‘weight:
limited to such- ‘glasses; for in the broadest aspect
S102
300,.H3BO3 45-2412,>and KHFzH52-_168."
thereof, the same may be used toproduce'opal
glasses, enamels, glazes, and other-ceramic com
*WAL'rEmrFRAsEa,
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