CA2124682A1 - Sol-gel process for providing a tailored gel microstructure - Google Patents
Sol-gel process for providing a tailored gel microstructureInfo
- Publication number
- CA2124682A1 CA2124682A1 CA002124682A CA2124682A CA2124682A1 CA 2124682 A1 CA2124682 A1 CA 2124682A1 CA 002124682 A CA002124682 A CA 002124682A CA 2124682 A CA2124682 A CA 2124682A CA 2124682 A1 CA2124682 A1 CA 2124682A1
- Authority
- CA
- Canada
- Prior art keywords
- selecting
- moles
- gel
- ethanol
- mole
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B19/00—Other methods of shaping glass
- C03B19/12—Other methods of shaping glass by liquid-phase reaction processes
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
- C01B33/157—After-treatment of gels
- C01B33/158—Purification; Drying; Dehydrating
- C01B33/1585—Dehydration into aerogels
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C1/00—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels
- C03C1/006—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels to produce glass through wet route
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/04—Glass compositions containing silica
- C03C3/06—Glass compositions containing silica with more than 90% silica by weight, e.g. quartz
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C2201/00—Glass compositions
- C03C2201/02—Pure silica glass, e.g. pure fused quartz
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C2203/00—Production processes
- C03C2203/20—Wet processes, e.g. sol-gel process
- C03C2203/26—Wet processes, e.g. sol-gel process using alkoxides
Abstract
An improved sol-gel process for fabricating large, crack-free gel monoliths (e.g., of silica) is described in which a specially-tailored gel microstructure is provided by adjusting the relative concentrations of an alcohol diluent (e.g., ethanol) and/or one or more catalysts (e.g., HC1 and HF). Controlled variations in the gel's average pore radius, bulk density, rupture modulus, and elastic modulus over a wide range can be tailored in this fashion.
This enables the process to be optimized for the particular application involved.
This enables the process to be optimized for the particular application involved.
Description
WOg3/13024 212 4 6 8 2 PCT~US92tlO695 ;-SOL-GEL PROCESS FOR PROVIDING A
TAILORED GEL MICROSTRUCTURE
BACKGROUND OF THE INVENTION
This invention relates genPrally to sol-gel pro~esses for producing monolithic articles of glass and, more particularly, to processes of t~is kind that are adapted to eliminate cracking of the gel during a final drying step.
High purity glass components typically are fabricated either by melting solid raw materials or by vapor deposition. Melting solid raw materials is a generally e~fective ~echnique, but difficul~y is sometimes encountered in maintaining purity, due to recontamination ~rom processing containers. In addition, energy costs due to high temperature proce~sing can sometime~ be excessi~e, and finishing costs to produce components of the desired final shapes can also so~etimes be excessive. Vapor deposition likewise is a generally effective technique for fabricating high purity glass components. However, it too can be very expensive due to a relatively low material collection efficiency, a hi~h investment cost in processing and pollution control ~quipment, and slow processing rates.
Resear h has recently been conducted into the 2 5 use of a sol -gel process f or f abricating high purity monolithic articles of ~lass. In such processes, a desired ~olution of glass-forming compounds, sol~ents and catalysts, i.e., s~l, is poured into a mol~ and allowed to react. Following hydrolysis and condensation reactions, the sol forms a porous matrix of solids, i.e., gel. With additional time, the gel shrinks in size by expelling fluids from its pores. The wet gel is then dried in a W~93/1~0~4 212 4 5 8 2 PCT/US92/10695 controlled environment, to remove remaining liquid from its pores, and it is then densified into a solid monolith.
Advantages of the sol-gel process include chemical purity and homogeneity, flexibility in ~he selection of compositions, relatively 1OW temperature processing, and the production of monolithic articles close to their desired final shapes, thereby minimizing finishing costs. Nevertheless, the sol-gel process has generally proven to be difficult to use in producing monoliths that are large and free of cracks. These cracks arise during the final drying step of the process, and they are believed to result from stresses due to capillary forces in the gel pores.
,. ~
Efforts to eliminate the cracking problem during the fabrication of dry 501~ gel monoliths have been diverse~ In one techni~ue, th~e gel is dried abov~ the supercritical temperature and pressure of the pore fluid.
In another technique, the wet gel body is placed inside a closed container with a few pinholes for venting khe evaporating pore liquid in a slow, controlled ~shion. In yet another technique, described in U.S. Patent No.
5,023,208, the pore size of ~he wet gel is enlarged by a hydrothermal aging treatment prior to drying. The enlarged pore size substantially reduces the capillary stresses generated during drying, so as to substantially reduce the p~ssibility of crackingO
~" '~ ,' Most of these techniques for eliminating ~he cracking problem are directed towards manipulating the ~-~
drying process parameters so as to minimize the capillary 30 stresses, without any particular emphasis on the ::~
micros~ructure ~f the wet gel and its pristine strength, ~:~
prior to the start of the drying process. Howe~er, if the ~`~
strength of the wet gel can be increased substantially by tailoring the sol composition and the correct choice of WO93/13024 212 4 fi 8 2 PCT/US92/1069~ .
catalyst before the drying process in initiated, it is expected that the gel's resistance to cracking will be much higher. Chances of failure can thereby be minimized substantially. It should be pointed out that, except in the case of the supercritical drying, capillary stresses - will always be generated in the gel body irrespective of the drying technique being used. Therefore, an increase of the gel's strength prior to drying usually is advantageous. The gel's strength, of course, is determined by its microstructure.
It also is important to note that the gel's microstructurel in combination with the drying process, has a significant effect on the ability to fabricate large, dry gel monoliths that a.re free of cracks. For example, it is extremely difficult to fabricate a large, crack-free dry gel structure, e.g,, a 3000 cc cylindrical shape 7 using the supercritical drying process, if the gel has an a~erage pore radius of only lO Angstroms, even though capillary pressure is non-existent~ Gels having an average pore radius on the order of lO0 Angstroms/ on the other hand, are more suitable for this purpose.
Conversely, large, crack-free gels of the same size dried by a pinhole drying process, or any other slow-drying process, are best fabricated by configuring the gels to ha~e smaller average pore radii, e.g., 20 to 30 Angstroms.
This is because smaller pore radii impart higher rupture modulus and density to the gel. The gels thereby have a higher probability of withstanding the capillary stress.
It should therefore be appreciated that there is a need for an ability to tailor the gel microstructure so as to obtain desired mechanical and structural properties for the gel prior to the drying process. The present invention satisfies this need.
W~93/1302q PCT/US92/10695 212~6~2 SUMMARY OF THE_INVENTION
The present invention resides in a sol-gel process for fabricating monoliths of g1ass by tailoring the wet gel microstructure prior to the star~ o~ the 5. drying process. In the case of silica, a sol is prepared by reacting the alkoxide tetraethy1 orthosilicate with deionized water, in the pr~sence of an a1coho1 diluent and a cata1yst. After thorough mixing, the sol is poured into a mold and allowed to stand at room temperature for several hours. With time, the solution gels and takes the shape of the mo1d. A wet gel structure with a high concentration of microscopic pores is thus formed. In accordance with the present invention, certain ge1 properties such as average pore size, pore surface area, total pore volume, bu1k density, rupture modu1us, and tensile modulus, can bP tai1Ored to sati~fy certain desired needs by adjusting the relative concentrations of the alcohol di1uent and cata1yst in the initial sol.
Mcre partieularly, when the alcohol is ethanol ~0 and the cata1ysts are hydrofluoric acid (HF) and hydroch1Oric acid (HC13, average pore radii in the dry gel can be tailored to se1ected values in the range of 10 to ~00 Angstroms by controlling the relative conc~ntrations of the ethano1 and the cata1yst. Corr~ponding1y, the gel's surface area can be tailored to sele~ted ~a1ues in the range of 600 to 1100 m per gram, and the gel's total pore volume can be tailored to selected values in the range of 0.7 to 3.6 cc per gram.
.,.......................................................... ~.~.
In another fea~ure of the invention, it has been ~i~
30 disco~ered that gel microstructure parameters 5uch as~!~','' '' a~erage pore radius, surface area, and total pore volume :~:
can be selected merely by varying the amount of alcohol included in the sol despite the t~pe of cata1yst used.
Similarly, when both HF and HCl catalysts are used, the 2 i 2 4 !6 ~ 2 gel's average pore radius can be selected merely by varying the concentration of ~F in the sol while maintaining the concentration of HCl constant. Further, the gel's bulk density can be selected merely ~y varying the concentration of HF in the sol while maintaining constant the concentration of ~Cl.
Further, the wet gel's rupture modulus and elastic modulus can be controllably selected merely by varying the amount of ethanol in the sol. This behavior was observed for gels prepared using only HF as the catalyst as well as for gels prepared using HF and HCl in combin~tion as the catalyst. Rupture moduli in the range of 0.1 to 2.0 megapascals and elastic moduli in the range of 1.0 to 40 megapascals can be tailored in this fashion.
Other features and aclvantages of the present invention should become appar~ent from the following detailed description~ which sets forth, by way of example, several preferred processes of th~ invention.
DETAILED DESCRIPTION OF THE INVENTION
This invention resides in a sol gel process for fabricating large monoliths of silica having a desired microstructure that imparts certain physical strength characteristics that make the monolith particularly useful in certain applications. In the case of silica, a sol is formed by mixing tetraethyl orthosilicate or TEOS
( (C2HsO) 4Si) with deionized water, a diluent, e~g., ethyl alcohol ~or ethanol (C2HsOH), and a catalyst, e.g., hydrofluoric acid (HF) and/or hydrochloric acid (HCl).
After stirring and placing in a 5uitable mold, hydrolysis and polymerization reactions occur, an~ a gel begins to form. These reactions are as follows:
(C2H5O) 4Si + 4H2O ~ 4C2H5OH + Si(OH) 4 Si(oH)4 ~ sio2 + 2H2O
W093/i30~ 2 1 2 4 6 8 2 PC~/US92/10695 After the hydrolysis and polymerization :~~
reactions are complete or near complete, the resulting porous silicon dioxide (sio2) gel matrix is dried. The microstructure of the gel matrix can have a signif icant effect on the ability of the wet silica gel body or - monolith to withstand any capillary forces encountered as the li~uid dries from the minute pores of the matrix. In accordance with the invention, this microstructure is -~
specially tailored so as to impart to the wet gel monolith ~-certain desired physical stren~th characteristics that enable it to withstand these capillary for~es. This ~:.
tailoring is achieved by carefully adjusting the relative ~-`
coneentrations of the ethanol diluent'and th~ HF and HCl catalysts.
~.
The process of the invention will be better -~
understood with reference to the illustrative examples ~set forth ~elow. :~
''''':-:
Tailorin~ of Gel Microstructure throuqh Variations of the Alcohol Content in the Sol -Examples 1-5 ,~
In Example 1-3, three solutions were prepared by -~
mixing 1.0 mole of TEOS in each case with 4.0 moles of ~;
ethanol (Exampl~ 1), 3.0 moles of ethanol (Example 2), and :
2.0 moles of ethanol (Example 3) in separate containers, ``
25 under continuous stirring. Another three solutîons were ~
prepared by mixing 0.05 mole of HF with 4.0 moles of ~ ;
deionize~ water. The second solutions were then added to the first three solutions, and stirring continued for 30 ~:-minutes. The resulting clear solutions were then poured into cylindrical containers and allowed to gel at room temperature~
' . . .
''`'';'''' , WO93/13024 2 1 2 ~ fi ~ 2 PCT/US92J1069~ `
In Example 4 and 5, two identical solutions were prepared by mixing 0.02 mole of HCl with 4.0 moles of deionized water. A separate solution was prepared by mixing l.0 mole of TEOS with l.0 mole of ethanol. One HCl/water solution was added to this TEOS/ethanol solution, under continuous stirring (Example 4), while the other HCl/ethanol solution was added to l.0 mole of TEOS, under continuous stirring (Example 5). Finally, 0.05 mole of HF was added dropwise to both solutions, and these final sols were poured into cylindrical molds and allowed to gel at room temperature.
Wet gel s prepared in accordance with these examples were aged for one week, at 70 C, and they were subsequently dried under controlled conditions.
Microstructural data on each of these dry gels were collected using an Autosorb-6 BE'r machine. These data are summarized in Table l.
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~xamples 6-8 In Examples 6~8, three wet gel samples were prepared using 1.0 mole of TEOS, 4.0 moles of deionized water, and 1.0 mole of ethanol (Example 6), 2.0 moles of ethanol (Example 7), and 4.0 moles of ethanol (~xample 8).
Two catalysts, including 0.02 mole of HCl together with 0.10 mole of HFr were used in all three examples. The mixing sequence vf chemicals was the same as described in Examples 1-5. The wet gels prepared in this way were aged for one week, at 70 C, and they were ~ubsaquently dried under ~ontrolled conditions. Microstructural data on ~ach `
of these dry gels were collected using an Autosorb-6 BET
machine. These data are shown in Table 2.
Example TEOS Ethanol Deion. HCl HF Avera~e P~r~
(Mole) (Mole~ Water (Mole) (Mole) Radius _ _~Mole) ~ lAnq.) ~ 1.0 1.0 4.0 0.020.10 ~0 ';
7 ~.0 2.0 4.0 0.020.10 50 8 1.0 4.0 4.0 0.020.10 80 `. .
The data of Tables 1 and 2 show that lncreasing the concentration of the ethanol diluent, while maintaining constant the soncentratlons of the TEOS and deionized water reactants and the catalyst(s), brings about an increased average pore radius, a decreased surfaGe area per unit weight, and an increased total pore volume per unit weight.
212~fi82 Tailor~ of Gel Microstructure throuqh Variations of HF Catalyst While HCl Catalyst Remains Constant Examples 9-12 In Examples 9-12, four wet gel samples were prepared using 1.0 mole of TEOS, 1.0 mole of ethanol~ 4.0 moles of deionized water, and 0.02 mole of HCl. Further, `~
an HF catalyst was added in the amounts of 0.03 mole in ~ :
Example 9, 0.05 mole in Example 10, 0.07 mole in Example :~
11, and 0.10 mole in Example 12. Tn each case, the mixin~
sequence of chemicals was as described in Examples ~-5.
The wet gel samples were aged for one-week, at 70^C, and :~
the samples were then dried under controlled conditions.
The microstructural properties were analyzed using an Autosorb-6 BET machine, and the results of that analysis ~
15 are summarized in Table 3. ~.
Example TEOS Ethanol Deion. HCl HF Average Pore (Mole) ~Mole) Water (Mole3 (Mole) ~adius _ _ (Mole~ _ ~Anq.L
9 1.0 1.0 4.0 0.02 0.03 15 1.0 1.0 ~.0 0.02 0.05 20 11 1.0 1.0 4.0 0.02 0.07 30 12 1.0 1.0 4.0 0.02 0.10 40 ,~, "~,~
Examples 13-17 In ~xamples 13-17, five wet gel samples were prepared using 1. 0 mole of TEOS, 2 . O moles of ethanol, 4 . O ~ `
moles of deionized water, and O . 02 mole of HCl. Further, an HF catalyst was added in the amounts of 0. 01 mole in Example 13, O . 03 mole in Example 14, O . 05 mole in Example ;~
15, O . 07 mole in F:xamp:Le 16, and O.10 mole in Example 17 .
In each case, the mixing sequence of chemicals was as , ~
WO93/l3024 PCT/US92/10695 212~682 `
described in Examples 1-5. The wet gel samples were aged for one week, at 70 C, and the samples were then dried under controlled conditions. The microstructural properties were analyzed using an Autosorb-~ B~T machine, and the results of than analysis are summarized in Table 4. ~.
Example TEOS Ethanol Deion. HCl HF kverage Pore (Mole) (Mole) Water (Mole) (Mole) Radius `~
~MoleL (Anq.l __ 13 1.0 2.~ 4.0 0.02 0.0} 10 `~
14 1.0 2.0 4.0 0.02 0.03 12 1.0 2.0 4.0 ~.02 0.05 20 ;~"~
16 1.0 2.0 4.0 ~.02 0.07 30 17 1.~ 2~0 4.0 0.02 0.10 50 Examples 18-22 -` .
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In Examples 18-22, five wet gel~ samples were prepared using 1.0 m~le:o~ TE~S, 4.0 moles of sthanol, 4.0 : ~-moles-of deionized;water, and 0.02 mole of HCl. Further,:
an HF catalyst was added in:the amounts of 0.~01 moles: in Example 18, 0.03 mole in Example 19, 0.05 mole in Example 20, 0.07 mole in Example 21, and 0.10 mole in Example 22.:
In each case, the mixing sequence of chemlcals was as~
described in Examples l-5. The wet gel samples were aged~ : :
for one week, at 70 C, and the samples were then dried under controlled conditions. The miGrostructura properties were analyzed using an Autosorb-6 BET m~chine, and the re5ults of that analysis are summarized in Table ~, .
WO~3/13~24 PCT/~S92/1069~
TABLE 5 :
Example TEOS Ethanol Deion~ HCl HF k~erage Pore (Mole~ (Mole) Water (Mole) (Mole) Radius ~
- LMole) _ _ (Ana.L _ -18 1.0 4.0 4.0 0.02 0~01 1 19 1.0 4.0 4~0 0~02 0.03 15 1.0 4.0 4,0 0.02 0.05 20 21 1.0 4.0 4.0 ~.02 0.07 3 ~2 1.0 4.0 4.V 0.02 0.10 40 .
The data of Tables 3, 4 and 5 show that increasing the concentration of the HF catalyst, while maintaining constant the concentrations of t~e TEOS and deionized water reactants, the ethanol diluent, and the HCl catalyst, brings about an increase in the averaye pore radius of the resulting dry g 1.
Tailorinq of_ el Bulk Density The dry gel samples of~ Examples 9-22 al50 were tested for bulk density. The test results~ are presented in Table 6. They show that increasing the concentration of the HF catalyst, while maintaining constant the concentrations of ~he TEOS and dei~nized water reactants, the ethanol diluent, and the HCl catalyst, brings about a reduction in the dry gells bulk density. The test results fu~ther show that increasing the concentration of the ethanol diluent, while maintaining constant~ the c~ncentrations of the TEOS and:deionize~ w~er reactants and the HCl and HF catalysts, brings about an increase in the dry gel's bulk density for ethanol concentrations in the range of 1.0 to 2.0 moles. That same variation, however, appears to have an inconclusive effect on the dry ~el's bulk density for ethanol concentrations in the range of 2.0 to 4.0 moles.
~Qg3/l302~l P~T/US~2Jl~695 Example TEOS Ethanol Deion. HCl HF Bulk (Mole) (Mole) Water (Mole) (Mole) Density _ _ (Mole) ~qms~cc) 9 1.0 1.0 4.0 0.02 0.03 0.597 ~-1~ 1.0 1.0 4.0 0.02 0.05 ~.409 11 1.0 1.0 4.0 0~2 0.07 00412 , 12 1.0 1.0 4.0 0.02 3.1~ 0,359 ~ 1.0 2.0 4O0 0.02 ~.0~ 2 14 1.0 2.0 4.0 ~.02 ~.03 0.911 .
1.0 2.0 4.0 0.02 O.OS 0.764 16 1.0 2.0 4.0 0.02 0.07 ~.664 17 1.0 2.0 4.0 0.02 0.10 0~576 :`~
1$ 1.0 ~.0 4.0 0.02 0.01 0.885 19 1.0 4.0 4~0 0.02 0.03 0.867 .
1.0 4.0 4.0 0~02 0.05 ~.7 21 1.0 4.0 4.0 0.02 0.07 : 0.656 22 1.0 4.0 4.0 0.02 0.10 0.567 Tailorinq of Gel_Elastic Modulus and Rupture ModuIus ;
20. Examples 23-25 ~ -~
In Examples 23-25, three wet gel samples were ~.
prepared u~ing 1.0 mole of TEOS, 3.0 moles of ethanol, 4.0 moles of deionized water, and 0.02 m~le ~f HCl. Further, ~:
an HF catalyst was added in the amounts of 0.03 mole in ~
25Example 23, 0~05 mole in Example 24, and 0.10 mole in ~:
Example 25. In each case, the mixing equenc:e of :~
chemicals was as described in Examples 1-5. The wet gel sampIes were aged for :one week, at 70 c, and while still submerged in ethanol were tested using a three-point bend WO93/13024 2 1 2 ~ 6 8 2 PCT/US92/10695 tester by fracture to determine their elastic moduli and rupture moduli. At the same time, the wet gel samples of Examples 9, 10, 12, 14, 15, 17, 19, 20 and 22 were similarly tested to determine their elastic moduli and rupture moduli.
The results of these tests are presented in Table 7. The results show that increasing the HF catalyst concentration, while maintaining constant the concentrations of the TEO~ and deionized water reactants, the ethanol diluent, and the HCl catalyst, generally decreases both the wet gel's elastic modulus and the rupture modulus of the wet gel. At the same time, the results show that increasing the ethanol concentration, while maintaining constant the concentrations of the TEO5 15 a:nd deionized water reactants a:nd HF and HCl s:~atalysts, generally brings about a decrease in the gel ' s elastic modulus and rupture modulus. This would intuitively follow from the increased average pore size brought about by these same variations.
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W~93/13024 PCT/US92/10695 The gel samples of Examples 3-5 also were tested for elastic moduli and rupture moduli, while still wet and immersed in ~thanol. The tests were conducted using a three-point bend tester by frac~ure. The test results, ;
which are presented in Table 8, confirm the conclusions from the data of Table 7. In particular, the tests results show that increasing the concentration of the ethanol diluent, while maintaining constant t~e concentrations of the TEOS and deionized water reactants - -and the single HF catalyst, brings about a decrease in both the elastic modulus and the rupture modulus of the wet gel. ~
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WO 93/13024 2 1 2 ~ 6 ~ ~ PCT/US92/10695 It should be appreciated from the foregoing datailed description that the present invention provides a technique for tailoring various microstructure -~
characteristics of a gel (e.g., silica) fabricated using .
a sol-gel process, by adjusting the relative concentrations of an alcohol diluent (e.g., ethanol) and/or one or more catalysts (e.g., HCl and HF). ~:
Controlled variations in the gel's average pore radius, ~.
bulk density, rupture modulus, and elastic modulus over a wide range can be tailored in this fashion. This enables the process to be optimized for the particular application :~-involved.
Although the invention has been described in ~ :
detail with reference only to the examples set forth ~-~
above, those of ordinary skill in the art will appreciate that various modifications can be made without departîng :~
from the invention. Accordingly~ the invention is defined only by the following claims.
.... . .
TAILORED GEL MICROSTRUCTURE
BACKGROUND OF THE INVENTION
This invention relates genPrally to sol-gel pro~esses for producing monolithic articles of glass and, more particularly, to processes of t~is kind that are adapted to eliminate cracking of the gel during a final drying step.
High purity glass components typically are fabricated either by melting solid raw materials or by vapor deposition. Melting solid raw materials is a generally e~fective ~echnique, but difficul~y is sometimes encountered in maintaining purity, due to recontamination ~rom processing containers. In addition, energy costs due to high temperature proce~sing can sometime~ be excessi~e, and finishing costs to produce components of the desired final shapes can also so~etimes be excessive. Vapor deposition likewise is a generally effective technique for fabricating high purity glass components. However, it too can be very expensive due to a relatively low material collection efficiency, a hi~h investment cost in processing and pollution control ~quipment, and slow processing rates.
Resear h has recently been conducted into the 2 5 use of a sol -gel process f or f abricating high purity monolithic articles of ~lass. In such processes, a desired ~olution of glass-forming compounds, sol~ents and catalysts, i.e., s~l, is poured into a mol~ and allowed to react. Following hydrolysis and condensation reactions, the sol forms a porous matrix of solids, i.e., gel. With additional time, the gel shrinks in size by expelling fluids from its pores. The wet gel is then dried in a W~93/1~0~4 212 4 5 8 2 PCT/US92/10695 controlled environment, to remove remaining liquid from its pores, and it is then densified into a solid monolith.
Advantages of the sol-gel process include chemical purity and homogeneity, flexibility in ~he selection of compositions, relatively 1OW temperature processing, and the production of monolithic articles close to their desired final shapes, thereby minimizing finishing costs. Nevertheless, the sol-gel process has generally proven to be difficult to use in producing monoliths that are large and free of cracks. These cracks arise during the final drying step of the process, and they are believed to result from stresses due to capillary forces in the gel pores.
,. ~
Efforts to eliminate the cracking problem during the fabrication of dry 501~ gel monoliths have been diverse~ In one techni~ue, th~e gel is dried abov~ the supercritical temperature and pressure of the pore fluid.
In another technique, the wet gel body is placed inside a closed container with a few pinholes for venting khe evaporating pore liquid in a slow, controlled ~shion. In yet another technique, described in U.S. Patent No.
5,023,208, the pore size of ~he wet gel is enlarged by a hydrothermal aging treatment prior to drying. The enlarged pore size substantially reduces the capillary stresses generated during drying, so as to substantially reduce the p~ssibility of crackingO
~" '~ ,' Most of these techniques for eliminating ~he cracking problem are directed towards manipulating the ~-~
drying process parameters so as to minimize the capillary 30 stresses, without any particular emphasis on the ::~
micros~ructure ~f the wet gel and its pristine strength, ~:~
prior to the start of the drying process. Howe~er, if the ~`~
strength of the wet gel can be increased substantially by tailoring the sol composition and the correct choice of WO93/13024 212 4 fi 8 2 PCT/US92/1069~ .
catalyst before the drying process in initiated, it is expected that the gel's resistance to cracking will be much higher. Chances of failure can thereby be minimized substantially. It should be pointed out that, except in the case of the supercritical drying, capillary stresses - will always be generated in the gel body irrespective of the drying technique being used. Therefore, an increase of the gel's strength prior to drying usually is advantageous. The gel's strength, of course, is determined by its microstructure.
It also is important to note that the gel's microstructurel in combination with the drying process, has a significant effect on the ability to fabricate large, dry gel monoliths that a.re free of cracks. For example, it is extremely difficult to fabricate a large, crack-free dry gel structure, e.g,, a 3000 cc cylindrical shape 7 using the supercritical drying process, if the gel has an a~erage pore radius of only lO Angstroms, even though capillary pressure is non-existent~ Gels having an average pore radius on the order of lO0 Angstroms/ on the other hand, are more suitable for this purpose.
Conversely, large, crack-free gels of the same size dried by a pinhole drying process, or any other slow-drying process, are best fabricated by configuring the gels to ha~e smaller average pore radii, e.g., 20 to 30 Angstroms.
This is because smaller pore radii impart higher rupture modulus and density to the gel. The gels thereby have a higher probability of withstanding the capillary stress.
It should therefore be appreciated that there is a need for an ability to tailor the gel microstructure so as to obtain desired mechanical and structural properties for the gel prior to the drying process. The present invention satisfies this need.
W~93/1302q PCT/US92/10695 212~6~2 SUMMARY OF THE_INVENTION
The present invention resides in a sol-gel process for fabricating monoliths of g1ass by tailoring the wet gel microstructure prior to the star~ o~ the 5. drying process. In the case of silica, a sol is prepared by reacting the alkoxide tetraethy1 orthosilicate with deionized water, in the pr~sence of an a1coho1 diluent and a cata1yst. After thorough mixing, the sol is poured into a mold and allowed to stand at room temperature for several hours. With time, the solution gels and takes the shape of the mo1d. A wet gel structure with a high concentration of microscopic pores is thus formed. In accordance with the present invention, certain ge1 properties such as average pore size, pore surface area, total pore volume, bu1k density, rupture modu1us, and tensile modulus, can bP tai1Ored to sati~fy certain desired needs by adjusting the relative concentrations of the alcohol di1uent and cata1yst in the initial sol.
Mcre partieularly, when the alcohol is ethanol ~0 and the cata1ysts are hydrofluoric acid (HF) and hydroch1Oric acid (HC13, average pore radii in the dry gel can be tailored to se1ected values in the range of 10 to ~00 Angstroms by controlling the relative conc~ntrations of the ethano1 and the cata1yst. Corr~ponding1y, the gel's surface area can be tailored to sele~ted ~a1ues in the range of 600 to 1100 m per gram, and the gel's total pore volume can be tailored to selected values in the range of 0.7 to 3.6 cc per gram.
.,.......................................................... ~.~.
In another fea~ure of the invention, it has been ~i~
30 disco~ered that gel microstructure parameters 5uch as~!~','' '' a~erage pore radius, surface area, and total pore volume :~:
can be selected merely by varying the amount of alcohol included in the sol despite the t~pe of cata1yst used.
