U.S. patent application number 11/250712 was filed with the patent office on 2009-07-02 for method of making a water resistant silicate-based ceramic composite material.
This patent application is currently assigned to Hottec, Inc.. Invention is credited to Richard L. Weir.
Application Number | 20090165677 11/250712 |
Document ID | / |
Family ID | 40688670 |
Filed Date | 2009-07-02 |
United States Patent
Application |
20090165677 |
Kind Code |
A1 |
Weir; Richard L. |
July 2, 2009 |
METHOD OF MAKING A WATER RESISTANT SILICATE-BASED CERAMIC COMPOSITE
MATERIAL
Abstract
A method of creating a water resistant, silicate-based ceramic
composite article is disclosed. The method comprises depositing the
silicate-based ceramic composite article in a container; immersing
the silicate-based ceramic composite article in a solution
comprising water and a soluble chemical that reacts with high
alkali ions present in the silicate-based ceramic composite article
and reduces the pH of the silicate-based ceramic composite article;
soaking the silicate-based ceramic composite article in the
solution for a period of time; removing the silicate-based ceramic
composite article from the solution; and drying the silicate-based
ceramic composite article.
Inventors: |
Weir; Richard L.; (Baltic,
CT) |
Correspondence
Address: |
TOBIN, CARBERRY, O'MALLEY, RILEY, SELINGER, P.C.
43 BROAD STREET, PO BOX 58
NEW LONDON
CT
06320
US
|
Assignee: |
Hottec, Inc.
Norwich
CT
|
Family ID: |
40688670 |
Appl. No.: |
11/250712 |
Filed: |
October 14, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60619322 |
Oct 18, 2004 |
|
|
|
Current U.S.
Class: |
106/600 |
Current CPC
Class: |
C04B 2111/28 20130101;
C04B 28/26 20130101; C04B 28/18 20130101; C04B 2111/27 20130101;
C04B 2103/0067 20130101; C04B 28/26 20130101; C04B 14/386 20130101;
C04B 22/124 20130101; C04B 40/0089 20130101 |
Class at
Publication: |
106/600 |
International
Class: |
C04B 12/04 20060101
C04B012/04 |
Claims
1. (canceled)
2. The method of claim 13, wherein said soluble chemical is an
alkali metal chloride salt and has a concentration of more than
about 10 percent by weight in said aqueous solution.
3. (canceled)
4. The method of claim 13, wherein, during step (b), said soluble
chemical is selected from the group consisting of calcium chloride,
magnesium chloride, aluminum chloride, ferrous chloride, zinc
chloride, calcium carbonate, calcium nitrate, and combinations
thereof.
5. (canceled)
6. The method of claim 13 wherein said aqueous solution is at a
temperature of about 30.degree. F. to 220.degree. F. during step
(b).
7. The method of claim 13 wherein during step (b) the aqueous
solution is subjected to one or more cycles of pressure change,
wherein the pressure applied to the solution is either greater or
less than atmospheric pressure.
8. The method of claim 13, further comprising: while carrying out
step (b), putting one or more surfaces of said silicate-based
ceramic composite article in contact with a mass of undissolved
crystals of said water soluble chemical.
9. (canceled)
10. The method of claim 13 wherein the silicate-based ceramic
composite article is immersed in said aqueous solution during the
step (b).
11. The method of claim 13 wherein the silicate-based ceramic
composite article is rinsed in water after removing the article
from contact with said aqueous solution and before drying, as part
of step (c).
12. A water resistant and fire resistant silicate based ceramic
structural composite article created according to the method of
claim 13.
