CA1260712A - Method of manufacturing monolithic glass members - Google Patents
Method of manufacturing monolithic glass membersInfo
- Publication number
- CA1260712A CA1260712A CA000470265A CA470265A CA1260712A CA 1260712 A CA1260712 A CA 1260712A CA 000470265 A CA000470265 A CA 000470265A CA 470265 A CA470265 A CA 470265A CA 1260712 A CA1260712 A CA 1260712A
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- CA
- Canada
- Prior art keywords
- pressure
- gel
- solution
- mol
- temperature
- 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.)
- Expired
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Classifications
-
- 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
- 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
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Life Sciences & Earth Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Glass Melting And Manufacturing (AREA)
- Manufacture, Treatment Of Glass Fibers (AREA)
- Silicon Compounds (AREA)
- Glass Compositions (AREA)
- Laminated Bodies (AREA)
Abstract
ABSTRACT:
Method of manufacturing monolithic glass members.
Monolithic glass members are manufactured by gelating a solution of an alkoxysilane in an alcoholic solvent in an autoclave. In this method, heating is carried out to above the critical temperature of the solvent and when the temperature is reached, the pressure is gradually removed. By providing in the space a pre-pressure of a gas which is so high that upon heating to the desired temperature the overall pressure is always higher than the saturation pressure of the solvent, it is prevented that boiling phenomena can occur.
Method of manufacturing monolithic glass members.
Monolithic glass members are manufactured by gelating a solution of an alkoxysilane in an alcoholic solvent in an autoclave. In this method, heating is carried out to above the critical temperature of the solvent and when the temperature is reached, the pressure is gradually removed. By providing in the space a pre-pressure of a gas which is so high that upon heating to the desired temperature the overall pressure is always higher than the saturation pressure of the solvent, it is prevented that boiling phenomena can occur.
Description
Method of manufacturing monolithic glass members The invention relates to a method of manufacturing monolithic glass members by preparing a monolithic gel from an alcoholic solution comprising an alkoxysilane compound, in which the monolithic gel i9 dried by heating it in a hermetically closed container to a temperature above the critical temperature of the solvent and then removing the pressure, after which the gel is heated to increase its density.
Such a method is known from Zar~ycki, Prassas 13 and Phalippou: "Synthetis of glasses from gels the problem of monolithic gels" in Journal of Materials Scienc0 17 (1982), pp. 3371-3379. This publication describes a method according to which a gel is prepared from a solution of tetramethoxysilane in methanol to which a quantity of wa-ter l5 is added which is sufficient for hydrolising the silane.
After the gel has formed, the vessel containing the gel is placed in an autoclave. An extra quantity of methanol is provided in the autoclave, so that~ when the critical temperature is reached, the cri-tical pressure is also 20 reached. After the temperature has risen to above the critial tempera-ture of methonol, the pressure in the au-to-clave is slowly reduced. In this manner a dry monolithic gel could be obtained without shrinkage having occurred during drying. According to the publication, evacuating takes 25 place in 3 to 4 hours. This drying time is particularly favourable when compared with drying times at atmospheric pressure which may take approximately a week (see, for example, Electronics Letters 18 (1982), p 499 "New Optical Fibre Fabrication Method").
The drying of a gel above the critical tempera-ture in an autoclave presents the advantage that no capillary forces can occur in the pores of the gel when the - ~ .
, ~ ...
~2~i~37~;2 pressure is removed because no liquid-vapour interface is formed in the pores.
In Nicolaon and Teichner: "Préparation des aérogels de silice à partir d'orthosilicate de méthyle en milieu alcoolique et leurs proprietés" Bull. de la Société Chimique de France 1968~ pp. 1gO6 -119 it is indicated that not only the drying of the gel under hypercritical conditions but also the formation of the gel itself may take place in the autoclave. ~or this purpose, vessels containing a solution suitable for the gel formation are placed in an autoclaveO The hydrolysis and the sub-sequent gelation take place in the closed autoclave during warming up to the hypercritical tempera-ture.
