Title of Invention | A PROCESS FOR MANUFACTURE OF AEROGELS |
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Abstract | An inorganic high strength aerogel having a density ranging from 0.4-1.4 gm/cc comprising carbon nanotubes functionalized in a methoxy alcohol homogenously dispersed by sonication in a metal oxide scaffold. |
Full Text | FORM-2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES 2003 Complete Specification (See section 10 and rule 13) A PROCESS FOR MANUFACTURE OF AEROGELS UNIVERSITY OF PUNE, an Organisation constituted under the Maharashtra State Universities Act of Ganeshkhind, Ganeshkhind Road, Pune 411 007, Maharashtra, India THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED. Field of Invention; This invention relates to a process for manufacture of aerogels. This invention also relates to aerogels manufactured by the above process. Background of the Invention A gel is generally a tenuous solid skeleton immersed in a liquid. Such liquid gels are also known as hydrogels. If the wet gels (hydrogels) are dried at ambient pressure, the gel shrinks to produce a small dry gel of high density and low porosity. But if the hydrogel is dried super-critically or sub-critically, the volume occupied by liquid is replaced by gas or air producing highly porous low density structures known as Aerogels. Thus aerogels are man made materials having ultra low density and large surface area. The low density is attributed to their highly porous structure. Aerogels are obtained by forming gel like materials of interest and slowly evaporating the liquid by super-critical or sub-critical drying process so as to obtain a solid monolithic material. In the process of evaporation of the liquid from the porous wet gel (also known as hydrogel) the liquid is replaced by air or gas and a network of particles is maintained. The most commonly used liquid solvent for aerogel preparation is alcohol. Alcohol is evaporated from the pores by heating the liquid at its critical temperature. By pouring the gel in an appropriate container aerogels of different shapes and sizes can be achieved. Aerogels can be divided into three major types: I. Organic Aerogels such as polyimide gels; generally formed by sol-gel polycondensation of resorcinol & formaldehyde. The hydrogels formed are subjected to supercritical drying to form organic aerogels. II. Carbon aerogels are generally produced by pyrolyzing organic aerogels in an inert atmosphere. III. Inorganic aerogels such as those of silica, titania, alumina; generally produced by solgel polycondesation of metals oxides to produce highly cross linked hydrogels which are subjected to supercritical drying to form inorganic aerogels. Since long time scientists have synthesized aerogels from different materials. [Reviews on the subject: J. Fricke, T. Tillotson, Thin Solid Films 297 (1997) 212-223, H. D. Gesser and P. C. Goswami, Chem. Rev. (1989), 89, 765] Aerogels made from silica are widely used in many applications. After the gel formation, the gels are dried either subcritically or supercritically. This produces a monolithic material. By following this usual procedure, low density silicagels are routinely obtained. Attempts have also been made to modify aerogels or create aerogel composites by altering their chemical composition or process parameters / steps to obtain aerogels / aerogel composites with desired blend of properties such as density, pore size, electrical conductivity, hydrophilic or hydrophobic properties and the like. US Patent No. 4873218, discloses the art of synthesizing a low density organic aerogel, typically a resorcinol - formaldehyde aerogel. US Patent 5360572 discloses an aerogel composite getter comprising a three di-mentional metal mash matrix completely coated on the interior surfaces with low density porous aerogel; the getter is used in decontamination system by mounting the getter in a gas duct or photocopy machine, fax machine or printer. US Patent application 20020025900 provides for an oxidation stable high temperature resistant, porous ceramic insulation obtained by pyrolyzing siloxane gels.. US application no.2004132845 discloses processes for preparation of polymide aerogels, carbon aerogels from the polymide aerogels, xerogel-aerogel hyprids and further impregnation of any or all of the above with highly dispersed transition metal clusters. The gel density of the polymide aerogels can be as low as 0.008 gm/cc and accessible surface area as high as 1300 m / g. US Patent application 20070037903 discloses a nano composite that included aerogel components and polymeric components and has decreased hydrophilicity and improved mechanical and electrical characteristics. However, aerogels described in the prior art are extremely fragile & get easily broken into pieces during handling. Secondly they cannot be used where strength of material or weight bearing is required along with low density. Thus there is a need for an aerogel and a process for production of an aerogel which has increased mechanical strength and yet retains the characteristics of low density, high porosity and high surface area. Objects of the Invention It is an object of this invention to provide an aerogel which has increased mechanical strength while retaining the characteristics of low density, high porosity and high surface area. It is also an object of this invention to provide a process for preparation of the aerogel with the aforesaid properties. It is also an object of this invention to provide .a simple economical process for preparation of the aerogel Summary According to this invention there is provided an aerogel containing well dispersed predetermined quantity of carbon nanotubes. Particularly but not limited thereto the aerogel is a silica aerogel and the aerogel of this invention contains a porous network of silica aerogel with carbon nanotubes uniformly dispersed in the silica-aerogel scaffold. Accordingly therefore the inorganic high strength aerogel of this invention has a density ranging from 0.4-1.4 gm/cc and comprises carbon nanotubes functionalized in a methoxy alcohol homogenously dispersed by sonication in a metal oxide aerogel scaffold. The oxide is typically selected from a group of oxides of silicon, titanium and aluminum. Typically, the methoxy alcohol is at least one alcohol selected from a group of alcohols consisting of 3-mercaptopropyltrimethoxysilane [MPTMS], 3 aminoprpyltriethoxysilane, [APS], 3 aminopropyltrimethoxysilane [MPTS], and nndiethylformamide [DMF]. Typically,the carbon nano tubes are single walled, multi walled or mixed i.e. both single walled and multiwalled. This invention also extends to a process for making an inorganic high strength aerogel comprising the steps of i. forming an inorganic aerogel by hydrolysis and condensation of at least one metal oxide to produce a highly cross linked hydrogel, ii. functionalizing carbon nano tubes in an alkoxyl alcohol solution , and homogenously dispersing the carbon nano tubes in the solution by sonication for 20 to 40 minutes to form a homogenous dispersion; iii. mixing the dispersion to the hydrogel before its gelation point and stirring to form a mixture; iv. supercritically or subcritically drying the mixture to form a high strength inorganic aerogel. Typically, the oxide is an oxide of an element selected from a group containing silicon, titanium and aluminium. Typically, the alkoxyl alcohol is at least one alcohol selected from a group of alcohols consisting of MPTMS, APS, MPTS, and DMF, preferably 3-mercaptopropyltrimethoxysilane (MPTMS). Typically, the ratio of the methoxyl alcohol to carbon nanotube solution ranges between 1: 5 to 1 : 100. Typically, the mixture is poured in a mold before drying. In accordance with a preferred embodiment of the invention the carbon nanotubes are multiwalled walled but they can also be single walled, or mixed. The carbon nanotubes are uniformly dispersed in an alcohol media of the alkoxyl , by typically first functionalizing the carbon nanotubes by dispersing CNTs in an alkoxyl alcohol, typical methoxyl or ethoxyl alcoholic solvent. In accordance with a preferred embodiment of the invention the aerogels are synthesized by the process of hydrolysis and condensation in an alkoxysilane acting as a functionalizing solvent is an alkoxylsilane. To avoid agglomeration in the process of dispersing the carbon nanotubes in the solvent the dispersant is subjected to continuous sonication, typically for 20 t0 40 minutes to keep the CNTs dispersed in the alcohol. A typical aerogel in accordance with this invention is prepared as under : A solution designated as solution A is prepared as follows: first the sol-gel reactant: water (5-15ml), ethyl alcohol (2-20ml), ammonium fluoride (0.05-2ml) and ammonia solution (0.01-1 ml) are reacted together. The resulting mixture is stirred vigorously for 15-30 minutes. Typically, tetraethoxyorthosilicate (TEOS) is added after 20-30 minutes. The mixture after addition of TEOS becomes turbid. The mixture is stirred vigorously until the solution becomes colorless again to obtain Solution A. A solution B is prepared by functionalizing CNT in an alcoholic solution with an alkoxyl group functionalizing agent, such as 3-mercaptopropyltrimethoxysilane (MPTMS). Typically, 10-100 ul of the methoxyl alcohol is reacted with 100-250 ul, 250 - 450 ul and 450-550 ul of CNT solutions. The CNTs can be single walled , multi walled or mixed. The solutions were sonicated continuously for 30 minutes to obtain three different solutions B. Alternative methoxyl group functionalizing agents can include APS, MPTS, and DMF. The solutions B were separately added into solution A just before gelation point, and were mixed well by stirring. A homogeneous dispersion of CNT in the mixtures were obtained. The aerogels obtained by use of a functional agent in accordance with this invention had a density ranging from 0.4-1.4 gm/cc, preferably between 0.4 and 0.6. The mixtures were poured into molds to obtain monolithic materials and were subcritically dried for approximately 8 days to obtain high strength aerogel pieces. Alternatively, the drying could also have been supercritical for about 8 days. The aerogels obtained in accordance with this invention were high strength silica-CNT aerogels. Three pieces of silica-CNT aerogel weighing about 15 mg could support 7.5 kg weight over them, that is five lakh times their own body weight. The density and strength of the samples was determined as follows. To measure the density of the aerogel produced in accordance with this invention, the weight of each piece of aerogel and its dimensions were measured. Each aerogel had a diameter of about 2 mm and a height of about 10 mm. The density of each gel was calculated by the formula: Density (p) = mass (gms) volume (cm3) Volume (for a cylindrical aerogel) = p r2 h Where, r is the radius and h is the hight of the cylinder. The samples were subjected to Micro-Vickers hardness test. Weights of 20 gm, 50 gm, and 100 gm were put on each aerogel. The hardness, H, was defined as the maximum load, L, divided by the indent surface area of the indent. Or VHN = 1.854P/area where P is the applied load in kg. The density, strength and hardness measured for the silica-CNT samples are as follows. Example Density gm/cc Hardness GPa 20 gm 50 gm 100 gm 1 0.7-1.4 0.74 0.40 0.22 2 0.9-1.0 0.64 0.36 0.20 3 0.4-0.6 0.62 0.37 0.20 Thus compared to any previously reported silica aerogels the present invention reports a higher strength aerogel, typically a silica aerogel developed using a new process in accordance with this invention . Typically the aerogels in accordance with this invention have a porosity greater than 90% and a surface area greater than 200 sq. m/gm - 500 sq. m/gm. The aerogels in accordance with this invention can be upscaled to obtain aerogels of any size or shape. In view of the wide variety of embodiments to which the principles of the present invention can be applied, it should be understood that the illustrated embodiments are exemplary only. The illustrated embodiments should not be taken as limiting the scope of the present invention. For example, the inter reactions between the additives may be taken in sequences other than those described, and more or fewer substances may be used. While various steps of the preferred embodiments have been described as being implemented, other embodiments implementations may alternatively be used, and vice-versa. We Claim: 1. An inorganic high strength aerogel having a density ranging from 0.4-1.4 gm/cc comprising carbon nanotubes functionalized in a methoxy alcohol homogenously dispersed by sonication in a metal oxide scaffold. 2. An inorganic high strength aerogel as claimed in claim 1, wherein the oxide is selected from a group of elements consisting of silicon, titanium and aluminum. 3. An inorganic high strength aerogel as claimed in claim 1, wherein the methoxy alcohol is at least one alcohol selected from a group of alcohols consisting of MPTMS, APS, MPTS, and DMF. 4. An inorganic high strength aerogel as claimed in claim 1, wherein the carbon nano tubes are single walled, multi walled or mixed. 5. A process for making an inorganic high strength aerogel comprising the steps of i. forming an inorganic aerogel by hydrolysis and condensation of at least one metal oxide to produce a highly cross linked hydrogel, ii. functionalizing carbon nano tubes in an alkoxyl alcohol solution, and homogenously dispersing the carbon nano tubes in the solution by sonication for 20 to 40 minutes to form a homogenous dispersion; iii. mixing the dispersion to the hydrogel before its gelation point and stirring to form a mixture; iv. supercritically or subcritically drying the mixture to form a high strength inorganic aerogel. 6. A process for making an inorganic high strength aerogel as claimed in claim 5, in which oxide is an oxide of an element selected from a group containing silicon, titanium and aluminium. 7. A process for making an inorganic high strength aerogel as claimed in claim 5, in which the alkoxyl alcohol is at least one alcohol selected from a group of alcohols consisting of MPTMS, APS, MPTS, and DMF. 8. A process for making an inorganic high strength aerogel as claimed in claim 5, in which the alkoxyl alcohol is 3-mercaptopropyltrimethoxysilane (MPTMS). 9. A process for making an inorganic high strength aerogel as claimed in claim 5, in which the ratio of the methoxyl alcohol to carbon nanotube solution ranges between 1: 5 to 1 : 100. 10. A process for making an inorganic high strength aerogel as claimed in claim 5, in which the mixture is poured in a mold before drying. ABSTRACT An inorganic high strength aerogel having a density ranging from 0.4-1.4 gm/cc comprising carbon nanotubes functionalized in a methoxy alcohol homogenously dispersed by sonication in a metal oxide scaffold. |
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2487-MUM-2007-ABSTRACT(7-9-2011).pdf
2487-MUM-2007-CLAIMS(AMENDED)-(29-3-2011).pdf
2487-MUM-2007-CLAIMS(AMENDED)-(30-3-2012).pdf
2487-MUM-2007-CLAIMS(AMENDED)-(7-9-2011).pdf
2487-MUM-2007-CLAIMS(MARKED COPY)-(29-3-2011).pdf
2487-MUM-2007-CLAIMS(MARKED COPY)-(30-3-2012).pdf
2487-MUM-2007-CORRESPONDENCE(11-11-2011).pdf
2487-mum-2007-correspondence(29-4-2008).pdf
2487-MUM-2007-CORRESPONDENCE(30-3-2012).pdf
2487-mum-2007-correspondence-received.pdf
2487-mum-2007-description (complete).pdf
2487-mum-2007-form 1(29-4-2008).pdf
2487-mum-2007-form 13(29-4-2008).pdf
2487-mum-2007-form 13(7-9-2011).pdf
2487-mum-2007-form 18(27-12-2007).pdf
2487-mum-2007-form 9(27-12-2007).pdf
2487-MUM-2007-MARKED COPY(7-9-2011).pdf
2487-MUM-2007-POWER OF AUTHORITY(7-9-2011).pdf
2487-MUM-2007-REPLY TO EXAMINATION REPORT(29-3-2011).pdf
2487-MUM-2007-REPLY TO HEARING(7-9-2011).pdf
2487-MUM-2007-SPECIFICATION(AMENDED)-(7-9-2011).pdf
Patent Number | 253013 | ||||||||||||
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Indian Patent Application Number | 2487/MUM/2007 | ||||||||||||
PG Journal Number | 25/2012 | ||||||||||||
Publication Date | 22-Jun-2012 | ||||||||||||
Grant Date | 14-Jun-2012 | ||||||||||||
Date of Filing | 18-Dec-2007 | ||||||||||||
Name of Patentee | UNIVERSITY OF PUNE | ||||||||||||
Applicant Address | GANESHKHIND, GANESHKHIND ROAD, PUNE-411 007, | ||||||||||||
Inventors:
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PCT International Classification Number | B01D39/20 | ||||||||||||
PCT International Application Number | N/A | ||||||||||||
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PCT Conventions:
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