Metal-silica sol-gel materials

Details Metal-silica sol-gel materials Metal-silica sol-gel materials

1994-04-12

2002-05-21

Hendrickson, Stuart L. (Department: 1754)

Compositions: ceramic

Ceramic compositions

Glass compositions, compositions containing glass other than...

C423S326000, C502S239000

Reexamination Certificate

active

06391808

ABSTRACT:

TECHNICAL FIELD
The present invention generally relates to sol-gel glasses containing a relatively low concentration of metal centers, which glass has unique sensor and catalytic properties.
BACKGROUND ART
The application of the sol-gel process to the synthesis of dense oxide glasses and ceramics has been the subject of escalating interest because of the low fabrication temperatures and compositional flexibility provided by these materials. The sol-gel process utilizes the condensation reactions of silicon and/or metal alkoxides to provide a low temperature, synthetically flexible route to optical quality glasses.
The overall reaction for the synthesis of a silica sol-gel glass is:
Si(OR
1
)
4
+2H
2
O→SiO
2
+4R
1
OH;
wherein tetramethylorthosilicate (TMOS) and tetraethylorthosilicate (TEOS) are the most common silicon alkoxides used. The ultimate production of a glassy material by this route, however, is accomplished in four primary stages: gelation, aging, drying/stabilization, and densification. The general process for forming sol-gels is taught in C. J. Brinker and G. Scherer,
Sol-Gel Science: The Physics and Chemistry of Sol-Gel Processing
(Academic Press, Boston, 1990) which is incorporated herein by reference.
The gelation step is composed of a series of condensation reactions in which silicon alkoxide condenses in the presence of water to form a Si—O—Si bonded network and alcohol by-products. The “gel” that forms from the condensation reactions is soft and contains incompletely reacted material (remaining SiOH and SiOR
1
functional groups), trapped organics (R
1
OH) and water. Aging of this gel (~3 months) results in further condensation to form Si—O—Si linkages (which is accompanied by a large amount of shrinkage) and the evaporation of water and R
1
OH. The aged gels are dried (~100° C.) and stabilized (~500° C.) to remove any remaining organic material and to complete the condensation process.
The material remaining after stabilization, known as “xerogel,” has the properties of a hard, transparent glass, not unlike conventional fused silica glass. However, unlike fused silica glass, xerogel is porous with surface areas on the order of 200 m
2
/g. This pore structure can ultimately be closed at temperatures above 1000° C. to yield a glass that is indistinguishable from fused silica glass.
The undensified silica xerogel material is unique because of its porous nature. Silica xerogels, acting as a host matrix, can be used to entrap and stabilize reactive chemical species while at the same time permitting small molecules to diffuse into the silica matrix and react. This imparts the reactivity of a particular functional group to an otherwise inert matrix.
Many of the materials made previously by the co-condensation of transition metals and silicon alkoxides have utilized relatively high metal concentrations and are often sintered into dense glasses. TiO
2
/silica sol-gels have been described extensively because of their importance as low thermal expansion glasses. Similarly, a good deal of work has also been reported on ZrO
2
silicas. Recently, the properties of several SiO
2
/V
2
O
5
materials have also been reported, including the bulk properties of densified glasses. A. Ghosh, et al.,
Appl. Phys. Lett.,
59:855 (1991); N. Tohge, et al.,
J. Non-Cryst. Solids,
63:95 (1984).
Baiker, et al. have described the selective catalytic reduction of nitric oxide with stabilized SiO
2
/V
2
O
5
xerogels that showed the highest catalytic activities at V
5+
concentrations between 1 and 10%. A. Baiker, et al.,
J. Catal.,
111:273 (1988).
The present invention relates to silica sol-gel compositions comprising relatively low concentrations of transition metals and uses thereof.
SUMMARY OF THE INVENTION
The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses.
The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor.
The present invention also relates to thermal and photochemical oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses.
The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.


REFERENCES:
patent: 4795687 (1989-01-01), Suzuki et al.
patent: 4851373 (1989-07-01), Hench et al.
patent: 5286890 (1994-02-01), Dougherty
A. Ghosh, et al.,Appl. Phys. Lett. 59(7):855-856 (1991) Aug.
N. Tohge, et al.,J. Non-Cryst. Solids 63:95-103 (1984) (No Month).
A. Baiker, et al.,J. Catal. 111:273-285 (1988) (No Month).
A.E. Stiegman, et al.,Chemistry of Materials 5(11):1591-1594 (1993) Nov.
V.S. Nagarajan, et al., “Crystallization studies of ZrO2-SiO2composite gels,”J. Materials Sci. 24:2140-2146 (1989) (No Month).
N. Nogami, et al., “ZrO2-Transformation-Toughened Glass-Ceramics Prepared by the Sol-Gel Process from Metal Alkoxides,”J. Am. Ceram. Soc. 69:99-102 (1986) (No Month).
I.M.M. Salvado, et al., “ZrO2-SiO2Materials Prepared by Sol-Gel.”J. Non-Cryst. Solids 100:330-338 (1988).
K. Kamiya, et al., “Preparation of glass fibres of the ZrO2-SiO2and Na2O-ZrO2systems from metal alkoxides and their resistance to alkaline solution,”J. Materials Sci. 15:1765-1771 (1980) (No Month).
M. Nogami, “Glass Preparation of the ZrO2-SiO2Systems by the Sol-Gel Process from Metal Alkoxides,”J. Non-Cryst. Solids 69:415-423 (1985) (No Month).
T. Gunji, et al., “Preparation of SiO2-TiO2Fibers From Polytitanosiloxanes,”J. Non-Cryst. Solids 107:149-154 (1989) (No Month).
K-L Walther, et al., “Characterization of Vanadia/Silica Mixed Gel Catalysts by Electron Paramagnetic Resonance Spectroscopy at 110 K,”J. Chem. Soc. Faraday Trans. 87(8):1217-1220 (1991) (No Month).
“Characterization of Vanadia/Silica Mixed Gel Catalysts by Vibrational Spectroscopy,”J. Catal. 116:595-599 (1989) (No Month).
K.S. Lee, “Third-Order Optical Nonlinearity of Poly(thienylene Vinylene) /Silica Sol-Gel Composite”,Synthetic Metals, 55-57 (1993) pp. 3992-3997 No Month.
M. Toki, et al., “Structure of poly(vinylpyrrolidone)-silica hybrid”,Polymer Bulletin 29, (1992), pp. 653-660 No Month.
C. J. Wung, et al., “Poly(p-phenylene vinylene)-silica composite: a novel sol-gel processed non-linear optical material for optical waveguides”,Polymer, 1991, vol. 32, No. 4, pp. 605-608 No Month.
E.J.A. Pope, et al., “Transparent silica gel-PMMA composite”,J. Mater.Res. vol. 4, No. 4, Jul./Aug. 1989, pp. 1018-1026.
V. Mehrotra, et al., “Electrically conducting glasses: incorporation of polypyrrole in a porous SiO2matrix”,Journal of Non-Crystalline Solids 136(1991), pp. 97-102 No Month.
B.R. Mattes, et al., “Polyaniline Sol-Gels and Their Third-Order Nonlinear Optical Effects”,Synthetic Metals, 41-43 (1991), pp. 3183-3187 No Month.

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