In these known methods the internal volume of the hermetically closed space used is smaller than the critical volume of the quantity of alcohol present, In ideal circumstances, no boiling phenomena should occur in the alcohol during -the heating to the hypercritical tempera-ture ."Ideal circumstances" is to be understood to mean 20 herein that the temperature in the hermetically sealed space can be uniformly raised without temperature gradients occurring. It has been found that this is very difficult to realise in practice, in particular with autoclaves of large capacity to which, however, one is limited in the 25 industrial performance of said processes. It has been found that in practice boiling phenomena by local oyer-heating in the gelating solution and after the formation of the gel can hardly be avoided. This results in damage to the monolithic gels.
Another disadvantage is that during the warming up to the critical temperature, liquid-gas interfaces often have been found to occur in practice in the pores of the gel.
Under the influence of the capillary forces thus occurring in the pores of the gel, shrinkage or even disintegration 35 of the gel may occurO
It is the object of the invention to avoid the disadvantages of the known methods. According to the ; ~:
:, .'' ' "':
:
: : ~
77~2 invention this object can be achieved by means of a method which is characterized in that a pre-pressure of a gas is providecl in the herme-tically closed container~
which pressure is so high that during the heating period to a temperature above the critical -temperature no boiling phenomena can occur in the solvent. The value of the pre-pressure can be established using the formula PV=nRT and the phase diagram(s) of the solvents used.
Experiments h~ve demonstrated that the value of the pre-pressure is decisive of the ultimate density (weight/volume) of the monolithic gel. It was found surprisingly that the higher the pre-pressure i~ chosen, the smaller is the density of the monolithic gels which are manufactured by means of the method according to the invention. By choosing a suitable pre-pressure i-t can ~e achieved that the mono-lithic gel, during the heating period to a temperature above the critical temperature and the subsequent removal of the pressure, does not shrink and hence 9 after drying, has a shape and dimensions just as they wereduring the formation of the gel. Obviously, the formation of the liquid-gas interfaces in the pores of the gel-is suppressed or the detrimental influence thereof is neutralised by applying a sufficiently high pre-pressure.
Preferably the volume of the hermetically closed container is smaller than the critical volume of the quantity of alcoholic solvent present in said container.
During the heating to the critical temperature, the overall pressure in the hermetically closed container at any temperature is always higher than -the saturation vapour pressure of the solvent used in the manufacture of the gel.
In a mixture of solvents having different critical temperatures, heating is carried out to a temperature above the highest critical -tempera-ture of any solvent present.
Suitable gases or low-boiling-point materials which~may be used for providing a pre-pressure are, for example, hydrogen, helium, nitrogen9 oxygen, chlorine, thionyl chloride and`argon.
, : .
7~;~
The ternperature to which may be hea-ted is limited in principle only by the pressure and temperature which the walls of the hermetically c]osable container can withstand and the temperature at which organic materials present in said container begin to carbonise9 however, said temperature should be above the critical temperature of the solvent(s). When a solvent is used which consists entirely or predominantly of ethanoll a pre-pressure of at least 5O Bar is preferably used, if shrinkage of the mono-lithic gel is to be avoided during the heating to thecritical temperature and the subsequent removal of the pressure.
It has been found that the removal of the pressure can be done particularly rapidly, for example, in less than one hour.
Suppressing the shrinkage is of particular importance if it is the object of the me-thod according to the invention to manufacture monolithic gels in the form of tubes, for example 9 in a cylindrical vessel in which a 20 cylinder is provided centrally, the axis of which coincides with the axis of the cylindrical vessel. If -the gel should shrink during the drying9 the monolithic gel could not easily be removed from such a mould without damage, Suitable starting materials for the manufac-ture 25 of monolithic gels consisting mainly of SiO2 are tetra-me-thoxysilane Si~OCH3)4 and tetraethoxy silane Si(aC2H5)~.
Compounds of other elements -the oxides of which are glass formers or which can form a glass with SiO2, may be added to the said materials in the relevant alcohols~ for example, 30 to adjust the refractive index of the glass member at a desired value obtained after increasing the densi-ty of the gel and/or to control other physical properties. Ex-amples of such compounds are alkoxy compounds of aluminium, titanium, boron, germanium and -the like. In certain cases, 35 nitrates~ carbonates, acetates and other compounds which decompose easily while forming oxides may also be used and which are soluble in the relevant solvents.