Similarly, when both HF and HCl catalysts are used, the 2 i 2 4 !6 ~ 2 gel's average pore radius can be selected merely by varying the concentration of ~F in the sol while maintaining the concentration of HCl constant. Further, the gel's bulk density can be selected merely ~y varying the concentration of HF in the sol while maintaining constant the concentration of ~Cl.
Further, the wet gel's rupture modulus and elastic modulus can be controllably selected merely by varying the amount of ethanol in the sol. This behavior was observed for gels prepared using only HF as the catalyst as well as for gels prepared using HF and HCl in combin~tion as the catalyst. Rupture moduli in the range of 0.1 to 2.0 megapascals and elastic moduli in the range of 1.0 to 40 megapascals can be tailored in this fashion.
Other features and aclvantages of the present invention should become appar~ent from the following detailed description~ which sets forth, by way of example, several preferred processes of th~ invention.
DETAILED DESCRIPTION OF THE INVENTION
This invention resides in a sol gel process for fabricating large monoliths of silica having a desired microstructure that imparts certain physical strength characteristics that make the monolith particularly useful in certain applications. In the case of silica, a sol is formed by mixing tetraethyl orthosilicate or TEOS
( (C2HsO) 4Si) with deionized water, a diluent, e~g., ethyl alcohol ~or ethanol (C2HsOH), and a catalyst, e.g., hydrofluoric acid (HF) and/or hydrochloric acid (HCl).
After stirring and placing in a 5uitable mold, hydrolysis and polymerization reactions occur, an~ a gel begins to form. These reactions are as follows:
(C2H5O) 4Si + 4H2O ~ 4C2H5OH + Si(OH) 4 Si(oH)4 ~ sio2 + 2H2O
W093/i30~ 2 1 2 4 6 8 2 PC~/US92/10695 After the hydrolysis and polymerization :~~
reactions are complete or near complete, the resulting porous silicon dioxide (sio2) gel matrix is dried. The microstructure of the gel matrix can have a signif icant effect on the ability of the wet silica gel body or - monolith to withstand any capillary forces encountered as the li~uid dries from the minute pores of the matrix. In accordance with the invention, this microstructure is -~
specially tailored so as to impart to the wet gel monolith ~-certain desired physical stren~th characteristics that enable it to withstand these capillary for~es. This ~:.
tailoring is achieved by carefully adjusting the relative ~-`
coneentrations of the ethanol diluent'and th~ HF and HCl catalysts.
~.
The process of the invention will be better -~
understood with reference to the illustrative examples ~set forth ~elow. :~
''''':-:
Tailorin~ of Gel Microstructure throuqh Variations of the Alcohol Content in the Sol -Examples 1-5 ,~
In Example 1-3, three solutions were prepared by -~
mixing 1.0 mole of TEOS in each case with 4.0 moles of ~;
ethanol (Exampl~ 1), 3.0 moles of ethanol (Example 2), and :
2.0 moles of ethanol (Example 3) in separate containers, ``
25 under continuous stirring. Another three solutîons were ~
prepared by mixing 0.05 mole of HF with 4.0 moles of ~ ;
deionize~ water. The second solutions were then added to the first three solutions, and stirring continued for 30 ~:-minutes. The resulting clear solutions were then poured into cylindrical containers and allowed to gel at room temperature~
' . . .
''`'';'''' , WO93/13024 2 1 2 ~ fi ~ 2 PCT/US92J1069~ `
In Example 4 and 5, two identical solutions were prepared by mixing 0.02 mole of HCl with 4.0 moles of deionized water. A separate solution was prepared by mixing l.0 mole of TEOS with l.0 mole of ethanol. One HCl/water solution was added to this TEOS/ethanol solution, under continuous stirring (Example 4), while the other HCl/ethanol solution was added to l.0 mole of TEOS, under continuous stirring (Example 5). Finally, 0.05 mole of HF was added dropwise to both solutions, and these final sols were poured into cylindrical molds and allowed to gel at room temperature.
Wet gel s prepared in accordance with these examples were aged for one week, at 70 C, and they were subsequently dried under controlled conditions.
Microstructural data on each of these dry gels were collected using an Autosorb-6 BE'r machine. These data are summarized in Table l.
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~xamples 6-8 In Examples 6~8, three wet gel samples were prepared using 1.0 mole of TEOS, 4.0 moles of deionized water, and 1.0 mole of ethanol (Example 6), 2.0 moles of ethanol (Example 7), and 4.0 moles of ethanol (~xample 8).
Two catalysts, including 0.02 mole of HCl together with 0.10 mole of HFr were used in all three examples. The mixing sequence vf chemicals was the same as described in Examples 1-5. The wet gels prepared in this way were aged for one week, at 70 C, and they were ~ubsaquently dried under ~ontrolled conditions. Microstructural data on ~ach `
of these dry gels were collected using an Autosorb-6 BET
machine. These data are shown in Table 2.
Example TEOS Ethanol Deion. HCl HF Avera~e P~r~
(Mole) (Mole~ Water (Mole) (Mole) Radius _ _~Mole) ~ lAnq.) ~ 1.0 1.0 4.0 0.020.10 ~0 ';
7 ~.0 2.0 4.0 0.020.10 50 8 1.0 4.0 4.0 0.020.10 80 `. .
The data of Tables 1 and 2 show that lncreasing the concentration of the ethanol diluent, while maintaining constant the soncentratlons of the TEOS and deionized water reactants and the catalyst(s), brings about an increased average pore radius, a decreased surfaGe area per unit weight, and an increased total pore volume per unit weight.
212~fi82 Tailor~ of Gel Microstructure throuqh Variations of HF Catalyst While HCl Catalyst Remains Constant Examples 9-12 In Examples 9-12, four wet gel samples were prepared using 1.0 mole of TEOS, 1.0 mole of ethanol~ 4.0 moles of deionized water, and 0.02 mole of HCl. Further, `~
an HF catalyst was added in the amounts of 0.03 mole in ~ :
Example 9, 0.05 mole in Example 10, 0.07 mole in Example :~
11, and 0.10 mole in Example 12. Tn each case, the mixin~
sequence of chemicals was as described in Examples ~-5.
The wet gel samples were aged for one-week, at 70^C, and :~
the samples were then dried under controlled conditions.
The microstructural properties were analyzed using an Autosorb-6 BET machine, and the results of that analysis ~
15 are summarized in Table 3. ~.
Example TEOS Ethanol Deion. HCl HF Average Pore (Mole) ~Mole) Water (Mole3 (Mole) ~adius _ _ (Mole~ _ ~Anq.L
9 1.0 1.0 4.0 0.02 0.03 15 1.0 1.0 ~.0 0.02 0.05 20 11 1.0 1.0 4.0 0.02 0.07 30 12 1.0 1.0 4.0 0.02 0.10 40 ,~, "~,~
Examples 13-17 In ~xamples 13-17, five wet gel samples were prepared using 1. 0 mole of TEOS, 2 . O moles of ethanol, 4 . O ~ `
moles of deionized water, and O . 02 mole of HCl. Further, an HF catalyst was added in the amounts of 0. 01 mole in Example 13, O . 03 mole in Example 14, O . 05 mole in Example ;~
15, O . 07 mole in F:xamp:Le 16, and O.10 mole in Example 17 .
