U.S. patent application number 09/784968 was filed with the patent office on 2002-03-07 for fabrication method of graded index silica glass.
This patent application is currently assigned to SAMSUNG ELECTRONIC CO., LTD.. Invention is credited to Park, Keun-Deok.
Application Number | 20020026809 09/784968 |
Document ID | / |
Family ID | 19687390 |
Filed Date | 2002-03-07 |
United States Patent
Application |
20020026809 |
Kind Code |
A1 |
Park, Keun-Deok |
March 7, 2002 |
Fabrication method of graded index silica glass
Abstract
A fabrication method of graded index silica glass is disclosed.
The method according to the present invention includes the steps of
dispersing to form sol by mixing a starting material with a
dispersion medium; molding the sol into a moisturized gel with a
predetermined shape using a molding frame and separating the
moisturized gel from the molding frame; drying the moisturized gel
under a predetermined temperature and humidity level to remove the
dispersion medium and to form a first dry gel having a
predetermined moisture content distribution, hydrolyzing the
moisture remained in the first dry gel and an additive solution by
putting the first dry gel into the additive solution; re-drying the
first dry gel, which underwent said hydrolysis, to form a second
dry gel; and, thermal processing the second dry gel by supplying
reaction gas thereto, removing impurities therefrom and annealing
for isolation.
Inventors: |
Park, Keun-Deok;
(Busan-kwangyeok-shi, KR) |
Correspondence
Address: |
KLAUBER & JACKSON
411 HACKENSACK AVENUE
HACKENSACK
NJ
07601
|
Assignee: |
SAMSUNG ELECTRONIC CO.,
LTD.
|
Family ID: |
19687390 |
Appl. No.: |
09/784968 |
Filed: |
February 16, 2001 |
Current U.S.
Class: |
65/17.2 ;
65/66 |
Current CPC
Class: |
C03B 2203/26 20130101;
C03B 19/12 20130101; C03B 2201/31 20130101 |
Class at
Publication: |
65/17.2 ;
65/66 |
International
Class: |
C03B 008/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 5, 2000 |
KR |
2000-52345 |
Claims
What is claimed is:
1. A method of fabricating graded index silica glass, comprising
the steps of: (a) preparing a sol by mixing a starting material
with a dispersion medium; (b) molding said sol to a predetermined
shape using a molding frame to obtain a wet gel and separating said
wet gel from said molding frame; (c) drying said wet gel under a
predetermined temperature and humidity to obtain a first dry gel
having a predetermined moisture-content distribution; (d)
hydrolyzing the moisture remained in said first dry gel by adding
an additive solution to said first dry gel; (e) re-drying said
first dry gel that is hydrolyzed to obtain a second dry gel; and,
(f) thermal processing said second dry gel by exposing reaction gas
for removing impurities from said second dry gel and annealing said
thermal processed dry gel for isolation.
2. The method of claim 1, wherein said starting material in said
dispersion step is fumed silica or silicon alkoxide.
3. The method of claim 1, wherein said dispersion medium in said
dispersing step is de-ionized water or alcohol.
4. The method of claim 1, wherein said additive solution in said
hydrolyzing step is an alkoxide compound stabilized by a
hydrolysis.
5. The method of claim 4, wherein said additive solution is
GeCl.sub.4.
6. The method of claim 4, wherein said additive solution is
germanium ethoxide.
7. The method of claim 1, wherein said moisture content
distribution in said drying step changes radically with the highest
moisture content along the axis of said first dry gel and the
lowest index being along the outer periphery.
Description
CLAIM OF PRIORITY
[0001] This application makes reference to and claims all benefits
accruing under 35 U.S.C. Section 119 from an application- for
FABRICATION METHOD OF GRADED INDEX SILICA GLASS filed earlier in
the Korean Industrial Property Office on Sep. 15, 2000 and there
duly assigned Ser. No. 52345/2000.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to a silica glass,
and more particularly to a fabrication method of silica glass by a
sol-gel process.
[0004] 2. Description of the Related Art
[0005] Optical fibers are made to exacting dimension and
compositional requirements. Normally, fiber manufacturing starts
with a preform, which is a large cylinder of glass with the same
composition as the final fiber, but at a much larger diameter.