':' '~ ' ' ' l~or various reasons to be explained hereinafter, tetraethoxysilane is preferably used in the metllod in accorclance wit1l the invention, and ethanol QS a solvent.
These sl1bstances can be obtained in a high purity, while ethanol is less poisonous than methanol.
When tetraethoxysilane is used, a solution is prepared which contains at least 1 g.mol of tetraethoxy-silane per litre of ethanol; at least 2 g,mol of water are added to the said solution per g.mol of tetrae-thoxysilane, ;0 the pH of which is brought at a value between 7 and 8 by means of a volatile base, for example, with ammonia~
If 4 to ~ g.mol of water per g.mol of tetraethoxy-silane are added to the solution of tetraethoxysilane in ethanol, little or no shrinkage has been found to occur 15 during the formation of the monolithic gel. The shape accuracy is largest with a quantity of 5 to 7 g.mol of water per g.mol of tetraethoxysilane. The concentration of tetraethoxysilane per litre of ethanol is preferably 2 to 6 g.mol.
If an aqueous solution of a volatile base is used to bring the quantity of water at the desired p~I, the added quantity of water is included in the quantity of water necessary for the hydrolysis.
When using the method according to the invention, 25 the solutions in vessels of the desired shape and dimension are placed in the autoclave. The vessel corresponds in shape and dimension to the shape and dimension of the monolithic gel which it is desired to manufacture. The vessel~ and optionally a cylinder placed therein, if a tubular gel is 30 manufactured, may consist of any material which is inert wi-th respect to the liquids used, for example, quartz~ In order to prevent adhesion it may be coated with a substance, for example, si~icone rubber and the like D
After the formation of the gel, increasing the 35 density may take place by heating for some time at a high temperature~ for example, at 1300 C. Dependent on the duration of heating, a more or less porous member is obtained. It is possible to manufacture a non-porous member, for example, by raising the -temperature -to 1300C at a rate of 300 C/hour, and main~aining this temperature for approximatel~ one hour. The heating may be carried out entirely or partly in a chlorine-containing atmosphere so as to expel the last hydrox-i1groups from the gel Glass members of any shape and porosity can be manufactured by means of the me-thod according to the inventionO The porosity depends on the leng-th of the heating period (densification period).
The glass members ob-tained by means of the method according to the invention ~ay be used in the manufacture of optical fibres, carrier members for catalysts (the members themselves may be used as a catalyst surface), for the selective separation of components and as molecular lS sieves.
The invention will now be described in greater detail with reference to the following specific examples.
xamE~
In order to make a solution having a molar ratio 20 of 4 C2H50H : 1 Si(OC2H5)4 : 6 H20, first 42 g of Si(OC2H5)4 and then 22 g of H20 are added to 37 g of C2H50H. The wa-ter has first been made alkaline with ammonia to pH = 8. By stirring at 50C~ the solution becomes clear, after which it is poured in four moulds. Saicl 25 moulds consist of tubes of approximately 15 mm diameter and 150 mm length closed at one end in which a rod of pyrex glass of 5 mm diameter is provided so as to be cen-tred. The moulds including the rods are covered with a thin layer of silicone rubber which serves as an anti-adhesion layer.
30 The mould~with the solution are placed in an autoclave of 500 ml capacity. After closing the autoclave nitrogen ~N2) is introduced until the pressure is 80 bar. The assembly is then heated to 300C at a ra-te of 1aO C/hour.
The overall pressure has then become 230 bar. After reaching 35 said temperature -the pressure is gradually removed at this temperature by opening a relief valve in such manner that the excessive pressure has dis~peared entirely after 7~2 approxima-tely ll5 rninutes. After cooling and opening the autoclave the moulds are removed. The moulds now comprise dry porous tubular gels which can be slid out of the tube and from the rod with some care without fracture. The dimensions correspond to those of the moulds. The tubes formed in this manner have a relative density of 0.14 g/cc and are only slightly translucent.