In each case, the mixing sequence of chemicals was as , ~
WO93/l3024 PCT/US92/10695 212~682 `
described in Examples 1-5. The wet gel samples were aged for one week, at 70 C, and the samples were then dried under controlled conditions. The microstructural properties were analyzed using an Autosorb-~ B~T machine, and the results of than analysis are summarized in Table 4. ~.
Example TEOS Ethanol Deion. HCl HF kverage Pore (Mole) (Mole) Water (Mole) (Mole) Radius `~
~MoleL (Anq.l __ 13 1.0 2.~ 4.0 0.02 0.0} 10 `~
14 1.0 2.0 4.0 0.02 0.03 12 1.0 2.0 4.0 ~.02 0.05 20 ;~"~
16 1.0 2.0 4.0 ~.02 0.07 30 17 1.~ 2~0 4.0 0.02 0.10 50 Examples 18-22 -` .
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In Examples 18-22, five wet gel~ samples were prepared using 1.0 m~le:o~ TE~S, 4.0 moles of sthanol, 4.0 : ~-moles-of deionized;water, and 0.02 mole of HCl. Further,:
an HF catalyst was added in:the amounts of 0.~01 moles: in Example 18, 0.03 mole in Example 19, 0.05 mole in Example 20, 0.07 mole in Example 21, and 0.10 mole in Example 22.:
In each case, the mixing sequence of chemlcals was as~
described in Examples l-5. The wet gel samples were aged~ : :
for one week, at 70 C, and the samples were then dried under controlled conditions. The miGrostructura properties were analyzed using an Autosorb-6 BET m~chine, and the re5ults of that analysis are summarized in Table ~, .
WO~3/13~24 PCT/~S92/1069~
TABLE 5 :
Example TEOS Ethanol Deion~ HCl HF k~erage Pore (Mole~ (Mole) Water (Mole) (Mole) Radius ~
- LMole) _ _ (Ana.L _ -18 1.0 4.0 4.0 0.02 0~01 1 19 1.0 4.0 4~0 0~02 0.03 15 1.0 4.0 4,0 0.02 0.05 20 21 1.0 4.0 4.0 ~.02 0.07 3 ~2 1.0 4.0 4.V 0.02 0.10 40 .
The data of Tables 3, 4 and 5 show that increasing the concentration of the HF catalyst, while maintaining constant the concentrations of t~e TEOS and deionized water reactants, the ethanol diluent, and the HCl catalyst, brings about an increase in the averaye pore radius of the resulting dry g 1.
Tailorinq of_ el Bulk Density The dry gel samples of~ Examples 9-22 al50 were tested for bulk density. The test results~ are presented in Table 6. They show that increasing the concentration of the HF catalyst, while maintaining constant the concentrations of ~he TEOS and dei~nized water reactants, the ethanol diluent, and the HCl catalyst, brings about a reduction in the dry gells bulk density. The test results fu~ther show that increasing the concentration of the ethanol diluent, while maintaining constant~ the c~ncentrations of the TEOS and:deionize~ w~er reactants and the HCl and HF catalysts, brings about an increase in the dry gel's bulk density for ethanol concentrations in the range of 1.0 to 2.0 moles. That same variation, however, appears to have an inconclusive effect on the dry ~el's bulk density for ethanol concentrations in the range of 2.0 to 4.0 moles.
~Qg3/l302~l P~T/US~2Jl~695 Example TEOS Ethanol Deion. HCl HF Bulk (Mole) (Mole) Water (Mole) (Mole) Density _ _ (Mole) ~qms~cc) 9 1.0 1.0 4.0 0.02 0.03 0.597 ~-1~ 1.0 1.0 4.0 0.02 0.05 ~.409 11 1.0 1.0 4.0 0~2 0.07 00412 , 12 1.0 1.0 4.0 0.02 3.1~ 0,359 ~ 1.0 2.0 4O0 0.02 ~.0~ 2 14 1.0 2.0 4.0 ~.02 ~.03 0.911 .
1.0 2.0 4.0 0.02 O.OS 0.764 16 1.0 2.0 4.0 0.02 0.07 ~.664 17 1.0 2.0 4.0 0.02 0.10 0~576 :`~
1$ 1.0 ~.0 4.0 0.02 0.01 0.885 19 1.0 4.0 4~0 0.02 0.03 0.867 .
1.0 4.0 4.0 0~02 0.05 ~.7 21 1.0 4.0 4.0 0.02 0.07 : 0.656 22 1.0 4.0 4.0 0.02 0.10 0.567 Tailorinq of Gel_Elastic Modulus and Rupture ModuIus ;
20. Examples 23-25 ~ -~
In Examples 23-25, three wet gel samples were ~.
prepared u~ing 1.0 mole of TEOS, 3.0 moles of ethanol, 4.0 moles of deionized water, and 0.02 m~le ~f HCl. Further, ~:
an HF catalyst was added in the amounts of 0.03 mole in ~
25Example 23, 0~05 mole in Example 24, and 0.10 mole in ~:
Example 25. In each case, the mixing equenc:e of :~
chemicals was as described in Examples 1-5. The wet gel sampIes were aged for :one week, at 70 c, and while still submerged in ethanol were tested using a three-point bend WO93/13024 2 1 2 ~ 6 8 2 PCT/US92/10695 tester by fracture to determine their elastic moduli and rupture moduli. At the same time, the wet gel samples of Examples 9, 10, 12, 14, 15, 17, 19, 20 and 22 were similarly tested to determine their elastic moduli and rupture moduli.
The results of these tests are presented in Table 7. The results show that increasing the HF catalyst concentration, while maintaining constant the concentrations of the TEO~ and deionized water reactants, the ethanol diluent, and the HCl catalyst, generally decreases both the wet gel's elastic modulus and the rupture modulus of the wet gel. At the same time, the results show that increasing the ethanol concentration, while maintaining constant the concentrations of the TEO5 15 a:nd deionized water reactants a:nd HF and HCl s:~atalysts, generally brings about a decrease in the gel ' s elastic modulus and rupture modulus. This would intuitively follow from the increased average pore size brought about by these same variations.
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W~93/13024 PCT/US92/10695 The gel samples of Examples 3-5 also were tested for elastic moduli and rupture moduli, while still wet and immersed in ~thanol. The tests were conducted using a three-point bend tester by frac~ure. The test results, ;
which are presented in Table 8, confirm the conclusions from the data of Table 7. In particular, the tests results show that increasing the concentration of the ethanol diluent, while maintaining constant t~e concentrations of the TEOS and deionized water reactants - -and the single HF catalyst, brings about a decrease in both the elastic modulus and the rupture modulus of the wet gel. ~
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WO 93/13024 2 1 2 ~ 6 ~ ~ PCT/US92/10695 It should be appreciated from the foregoing datailed description that the present invention provides a technique for tailoring various microstructure -~
characteristics of a gel (e.g., silica) fabricated using .
a sol-gel process, by adjusting the relative concentrations of an alcohol diluent (e.g., ethanol) and/or one or more catalysts (e.g., HCl and HF). ~:
Controlled variations in the gel's average pore radius, ~.
bulk density, rupture modulus, and elastic modulus over a wide range can be tailored in this fashion. This enables the process to be optimized for the particular application :~-involved.
Although the invention has been described in ~ :
detail with reference only to the examples set forth ~-~
above, those of ordinary skill in the art will appreciate that various modifications can be made without departîng :~
from the invention. Accordingly~ the invention is defined only by the following claims.
.... . .
Claims (15)
1. A method for forming a dry gel body comprising the steps of:
selecting effective amounts of an alkyl orthosilicate, water, an alcohol and a catalyst comprising a mixture of hydrofluoric acid and hydrochloric acid, reacting together the selected amounts of the alkyl orthosilicate and water, in the presence of the selected amounts of the alcohol and the catalysts to form a porous wet gel; and drying the wet gel;
wherein the amounts of the alcohol and the catalyst selected in the step of selecting are selected so as to provide the wet gel with microstructural features that increase the strength of the wet gel to withstand capillary stresses, thereby substantially eliminating the possibility of the gel cracking during the drying step without needing to enlarge the average pore size of the wet gel.
selecting effective amounts of an alkyl orthosilicate, water, an alcohol and a catalyst comprising a mixture of hydrofluoric acid and hydrochloric acid, reacting together the selected amounts of the alkyl orthosilicate and water, in the presence of the selected amounts of the alcohol and the catalysts to form a porous wet gel; and drying the wet gel;
wherein the amounts of the alcohol and the catalyst selected in the step of selecting are selected so as to provide the wet gel with microstructural features that increase the strength of the wet gel to withstand capillary stresses, thereby substantially eliminating the possibility of the gel cracking during the drying step without needing to enlarge the average pore size of the wet gel.
2. A method as defined in claim 1, wherein:
the alkyl orthosilicate selected in the step of selecting includes tetraethyl orthosilicate;
the alcohol selected in the step of selecting is ethanol; and the amounts of ethanol and the catalyst selected in the step of selecting are selected so as to provide a gel having an average pore radius in the range of 10 to 100 Angstroms.
the alkyl orthosilicate selected in the step of selecting includes tetraethyl orthosilicate;
the alcohol selected in the step of selecting is ethanol; and the amounts of ethanol and the catalyst selected in the step of selecting are selected so as to provide a gel having an average pore radius in the range of 10 to 100 Angstroms.
3. A method as defined in claim 2, wherein the relative proportions of alkyl orthosilicate, water, and alcohol selected in the step of selecting are 1 mole, 4 moles and up to 4 moles, respectively.
4. A method as defined in claim 3, wherein the relative proportions of the catalyst selected in the step of selecting are up to 0.1 moles hydrofluoric acid and up to 0.02 moles hydrochloric acid.
5. A method as defined in claim 1, wherein:
the alkyl orthosilicate selected in the step of selecting includes tetraethyl orthosilicate;
the alcohol selected in the step of selecting is ethanol; and the amounts of ethanol and the catalyst selected in the step of selecting are selected so as to provide a dry gel having a bulk density in the range of 0.3 to 1.2 grams per cc.
the alkyl orthosilicate selected in the step of selecting includes tetraethyl orthosilicate;
the alcohol selected in the step of selecting is ethanol; and the amounts of ethanol and the catalyst selected in the step of selecting are selected so as to provide a dry gel having a bulk density in the range of 0.3 to 1.2 grams per cc.
6. A method as defined in claim 5, wherein the relative proportions of alkyl orthosilicate, water, and alcohol selected in the step of selecting are 1 mole, 4 mole and up to 4 moles respectively.
7. A method as defined in claim 6, wherein the relative proportions of the catalyst selected in the step of selecting are up to 0.1 moles hydroflyoric acid and up to 0.02 moles hydrochloric acid.
8. A method as defined in claim 1, wherein:
the alkyl orthosilicate selected in the step of selecting includes tetraethyl orthosilicate;
the alcohol selected in the step of selecting is ethanol; and the amounts of ethanol and the catalyst selected in the step of selecting are selected so as to provide a wet gel having a rupture modulus of at least 0.1 megapascals.
the alkyl orthosilicate selected in the step of selecting includes tetraethyl orthosilicate;
the alcohol selected in the step of selecting is ethanol; and the amounts of ethanol and the catalyst selected in the step of selecting are selected so as to provide a wet gel having a rupture modulus of at least 0.1 megapascals.
9. A method as defined in claim 8, wherein the relative proportions of alkyl orthosilicate, water and alcohol selected in the step of selecting are 1 mole, 4 moles and up to 4 moles respectively.
10. A method as defined in claim 9, wherein the relative proportions of the catalyst selected in the step of selecting are up to 0.1 moles hydro fluoric acid and up to 0.02 moles hydrochloric acid.
11. A method as defined in claim 1, wherein:
the alkyl orthosilicate selected in the step of selecting includes tetraethyl orthosilicate;
the alcohol selected in the step of selecting is ethanol; and the amount of ethanol and the catalyst selected in the step of selecting are selected so as to provide a wet gel having an elastic modulus of at least 1.0 megapascals.
the alkyl orthosilicate selected in the step of selecting includes tetraethyl orthosilicate;
the alcohol selected in the step of selecting is ethanol; and the amount of ethanol and the catalyst selected in the step of selecting are selected so as to provide a wet gel having an elastic modulus of at least 1.0 megapascals.
12. A method as defined in claim 11, wherein the relative proportions of alkyl orthosilicate, water and alcohol selected in the step of selecting are 1 mole, 4 moles and up to 4 moles, respectively.
13. A method as defined in claim 12, wherein the relative proportions of the catalyst selected in the step of selecting are up to 0.1 moles hydrofluoric acid and up to 0.02 moles hydrochloric acid.
14. A method as defined in claim 1, wherein:
the alkyl orthosilicate selected in the step of selecting includes tetraethyl orthosilicate;
the alcohol selected in the step of selecting is ethanol; and the relative proportions of alkyl orthosilicate, water and alcohol selected in the step of selecting are 1 mole, 4 moles and up to 4 moles respectively.
the alkyl orthosilicate selected in the step of selecting includes tetraethyl orthosilicate;
the alcohol selected in the step of selecting is ethanol; and the relative proportions of alkyl orthosilicate, water and alcohol selected in the step of selecting are 1 mole, 4 moles and up to 4 moles respectively.