Different methods are used to make the preform. One of the methods
includes Modified Chemical Vapor Deposition (MCVD), where
high-performance single-mode fiber is made. The conventional
optical transferring media such as lens or optical fiber with a
convex graded index are fabricated through the MCVD process. The
mechanisms of the MCVD process is disclosed on pages 138-147 of
J.Colloid Interface Sci. 69, which is a thesis authored by Walker;
K. L., Homsy, G. M. and Geyling, F. T. in the U.S. in 1979. This
publication discloses a process of fabricating a silica glass by
supplying and depositing raw material gas inside of a depositing
tube, to which heat treatment is applied from outside.
[0006] In particular, the heat treatment using a burner which is
supplied from outside forms a temperature field inside the
depositing tube. If a critical temperature is formed inside the
depositing tube through the heating via the burner, a rapid
oxidization reaction occurs, thereby generating glass particles.
The generated glass particles form a particle orbit due to the
thermophoretic force generated by the temperature field. The glass
particles move toward inside the depositing tube as the temperature
of inner wall of the depositing tube is higher than the temperature
of the gas. Therefore, some of the glass particles are evaporated
on the inner surface of the depositing tube.
[0007] Gradient-index glass is often made in the form of solid
cylindrical bodies, where the index of such bodies changes
radially, usually with the highest index being along the axis of
the cylinder and the lowest index located at the outer periphery.
When fabricating such a silica glass using the MCDV method
described above, it is sometimes difficult to properly control the
amount of raw material gas supplied to the depositing tube in the
course of deposition process to form the gradient-index profile
inside of the silica glass. In addition, it requires a very long
fabrication time during the deposition, and the cost of
manufacturing is high.
SUMMARY OF THE INVENTION
[0008] It is, therefore, an object of the present invention to
provide a method of fabricating gradient-index silica glass with a
simpler fabricating process and lower fabricating cost than the
modified chemical vapor-phase deposition (MCVD) process known in
the prior art system.
[0009] Accordingly, there is provided a fabrication method of
graded index silica glass, comprising the steps of: dispersing by
mixing a starting material with a dispersion medium to form sol;
molding by putting the sol within a molding frame to form
moisturized gel and separating the moisturized gel from the molding
frame; drying the moisturized gel under pre-set temperature and
humidity and removing the dispersion medium inside of the
moisturized gel to form a first dry gel having a pre-set moisture
containing dispersion; hydrolyzing to induce hydrolysis between the
remaining moisture inside of the first dry gel and an additive
solution by putting the first dried gel into the additive solution;
re-drying to form a second dry gel by re-drying the first dry gel,
which underwent the hydrolysis; and, heating by supplying a
reaction gas to the second dry gel, removing impure materials
therefrom, and annealing the resultant material for
vitrification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The above and other objects, features, and advantages of the
present invention will become more apparent from the following
detailed description when taken in conjunction with the
accompanying drawing, in which:
[0011] FIG. 1 is a flow chart showing a fabrication method of
graded index silica glass using a sol-gel process according to a
preferred of the present invention;
[0012] FIG. 2 is a graph illustrating the moisture content of a gel
during drying stage a preferred of the present invention;
[0013] FIG. 3 is a graphical representation of a hydrolysis process
according to a preferred of the present invention; and,
[0014] FIG. 4 is a graphical representation of all phases according
to a preferred of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] A preferred example of the present invention will be
described herein below with reference to the accompanying drawing.
For the purpose of clarity, well-known functions or constructions
are not described in detail as they would obscure the invention in
unnecessary detail.
[0016] FIG. 1 is a flow chart showing the method for fabricating a
gradient-index silica glass by a sol-gel process according to the
preferred embodiment of the present invention. Referring to FIG. 1,
the fabrication method of gradient-index silica glass using the
sol-gel process comprises the following steps: dispersing step
(100), molding step (200), drying step (300), hydrolyzing step
(400), re-drying step (500), and thermal processing step (600).
[0017] 1. Dispersing Step 100
[0018] According to the embodiment of the present invention, the
dispersing step 100 involves forming a sol by mixing a starting
material, preferably under agitation, with a dispersion medium in a
controlled manner, so that the starting material can be uniformly
dispersed into the dispersion medium. In this step, the dispersion
agent may be added to enhance the dispersion process. Preferably,
fuming silica or silicon alkoxide is used as the starting material,
and de-ionized water or alcohols is used as the dispersion medium.
Any well known dispersion agent in this art may be added to the
mixture of the starting material and the dispersion medium.
[0019] 2. Molding Step 200
[0020] According to the embodiment of the present invention, the
molding step 200 is directed to molding the sol into a moisturized
gel in a predetermined shape for sufficient time in order to form a
gel, then separating the moisturized gel from the molding frame.
Here, a binding agent and a gelation promoter may be added to the
sol in this molding step 200 for the purpose of binding the sol
particles.
[0021] 3. Drying Step 300
[0022] According to the embodiment of the present invention, the
drying step 300 includes drying the moisturized gel under a
prescribed temperature and humidity conditions, and removing the
dried gel so as to form a first dry gel with a prescribed moisture
content. The temperature and humidity conditions in the step 300
are determined by considering the components of the moisturized
gel, properties of the silica glass to be obtained as a final
product, etc. Depending on the example, the moisture content
distribution may exhibit a parabolic shape with respect to the
distance from the axis of the dry gel. Referring to FIG. 2, the
moisture content is reduced in reverse proportion to the distance
from the center of the first dry gel.
[0023] 4. Hydrolyzing Step 400
[0024] According to the embodiment of the present invention, the
hydrolyzing step 400 involves inducing a hydrolysis of the moisture
remained in the first dry gel and the additive solution, by putting
the first dry gel into the additive solution (i.e., GeCl.sub.4
containing Ge or germanium ethoxide). To be specific, the
hydrolyzing step 400 includes a step of forming an additive content
distribution, which is identical to the moisture content
distribution within the first dry gel, by using the reaction of the
additive solution with the moisture within the first dry gel.
[0025] An alkoxide and GeCl.sub.4 compounds have an OH sequence at
the end by the hydrolysis process, thus the OH sequence is
hydric-combined with an OH sequence of a gel particle. Here,
GeCl.sub.4 containing Ge or germanium ethoxide may be used as an
additive solution. Thus, putting the first dry gel into the
GeCl.sub.4 results in a hydrolyzing reaction between the moisture
within the first dry gel and the GeCl.sub.4.
[0026] The content distribution within the first dry gel after
undergoing the above hydrolyzing step is the same as that within
the first dry gel. Referring to FIG. 3, if the moisture content
distribution within the first dry gel makes a parabolic shape, the
Ge content distribution within the first dry gel also makes the
same parabolic shape. At this time, the additive with liquidity
loses the liquidity after undergoing the hydrolysis and has a
stable distribution by being bound with silica matrix particles.
That is, the hydrolyzed material is hydric-combined with an OH
sequence of silica matrix. Here, the temperature may be increased
to be less than 100 Cfor the purpose of accelerating the
hydrolyzing reaction.
[0027] 5. Re-drying Step 500
[0028] According to the embodiment of the present invention, the
re-drying step 500 is a step of forming a second dry gel by
re-drying the first dry gel after undergoing the hydrolyzing step,
as described in the preceding paragraphs, so as to remove the
moisture remained in the first dry gel.
[0029] 6. Thermal Processing Step 600
[0030] According to the embodiment of the present invention, the
thermal processing step 600 involves isolating the second dry gel
by supplying reaction gas to remove impurities and for annealing.
In particular, the thermal processing step 600 comprises the steps
of: low thermal processing to decompose the organic matter within
the second dry gel and remove the metallic impurities and OH
sequence, etc. within the gel, by heating the gel under the
atmosphere of Cl gas; and annealing the second dry gel that
underwent the low thermal application inside an annealing furnace
under the atmosphere of He gas for isolation.
[0031] Referring to FIG. 4, the present invention provides a novel
way in fabricating a graded-index silica glass through a sol-gel
type process. As shown in FIG. 4, the formation of graded-index
silica glass is achieved basically by preparing a gel; drying the
moisturized gel under pre-set temperature and humidity; hydrolyzing
to induce hydrolysis between the remaining moisture inside of the
dry gel and an additive solution.
[0032] As described above, the fabrication method of graded-index
silica glass according to the present invention has advantages in
that a simpler and shorter fabricating process that is more
economical than the conventional MCVD process is achieved.
* * * * *