Example II:
A solution consisting of 26 g of e-thanol, 30 g of Si(OC2H5)4 and 20 g of H20 (pH = 8), which corresponds to a molar ratio of 4 : 1 : 8, is prepared and provided in the moulds in the same manner as described in Example I. Said moulds consis-t of tubes of 15 mm diameter and 150 mm length closed at one end and they are coated on their insides with a thin layer of silicone rubber. After introducing the moulds in the autoclave and closing of the autoclave (capacity 500 ml) the pressure is increased to 80 bar by means of nitrogen before heating the assembly to 300C at a rate of 100 C/hour. The final pressure then is 190 bar.
After removing the pressure and cooling, the autoclave is opened and the moulds are removed, The porous rods formecl slide from the moulds without any difficulty~are slightly translucent and have a density of 0.13 g/cc~
Experimen-ts carried out in a corresponding manner but with a pre-pressure of 40 bar and lO bar, respec-tively~ and a final pressure of 145 and 90 bar, respec-tively~ result in rods having a density of 0.14 g/cc and 0.27 g/cc, respectively. The last-mentioned gel is significantly smaller in volume than the original solution.
....~...
Such a method is known from Zar~ycki, Prassas 13 and Phalippou: "Synthetis of glasses from gels the problem of monolithic gels" in Journal of Materials Scienc0 17 (1982), pp. 3371-3379. This publication describes a method according to which a gel is prepared from a solution of tetramethoxysilane in methanol to which a quantity of wa-ter l5 is added which is sufficient for hydrolising the silane.
After the gel has formed, the vessel containing the gel is placed in an autoclave. An extra quantity of methanol is provided in the autoclave, so that~ when the critical temperature is reached, the cri-tical pressure is also 20 reached. After the temperature has risen to above the critial tempera-ture of methonol, the pressure in the au-to-clave is slowly reduced. In this manner a dry monolithic gel could be obtained without shrinkage having occurred during drying. According to the publication, evacuating takes 25 place in 3 to 4 hours. This drying time is particularly favourable when compared with drying times at atmospheric pressure which may take approximately a week (see, for example, Electronics Letters 18 (1982), p 499 "New Optical Fibre Fabrication Method").
The drying of a gel above the critical tempera-ture in an autoclave presents the advantage that no capillary forces can occur in the pores of the gel when the - ~ .
, ~ ...
~2~i~37~;2 pressure is removed because no liquid-vapour interface is formed in the pores.
In Nicolaon and Teichner: "Préparation des aérogels de silice à partir d'orthosilicate de méthyle en milieu alcoolique et leurs proprietés" Bull. de la Société Chimique de France 1968~ pp. 1gO6 -119 it is indicated that not only the drying of the gel under hypercritical conditions but also the formation of the gel itself may take place in the autoclave. ~or this purpose, vessels containing a solution suitable for the gel formation are placed in an autoclaveO The hydrolysis and the sub-sequent gelation take place in the closed autoclave during warming up to the hypercritical tempera-ture.
In these known methods the internal volume of the hermetically closed space used is smaller than the critical volume of the quantity of alcohol present, In ideal circumstances, no boiling phenomena should occur in the alcohol during -the heating to the hypercritical tempera-ture ."Ideal circumstances" is to be understood to mean 20 herein that the temperature in the hermetically sealed space can be uniformly raised without temperature gradients occurring. It has been found that this is very difficult to realise in practice, in particular with autoclaves of large capacity to which, however, one is limited in the 25 industrial performance of said processes. It has been found that in practice boiling phenomena by local oyer-heating in the gelating solution and after the formation of the gel can hardly be avoided. This results in damage to the monolithic gels.
Another disadvantage is that during the warming up to the critical temperature, liquid-gas interfaces often have been found to occur in practice in the pores of the gel.
Under the influence of the capillary forces thus occurring in the pores of the gel, shrinkage or even disintegration 35 of the gel may occurO
It is the object of the invention to avoid the disadvantages of the known methods. According to the ; ~:
:, .'' ' "':
:
: : ~
77~2 invention this object can be achieved by means of a method which is characterized in that a pre-pressure of a gas is providecl in the herme-tically closed container~
which pressure is so high that during the heating period to a temperature above the critical -temperature no boiling phenomena can occur in the solvent. The value of the pre-pressure can be established using the formula PV=nRT and the phase diagram(s) of the solvents used.
Experiments h~ve demonstrated that the value of the pre-pressure is decisive of the ultimate density (weight/volume) of the monolithic gel. It was found surprisingly that the higher the pre-pressure i~ chosen, the smaller is the density of the monolithic gels which are manufactured by means of the method according to the invention. By choosing a suitable pre-pressure i-t can ~e achieved that the mono-lithic gel, during the heating period to a temperature above the critical temperature and the subsequent removal of the pressure, does not shrink and hence 9 after drying, has a shape and dimensions just as they wereduring the formation of the gel. Obviously, the formation of the liquid-gas interfaces in the pores of the gel-is suppressed or the detrimental influence thereof is neutralised by applying a sufficiently high pre-pressure.
Preferably the volume of the hermetically closed container is smaller than the critical volume of the quantity of alcoholic solvent present in said container.
During the heating to the critical temperature, the overall pressure in the hermetically closed container at any temperature is always higher than -the saturation vapour pressure of the solvent used in the manufacture of the gel.
In a mixture of solvents having different critical temperatures, heating is carried out to a temperature above the highest critical -tempera-ture of any solvent present.
Suitable gases or low-boiling-point materials which~may be used for providing a pre-pressure are, for example, hydrogen, helium, nitrogen9 oxygen, chlorine, thionyl chloride and`argon.
, : .
7~;~
The ternperature to which may be hea-ted is limited in principle only by the pressure and temperature which the walls of the hermetically c]osable container can withstand and the temperature at which organic materials present in said container begin to carbonise9 however, said temperature should be above the critical temperature of the solvent(s). When a solvent is used which consists entirely or predominantly of ethanoll a pre-pressure of at least 5O Bar is preferably used, if shrinkage of the mono-lithic gel is to be avoided during the heating to thecritical temperature and the subsequent removal of the pressure.
It has been found that the removal of the pressure can be done particularly rapidly, for example, in less than one hour.
Suppressing the shrinkage is of particular importance if it is the object of the me-thod according to the invention to manufacture monolithic gels in the form of tubes, for example 9 in a cylindrical vessel in which a 20 cylinder is provided centrally, the axis of which coincides with the axis of the cylindrical vessel. If -the gel should shrink during the drying9 the monolithic gel could not easily be removed from such a mould without damage, Suitable starting materials for the manufac-ture 25 of monolithic gels consisting mainly of SiO2 are tetra-me-thoxysilane Si~OCH3)4 and tetraethoxy silane Si(aC2H5)~.
Compounds of other elements -the oxides of which are glass formers or which can form a glass with SiO2, may be added to the said materials in the relevant alcohols~ for example, 30 to adjust the refractive index of the glass member at a desired value obtained after increasing the densi-ty of the gel and/or to control other physical properties. Ex-amples of such compounds are alkoxy compounds of aluminium, titanium, boron, germanium and -the like. In certain cases, 35 nitrates~ carbonates, acetates and other compounds which decompose easily while forming oxides may also be used and which are soluble in the relevant solvents.
':' '~ ' ' ' l~or various reasons to be explained hereinafter, tetraethoxysilane is preferably used in the metllod in accorclance wit1l the invention, and ethanol QS a solvent.
These sl1bstances can be obtained in a high purity, while ethanol is less poisonous than methanol.
When tetraethoxysilane is used, a solution is prepared which contains at least 1 g.mol of tetraethoxy-silane per litre of ethanol; at least 2 g,mol of water are added to the said solution per g.mol of tetrae-thoxysilane, ;0 the pH of which is brought at a value between 7 and 8 by means of a volatile base, for example, with ammonia~
If 4 to ~ g.mol of water per g.mol of tetraethoxy-silane are added to the solution of tetraethoxysilane in ethanol, little or no shrinkage has been found to occur 15 during the formation of the monolithic gel. The shape accuracy is largest with a quantity of 5 to 7 g.mol of water per g.mol of tetraethoxysilane. The concentration of tetraethoxysilane per litre of ethanol is preferably 2 to 6 g.mol.
If an aqueous solution of a volatile base is used to bring the quantity of water at the desired p~I, the added quantity of water is included in the quantity of water necessary for the hydrolysis.
When using the method according to the invention, 25 the solutions in vessels of the desired shape and dimension are placed in the autoclave. The vessel corresponds in shape and dimension to the shape and dimension of the monolithic gel which it is desired to manufacture. The vessel~ and optionally a cylinder placed therein, if a tubular gel is 30 manufactured, may consist of any material which is inert wi-th respect to the liquids used, for example, quartz~ In order to prevent adhesion it may be coated with a substance, for example, si~icone rubber and the like D
After the formation of the gel, increasing the 35 density may take place by heating for some time at a high temperature~ for example, at 1300 C. Dependent on the duration of heating, a more or less porous member is obtained. It is possible to manufacture a non-porous member, for example, by raising the -temperature -to 1300C at a rate of 300 C/hour, and main~aining this temperature for approximatel~ one hour. The heating may be carried out entirely or partly in a chlorine-containing atmosphere so as to expel the last hydrox-i1groups from the gel Glass members of any shape and porosity can be manufactured by means of the me-thod according to the inventionO The porosity depends on the leng-th of the heating period (densification period).
The glass members ob-tained by means of the method according to the invention ~ay be used in the manufacture of optical fibres, carrier members for catalysts (the members themselves may be used as a catalyst surface), for the selective separation of components and as molecular lS sieves.
The invention will now be described in greater detail with reference to the following specific examples.
xamE~
In order to make a solution having a molar ratio 20 of 4 C2H50H : 1 Si(OC2H5)4 : 6 H20, first 42 g of Si(OC2H5)4 and then 22 g of H20 are added to 37 g of C2H50H. The wa-ter has first been made alkaline with ammonia to pH = 8. By stirring at 50C~ the solution becomes clear, after which it is poured in four moulds. Saicl 25 moulds consist of tubes of approximately 15 mm diameter and 150 mm length closed at one end in which a rod of pyrex glass of 5 mm diameter is provided so as to be cen-tred. The moulds including the rods are covered with a thin layer of silicone rubber which serves as an anti-adhesion layer.
30 The mould~with the solution are placed in an autoclave of 500 ml capacity. After closing the autoclave nitrogen ~N2) is introduced until the pressure is 80 bar. The assembly is then heated to 300C at a ra-te of 1aO C/hour.
The overall pressure has then become 230 bar. After reaching 35 said temperature -the pressure is gradually removed at this temperature by opening a relief valve in such manner that the excessive pressure has dis~peared entirely after 7~2 approxima-tely ll5 rninutes. After cooling and opening the autoclave the moulds are removed. The moulds now comprise dry porous tubular gels which can be slid out of the tube and from the rod with some care without fracture. The dimensions correspond to those of the moulds. The tubes formed in this manner have a relative density of 0.14 g/cc and are only slightly translucent.
Example II:
A solution consisting of 26 g of e-thanol, 30 g of Si(OC2H5)4 and 20 g of H20 (pH = 8), which corresponds to a molar ratio of 4 : 1 : 8, is prepared and provided in the moulds in the same manner as described in Example I. Said moulds consis-t of tubes of 15 mm diameter and 150 mm length closed at one end and they are coated on their insides with a thin layer of silicone rubber. After introducing the moulds in the autoclave and closing of the autoclave (capacity 500 ml) the pressure is increased to 80 bar by means of nitrogen before heating the assembly to 300C at a rate of 100 C/hour. The final pressure then is 190 bar.
After removing the pressure and cooling, the autoclave is opened and the moulds are removed, The porous rods formecl slide from the moulds without any difficulty~are slightly translucent and have a density of 0.13 g/cc~
Experimen-ts carried out in a corresponding manner but with a pre-pressure of 40 bar and lO bar, respec-tively~ and a final pressure of 145 and 90 bar, respec-tively~ result in rods having a density of 0.14 g/cc and 0.27 g/cc, respectively. The last-mentioned gel is significantly smaller in volume than the original solution.
....~...