15. A method as defined in claim 14, wherein the relative proportions of the catalyst selected in the step of selecting are up to 0.1 moles hydrofluoric acid and up to 0.02 moles hydrochloric acid.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/811,326 US5264197A (en) | 1991-12-20 | 1991-12-20 | Sol-gel process for providing a tailored gel microstructure |
| US07/811,326 | 1991-12-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2124682A1 true CA2124682A1 (en) | 1993-07-08 |
Family
ID=25206241
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002124682A Abandoned CA2124682A1 (en) | 1991-12-20 | 1992-12-11 | Sol-gel process for providing a tailored gel microstructure |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US5264197A (en) |
| EP (1) | EP0617700B1 (en) |
| JP (1) | JPH07506325A (en) |
| AU (1) | AU661366B2 (en) |
| CA (1) | CA2124682A1 (en) |
| DE (1) | DE69211158T2 (en) |
| WO (1) | WO1993013024A1 (en) |
Families Citing this family (29)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3314935B2 (en) * | 1992-05-20 | 2002-08-19 | イー・アイ・デユポン・ドウ・ヌムール・アンド・カンパニー | Method for making inorganic gel |
| US5399535A (en) * | 1993-08-17 | 1995-03-21 | Rohm And Haas Company | Reticulated ceramic products |
| WO1995017347A1 (en) * | 1993-12-23 | 1995-06-29 | Ppg Industries, Inc. | Silica aerogel produced under subcritical conditions |
| US5473826A (en) * | 1994-08-19 | 1995-12-12 | Yazaki Corporation | Process for drying sol-gel derived porous bodies at elevated subcritical temperatures and pressures |
| US5510147A (en) * | 1995-03-03 | 1996-04-23 | International Paper Company | Sol gel barrier films |
| DE19538333A1 (en) * | 1995-10-14 | 1997-04-17 | Basf Ag | Process for the subcritical production of aerogels |
| US6158245A (en) * | 1997-07-29 | 2000-12-12 | Physical Optics Corporation | High efficiency monolithic glass light shaping diffuser and method of making |
| US6446467B1 (en) * | 1997-07-29 | 2002-09-10 | Physical Optics Corporation | Monolithic glass light shaping diffuser and method for its production |
| US6334988B1 (en) * | 1998-08-21 | 2002-01-01 | The University Of Vermont And State Agricultural College | Mesoporous silicates and method of making same |
| US6620368B1 (en) | 2000-07-13 | 2003-09-16 | Simax Technologies, Inc. | Sol-gel process for production of oxide-based glass and ceramic articles |
| US7125912B2 (en) * | 2001-10-09 | 2006-10-24 | Simax Technologies, Inc. | Doped sol-gel materials and method of manufacture utilizing reduced mixing temperatures |
| US7026362B2 (en) | 2001-10-09 | 2006-04-11 | Simax Technologies, Inc. | Sol-gel process utilizing reduced mixing temperatures |
| US7001568B2 (en) * | 2002-02-01 | 2006-02-21 | Simax Technologies, Inc. | Method of removing liquid from pores of a sol-gel monolith |
| US7000885B2 (en) | 2002-02-01 | 2006-02-21 | Simax Technologies, Inc. | Apparatus and method for forming a sol-gel monolith utilizing multiple casting |
| US6928220B2 (en) * | 2002-02-01 | 2005-08-09 | Simax Technologies, Inc. | Sol-gel-derived optical fiber preform and method of manufacture |
| US20030147606A1 (en) * | 2002-02-01 | 2003-08-07 | Shiho Wang | Sol-gel-based optical preforms and methods of manufacture |
| US20040194511A1 (en) * | 2002-02-01 | 2004-10-07 | Chih-Hsing Cheng | Sol-gel-derived halogen-doped glass |
| US8815200B2 (en) * | 2004-12-02 | 2014-08-26 | The University Of Vermont And State Agricultural College | Mesoporous inorganic oxide spheres and method of making same |
| US7439272B2 (en) * | 2004-12-20 | 2008-10-21 | Varian, Inc. | Ultraporous sol gel monoliths |
| CN100372077C (en) * | 2004-12-27 | 2008-02-27 | 兰州大学 | Method for preparing porous thin film material with low dielectric constant |
| PT103257B (en) | 2005-04-05 | 2007-05-31 | Inst Superior Tecnico | METHOD OF SUBCRYTIC PRODUCTION OF SYMBOLS AND ALTERNATIVE AEROGISES HYBRID OF MODIFIED SILICA AND LATEX WITH ALCOXYSILAN GROUPS |
| EP1897860A1 (en) * | 2006-09-07 | 2008-03-12 | Degussa Novara Technology S.p.A. | Sol-gel process |
| US7750056B1 (en) | 2006-10-03 | 2010-07-06 | Sami Daoud | Low-density, high r-value translucent nanocrystallites |
| JP5049624B2 (en) * | 2007-03-26 | 2012-10-17 | 株式会社東芝 | Metal fine particle dispersed film and method for producing metal fine particle dispersed film |
| EP2088128B1 (en) | 2007-12-10 | 2015-04-08 | Cristal Materials Corporation | Method for the production of glassy monoliths via the sol-gel process |
| TW201004869A (en) * | 2008-06-10 | 2010-02-01 | Nanotune Technologies Corp | Nanoporous materials and related methods |
| WO2012088758A1 (en) | 2010-12-27 | 2012-07-05 | The Hong Kong University Of Science And Technology | Inorganic gel for controlled releasing of fragrance and disinfectant |
| US10254164B2 (en) | 2015-04-16 | 2019-04-09 | Nanommics, Inc. | Compact mapping spectrometer |
| CN107128933B (en) * | 2017-06-15 | 2020-01-14 | 武汉理工大学 | Supercritical drying preparation method of silicon dioxide aerogel thermal insulation material |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2794002A (en) * | 1953-12-14 | 1957-05-28 | Universal Oil Prod Co | Method for producing solid siliceous catalyst |
| GB948135A (en) * | 1960-08-29 | 1964-01-29 | Unilever Ltd | Improvements relating to organic silicates |
| FR1568817A (en) * | 1967-11-30 | 1969-05-30 | ||
| JPS55100231A (en) * | 1979-01-19 | 1980-07-31 | Hitachi Ltd | Production of optical fiber base material |
| JPS5926911A (en) * | 1982-08-04 | 1984-02-13 | Toyo Soda Mfg Co Ltd | Spherical porous silica gel and its preparation |
| US4851150A (en) * | 1984-02-27 | 1989-07-25 | University Of Florida | Drying control chemical additives for rapid production of large sol-gel derived silicon, boron and sodium containing monoliths |
| NL8403667A (en) * | 1984-12-03 | 1986-07-01 | Philips Nv | METHOD FOR THE MANUFACTURE OF MONOLITIC GLASS BODIES |
| US4849378A (en) * | 1985-02-25 | 1989-07-18 | University Of Florida | Ultraporous gel monoliths having predetermined pore sizes and their production |
| NL8802643A (en) * | 1988-10-27 | 1990-05-16 | Philips Nv | METHOD FOR MANUFACTURING A MONOLITHIC SILICA AIRBIRD |
| US5023208A (en) * | 1989-12-19 | 1991-06-11 | Orion Laboratories, Inc. | Sol-gel process for glass and ceramic articles |
-
1991
- 1991-12-20 US US07/811,326 patent/US5264197A/en not_active Expired - Lifetime
-
1992
- 1992-12-11 EP EP93900174A patent/EP0617700B1/en not_active Expired - Lifetime
- 1992-12-11 DE DE69211158T patent/DE69211158T2/en not_active Expired - Fee Related
- 1992-12-11 WO PCT/US1992/010695 patent/WO1993013024A1/en active IP Right Grant
- 1992-12-11 AU AU32476/93A patent/AU661366B2/en not_active Ceased
- 1992-12-11 JP JP5511699A patent/JPH07506325A/en active Pending
- 1992-12-11 CA CA002124682A patent/CA2124682A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| AU661366B2 (en) | 1995-07-20 |
| DE69211158T2 (en) | 1996-10-02 |
| JPH07506325A (en) | 1995-07-13 |
| WO1993013024A1 (en) | 1993-07-08 |
| US5264197A (en) | 1993-11-23 |
| EP0617700A1 (en) | 1994-10-05 |
| DE69211158D1 (en) | 1996-07-04 |
| AU3247693A (en) | 1993-07-28 |
| EP0617700B1 (en) | 1996-05-29 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |