Title of Invention

"A PROCESS FOR THE PREPARATION OF NANOMATERIAL."

Abstract

A process for nanomaterials defined as materials with grain size less than 100 nm has been disclosed. The nanomaterials are important as these exhibits markedly improved characteristics due to size reduction. The invented process presents a procedure for preparation of different types of nanomaterials that are useful for different applications. In this a liquid precursor is sprayed in presence of a reactive gas and a hot inert gas is simultaneously employed to obtain a nanomaterial in dry powder form. The process is simple and involves a single step/stage. Process gives controlled size of nanomaterials. The process is suitable for production of nanomaterials from few grams to hundreds of kilograms per hour.

Full Text

The present invention relates to a process for the preparation of nanomaterials having the particles size less than 100 nm. Nanomaterials have become important in recent years because of the markedly different electrical, optical and structural properties of these as compared to those in the conventional bulk form. For example, semiconductor nanocrystals exhibit a continuous shift of the absorption energy to higher energies due to quantum confinement. Further, it is an observed fact that in bulk crystalline luminescent materials there is a decrease in emission intensity after size reduction by conventional means, whereas, an increase of the efficiency of nanocrystalline phosphor compared to the bulk material is in direct contrast. This makes semiconductor nano-structure physics one of the frontier areas of research in condensed matter physics. An influence of the particle size on the luminescence decay time has also been reported. The enormous global interest in the field is also due to the fabrication of devices using nanomaterials with special and advanced features. Nanotechnology being an emerging and pioneer area, there is still a lot of scope for development of new techniques and processes for preparation of nanomaterials. The development of nanomaterials for devices and varied applications will depend on basic understanding of the mechanism of enhancement in properties and changes in structure of these down to quantum level. These developments are demanding refinement of existing and a search for newer preparation processes of nanomaterials with an emphasis on control of particle size and morphology. A number of synthesis processes for nanomaterials such as chemistry by microwaves, mechanochemistry, self-assembly, lithography, template and membrane based synthesis have been developed and employed by scientists, chemists and engineers the world over, but the researcher will always be on look out to produce nanomaterials with a cheaper, cleaner, reliable and industrially feasible techniques. Realization of these challenges is possible only with control of thermodynamics and kinetics of reaction, nucleation, growth, aging etc. in process. The technique must also take care of crystallization with- the symmetry of parent as well as dopant atoms at surface of nanomaterials as surface to volume ratio of these materials is very high. A number of patents have appeared on preparation of nanomaterials with different processes. Matson et al filed US Patent 5,238,671 in August 1993 for preparation of nanomaterials by chemical reactions involving reverse micelle/microemulsion systems. In this a microemulsion of a polar fluid e.g. an aqueous fluid is made in non-polar fluid in supercritical state. Reactants are introduced into the micelles via non-polar fluid, which is a continuous phase. Gallagher et al patented (US Pat 5,525,377 June 1996) a method of manufacturing encapsulated doped particles of size nanostructured material inside a mesoporous material. A monolayer of charged functional group of nanomaterial to be produced is attached on the inside wall of mesoporous material by reaction. Then nanomaterial is generated by reduction/oxidation etc. Mark and Gareth patented (GB2381530) a process for preparing water soluble particles of luminescent materials. It involves coating particles of the luminescent material with an organic acid or Lewis base such that the surface of the coating possesses one or more reactive group so that these can be used for biotagging. Jose et al claimed (EP1339075) synthesis of magnetic nanoparticles via decomposition of organometallic precursors in solution in presence of a reaction gas and a mixture of organic ligands. Another process for synthesis of nanomaterials particularly of carbon has been patented by Peter et al (WO2004007361). Processes/techniques disclosed above in the prior art disclosures for preparation of nanomaterials involve use of large number of energy and cost intensive starting chemicals and generally there are many stages in the processes. At times, by products are produced that are a big environmental hazard. These extra steps in the processes make the end product, a nanomaterial very costly. Some of the processes are for a specific type of chemical compound or an application. The main object is to provide a process for preparation of different types of nanomaterials, such as nano sized oxides, carbonates, sulphides, and other salts Another object of present invention is to provide a variety of nanomaterials, such as semiconductors, magnetic materials, opto electronic material, ceramic material etc.. Yet another object of present invention is to provide nanomaterial in dry powder form. Yet another object of present invention is to provide nanomaterial from a process that involves almost a single step/stage Still another object of present invention is to provide nanomaterials for different applications. Accordingly, the present invention provides a process for the preparation of nanomaterial having the particles size of less than 100 nm, which comprises injecting an aqueous solution of precursor in the form of a spray in a chamber through an inlet port, reacting the above said spray with a reactant gas introduced in the above said chamber through another inlet, in the presence of a hot air, nitrogen or oxygen introduced simultaneously through yet another inlet port in the same chamber to obtain the desired nanomaterial and collecting it through an out let port of the said chamber. In an embodiment of the present invention the precursor used is containing at least one radical of the desired nanomaterial obtained. In yet another embodiment the precursor used is selected from salts of alkali and alkaline earth elements, transition metal elements, transition metal complexes and a mixture thereof. In yet another embodiment the reactant gas used is containing a radical different from the precursor radical for obtaining the desired nanomaterial. In yet another embodiment the reactant gas used is selected from hydrogen sulphide, sulphur dioxide, carbon dioxide and nitrogen dioxide. In yet another embodiment the reactant gas used is introduced into the chamber in such a manner to have a maximum contact with the spray. In yet another embodiment the reactant gas used is either pure or can be diluted or mixed with an inert gas to control the rate of the reaction. In yet another embodiment the reactant gas used is introduced either along or counter to the direction of the spray or radial to spray or in a mixed pattern. In yet another embodiment the hot air, nitrogen or inert gas used is introduced either along or counter to the direction of the spray or radial to spray or in a mixed pattern. In yet another embodiment the hot air, hot nitrogen or hot inert gas used is for evaporating the solvent from the resultant nanomaterial. In yet another embodiment the temperature of the hot air, hot nitrogen or hot inert gas used is in the range of 50-250 °C. In yet another embodiment the hot gas used act as a reactant gas in the event of a reaction between the hot gas and the precursor material resulting in the production of the desired nanomaterial. In yet another embodiment the size of the nanomaterial obtained is controlled by the size of droplets or drops of the spray of liquid precursor used in the reaction. In yet another embodiment the particle size of the nanomaterial obtained is controlled by the concentration of the anion constituent of the liquid precursor used in the reaction.- The process of the present invention is simple and involves a single step/stage and gives controlled size of nanomaterials. The process is suitable for production of nanomaterials from few grams to hundreds of kilograms per hour. The invention has diverse applications, as preparation of nanomaterials is very important nowadays as these materials are finding newer and crucial high-tech applications everyday. Some of the applications are very high-resolution displays, smart windows, dye-sensitised solar cells, and sensors for various applications, batteries, large value capacitors and others, which are changing fundamental and industrial perspective. Future deployment of nanomaterials in device and varied applications will depend on basic understanding of the mechanism of enhancement in properties and changes in structure of these down to quantum level. These developments are demanding refinement of existing and a search for new preparation processes of nanomaterials with an emphasis on control of particle size and morphology. A number of synthesis processes for nanomaterials as described in prior art have been developed and employed by scientists, chemists and engineers the world over, but to produce nanomaterials with a cheaper, cleaner, reliable and industrially feasible technique, inventors are always on look out. Realization of these challenges is possible only with control of thermodynamics and kinetics of reaction, nucleation, growth, aging etc. in process. The technique must also take care of crystallization with the symmetry of parent as well as dopant atoms at surface of nanomaterials as surface to volume ratio of these materials is very high. In this invention, a spray of precursor solution containing one radical of host material is introduced in a chamber from one port and a reactant gas with other radical of the host from other port and simultaneous introduction of hot air or inert gas from another point and a dried nanomaterials in powder form is collected with adjacent collecting equipment in one-step process. The inventive step involved a reaction of an aqueous solution of liquid precursor material with a reactant gas under spray condition with simultaneous drying of the resultant nanomaterial by a hot gas. Novelty of the present invention is in providing a simple process to produce nanomaterials on commercial scale that gives a nanomaterial, which is a single chemical compound or a homogeneous mixture of a number of chemical compounds. The process has many control parameters to adjust particle size, morphology etc of nanomaterials produced. The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of the present invention. Example 1 Aqueous solution of cadmium nitrate (0.1 M) is sprayed in a chamber from top mid region in 10-50 micrometer droplet size range. Hydrogen sulfide gas is introduced in direction radial to the spray. Hot nitrogen gas at temperature 150 °C is introduced from mid region at the bottom of the chamber. Nanosized cadmium sulfide dry 50-70 nm powder is collected by cyclone from top outlet diagonally/diametrically opposite to hydrogen sulfide gas inlet. Example 2 Aqueous solution of calcium hydroxide (0.01 M) is sprayed in a chamber from top mid region in 10-50 micrometer droplet size range. Sulfur dioxide gas is introduced in direction parallel to the spray from a large area annular distributor. Hot air at temperature 200 °C is introduced from mid region at the bottom of the chamber. Nanosized calcium sulfate dry 40-70 nm size powder is collected by cyclone from top outlet. Example 3 Aqueous solution of zinc ammonia chloro complex (0.1 M) sprayed in a chamber from top mid region in 20-50 micrometer droplet size range using by air flow from an annular opening next to the solution outlet. Hydrogen sulfide gas is introduced from another annular opening next to the air opening in the same direction as the spray. Hot air at temperature 200-220 °C is introduced from the next adjacent annular opening again in the same direction as spray. Nanosized zinc sulfide dry 50-100 nm powder is collected by cyclone from bottom outlet of the chamber. Example 4 Aqueous solution of zinc ammonia chloro complex (0.1 M) mixed with 0.01 M manganese chloride in ratio 1:01 is sprayed in a chamber from top mid region in 10-50 micrometer droplet size range. Hydrogen sulfide gas is introduced in direction radial to the spray at a distance 0.2 of the radius of chamber. Hot nitrogen gas at temperature 200 °C is introduced from mid region at the bottom of the chamber. Nanosized luminescent zinc sulfide doped manganese dry 50-70 nm powder is collected by cyclone from top outlet diagonally/diametrically opposite to hydrogen sulfide gas inlet. Main advantages of the invention are: 1. The process is suitable for preparation of different types of nanomaterials used for variety of applications such as semiconducting, insulating, magnetic, luminescent and optical etc. 2. The process provides nanomaterials in dry powder form. 3. The process is less cumbersome due to very limited number (almost one) of steps involved. We claim: 1. A process for the preparation of nanomaterial having the particles size of less than 100 nm, which comprises injecting an aqueous solution having concentration in the range of 0.01 M to 0.1 M of precursor containing atleast one radical of desired nanomaterial in the form of a spraying 10-50 micrometer droplet size range in a chamber through an inlet port, reacting the above said spray with a reactant gas introduced in the above said chamber through another inlet, in the presence of a hot air, nitrogen or oxygen at a temperature in the range of 50-250°C introduced simultaneously through yet another inlet port in the same chamber to obtain the desired nanomaterial and collecting it through an out let port of the said chamber. 2. A process as claimed in claim 1, wherein the precursor used is selected from salts of alkali and alkaline earth elements, transition metal elements, transition metal complexes and a mixture thereof. 3. A process as claimed in claims 1-2, wherein the reactant gas used is containing a radical different from the precursor radical for obtaining the desired nanomaterial. 4. A process as claimed in claims 1-3, wherein the reactant gas used is selected from hydrogen sulphide, sulphur dioxide, carbon dioxide and nitrogen dioxide. 5. A process as claimed in claims 1-4, wherein the reactant gas used is introduced into the chamber in such a manner to have a maximum contact with the spray. 6. A process as claimed in claims 1-5, wherein the reactant gas used is either pure or can be diluted or mixed with an inert gas to control the rate of the reaction. 7. A process as claimed in claims 1-6, wherein the reactant gas used is introduced either along or counter to the direction of the spray or radial to spray or in a mixed pattern. 8. A process as claimed in claims 1-7, wherein the hot air, nitrogen or inert gas used is introduced either along or counter to the direction of the spray or radial to spray or in a mixed pattern. 9. A process as claimed in claims 1-8, wherein the hot air, hot nitrogen or hot inert gas used is for evaporating the solvent from the resultant nanomaterial. 10. A process as claimed in claims 1-9, wherein the temperature of the hot air, hot nitrogen or hot inert gas used is preferably in the range of 150-220 °C. 11. A process as claimed in claims 1-10, wherein the hot gas used act as a reactant gas in the event of a reaction between the hot gas and the precursor material resulting in the production of the desired nanomaterial.

Documents:

1984-DEL-2005-Abstract-(05-09-2011).pdf

1984-del-2005-abstract.pdf

1984-DEL-2005-Claims-(05-09-2011).pdf

1984-del-2005-claims.pdf

1984-DEL-2005-Correspondence Others-(05-09-2011).pdf

1984-del-2005-correspondence-others.pdf

1984-del-2005-description (complete).pdf

1984-del-2005-form-1.pdf

1984-del-2005-form-18.pdf

1984-del-2005-form-2.pdf

1984-DEL-2005-Form-3-(05-09-2011).pdf

1984-del-2005-form-3.pdf

1984-del-2005-form-5.pdf