Method for the production of single crystalline MgTiO3 flakes

Abstract

The present invention is related to a method for the production of single crystalline MgTiO.sub.3 flakes, in particular in the geikielite crystal structure, to single crystalline MgTiO.sub.3 flakes obtained by this method as well as to the use thereof, in particular as pigments in several application media.

Claims

1. A method for preparing single crystalline MgTiO.sub.3 flakes by the following steps: a) forming a MgTiO.sub.3 precursor by mixing at least a titanium compound, a magnesium compound and a phosphorous compound in an aqueous medium, which is held at a pH value of 6 to 8, and b) calcining the MgTiO.sub.3 precursor at a temperature of 800 C. to 1400 C. as a single calcination step.

2. The method according to claim 1, wherein a fluxing agent is present in the mixing step.

3. The method according to claim 2, wherein the fluxing agent is one or more compounds selected from the group consisting of: Na.sub.2SO.sub.4, K.sub.2SO.sub.4, NaCl and KCl.

4. The method according to claim 1, which further comprises drying the MgTiO.sub.3 precursor prior to the calcination step.

5. The method according to claim 1, wherein the calcining is in an oxygen containing atmosphere.

6. The method according to claim 2, wherein a product obtained in the calcination step is treated with water.

7. The method according to claim 1, wherein the titanium compound is one or more compounds selected from the group consisting of: titanium tetrachloride, titanyl sulfate, titanium sulfate and titanium trichloride.

8. The method according to claim 1, wherein the magnesium compound is one or more compounds selected from the group consisting of: magnesium chloride, magnesium sulfate and magnesium carbonate.

9. The method according to claim 1, wherein the phosphorous compound is one or more compounds selected from the group consisting of: trisodium phosphate, phosphorous pentoxide, phosphoric acid, phosphorous acid and tripotassium phosphate.

10. The method according to claim 1, wherein the single crystalline MgTiO.sub.3 flakes prepared have a geikielite crystal structure.

11. The method according to claim 1, wherein the single crystalline MgTiO.sub.3 flakes prepared have a particle diameter of 10 to 100 m, according to an equivalent of a corresponding circle diameter.

12. The method of claim 1, wherein the aqueous medium is held at a pH value of 7.

13. The method of claim 1, wherein the phosphorus compound is a phosphate compound.

14. The method of claim 1, wherein the phosphorus compound is one or more compounds selected from the group consisting of phosphoric acid, phosphates, condensed phosphoric acid, and condensed phosphate.

15. The method of claim 1, wherein the calcining of the MgTiO.sub.3 precursor is at a temperature of greater than 1000 C. to 1250 C. as a single calcination step.

16. A method for preparing single crystalline MgTiO.sub.3 flakes by the following steps: a) forming a MgTiO.sub.3 precursor by mixing at least a titanium compound, a magnesium compound and a phosphorous compound in an aqueous medium, and b) calcining the MgTiO.sub.3 precursor at a temperature of 800 C. to 1400 C. as a single calcination step, wherein a fluxing agent is present in the mixing step, which is one or more compounds selected from the group consisting of: Na.sub.2SO.sub.4, K.sub.2SO.sub.4, NaCl and KCl, and/or the phosphorous compound is one or more compounds selected from the group consisting of: trisodium phosphate, phosphorous pentoxide, phosphorous acid and tripotassium phosphate.

17. A method for preparing single crystalline MgTiO.sub.3 flakes by the following steps: a) adding a phosphorous compound, a titanium compound and a magnesium compound to an aqueous medium, forming a MgTiO.sub.3 precursor by mixing at least the titanium compound, the magnesium compound and the phosphorous compound in the aqueous medium, wherein the phosphorous compound is added to the aqueous medium prior to the addition of the titanium compound and/or the magnesium compound to the aqueous medium, and b) calcining the MgTiO.sub.3 precursor at a temperature of 800 C. to 1400 C. as a single calcination step.

18. The method of claim 17, wherein the phosphorous compound is added to the aqueous medium prior to the addition of the titanium compound to the aqueous medium.

19. The method of claim 17, wherein the phosphorous compound is added to the aqueous medium prior to the addition of the magnesium compound to the aqueous medium.

20. The method of claim 17, wherein the aqueous medium is held at a pH value of 6 to 8.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a SEM image of the surface of the single crystalline MgTiO.sub.3 flakes obtained by the production method in accordance with an embodiment of the present invention.

(2) FIG. 2 is a flowchart showing the production method for the production of single crystalline MgTiO.sub.3 flakes in accordance with a preferred embodiment of the present invention.

(3) Hereinafter, the present invention will be described in more detail by referencing an example, however, the present invention is not limited to this example.

EXAMPLE 1

(4) Into 1600 g of deionized water, 5.6 g of sodium phosphate is added and stirred while heating to 95 C. Into this solution, a total amount of 210 g of titanium tetrachloride solution (including 64 g of titanium tetra-chloride and 10 g of magnesium dichloride, 32.0% concentration in water) is added over the course of two hours while adjusting the pH with sodium hydroxide aqueous solution (32.0% concentration). After adding all of titanium tetrachloride solution, the pH is raised to 7. Further, 130 g of sodium sulfate is added under stirring. Afterwards, the resulting solution is dried and, finally, calcined at 1000 C. for two hours. After cooling, the obtained product is washed within warm water under agitation in order to remove chloride and sodium sulfate, and the MgTiO.sub.3 flakes are obtained.

(5) The obtained MgTiO.sub.3 flakes have an average particle diameter of 30 m and most of them show a circle shape or hexagonal shape. From the X-ray diffraction analysis, the main surface of the flake exhibits the (100) orientation and the crystal structure is the geikielite type. Further, the analysis with electron microscope confirmed that they are single crystals.

(6) The single crystalline MgTiO.sub.3 flakes obtained by the production method according to the present invention can be utilized as pigments for paints, inks, coating compositions, plastics, and cosmetics, and as photocatalysts, host material for dye sensitized solar cells, UV absorbents or as water repellents.