13. A method of creating a water resistant and fire resistant
ceramic structural composite article comprising the steps of: (a)
intermixing carbon fibers with an alkali metal silicate solution
and drying the mixture, to coat the fibers and interconnect the
fibers with an alkali metal silicate binder, thereby forming a
fire-resistant silicate-base ceramic composite article having a
particular shape and structural integrity, which article is soluble
in water; (b) contacting said fire-resistant silicate-base ceramic
composite article with an aqueous solution comprising a soluble
chemical which provides metal ions that replace the alkali metal
ions of said alkali metal silicate binder, wherein said soluble
chemical is selected from the group consisting of a strong anion
salt, a metallic salt with an acid radical, and combinations
thereof, using a time of contacting and temperature of solution and
a concentration of said soluble chemical in said solution that
effects the replacement of said alkali metal ions and maintains
said particular shape; (c) removing said article from contact with
said solution and drying the article; wherein said particular shape
and said structural integrity are substantially unchanged; and,
wherein the replacement of said ions in the binder makes the
fire-resistant silicate-base ceramic composite article into a water
resistant article.
14. A water resistant and fire resistant silicate based ceramic
structural composite article created according to the method of
claim 8.
15. The method of claim 13 further comprising: (d) contacting the
article after step (c) with an alkali metal silicate solution of
the same kind as used in step (a); and then, subjecting the article
to step (b) and step (c) again.
16. The method of claim 15 wherein one or more cycles of pressure
change relative to atmospheric pressure are applied to the solution
during step (d) and during each of the steps (b).
Description
PRIORITY CLAIM
[0001] This application claims priority to Provisional Patent
Application Ser. No. 60/619,322, entitled "Method of Making Water
Resistant Silicate Based Ceramic Composite" filed on Oct. 18, 2004,
the disclosure of which is incorporated herein by reference in its
entirety.
BACKGROUND
[0002] The present disclosure relates to composite articles, in
particular, a light weight, high strength composite article that is
both temperature and water resistant.
[0003] It has been determined that it would be cost effective to
utilize light weight, fire resistant composite articles in the
construction of military vehicles, such as aircraft, ships,
amphibious vehicles, and the like, as well as for structures. U.S.
Pat. No. 4,936,939 to Woolum discloses a graphite fabric reinforced
ceramic matrix composite material that has good mechanical and
thermal characteristics. The '939 patent discloses a composite
article that comprises alkali silicate with ceramic powder fillers
that are manufactured and dried. The dried silicate composite
article is placed in a treatment bath consisting of a soluble
multivalent cation salt where the resulting combination of cation,
cation salt, and pH result in an insoluble ceramic cation silicate
binder matrix composite article. These conventional composite
articles made of alkali silicates have passed dry strength and fire
resistance tests, but lose integrity when exposed to moisture or
water. The highly alkaline nature of the ions that remain in the
composite article after formation will dissolve the silicates when
exposed to moisture or water, resulting in the loss of integrity of
the composite article. Since these conventional composite articles
are not water resistant, they are not suitable for military
vehicles or for exterior uses.
[0004] What is needed in the art is a post-treatment process that
is simple, cost effective, and provides the necessary water
resistance to composite articles rendering the composite articles
light weight, high strength, resistant to high temperatures, able
to pass fire rating tests and water resistant.
SUMMARY
[0005] The disclosure is directed toward a method of creating a
water resistant, silicate-based ceramic composite article. The
method comprises depositing the silicate-based ceramic composite
article in a container; immersing the silicate-based ceramic
composite article in a solution comprising water and a soluble
chemical that reacts with high alkali ions in the silicate-based
ceramic composite article and reduces the pH of the silicate-based
ceramic composite article; soaking the silicate-based ceramic
composite article in the solution for a period of time; removing
the silicate-based ceramic composite article from the solution; and
drying the silicate-based ceramic composite article.
[0006] The disclosure is also directed towards a water resistant
silicate-based ceramic composite article created by the above
method.
DETAILED DESCRIPTION
[0007] Persons of ordinary skill in the art will realize that the
following disclosure is illustrative only and not in any way
limiting. Other embodiments of the invention will readily suggest
themselves to such skilled persons having the benefit of this
disclosure.
[0008] The present invention is a method for the creation of a
water resistant, fire resistant, light weight composite material
that can be used for the production of articles and structures. The
conventional composite articles made of alkali silicates lose
integrity when exposed to moisture or water. The highly alkaline
nature of the ions that remain in the composite article after
formation will dissolve the silicates when exposed to moisture or
water, resulting in the loss of integrity of the composite article.
The present invention is a method of treating conventional
composite articles made of alkali silicates to become water
resistant.
[0009] The method includes depositing a conventional high alkaline
silicate-based composite article in a treatment bath comprising
water and any soluble chemical that reacts with the high alkali
silicate ion of the composite article to reduce the pH of the
composite article. One example is a strong anion salt. The
available cations associated with the anion salt would react with
the high alkaline silicate ions and perform an ion exchange. The
high alkaline silicate ions would combine with the strong anions
and form a stable salt. In another example, the soluble chemical
can be a metallic salt with an acid radical, which would form an
insoluble silicate compound after the reaction. This binding of the
high alkaline silicate ions stops the high alkaline silicate ions
from creating the alkali condition that causes the composite
article to break down when exposed to moisture or water. The
resulting composite article becomes water resistant.
[0010] The ion exchange (or reaction) occurs in a manner that
allows the composite article to retain its shape during the process
of conversion to water resistance. The method can be utilized in
various environmental conditions, including normal room
temperature, which would permit the convenient treatment of large
structures in simple tanks. The resulting composite article, having
been treated by the solution (or cation silicate bonding matrix),
is light weight, high strength, resistant to high temperatures,
able to pass fire rating tests, and, most importantly, water
resistant.
[0011] The method of making a composite article is known in the
art. The composite article can be made by any number of
conventional methods of fiber reinforced technology using a high
alkaline silicate solution as a binder matrix for the composite
article. Generally, a sodium silicate solution or potassium
silicate solution acts as the binder matrix. This high alkaline
binder solution is normally mixed with ceramic powders, such as
aluminum oxide or silica powders, to act as further reinforcing
elements. For the present invention, the preferred composite
article to be treated can be comprised of any combination of fibers
and powders that use the high alkali silicate solution as a binder
matrix.
[0012] In order to create a water resistant composite article, the
composite article is treated according to the following method. A
composite article, created using a high alkaline silicate solution
as a binder matrix, is immersed in a container having a solution.
The solution comprises water and any soluble chemical that reacts
with the high alkali silicate ions of the composite article to
reduce the pH of the composite article. An example is a soluble
salt. When the soluble salt dissolves in the water, it breaks into
its ions (i.e., cations and anions). The soluble salt can be any
soluble salt that when reacted with an alkali silicate of the
silicate-based ceramic composite article results in a near neutral
pH. The soluble chemical can be any chemical that causes the ion
exchange, such as calcium chloride, magnesium chloride, aluminum
chloride, ferrous chloride, zinc chloride, calcium carbonate,
calcium nitrate, and the like, and combinations thereof.
[0013] Once immersed, the composite article undergoes a chemical
reaction (or ion exchange) in which the high alkaline silicate ions
in the composite article (i.e., from the high alkaline silicate
binder utilized in the creation of the composite article) binds
with the heavier and less alkaline ions of the solution to create a
stable salt (or insoluble silicate compound) that remains in the
solution (or on the exterior of the composite article, which is
easily removed with water). That is, the high alkaline cations in
the composite article bind with the silicates in the composite
article to create a cation silicate within the composite article.
The resulting composite article is a water resistant composite
article that retains its solid form, dimensions and integrity after
being treated with the method of the present invention.
[0014] The actual stoichiometry chemical reactions are not
presented because of the many combinations of the silicate
structures and crystals that can be utilized. However, an example
of the ion exchange process is demonstrated below using calcium
chloride:
Sodium Silicate+Calcium Chloride=Calcium Silicate+Sodium
Chloride
[0015] This reaction of sodium silicate and calcium chloride
produces an insoluble calcium silicate and the stable salt of
sodium chloride.
[0016] The method of the present invention can be performed under a
variety of environmental conditions. The soaking of the composite
article can be completed when applying a vacuum to the environment
in order to speed up the soaking process by eliminating any
entrapped air that might block penetration of the treatment
chemical. The amount of vacuum applied can be about 0 inches of
mercury to about 30 inches of mercury. A cycling of applying vacuum
followed by releasing to atmospheric conditions can also be
utilized. Likewise, varying or cycling the pressure of the
environment can facilitate the process. The pressure applied can
vary from about 0 pounds per square inch (psi) to about 100
atmospheres. It is contemplated that a dual environment which
varies the applied vacuum and pressure can also facilitate the
reaction.
[0017] In order to be cost effective, the ideal temperature for
treatment of the composite article is having the solution at room
temperature. However, the temperature of the solution can be varied
to facilitate the reaction, with a temperature range of about
30.degree. F. to about 220.degree. F. contemplated. Likewise, the
time of treatment can be from about 30 minutes to about 500 hours,
with about 24 hours to about 48 hours preferred. The temperature
and time utilized is dependent upon the thickness of the composite
art and can be determined easily by one skilled in the art.
[0018] Other cost effective and time saving measures include
varying the concentrations of the soluble salt in the solution to
be from about 5% by weight to about 100% by weight. The composite
article can also be deposited in a solution containing crystals, be
covered with crystals, or be encapsulated by crystals of the
soluble chemical. Additionally, surfactants or wetting agents can
be added to the solution in order to improve, enhance and
facilitate the ion exchange or reaction.
[0019] The size and thickness of the composite article can vary
depending upon the desired resulting product. One skilled in the
art can easily determine the concentration of the solution,
duration of processing, environmental conditions, etc., in order to
achieve a water resistant composite article.
[0020] The following examples are illustrative of the present
invention, and should not limit the scope of the present invention.
Each example described herein was performed on flat rectangular
composite articles formed by sodium silicate, aluminum oxide powder
and carbon fibers. The composite article was between about 0.100
inches thick and about 0.375 inches thick. Each composite article
was produced by hand lay-up and autoclave techniques, and dried
until there was no further weight loss by drying.
Example 1
[0021] A composite article of about 6 inches wide by about 6 inches
in length and about 1/8 inch thick was placed in a container having
a solution of 20% by weight calcium chloride and allowed to stand
at room temperature conditions for 24 hours. A control sample of
the same composite article was placed in pure water next to the
composite article being treated. After 24 hours, the treated
composite article appeared to be unchanged and the control sample
had disintegrated and delaminated (i.e., the carbon fiber cloth was
separated). The treated composite article was subsequently rinsed
in water and dried. The treated composite article was dried at
170.degree. F. for 4 hours and then the temperature was raised to
250.degree. F. for an additional 4 hours. The dried treated
composite article retained its strength and appeared unchanged by
the treatment process. The dried treated composite article was
placed in plain water for 24 hours. When removed, it had absorbed
little water and was mechanically strong and appeared unchanged.
The treated composite article was placed in another container of
water for a period of 1 month and was checked periodically. There
appeared to be a slight softening at the corners of the treated
composite article, and yet it remained unchanged.
Example 2
[0022] Several strips, about 1 inch wide by about 6 inches in
length, were produced from a sodium silicate bonded carbon fiber
composite article. The strips of the composite article were placed
in several different pint containers containing a calcium chloride
treatment solution (i.e., one strip per container). Each container
had a different concentration by weight of calcium chloride. The
concentrations were 0%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%,
90%, and 100% with crystals that had not dissolved. The treated
strips of composite articles were placed in the solutions for a
period of 24 hours. The results indicate that the strip of
composite article that was placed in the 0% (or pure water)
solution container completely dissolved. The strip of composite
article placed in the container having the 5% solution was not
disintegrated, but was softened. Each of the remaining strips of
composite article exhibited good strength after treatment. It was
concluded that the concentration of 5% solution did not have
sufficient calcium and chloride ions to cause the appropriate
reaction. The example illustrates that treatment of a composite
article is successful over a large range of concentrations, as long
as there is a sufficient mass and concentrations of soluble
chemical.
Example 3
[0023] Several strips, about 1 inch wide by about 6 inches in
length by 1/8 inch thick were produced from a sodium silicate
bonded carbon fiber composite article. The strips of composite
article were placed in pint containers containing a 50% percent (by
weight) solution of a single salt (i.e., one strip per container).
The salts utilized included: calcium chloride, zinc chloride,
magnesium chloride, iron chloride, calcium chloride, calcium
carbonate and calcium nitrate. The strips of composite article were
immersed in the solutions for 24 hours, removed from the
containers, rinsed, and dried. The strips of composite article were
then placed in water for 24 hours at room temperature, removed, and
examined. All strips of composite article appeared to have retained
their integrity, resisting weakening by water, and therefore, were
water resistant.
Example 4
[0024] A dish about 8 inches wide by about 8 inches in length by
about 2 inches deep was filled to a depth of about 3/8 inch with
commercial grade calcium chloride crystals. A sodium silicate
bonded carbon fiber composite article, of about 6 inches wide by
about 6 inches in length and about 1/8 inch thick, was placed
directly on the crystals in the dish. A layer of the calcium
chloride crystals, about 3/8 inch thick, was placed over the
composite article. A 50% solution of calcium chloride and water was
slowly added to cover the composite article and the layers of
crystals (without disturbing them). The dish was covered and placed
in a 170.degree. F. oven for 24 hours. The dish was removed from
the oven and allowed to cool where upon the mass hardened
encapsulating the treated composite article. The mass was removed
from the dish and placed in a bucket of warm water to dissolve the
mass. Eventually, the crystal mass was removed from around the
treated composite article. The treated composite article was rinsed
in water and then dried. The treated composite article appeared
unchanged from its pretreatment condition. The treated composite
article was weighed and had a dried weight greater then the
untreated sample, indicating that the treated composite article had
undergone a chemical change. It is important to note that any
adsorbed moisture would be a large percentage of the weight and
changes in the weight may mask any real changes in the weight of
the treated composite article from the ion exchange. The treated
composite article was then placed in a 5 gallon pail of water for 1
month and examined periodically. The treated composite article did
not appear to change shape over that period or show any softening,
even at the corners.
Example 5
[0025] A treated composite article was prepared as in Example 4.
The treated composite article was then dried and subjected to a
propane torch flame for 30 minutes (having a measurement of about
1900.degree. F. by pyrometer). There was some loss of the surface
material covering the carbon fiber weave and the weave has a bright
orange glow. The side opposite to the flame had a dull orange glow
but there was no penetration of the flame through the composite
sample. There was virtually no smoke or fumes generated. The
treated composite article proved to be an adequate fire
barrier.
Example 6
[0026] A sodium silicate bonded carbon fiber composite article of
about 26 inches wide by about 26 inches length and about 3/8 inch
thick was produced. A frame was created having measurements of
about 30 inches wide by about 30 inches in length by about 2 inches
deep. A plastic sheet was placed in the frame to act as a
waterproof liner. About 1/2 inch thick layer of calcium chloride
crystals was deposited within the frame on the plastic sheet. The
composite article was laid on to the layer of crystals and an
additional layer of calcium chloride crystals was placed on top of
the composite article to a thickness of about 1/2 inch to create a
crystal bed. A prepared 50% solution of water and calcium chloride
was produced and gently poured into the frame, without disturbing
the crystal bed. The composite article was treated for a period of
64 hours at room temperature. The treated composite article was
removed, rinsed in water, and then soaked in water. The treated
composite article showed no signs of softening. Subsequently, the
treated composite article was cut up into samples and the edges
were examined. The samples were soaked in tap water. The results
indicate that the samples resisted water. Additionally, a sample
cut from the treated composite article was subjected to the fire
test as in Example 5. The treated composite article sample proved
to be an adequate fire barrier.
Example 7
[0027] A treated composite article was prepared as in Example 4.
The treated composite article was then placed in a device to apply
a hydro-test. The hydro-test comprises placing the treated
composite article in a frame in which water is exposed to only one
side of the treated composite article at various pressures. The
hydro-test was completed in order to show that the treated
composite article could hold back water at a pressure of 15 psi for
a period of 30 minutes. The treated composite article remained
structurally sound over the duration of the test, as well as an
additional 30 minutes. A small amount of water appeared to drip
through two specific spots in the treated composite article. This
small amount of water was attributed to small voids in the treated
composite article. However, during the test, the water seepage did
not appear to increase. The results indicate that the treated
composite article passed the hydro-test and was water
resistant.
Example 8
[0028] A thicker sodium silicate bonded carbon fiber composite
article of about 6 inches wide by about 6 inches in length and
about 1/4 inch thick was carefully prepared to minimize voids. The
composite article was treated as in Example 4 for a period of 72
hours. The hydro-test, as described in Example 7, was completed on
the treated composite article. The results indicate that the
treated composite article had no seepage, passed the hydro-test,
and was water resistant.
Example 9
[0029] A potassium silicate bonded carbon fiber composite article
of about 6 inches wide by about 6 inches in length and about 1/8
inch thick was produced. The composite article was treated as in
Example 4 for 48 hours. The treated composite article was placed in
water for 1 month and checked periodically. The treated composite
article showed the same water resistance as the treated composite
article in Example 4.
Example 10
[0030] A composite article was prepared as in Example 4. The
treatment tray was placed in a vacuum chamber and vacuum was
applied to about 28.5 inches of mercury and then released to
atmosphere. This was repeated 6 times. When observed, there were
small traces of bubbles indicating that there were small voids in
the composite article. The treatment was allowed to stand at room
temperature for 48 hours. The treated composite article was rinsed
in water and then dried. The treated composite article was then
placed in a tray of sodium silicate solution and the
vacuum-to-atmosphere cycle was repeated 6 times. The treated
composite article was then dried slowly at rising temperatures up
to about 300.degree. F. The treated composite article was then
treated a second time in a solution of 50% calcium chloride with
the vacuum-to-atmosphere cycle for 6 times. The treated composite
article remained in the solution for 24 hours. The treated
composite article was then dried and placed in a vacuum chamber.
During the applied vacuum, virtually no bubbles were observed in
the treated composite article. It was determined that multiple
treatments can seal voids and can create a denser article.
[0031] The present invention is a method for the creation of a
water resistant, fire resistant, light weight composite material
that can be used for the production of articles, vehicles and
structures. The present invention is also an article created
according to this method. Water resistant composite articles are
needed in order to make articles that are light weight, high
strength, resistant to high temperatures, and able to pass fire
rating tests for use in all military vehicles and exterior
structures.
[0032] There are several benefits to using this method and the
articles produced from this method. The composite article retains
its shape during the process of conversion to water resistance. The
method can be utilized in various environmental conditions,
including normal room temperature, which would permit the
convenient treatment of large structures in simple tanks. The
method is cost effective by not requiring expensive treatment
facilities or dangerous and environmentally hazardous chemicals and
materials. The method can be completed by applying a vacuum to the
composite article or by pressure chamber immersion. The resultant
composite article, having been treated by the cation silicate
bonding matrix, is light weight, high strength, resistant to high
temperatures, able to pass fire rating tests, and, most
importantly, water resistant.
[0033] While the invention has been described with reference to an
exemplary embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings without
departing from the essential scope thereof. Therefore, it is
intended that the invention not be limited to the particular
embodiment disclosed as the best mode contemplated for carrying out
this invention.
[0034] What is claimed is:
* * * * *