Method for producing transition metal oxide fine particles

Abstract

Disclosed is a method for producing transition metal oxide fine particles having a size smaller than several micrometers (μm), and more preferably, having a size of several hundred nanometers (nm). To this end, the method for producing transition metal oxide fine particles of the present invention comprises dissolving a transition metal oxide in a strongly basic aqueous solution, and titrating same with a strongly acidic aqueous solution, thereby precipitating transition metal oxide fine particles.

1 . A method of producing transition metal oxide fine particles comprising:
 heating and agitating a strong base aqueous solution;   adding and dissolving a transition metal oxide into the heated strong base aqueous solution;   forming a mixed aqueous solution by a strong acid aqueous solution to the strong base aqueous solution in which the transition metal oxide is dissolved, and by agitating and dissolving solids at an interface between the strong base aqueous solution and the strong acid aqueous solution;   controlling a speed or an amount of the strong aqueous solution to be added to the strong base aqueous solution, to adjust pH of the mixed aqueous solution and to precipitate transition metal oxide fine particles; and   separating the transition metal oxide fine particles from the mixed aqueous solution, and washing, drying and heat-treating the separated transition metal oxide fine particles.   
     
     
         2 . The method of producing the transition metal oxide fine particles of  claim 1 , wherein
 the strong base aqueous solution is prepared by mixing water and sodium hydroxide (NaOH) having a mass ratio within a range of 6:1 to 10 to 1, and sodium hydroxide mixed with the water has a purity of 99% or more.   
     
     
         3 . The method of producing the transition metal oxide fine particles of  claim 1 , wherein the heating and the agitating of the strong base aqueous solution includes heating the strong base aqueous solution to be within a range of 60° C. to 105° C. and agitating the strong base aqueous solution within a range of 600 rpm to 700 rpm. 
     
     
         4 . The method of producing the transition metal oxide fine particles of  claim 1 , wherein the transition metal oxide comprises at least one selected from a group constituting of molybdenum trioxide and tungsten trioxide, and
 the dissolving of the transition metal oxide into the strong base aqueous solution includes sequentially dissolving the molybdenum trioxide and the tungsten trioxide into the strong base aqueous solution.   
     
     
         5 . The method of producing the transition metal oxide fine particles of  claim 4 , wherein a temperature when dissolving the tungsten trioxide into the strong base aqueous solution is less than a temperature when dissolving the molybdenum trioxide into the strong base aqueous solution, and
 the molybdenum trioxide dissolved into the strong base aqueous solution has a purity of 99.5% or more and the tungsten trioxide dissolved into the strong base aqueous solution has a purity of 99% or more.   
     
     
         6 . The method of producing the transition metal oxide fine particles of  claim 1 , wherein the dissolving of the transition metal oxide into the strong base aqueous solution; includes dissolving the transition metal oxide into a saturated state, or agitating the transition metal oxide while being heated until the solids of the strong base aqueous solution are completely dissolved, or agitating the transition metal oxide while being heated until the strong base aqueous solution becomes transparent. 
     
     
         7 . The method of producing the transition metal oxide fine particles of  claim 1 , wherein the dissolving of the transition metal oxide into the strong base aqueous solution includes maintaining agitation conditions and heating temperature conditions during the heating and the agitating of the strong base aqueous solution. 
     
     
         8 . The method of producing the transition metal oxide fine particles of  claim 1 , wherein the forming the mixed aqueous solution includes:
 adding the strong acid aqueous solution to the strong base aqueous solution;   stopping the adding of the strong acid aqueous solution to the strong base aqueous solution based on the solids being generated at the interface;   agitating the mixed aqueous solution until the solids are dissolved into the mixed aqueous solution; and   again adding a strong acid aqueous solution to the strong base aqueous solution when the solids are dissolved into the mixed aqueous solution, and   wherein the strong acid solution comprises 60% to 75% nitric acid.   
     
     
         9 . The method of producing the transition metal oxide fine particles of  claim 1 , wherein the precipitating of the transition metal oxide fine particles includes
 generating the transition metal oxide fine particles by adjusting pH of the mixed aqueous solution, or   generating the transition metal oxide fine particles by lowering the pH of the mixed aqueous solution to be within a range of 7.9 or 8.1.   
     
     
         10 . The method of producing the transition metal oxide fine particles of  claim 1 , wherein the separating of the transition metal oxide fine particles from the mixed aqueous solution includes filtering the transition metal oxide fine particles by a membrane,
 the washing of the separated transition metal oxide fine particles; includes washing the transition metal oxide fine particles with distilled water of 100 g or less, and   additionally washing the transition metal oxide fine particles with an ethanol aqueous solution.   
     
     
         11 . The method of producing the transition metal oxide fine particles of  claim 1 , wherein the drying of the transition metal oxide fine particles includes freezing-drying of the transition metal oxide fine particles. 
     
     
         12 . The method of producing the transition metal oxide fine particles of  claim 1 , wherein the drying of the transition metal oxide fine particles includes:
 primarily drying the transition metal oxide fine particles at room temperature for at least 24 hours; and   secondarily drying the transition metal oxide fine particles in a vacuum environment at a temperature higher than the room temperature.   
     
     
         13 . The method of producing the transition metal oxide fine particles of  claim 1 , wherein the heat-treating of the transition metal oxide fine particles; includes drying the transition metal oxide fine particles separated from the mixed aqueous solution, and then heat treating the transition metal oxide fine particles at a temperature within a range of 380° C. to 450° C. for at least 30 minutes. 
     
     
         14 . A method of producing transition metal oxide fine particles comprising:
 providing a strong base aqueous solution by heating and agitating after adding a sodium hydroxide and a surfactant to water;   adding a transition metal oxide to the heated strong base aqueous solution, and dissolving the transition metal oxide into the strong base aqueous solution;   forming a mixed aqueous solution by adding a strong acid aqueous solution to the strong base aqueous solution in which the transition metal oxide is dissolved, and by agitating and dissolving solids at an interface between the strong base aqueous solution and the strong acid aqueous solution;   controlling a speed or an amount of the strong aqueous solution to be added to the strong base aqueous solution, to adjust pH of the mixed aqueous solution and to precipitate transition metal oxide fine particles; and   separating the transition metal oxide fine particles from the mixed aqueous solution, and washing, drying and heat-treating the separated transition metal oxide fine particles.   
     
     
         15 . The method of producing the transition metal oxide fine particles of  claim 14 , wherein the surfactant comprises at least one selected from a cationic surfactant, an amphoteric surfactant, an anionic surfactant and a nonionic surfactant, and
 the added surfactant has a mass ratio of 0.5 g or less per 1 L of water.   
     
     
         16 . The method of producing the transition metal oxide fine particles of  claim 14 , wherein the transition metal oxide comprises at least one selected from a group consisting of a molybdenum trioxide and a tungsten trioxide, and
 the dissolving of the transition metal oxide into the strong base aqueous solution includes sequentially dissolving the molybdenum trioxide and the tungsten trioxide into the strong base aqueous solution.   
     
     
         17 . The method of producing the transition metal oxide fine particles of  claim 14 , wherein the dissolving of the transition metal oxide into the strong base aqueous solution; includes agitating the transition metal oxide at a speed within a range of 100 rpm to 300 rpm and heating the transition metal oxide at a temperature within a range of 50° C. to 100° C., until the strong base aqueous solution become transparent. 
     
     
         18 . The method of producing the transition metal oxide fine particles of  claim 14 , wherein the forming of the mixed aqueous solution includes:
 adding the strong acid aqueous solution to the strong base aqueous solution;   stopping the adding of the strong acid aqueous solution to the strong base aqueous solution based on the solids being generated at the interface;   agitating the mixed aqueous solution until the solids are dissolved into the mixed aqueous solution; and   again adding a strong acid aqueous solution to the strong base aqueous solution when the solids are dissolved into the mixed aqueous solution, and   wherein the strong acid solution comprises 60% to 75% nitric acid.   
     
     
         19 . The method of producing the transition metal oxide fine particles of  claim 14 , wherein the drying of the transition metal oxide fine particles includes:
 primarily drying the transition metal oxide fine particles at a room temperature for at least 24 hours; and   secondarily drying the transition metal oxide fine particles in a vacuum environment at a temperature higher than the room temperature, and   wherein the heat-treating of the transition metal oxide fine particles; includes drying the transition metal oxide fine particles separated from the mixed aqueous solution, and then heat treating the transition metal oxide fine particles at a temperature within a range of 380° C. to 450° C. for at least 30 minutes.   
     
     
         20 . The method of producing the transition metal oxide fine particles of  claim 14 , wherein after the heat-treating of the transition metal oxide fine particles, the transition metal oxide fine particles are made of MoWO6 having a structure of Chemical Formula 1 below: