Nanometric tin-containing metal oxide particle and dispersion, and preparation method and application thereof

Abstract

There is disclosed a tin-containing metal oxide nanoparticle, which has an index of dispersion degree less than 7 and a narrow particle size distribution which is defined as steepness ratio less than 3. There is disclosed dispersion, paint, shielding film and their glass products which comprise the said nanoparticles. Besides, there are also disclosed processes of making the tin-containing metal oxide nanoparticle and their dispersion. The tin-containing metal oxide nanoparticles and their dispersion disclosed herein may be applied on the window glass of houses, buildings, vehicles, ships, etc. There is provided an excellent function of infrared blocking with highly transparent, and to achieve sunlight controlling and thermal radiation controlling.

Claims

1. A method for preparing a dispersion of tin-containing metal oxide nano-particles, wherein the tin-containing metal oxide comprises tin element and an aid metallic element other than tin selected from antimony, indium, titanium, copper, zinc, zirconium, cerium, yttrium, lanthanum, niobium or a mixture thereof; and the tin-containing metal oxide nano-particles have an initial average particle diameter of 2-50 nm, a particle diameter distribution as defined with an Index of dispersion degree of less than 7 and a steepness ratio of less than 3, the method comprises steps of: (1) reacting a solution containing tin ions and a solution containing ions of the aid metallic element other tin with a solution of precipitating agent at a temperature of less than 100 C. under a non-acidic condition in an aqueous medium comprising at least one of alcohols, amides, ketones, epoxides and mixtures thereof to form tin-containing metal oxide precursor particles and a first by-product in ionic form; wherein the precipitating agent is selected from alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal bicarbonates, ammonia, organic bases and mixtures thereof; (2) separating the tin-containing metal oxide precursor particles from the first by-product in ionic form to obtain tin-containing metal oxide precursor particles substantially free of ionic impurities; (3) reacting the tin-containing metal oxide precursor particles substantially free of Ionic impurities with an oxidizing agent or a reducing agent at a temperature of 150-400 C. and a pressure of 5 to 10 atmospheres to obtain tin-containing metal oxide particles and a second by-product in ionic form; (4) coating the tin-containing metal oxide particles with a surfactant in an amount of 0.01% to 30% relative to the weight of tin-containing metal oxide particle to obtain coated tin-containing metal oxide particles, wherein the surfactant is selected from a non-silane surface modifying agent, a silane coupling agent, a titanate coupling agent, or a mixture thereof, and the non-silane surface modifying agent is selected from cationic surfactants, non-ionic surfactants, polymeric surfactants and mixtures thereof; (5) separating the coated tin-containing metal oxide particles from the second by-product in ionic form to obtain tin-containing metal oxide nano-particles substantially free of ionic impurities; (6) adding a dispersion medium and a dispersing agent to the tin-containing metal oxide nano-particles substantially free of Ionic impurities to obtain the dispersion of tin-containing metal oxide nano-particles, wherein, when the dispersion medium is water in step (6), the dispersing agent is one or more selected from ethanolamine, triethanolamine, triethylamine, diisopropanol amine, tetramethylammonium hydroxide, polyvinyl alcohol, methacryloxy silane, polyacrylic acid ammonium salt dispersing agent, polyacrylic acid sodium salt dispersing agent, polysiloxane dispersing agent, polyamide dispersing agent, polymer block copolymer dispersing agent; and when the disperse medium is an organic solvent the dispersing agent is one or more selected from octylamine, polycarboxylic salt dispersing agents, polycarboxylic-sulfonic copolymer dispersing agents, polymaleicanhydride copolymer dispersing agents, silane coupling agents, titanate coupling agents.

2. The method according to claim 1, wherein the separating of step (2) or (4) is carried out by any one of methods of liquid-liquid phase transfer, liquid-liquid phase transfer after washing, centrifugation after washing, filtration after washing.

3. The method according to claim 1, wherein the reacting of step (1) is carried out at a temperature range of 40-80 C., under substantially alkaline condition, the aqueous medium comprising one or more alcohols mixed with water, wherein the alcohols have a volume of 1% to 99% relative to water.

4. The method according to claim 1, wherein the tin ions and/or ions of other metal in step (1) are derived from their acetate, halide, nitrate, phosphate, sulfate, perchlorate, borate, iodate, carbonate, perchlorate, tartrate, formate, gluconate, lactate, sulfamate, hydrates or mixtures of these salts.

5. The method according to claim 1, wherein said oxidizing agent in step (3) is a peroxide selected from Na.sub.2O.sub.2, K.sub.2O.sub.2, H.sub.2O.sub.2 and peroxyacetic acid, and the reducing agent in step (3) is selected from hydrazine hydrate, ethylenediamine, oxalic acid, formaldehyde, acetaldehyde, metallic tin powder, sodium borohydride and a mixture thereof.

6. The method according to claim 1, wherein said step (1) and/or step (3) is carried out under high shear condition.

7. The method according to claim 1, wherein, in step (8), the dispersing agent has an amount in range of 5% to 20% based on the weight of tin-containing metal oxide nano-particles.

8. The method according to claim 1, wherein the tin-containing metal oxide nano-particles have a crystal structure selected from tetragonal cassiterite, bixbyite, tetragonal cassiterite-like and bixbyite-like structure.

9. The method according to claim 1, wherein the tin-containing metal oxide is an antimony-tin oxide or an indium-tin oxide.

10. The method according to claim 1, wherein the dispersion has a solid content of the tin-containing metal oxide nanoparticles of at least 5%.

11. The method according to claim 1, further comprising the following step: (7) adding a dispersion of nano-sized zinc oxide, titanium oxide or cerium oxide to the dispersion of tin-containing metal oxide nano-particles.

Description

BRIEF DESCRIPTION OF DRAWING

(1) The accompany drawing illustrate a disclosed embodiment and serves to explain the principles of the disclosed embodiment. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition of the limits of the invention.

(2) FIGS. 1A and 1B are optimized schematic diagrams of the flow chart described in this invention, wherein FIG. 1A is the schematic diagrams of the flow chart for implementing the process for the production of tin-containing metal oxide particles and their dispersion, and FIG. 1B is the schematic diagrams of the flow chart for implementing the process for the further production of dispersion of nano-sized metal oxide composite.

(3) FIGS. 2A and 2B show the high resolution transmission electron microscope (HRTEM) images of monodispersed ATO nanoparticles prepared in example 1 below. FIG. 2A was obtained at 50 k magnification and FIG. 2B was obtained at 500 k magnification.

(4) FIG. 3 shows a dynamic light scattering (DLS) pattern of the monodispersed ATO nanoparticles prepared in example 1 below.

(5) FIG. 4 shows the HRTEM images of monodispersed ATO nanoparticles prepared in example 3 below. It was obtained at 50 k magnification.

(6) FIG. 5 shows an X-ray Diffraction (XRD) pattern of monodispersed ATO nanoparticles prepared in example 3 below.

(7) FIG. 6 shows a DLS pattern of the monodispersed ATO nanoparticles prepared in example 3 below.

(8) FIGS. 7A and 7B show the HRTEM images of monodispersed ATO nanoparticles prepared in example 4 below. FIG. 7A was obtained at 50 k magnification and FIG. 7B was obtained at 500 k magnification.

(9) FIGS. 8A and 8B show the HRTEM images of monodispersed ATO nanoparticles prepared in example 6 below. FIG. 8A was obtained at 50 k magnification and FIG. 8B was obtained at 500 k magnification.

(10) FIG. 9 shows the UV-Vis-NIR spectrum of ATO nanoparticles with different antimony doping levels dispersed in water with 5% of solid content prepared in example 7 below.

(11) FIG. 10 shows the UV-Vis-NIR spectrum of ATO nanoparticles dispersed in water with different solid content prepared in example 8 below.

(12) FIG. 11 shows the UV spectrum of ATO nanoparticles and ATO+CeO.sub.2 or ATO+ZnO metal oxide nanoparticles composite dispersed in water with 5% of solid content prepared in example 9 below.

(13) FIGS. 12A and 12B show the UV-Vis-NIR spectrum of glass coated by aqueous acrylic acid paint containing ATO nanoparticles or ATO+ZnO nanoparticles using dip-coating method or gravity-coating method in example 10 below. FIG. 12A shows the UV part of the spectrum, and FIG. 12B shows the whole spectrum.

DETAILED DESCRIPTION OF DRAWINGS

(14) Referring to FIG. 1A, there is provided a process for the preparation of the dispersion of other metal-doped tin oxide. In the first step, a mixed metal salts solution (12) formed by mixing tin salt solution and other metal salt solution (such as mixed salt solution of tin chloride and antimony chloride) is mixed with a precipitant solution (14), which is alkali (such as potassium hydroxide, sodium hydroxide or ammonia solution). The precipitating reaction is carried out in a reaction zone (10) which may be a beaker, a flask or a reactor. A shear force is applied to the mixture during the mixing and reacting step. The reaction zone (10) is typically maintained at a temperature of between 5 degrees Celsius to 95 degrees Celsius, at atmospheric pressure and at a pH of 7.5 to 10. Within the reaction zone (10), the tin-containing metal oxide precursor particles and the by-products thereof are formed.

(15) The separation of the tin-containing metal oxide precursor particles and the by-products thereof is carried out during the separating step (20) to remove the ionic by-products (22). In the high temperature and high pressure reaction zone (30), both tin-containing metal oxide precursor particles and oxidizing agents (or reducing agents based on the requirement of the doping agent) are added, for antimony-doped tin oxide, normally oxidizing agent is required and for indium-doped tin oxide, normally reducing agent is required. The reacting step to the tin-containing metal oxide precursor solution is maintained for a certain time under high temperature and high pressure condition, and a shear force is applied to the mixture to ensure the uniformly formation of the tin-containing metal oxide crystalline particles. The high temperature and high pressure reaction zone is typically maintained at a temperature of between 120 degrees Celsius to 500 degrees Celsius and at a pressure of between 1 atmosphere to 20 atmospheres.

(16) The suspension of tin-containing metal oxide is taken from the high temperature and high pressure reaction zone, and a surfactant (42) is added for coating (40) of the tin-containing metal oxide particles. The surfactant may be selected from, but not limited to, the group consisting of oleic acid, sodium oleate, sodium abietate, sodium stearate, sodium octoate, sodium linoleate, hexadecyltrimethyl ammonium bromide, silane coupling agent, titanate coupling agent, sugar, ethylene glycol, maltose, citric acid, sodium citrate or mixtures thereof.

(17) After the coating step, the ionic by-products in the tin-containing metal oxide crystalline particles are removed during a separating step (50) such as phase transfer, or washing methods, etc.

(18) Optionally, a dispersing agent is added to the tin-containing metal oxide crystalline particles after removing the ionic by-products for further dispersion. For dispersing agent selection, if the disperse medium is water, one or more dispersing agents may be selected from, but not limited to, the group consisting of: ethanolamine, triethanolamine, triethylamine, diisopropanol amine, tetramethylammonium hydroxide, sodium metaphosphate, sodium hexametaphosphate, polyvinyl alcohol, methacryloxy silane, polyacrylic acid ammonium salt dispersing agent, polyacrylic acid sodium salt dispersing agent, polysiloxane dispersing agent, polyamide dispersing agent, polymer block copolymer dispersing agent; if the disperse medium is an organic solvent, one or more dispersing agents may be selected from, but not limited to, the group consisting of: polycarboxylic salt dispersing agent, polycarboxylic-sulfonic copolymer dispersing agent, polymaleicanhydride copolymer dispersing agent, silane coupling agent, titanate coupling agent. The concentration of the surfactants and dispersing agents mentioned above is in the range of about 5% to about 20% based on the weight of tin-containing metal oxide particles.

(19) After that, the tin-containing metal oxide crystalline nanoparticles may be dried by traditional methods (such as oven drying, spray drying, rotary-evaporation drying, etc.) to form tin-containing metal oxide powder product (55), or added into disperse medium (62) for dispersing (60) to produce dispersion of nano-sized tin-containing metal oxide (65).

(20) Optionally, if the disperse medium is water, the dispersion of tin-containing metal oxide particles in aqueous phase may be obtained by adjusting the pH value of the dispersion.

(21) Referring to FIG. 1B, a disperse medium (80) is further used for mixing (80) of tin-containing metal oxide nanoparticles (55) or their dispersion (65) prepared according to FIG. 1A which may block IR and nano-sized metal oxide such as zinc oxide, titanium oxide and cerium oxide nanoparticle (72) or their dispersions (74) with good compatibility which may block UV to form a dispersion of metal oxide composite (80) for both UV and IR blocking.

(22) In one embodiment, an organic solvent, such as hexane, is added to the mixture of tin-containing metal oxide crystalline particles after modified by surfactants and ionic by-products.

(23) For example, in a reaction to produce antimony-doped tin oxide (ATO) from SnCl.sub.4 and SbCl.sub.3 mixed metal salt solution (12) and ammonia solution as precipitant solution (14), the ionic by-products may include Cl.sup., NH.sub.4.sup.+, small amount of Sn.sup.4+, Sb.sup.3+ and ions without completely hydrolysed containing tin and antimony. During the process of separating the antimony-doped tin oxide crystalline particles and the ionic by-products, the phase transfer method is used normally as the tin-containing metal oxide crystalline particles coated with specific surfactant are easily to be dissolved in organic phase, hence after adding the organic solvent, the tin-containing metal oxide crystalline particles are completely dissolved or suspended as monodispersion in the organic phase, while the ionic by-products are remained in the aqueous phase solution.

(24) An immiscible mixture of an organic phase medium an aqueous phase medium is formed. The aqueous phase medium containing the ionic by-products may be separated from the organic phase medium by liquid-liquid phase separating apparatus (such as a separating funnel).

(25) In another embodiment, an aqueous medium is added to the mixture of the tin-containing metal oxide particles and the ionic by-products, such as water, alcohols, amides, ketones, epoxides, or mixtures thereof, to wash and further dissolve the ionic by-products; the tin-containing metal oxide crystalline particles settle to the bottom of the reaction mixture and can be separated from the ionic by-products via centrifugation or any other physical separation process (such as filtration). The ionic by-products remain in the supernatant and are decanted after centrifugation. The tin-containing metal oxide particles can be re-dispersed to form monodispersion in the polar medium.

(26) The resultant tin-containing metal oxide particles are freely dissolved in a suitable solvent (62) to form a highly concentrated monodispersion (65) that comprises the surfactant coated tin-containing metal oxide crystalline particles. If an organic solvent is used in the separating step (50), the resultant tin-containing metal oxide particles are dissolved or dispersed (60) in the organic phase medium. If a polar solvent is used in the separating step (50), the resultant tin-containing metal oxide particles are dissolved or dispersed (60) in the polar phase medium. While the medium (62) used for dissolving or dispersing may be the same as or different from the one used in the separating step (20 or 50).

EXAMPLE

(27) The present invention will be further described in greater details by reference to specific examples, which should not be considered as in any way limiting the scope of the invention.

Example 1

(28) 350.8 g of tin tetrachloride pentahydrate dissolved in 1 L of 2.5M diluted hydrochloric acid, and then 22.8 g of antimony trichloride was added under vigorous stirring to a solution of tin tetrachloride, maintaining the vigorous stirring to form a uniform suspension.

(29) During the vigorous stirring, 1 L of 6M aqueous ammonia was added to the suspension, then keep at 60 C. for 20 min. The resulting pale yellow slurry was centrifuged and re-dispersed into 1.5 L of water, then centrifuged again, and repeated the above procedure until nearly no ionic impurities.

(30) The resulted filter cake was re-dispersed in around 1 L of water, and transferred to a hydrothermal reactor with adding 100 ml of hydrogen peroxide. The slurry was heated to 250 C., and held for 8 hours.

(31) When the hydrothermal reactor was cooled to room temperature, the dark blue slurry was centrifuged and washed by water, then centrifuged to obtain a cake.

(32) The cake was re-dispersed to about 600 mL of water, adding 7.5 g of triethanolamine, then add 300 mL of methanol solution containing 22.5 g of cetyl trimethyl ammonium bromide and stirred for about 10 min. The slurry was centrifuged, and dispersed into 1.5 L of water, centrifuged again, washed with water and acetone to remove excess surfactants and ionic impurities. The cake obtained by centrifugation was re-dispersed into 600 mL of acetone and evaporated under reduced pressure until dryness without acetone.

(33) A further quantity of toluene, and 3 g octylamine were added to finally form blue ATO dispersion in toluene with the solid content of nano-particles (based on the weight of the dispersion) at 40%.

(34) FIGS. 2A and 2B showed TEM results indicating that the initial average particle diameter of the prepared ATO was between 5 to 7 nm, non-agglomerated among particles, nearly monodispersion. FIG. 3 showed a dynamic light scattering particle diameter analyzer test results indicating that the secondary average particle diameter was about 30 nm, D 90=53.1 nm. The resultant dispersion of the granules was the index of dispersion degree of 5.4, steepness ratio of 2.5, indicating that the particles have good dispersing properties in dispersion.

Comparative Example 1

(35) 350.8 g of tin tetrachloride pentahydrate was dissolved in 1 L of 2.5M diluted hydrochloric acid, then adding 22.8 g of antimony trichloride with vigorous stiffing until forming a uniform suspension.

(36) During the vigorous stirring, 1 L of 6M aqueous ammonia was added to the suspension and keep at 60 C. for 20 min.

(37) The resulted pale yellow pigment slurry was transferred to the hydrothermal reactor, with adding 100 mL of hydrogen peroxide. The slurry was heated to 250 C. and maintained for 8 hours.

(38) When hydrothermal reactor cooling down to room temperature, the blue-gray slurry was collected and centrifuged to obtain a cake.

(39) The cake even after washing many times still cannot get a dark blue cake similar to examples 1. Additionally, this filter cake even washed and re-modified in any case, can not be dispersed to form a monodispersed dispersion.

(40) After drying the cake analysed by XRD tests, showing that despite cassiterite tetragonal structure (JCPDS21-1250) peaks appeared, but there were many impurity peaks. Dynamic light scattering particle diameter analyzer displayed that the average secondary particle diameter was greater than 1 .mu.m, with wide and bimodal particle diameter distribution.

(41) This comparative example illustrates that tin-containing metal oxide precursor particles (or tin-containing metal oxide particles) separating in time with an ionic by-product is a very key step to the preparation and the formation of monodispersed dispersion of tin-containing metal oxide.

Example 2

(42) Steps before the hydrothermal treatment and hydrothermal treatment conditions and procedures were the same to described in Example 1.

(43) When hydrothermal reactor cooling down to room temperature, blue slurry was collected and centrifuged, then washed and dispersed in water, centrifuged again to obtain a cake.

(44) The cake was re-dispersed to 1 L of methanol with 2.5 g of tetramethyl ammonium hydroxide and 500 mL of methanol containing 44.5 g of Titanate coupling agent (product name: NDZ-311) and stirred for 10 min. The slurry was centrifuged and sufficiently dispersed into 1 L of methanol and centrifuged again. The sediment was redispersed into 600 mL of butyl acetate, together with 7.5 g of another titanate coupling agent (product name: NDZ-109). The suspension was evaporated to dryness under reduced pressure to collect the dark blue powder.

(45) The powder was re-dispersed into the butyl acetate to the solid content of ATO nano-particles (based on the weight of the dispersion) at 40%.

(46) The test results showed that the particle diameter and size distribution of nano-ATO was similar to example 1. The resulting dispersion of the particles have the index of dispersion degree of 5.5 and the steepness ratio of 2.6.

Example 3

(47) 350.8 g of tin tetrachloride pentahydrate was dissolved in 1.5 L of methanol, then adding 22.8 g of antimony trichloride with stirring to a clear solution.

(48) During the stirring, 1 L of 6M aqueous ammonia was added to the solution and maintained at 60 C. for 30 min.

(49) The resulted pale yellow slurry was centrifuged and re-dispersed into 1.5 L of water, centrifuged again, repeated the above procedure until nearly no ionic impurities.

(50) The resulted cake was re-dispersed into 1 L of water and transferred to hydrothermal reactor, with adding 100 mL of hydrogen peroxide. The slurry was heated to 290 C. and maintained for 8 hours.

(51) When hydrothermal reactor cooling down to room temperature, the blue slurry was collected and centrifuged, then washed and dispersed with water, and centrifuged to obtain a dark blue cake.

(52) The cake was re-dispersed into 600 mL of water, with 7.5 g of tetramethyl ammonium hydroxide and 300 mL of methanol solution containing 22.5 g of cetyl trimethyl ammonium bromide and stirred for 10 min. The slurry was centrifuged and dispersed into 1.5 L of water, centrifuged again, washed with water and acetone separately to remove excess surfactants and ionic impurities, to obtain the cake, which was re-dispersed into 600 mL of acetone. The suspension was evaporated to dryness under reduced pressure to remove acetone.

(53) A certain quantity of toluene and 3 g octylamine were added to finally form a blue toluene dispersion of ATO nano-particles with the solid content (based on the weight of the dispersion) at 40%.

(54) The particle diameter and XRD tests was performed. FIG. 4 showed TEM results indicating that the obtained initial average particle diameter of the prepared individual ATO nanoparticles were 5 to 6 nm, no aggregation among particles, nearly monodispersion. XRD results in FIG. 5 showed the tetragonal cassiterite structure (JCPDS 21-1250) without impurity peak, indicating is doped antimony oxide was not in the form of a separate oxide, but into the crystal lattice of tin oxide. FIG. 6 of a dynamic light scattering particle diameter analyzer test results showed that the average secondary particle diameter of about 22 nm, D 90=48.1 nm. The resulted index of dispersion degree in the dispersion was 3.5 and steepness ratio 1.9, indicating a narrow particle diameter distribution in dispersions.

Example 4

(55) Steps before the hydrothermal treatment and hydrothermal treatment conditions and procedures were the same to described in Example 3.

(56) When hydrothermal reactor cooling down to room temperature, blue slurry was collected and centrifuged, then washed and dispersed by 1.5 L of water, centrifuged again to obtain a cake, which was re-dispersed to 1.5 L of 30% aqueous ethanol and centrifuged. The filter cake was dispersed in 70% aqueous ethanol and centrifuged. The resulted cake was redispersed into 1 L of ethanol and centrifuged to obtain a cake.

(57) The last filter cake was dried at about 50 C. and pulverized to obtain ATO powder.

(58) The amount of water was added to the dry powder, then 1% weight of ATO of tetramethyl ammonium hydroxide was added, treated by a homogenizer to disperse ATO uniformly in water, and finally to form the water-based dispersion of ATO nano-particles with the solids content (based on the weight of the dispersion) at 40%.

(59) FIGS. 7A and 7B showed TEM results indicating that uniform size of ATO nano-particles with the initial average particle diameter of the individual particles of about 8 to 10 nm. XRD results showed that the structure of tetragonal cassiterite structure (JCPDS 21-1250). A dynamic light scattering particle diameter analyzer showed that the average secondary particle diameter was about 50 nm. The resulted dispersion of the particles have the index of dispersion degree of 4.2 and the steepness ratio of 2.2.

Example 5

(60) Steps before the hydrothermal treatment and hydrothermal treatment conditions and procedures were the same to described in Example 3.

(61) When hydrothermal reactor cooling down to room temperature, blue slurry was collected and centrifuged, then washed and dispersed by 1.5 L of water, centrifuged again. Dark blue filter cake was re-dispersed in an aqueous methanol solution (methanol and water by weight ratio of 9:1) to form 100 ml of suspension with solid content at 30%, which was warmed to 60-70 C. Under stirring, 7 g of -methacryloxypropyl trimethoxy silane was added and maintained for 1 day. Then, the slurry was cooled to room temperature, after adding 2 g of cetyl trimethyl ammonium bromide, and stirred for 10 minutes.

(62) The suspension was washed, centrifuged and separated to obtain a cake.

(63) The filter cake was dispersed by ethanol, then added 1 g of octylamine. After rotary evaporation, butyl acetate was added to obtain the dark blue nano-ATO dispersion in the dispersion medium of butyl acetate with the solid content at 40%.

(64) Particle diameter and size distribution of ATO nano-particles is similar to Example 3. The resulted dispersion of the particles have the index of dispersion degree of 5.2 and the steepness ratio of 2.1.

Example 6

(65) 35.08 g of tin tetrachloride pentahydrate was dissolved in 1.5 L of methanol with 293 g indium trichloride tetrahydrate under stirring to a clear solution.

(66) During stirring, 1 L of 6M aqueous ammonia was added to the previous solution, and maintained for 30 min at 60 C. The resulted slurry was centrifuged and re-dispersed into 1.5 L of water, centrifuged again, and repeated the above procedure until nearly no ionic impurities.

(67) The filter cake was re-dispersed in 1 L of water and transferred to hydrothermal reactor, with adding 100 mL of hydrazine hydrate. The slurry was heated to 290 C. and maintained for 8 hours.

(68) When hydrothermal reactor cooling down to room temperature, the blue slurry was collected and centrifuged, then washed and dispersed with water, and centrifuged to obtain a cake.

(69) The cake was re-dispersed into 600 mL of water, with 7.5 g of tetramethyl ammonium hydroxide and 300 mL of methanol solution containing 22.5 g of cetyl trimethyl ammonium bromide and stirred for 10 min. The slurry was centrifuged and sufficiently dispersed into 1.5 L of water, centrifuged again, washed with water and acetone separately to remove excess surfactants and ionic impurities, to obtain the cake, which was re-dispersed into 600 mL of acetone. The suspension was evaporated to dryness under reduced pressure to remove acetone.

(70) A certain quantity of toluene and 3 g octylamine were added to finally form a dark blue toluene dispersion of ITO nano-particles with the solid content (based on the weight of the dispersion) at 40%.

(71) FIGS. 8A and 8B showed TEM results that the initial average particle diameter of individual ITO nanoparticles was about 7 nm. A dynamic light scattering particle diameter analyzer showed that the average secondary particle diameter was about 60 nm. The resultant dispersion have index of dispersion degree of 6.4 and steepness ratio of 2.7.

Example 7

(72) 35.08 g of tin tetrachloride pentahydrate was dissolved in 1.5 L of water containing hydrochloric acid, then adding 293 g of indium trichloride tetrahydrate under stirring to form a clear solution.

(73) During stirring, 1 L of 6M aqueous ammonia solution was added to the solution with pH to about 7 and heated to 70 C., maintained for 30 min. The resulted slurry was centrifuged and re-dispersed into 1.5 L of water, centrifuged again, repeated the above procedure until nearly no ionic impurities.

(74) The filter cake was re-dispersed into 1 L of ethanol and transferred to a hydrothermal reactor, together with 4 g of citric acid. The slurry was heated to 290 C. and maintained for 8 hours.

(75) When hydrothermal reactor cooling down to room temperature, the blue slurry was collected and centrifuged, then washed and dispersed with water, and centrifuged to obtain a cake.

(76) The cake was re-dispersed into 600 mL of water, with 7.5 g of tetramethyl ammonium hydroxide and 300 mL of methanol solution containing 22.5 g of cetyl trimethyl ammonium bromide and stirred for 10 min. The slurry was centrifuged and sufficiently dispersed into 1.5 L of water, centrifuged again, washed with water and acetone separately to remove excess surfactants and ionic impurities, to obtain the cake, which was re-dispersed into 600 mL of acetone. The suspension was evaporated to dryness under reduced pressure to remove acetone.

(77) A certain quantity of toluene and 3 g octylamine were added to finally form a dark blue toluene dispersion of ITO nano-particles with the solid content (based on the weight of the dispersion) at 40%.

(78) The properties of the prepared ITO nano-particles and their dispersion were similar to example 6.

Example 8

(79) This embodiment is application example.

(80) In this example, the manufacturing method of ATO nano-particles in a water-based dispersion is the same to in Example 4, except that the hydrothermal temperature is 260 C., treatment time for 15 hours while the amount of antimony (antimony relative to the ATO mole percent) of 5%, 7.5%, 10%, 12.5%. Prepared ATO nanoparticles was tested by TEM, XRD, dynamic light scattering particle diameter analyzer showing that the results are similar to example 4.

(81) The obtained aqueous dispersion of ATO nano-particles in various antimony concentrations with 40% of solids content were diluted to 5% aqueous solution. UV-visible-IR spectroscopy showed the change in the properties of IR blocking (seen in FIG. 9), indicating that adjusting the concentration of antimony in ATO nano-particles can cause changes in IR blocking performance in the application system. Usually, the higher the antimony, the better the IR blocking. when the content of antimony is more than 12%, the IR blocking performance did not change much. This variation shows that controlling the content of antimony in ATO nano-particles can regulate the performance of IR blocking.

Example 9

(82) This embodiment is application example.

(83) In this example, the manufacturing method of ATO nano-particles in a water-based dispersion is the same to in Example 4, except that the hydrothermal temperature is 260 C., time for 15 hours. Prepared ATO nanoparticles was tested by TEM, XRD, dynamic light scattering particle diameter analyzer showing that the results are similar to example 4.

(84) The obtained aqueous dispersion with 40% of solids content of ATO nano-particles were diluted to 5%, 2.5%, 1.25% of solids content of the aqueous solution, and found the change of IR blocking performance by testing UV-visible-IR spectroscopy (see FIG. 10). The higher the solids of the ATO nano-particles, the better the IR blocking. This variation shows that controlling the solids content of ATO nano-particles in the application system can regulate the performance of IR blocking.

Example 10

(85) This embodiment is application example.

(86) In this example, the manufacturing method of ATO nano-particles in a water-based dispersion is the same to in Example 4, except that the hydrothermal temperature is 260 C., time for 15 hours. Prepared ATO nanoparticles was tested by TEM, XRD, dynamic light scattering particle diameter analyzer showing that the results are similar to example 4.

(87) The obtained aqueous dispersion with 40% of solids content of ATO nano-particles were diluted to 5% of solids content of the aqueous solution, and prepared the composite metal oxide dispersions by mixing with ZnO or CeO.sub.2 aqueous dispersion in same solid content in preparation of PCT/SG2008/000442, separately. UV-visible-IR spectroscopy testing found the dispersion had IR blocking property similar to example 8, moreover, the addition of ZnO or CeO2 showed significant UV blocking. The UV transmittance testing results was shown in FIG. 11. This variation shows that altering amount of UV blocking additives, such as ZnO or CeO.sub.2 to control the performance of UV blocking.

Example 11

(88) The aqueous dispersion of nano ATO prepared as described in example 4 in the present invention, alone or combination with nano zinc oxide aqueous dispersion prepared in PCT/SG2008/000442, was/were added to the aqueous acrylic acid coatings. In this coating formulation, the acrylic resin comprised 20 wt % of the total amount of the coating, which also contained a small amount of levelling agents and other additives. ATO nanoparticles accounted for 10 wt % of the total amount, ZnO nanoparticles 5 wt % of that.

(89) The coating was coated on the glass through the dip-coating or the gravity-coating method, respectively. Controlling the thickness of the coating on the glass was about 40 microns. In accordance with China National Standard GB/T 2680-94 (or international standard E 903-96), the glass coated with this coating was analyzed by UV-visible-IR spectroscopy, as shown in FIGS. 12A and 12B. FIG. 12A showed that ATO nano-particles in the coating showed good IR blocking property, and ZnO nano-particles for UV blocking function separately, without affecting the visible light transmittance. The specific solar control properties were shown in the following table.

(90) TABLE-US-00001 TABLE 1 Different UV blocking Visible light types of glass (350 nm) transmittance coating (%) (550 nm) (%) IR blocking (%) ATO + ZnO, dip- 90% 80% 63% coating ATO + ZnO, gravity 95% 85% 65% coating ATO, dip-coating / 83% 73% ATO, gravity coating / 90% 70%

Comparative Example 2

(91) To disperse commercially available ATO nano-powder with the initial average particle diameter of 8-10 nm similar to the present invention and the same amount of the same surfactant mentioned in example 4 by conventional ball milling methods for 8 hours, ATO dispersion was obtained with 123 nm of the average secondary particle diameter analysed immediately by dynamic light scattering particle diameter analyser. The resulted dispersion of the particles had index of dispersion degree of 12.2 and the steepness ratio of 4.1. (poor stability of the dispersion as settling at the bottom of the container 2 days later. The dispersion was analysed by a dynamic light scattering particle diameter analyzer again, showing that the average secondary particle diameter increased to 253 nm and particle diameter distribution is further widened.)

(92) The dispersion of nano-ATO by the ball milling for 8 hours was rapidly adopted to water-based acrylic paint in the same methods and amount as in example 10, which was applied on the glass by gravity coating method, with coatings thickness to 40 microns. In accordance with China National Standard GB/T 2680-94 (or international standard E 903-96), the glass coated with the coating was tested UV-visible-IR spectroscopy showing its specific solar control performance in the following table.

(93) TABLE-US-00002 TABLE 2 UV blocking Visible light Different types of (350 nm) transmittance (550 nm) IR glass coating (%) (%) blocking (%) ATO on commercial / 55% 73% Market ATO prepared in / 90% 75% Example 4

(94) Judging from the appearance, the glass coated with commercial ATO dispersion by ball milling looked blue and pale without translucent character; while the glass coated with nano ATO produced in Example 4 of the present invention had the light blue transparent feature. The Comparative Example 2 shows that dispersability of ATO nano-particles have an impact on the transparency of coated glass. Only monodispersed particles in the present invention can achieve high transparency and IR blocking performance of the glass at the same time.

(95) Applications

(96) It will be appreciated that the disclosed process can enable direct synthesis of tin-containing metal oxide nanoparticles or tin-containing metal oxide nanoparticles in monodispersed state and for further preparation of dispersion of metal oxide nanocomposites for UV and IR blocking. The dispersion of tin-containing metal oxide nanoparticles or dispersion of metal oxide nanocomposites for UV and IR blocking may have a high concentration as defined by its high solid loading.

(97) Advantageously, all the reactants used in the disclosed process are commercially available and economically priced. More advantageously, the process does not require the use of high temperature calcination. This lowers the cost of the production and reduces the deterioration of the equipment used in the process. There is no addition need for the use of expensive reactants for the large scale production of the tin-containing metal oxide nanoparticles, their dispersion and dispersion of metal oxide nanocomposites for UV and IR blocking.

(98) Advantageously, the monodispersion produced from the disclosed process may be more stable as compared to known particles from other methods, also with advantages that the particles do not agglomerate, and the dispersion do not have ionic impurities. The disclosed monodispersion can be kept for a period of more than one month without any appreciable loss in stability properties. The nano-sized tin-containing metal oxide particles can be re-dispersed in a solvent to substantially reform into a monodispersion, without any appreciable loss in physical stability.

(99) Advantageously, the disclosed process enables a highly concentrated dispersion of nano-sized tin-containing metal oxide, or dispersion of metal oxide nanocomposites for UV and IR blocking. This may significantly reduce the amount of storage space and the cost of transportation as compared to known products of tin-containing metal oxide nanoparticles and their dispersion.

(100) Advantageously, the liquid-liquid phase transfer step may provide a simple and effective solution to remove the by-products that may be ionic in nature that cause destabilization of the monodispersion.

(101) It will be appreciated that the capacity of the process can be scaled up to form larger quantities of tin-containing metal oxide nanoparticles, their dispersion, and dispersion of metal oxide nanocomposites for UV and IR blocking, without affecting the stability and particle size distribution of the product.

(102) Advantageously, the tin-containing metal oxide nanoparticles may be re-dispersed in a suitable dispersing medium that may be dependent on the needs of the user for the end-product. Accordingly, a polar solvent or a non-polar solvent may be used as the dispersing medium. The dispersion of tin-containing metal oxide nanoparticles or dispersion of metal oxide nanocomposites for UV and IR blocking may be suitable for use in an organic matrix material, such as a polymeric material, according to the requirements of the end-product, for application of glass paint or shielding film. As using the tin-containing metal oxide nanoparticles prepared with disclosed process, the secondary particle size may be controlled in nano-scale, to result in highly transparent glass coating or shielding film for both UV and IR blocking without affect the visible light transmittance, and hence to achieve good transparent effect and thermal insulation effect for glass.

(103) It will be apparent the various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.