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of manufacturing monolithic glass members by preparing a monolithic gel from a solution comprising an alcoholic solvent and an alkoxy silane, in which the monolithic gel is dried by heating it in a hermetically closed container to a temperature above the critical temperature of the solvent and then removing the pressure at this temperature, after which the monolithic gel is heated to increase its density, characterized in that a pre-pressure of a gas is provided in the hermetically closed container which is so high that during the heating to a temperature above the critical temperature no boiling phenomena can occur in the solvent.
2. A method as claimed in Claim 1, characterized in that the formation of the gel takes place in the hermetically closed container.
3. A method as claimed in Claim 1, characterized in that, when ethanol is used as a solvent, a pre-pressure of at least 50 bar is used.
4. A method as claimed in Claim 1, characterized in that the gel is manufactured from a solution in ethanol which contains tetraethoxysilane.
5. A method as claimed in Claim 4, characterized in that a solution is prepared comprising at least 1 mol of tetraethoxysilane per litre of ethanol, that at least 2 mol of water are added to said solution per mol of tetraethoxysilane the pH of which is brought at a pH of between 7 and 8 by means of a volatile base, and that gelation takes place in the autoclave.
6. A method as claimed in Claim 5, characterized in that 4 to 8 mol of water per mol of tetraethoxysilane present are added to the solution.
7. A method as claimed in Claim 6, characterized in that 5 to 7 mol of water per mol of tetraethoxysilane are added.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL8304348A NL8304348A (en) | 1983-12-19 | 1983-12-19 | METHOD FOR THE MANUFACTURE OF MONOLITHIC GLASS BODIES |
| NL8304348 | 1983-12-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1260712A true CA1260712A (en) | 1989-09-26 |
Family
ID=19842892
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000470265A Expired CA1260712A (en) | 1983-12-19 | 1984-12-17 | Method of manufacturing monolithic glass members |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0147887B1 (en) |
| JP (1) | JPS60151232A (en) |
| AT (1) | ATE33128T1 (en) |
| AU (1) | AU3686584A (en) |
| CA (1) | CA1260712A (en) |
| DE (1) | DE3470026D1 (en) |
| NL (1) | NL8304348A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4788164A (en) * | 1987-01-28 | 1988-11-29 | Hoechst Celanese Corporation | Inorganic-organic composite compositions with sustained release properties |
| IT1230708B (en) * | 1989-02-10 | 1991-10-29 | Enichem Spa | GLASS MONOLITHS CONSISTING OF SILICON OXIDE AND TITANIUM OXIDE AND PROCEDURE FOR THEIR PREPARATION. |
| JPH0413726U (en) * | 1990-05-24 | 1992-02-04 | ||
| JPH0725126U (en) * | 1993-10-13 | 1995-05-12 | 株式会社サンカシ | Fittings for handrails |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2507171A1 (en) * | 1981-06-04 | 1982-12-10 | Zarzycki Jerzy | MONOLITHIC SILICA AEROGELS, THEIR PREPARATION AND THEIR USE FOR THE PREPARATION OF SILICA GLASS ARTICLES AND THERMALLY INSULATING MATERIALS |
-
1983
- 1983-12-19 NL NL8304348A patent/NL8304348A/en not_active Application Discontinuation
-
1984
- 1984-12-11 EP EP84201834A patent/EP0147887B1/en not_active Expired
- 1984-12-11 DE DE8484201834T patent/DE3470026D1/en not_active Expired
- 1984-12-11 AT AT84201834T patent/ATE33128T1/en not_active IP Right Cessation
- 1984-12-17 CA CA000470265A patent/CA1260712A/en not_active Expired
- 1984-12-17 JP JP59266067A patent/JPS60151232A/en active Granted
- 1984-12-18 AU AU36865/84A patent/AU3686584A/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| EP0147887A3 (en) | 1985-08-14 |
| JPS60151232A (en) | 1985-08-09 |
| ATE33128T1 (en) | 1988-04-15 |
| NL8304348A (en) | 1985-07-16 |
| EP0147887A2 (en) | 1985-07-10 |
| DE3470026D1 (en) | 1988-04-28 |
| EP0147887B1 (en) | 1988-03-23 |
| JPS6232135B2 (en) | 1987-07-13 |
| AU3686584A (en) | 1985-07-04 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |