Water-insoluble metal hydrate containing an alkali metal and preparation methods thereof

Abstract

The present invention relates to a novel method for preparing a water-insoluble metal hydroxide, and a use thereof. The water-insoluble metal hydroxide of the present invention is conveniently and efficiently prepared s through the high-temperature heat treatment step two times and the washing step, and thus contains a small amount of an alkali metal and has a high crystallinity and a phase purity. The water-insoluble metal hydroxide of the present invention or metal oxide therefrom exhibits an absorption wavelength at a low wavelength range (for example, 490 nm or less) and a light emitting wavelength at a high wavelength range (for example, from 500 nm or more to less than 1,100 nm). Accordingly, the water-insoluble metal hydroxide of the present invention may be efficiently used in various applications such as a fire retardant, an antacid, an adsorbent and so forth, and may also be doped with another metal ion to be utilized as a raw material for fabricating a catalyst, a fluorescent material, an electrode material, a secondary battery material and the like.

Claims

1. A method for preparing a water-insoluble metal hydroxide, comprising the steps of: (a) combusting a mixed aqueous solution of a metal salt, an alkali salt and an urea at a temperature of from more than 400 C. to less than 700 C.; (b) subjecting a powder obtained in step (a) to heat treatment at a temperature of 700 C. to 1,300 C.; and (c) washing a powder obtained in step (b) with an aqueous solution, wherein the metal salt is one or more metal salts selected from the group consisting of a lanthanide metal, a transition metal and a post-transition metal, and the water-insoluble metal hydroxide is represented by the following Formula 2:
(M.sub.1-yM.sub.y)O.sub.x/2(OH).sub.3-x:N.sub.w Formula 2 in the Formula 2, M and M are each one or more metals selected from the group consisting of a lanthanide metal, a transition metal and a post-transition metal; N is an alkali or alkaline earth metal; and y is a real number of 0<y 0.50, x is a real number of 0x 2.9 and w is a real number of 0.001w0.5.

2. The method of claim 1, wherein the lanthanide metal is La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu.

3. The method of claim 1, wherein the transition metal is Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Mo, Ru, Rh, Ag, Cd, lr, W, Au or Hg.

4. The method of claim 1, wherein the post-transition metal is Al, Ga, In, Sn, Tl, Pb or Bi.

5. The method of claim 1, wherein the alkali salt is an alkali metal or alkaline earth metal salt.

6. The method of claim 5, wherein the alkali metal or alkaline earth metal salt is a salt compound comprising Li, Na, K, RID, Cs, Fr, Be, Mg, Ca, Sr, Ba or Ra.

7. The method of claim 1, wherein the alkali salt comprises an amount of at least one equivalent or larger than an amount of the metal salt.

8. The method of claim 1, wherein an amount of the alkali salt remaining in the metal hydroxide is in a range of 0.001 to 50 atm % compared with that of the metal salt.

9. The method of claim 1, wherein a heat treatment time in step (b) is carried out for 1 to 4 hours.

10. The method of claim 1, wherein the method further comprises a step of removing the aqueous solution.

11. The method of claim 1, wherein the water-insoluble metal hydroxide exhibits a fluorescent or light emitting property.

12. The method of claim 1, wherein the water-insoluble metal hydroxide exhibits an absorption wavelength of 490 nm or less and a light emitting wavelength in a range of 500 nm to 1,100 nm.

13. The method of claim 1, wherein the water-insoluble metal hydroxide is represented by the following Formula 3 when the water-insoluble metal hydroxide comprises three or more metals:
(M.sub.1-z-rM.sup.a.sub.zM.sup.b.sub.r)O.sub.x/2(OH).sub.3-x;N.sub.w Formula 3 in the Formula 3, M, M.sup.a and M.sup.b are each one or more metals selected from the group consisting of a lanthanide metal, a transition metal and a post-transition metal; N is an alkali or alkaline earth metal; and each z and r is a real number of 0 <z <0.50 and 0<r<0.50, x is a real number of 0x2.9, and w is a real n mber of 0.001w0.5.

14. The method of claim 1, wherein the method further comprises a step of heating the water-insoluble metal hydroxide in a temperature range of 300C to 1,400 C. to obtain a water-insoluble metal oxide.

15. A light emitting device comprising the fluorescent water-insoluble metal hydroxide prepared according to the method of claim 1, and a excitation light source of 490 nm or less.

16. The light emitting device of claim 14, wherein the light ernitting device is a white light emitting diode (LED).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view illustrating the preparation method of a water-insoluble hydroxide according to the present invention.

(2) FIG. 2 represents XRD patterns of the water-insoluble hydroxides produced according to Examples 1 to 8 of the present invention.

(3) FIG. 3 shows XRD patterns of the water-insoluble hydroxides produced according to Examples 9 to 11 of the present invention.

(4) FIG. 4 illustrates XRD patterns of the yttrium hydroxides produced depending on alkali salts at different concentrations according to Examples 1 and 12 to 16 of the present invention.

(5) FIG. 5 is XRD patterns of the yttrium hydroxides produced by heat treatment at different atmospheres (99% or more of oxygen, hydrogen, and nitrogen) according to Examples 17 to 19 of this invention.

(6) FIG. 6 represents XRD patterns of the yttrium oxides produced by performing heat treatment at different temperatures according to Examples 20 to 22 of the present invention.

(7) FIG. 7 shows a XRD patterns of the yttrium hydroxides prepared into alkali salts according to Examples 23 to 26 of the present invention.

(8) FIG. 8 illustrates a SEM image of the yttrium hydrate fabricated according to Example 1 of this invention.

(9) FIG. 9 is a XRD patterns of the terbium-doped yttrium hydroxide which is prepared according to Example 27 of the present invention.

(10) FIG. 10 represents a light emission spectrum of the terbium-doped yttrium hydroxide which is prepared according to Example 27.

(11) FIG. 11 is a light emission spectrum of both terbium and ytterbium-doped yttrium hydroxide, which is prepared according to Example 28.

(12) FIGS. 12a and 12b illustrate an absorption and light emission spectra of the europium-doped yttrium hydroxide, respectively, which is prepared according to Example 29.

(13) FIG. 13 represents an XRD pattern of the yttrium oxide prepared according to Example 28 of the present invention.

(14) FIG. 14 illustrates a SEM image of the yttrium oxide prepared according to Example 28 of this invention.

(15) FIG. 15 is a XRD pattern of the powder prepared according to Comparative Example 1 of the present invention.

(16) FIG. 16 shows a XRD pattern of the yttrium oxide prepared according to Comparative Example 2 of this invention.

DETAILED DESCRIPTION OF THE DISCLOSURE

(17) Hereinafter, the present invention will now be described in further detail by examples. It would be obvious to those skilled in the art that these examples are intended to be more concretely illustrative and the scope of the present invention as set forth in the appended claims is not limited to or by the examples.

EXAMPLE

(18) Reagents and Instruments

(19) Rare earth-based metal nitrates used to prepare a water-insoluble metal is hydroxide are as follows: Y(NO.sub.3).sub.3.6H.sub.2O, Gd(NO.sub.3).sub.3.6H.sub.2O, Eu(NO.sub.3).sub.3.6H.sub.2O, Er(NO.sub.3).sub.3.5H.sub.2O, Tm(NO.sub.3).sub.3.xH.sub.2O, Yb(NO.sub.3).sub.3.6H.sub.2O, Pr(NO.sub.3).sub.3.6H.sub.2O, and Tb(NO.sub.3).sub.3.6H.sub.2O Products were purchased from Aldrich product (USA). In addition, other Ca(NO.sub.3).sub.2, Co(NO.sub.3).sub.3.6H.sub.2O, and Mg(NO.sub.3).sub.3.6H.sub.2O nitrates were obtained from Daejung Chemical & Metals Co., Ltd. NaNO.sub.2, Na.sub.2CO.sub.3.H.sub.2O, NaOH, NaNO.sub.3, and LiNO.sub.3.H.sub.2O alkali metal salts and urea were used in products from Daejung Chemical & Metals Co., Ltd.

(20) In order to investigate the phase of the hydrates produced, X-ray diffraction (XRD) patterns obtained by using a Bruker D8 Advance device were analyzed. For component analysis, X-ray fluorescence spectrometry was performed using a Shimadzu device, and a Perkin Elmer LS-40 device was used for measurement of photoluminescence spectrum. In order to obtain a scanning electron microscope (SEM) image, a SEM device manufactured by FEI Co. was used at 15 kV electron beam.

Examples 1 to 26

Preparation of Metal Hydroxides Containing Alkali Metal

(21) A metal salt (0.01 mol), an alkali salt (0.015-0.25 mol) and an urea (0.02 mol) were put into a 200 ml-alumina crucible, and 50 ml of water was added thereto, followed by stirring the mixture until it became a transparent solution, and then the resulting product was transferred to an electric furnace pre-heated to 500 C. First, while the urea was combusted at about 5 min after water was evaporated, flame was produced and lasted for several seconds to several minutes to be extinguished. The combustion product was a white powder, and was again subjected to heat treatment at 800 C. or more in an electric furnace for 2 hrs. The heat-treated powder was cooled down to room temperature, and then washed five times with 10 ml of water. The remaining water-insoluble solid was separated with a centrifuge, and then dried at room temperature to obtain a water-insoluble metal hydroxide as a solid. The precursors used to prepare metal hydroxides in the present invention and the resulting products thereof are shown in the following Table 1, respectively. The XRD patterns of the metal hydrate prepared in each Example are illustrated in FIGS. 2 to 7. FIG. 8 is a SEM image of the yttrium hydroxide produced according to Example 1. The XRF component analysis results of the metal hydrate prepared in Example 1 are shown in Table 2. In the results of Table 2, it was confirmed that a large amount of alkali components were remaining when the washing step was performed after the heat treatment at 900 C.

(22) TABLE-US-00001 TABLE 1 Heat Metal salt Alkali salt treatment Metal hydroxide precursor precursor condition Example 1 Y(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O NaNO.sub.2 atmosphere 0.01 mol 0.025 mol at 900 C. Example 2 Gd(OH).sub.3:Na Gd(NO.sub.3).sub.36H.sub.2O The same as The same as described described above above Example 3 Eu(OH).sub.3:Na Eu(NO.sub.3).sub.36H.sub.2O The same as The same as described described above above Example 4 Er(OH).sub.3:Na Er(NO.sub.3).sub.35H.sub.2O The same as The same as described described above above Example 5 Tm(OH).sub.3:Na Tm(NO.sub.3).sub.3xH.sub.2O The same as The same as described described above above Example 6 Yb(OH).sub.3:Na Yb(NO.sub.3).sub.36H.sub.2O The same as The same as described described above above Example 7 Pr(OH).sub.3:Na Pr(NO.sub.3).sub.36H.sub.2O The same as The same as described described above above Example 8 Tb(OH).sub.3:Na Tb(NO.sub.3).sub.36H.sub.2O The same as The same as described described above above Example 9 Ca(OH).sub.3:Na Ca(NO.sub.3).sub.2 The same as The same as described described above above Example Co(OH).sub.3:Na Co(NO.sub.3).sub.36H.sub.2O The same as The same as 10 described described above above Example Mg(OH).sub.3:Na Mg(NO.sub.3).sub.36H.sub.2O The same as The same as 11 described described above above Example Y(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O NaNO.sub.2 The same as 12 0.015 mol described above Example Y(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O NaNO.sub.2 The same as 13 0.035 mol described above Example Y(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O NaNO.sub.2 The same as 14 0.050 mol described above Example Y(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O NaNO.sub.2 The same as 15 0.100 mol described above Example Y(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O NaNO.sub.2 The same as 16 0.250 mol described above Example Y(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O NaNO.sub.2 oxygen 99% 17 0.025 mol at 900 C. Example Y(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O NaNO.sub.2 hydrogen 18 0.025 mol 99% at 900 C. Example Y(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O NaNO.sub.2 nitrogen 19 0.025 mol 99% at 900 C. Example Y(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O NaNO.sub.2 atmosphere 20 0.035 mol at 800 C. Example Y(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O NaNO.sub.2 atmosphere 21 0.035 mol at 1,000 C. Example Y(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O NaNO.sub.2 atmosphere 22 0.035 mol at 1,200 C. Example Y(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O Na.sub.2CO.sub.3H.sub.2O atmosphere 23 0.025 mol at 900 C. Example Y(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O NaOH atmosphere 24 0.025 mol at 900 C. Example Y(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O NaNO.sub.3 atmosphere 25 0.025 mol at 900 C. Example Y(OH).sub.3:Li Y(NO.sub.3).sub.36H.sub.2O LiNO.sub.3H.sub.2O atmosphere 26 0.025 mol at 900 C. Example Y.sub.0.95Tb.sub.0.05(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O NaNO.sub.2 The same as 27 Tb(NO.sub.3).sub.36H.sub.2O 0.025 mol described above Example Y.sub.0.85Tb.sub.0.05Yb.sub.0.15(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O The same as The same as 28 Tb(NO.sub.3).sub.36H.sub.2O described described Yb(NO.sub.3).sub.36H.sub.2O above above Example Y.sub.0.95Eu.sub.0.05(OH).sub.3:Na Y(NO.sub.3).sub.36H.sub.2O The same as The same as 29 Eu(NO.sub.3).sub.36H.sub.2O described described above above

(23) TABLE-US-00002 TABLE 2 Comparison of XRF Component Analysis of Combustion Product and Final Product in Example 1 of the Present Invention Sample Na atm % Y atm % Combustion product (after combustion oxidation) 35 65 Before washing after heat treatment at 900 C. 41 59 After washing after heat treatment at 900 C. 30 70 Comparative Example 1 1 99 (After washing without heat treatment)

Example 27

Preparation of Hydroxide Doped with Two Water-Insoluble Metals

(24) Yttrium nitrate (Y(NO.sub.3).sub.3.6H.sub.2O, 0.0095 mol), terbium nitrate (Tb(NO.sub.3).sub.3.6H.sub.2O, 0.0005 mol) were mixed with sodium nitrite (NaNO.sub.2, 0.015-0.25 mol) and urea (0.02 mol), and the mixture was put into a 200 ml-alumina crucible, and 50 ml of water was added thereto, followed by stirring the mixture until it became a transparent solution, and then the resulting product was transferred to an electric furnace pre-heated to 500 C. After water was evaporated, the combustion (oxidation) reaction started, lasted for several minutes, and then stopped. The combustion product was a white powder, and was again subjected to heat treatment at 900 C. in an electric furnace for 2 hrs. The heat-treated powder was cooled down to room temperature, and then washed five times with 10 ml of water. The remaining solid was separated by a centrifuge, and then dried at room temperature to obtain a terbium-doped yttrium hydrate as a solid. The produced hydrate exhibits a bright green light emission when an UV light source is radiated at 365 nm. The XRD pattern and photo light emission spectrum of the corresponding hydroxide were illustrated in FIGS. 9 and 10, respectively.

Example 28

Preparation of Hydroxide Doped with Three Water-Insoluble Metals

(25) Yttrium nitrate (Y(NO.sub.3).sub.3.6H.sub.2O, 0.0085 mol), terbium nitrate (Tb(NO.sub.3).sub.3.6H.sub.2O, 0.0005 mol), and ytterbium nitrate (Yb(NO.sub.3).sub.3.6H.sub.2O, 0.0015 mol) were mixed with sodium nitrite (NaNO.sub.2, 0.015-0.25 mol) and urea (0.02 mol), and the mixture was put into a 200 ml-alumina crucible, 50 ml of water was added thereto, the mixture was stirred until the mixture became a transparent solution, and then the resulting product was transferred to an electric furnace pre-heated to 500 C. The remaining process was performed in the same manner as in Example 27. The XRD pattern of the corresponding hydrate was obtained is similarly to the results of Example 27 (result not shown), and the light emission spectrum was shown in FIG. 11.

Example 29

Preparation of Hydroxide Doped with Two Water-Insoluble Metals

(26) As in Example 27, two nitrates were used, but europium nitrate (Eu(NO.sub.3).sub.3.6H.sub.2O, 0.0005 mol) instead of terbium nitrate (Tb(NO.sub.3).sub.3.6H.sub.2O, 0.0005 mol) was used to perform the process in the same manner as in Example 27. The XRD pattern of the corresponding hydroxide was shown as in FIG. 9, and the light emission spectrum was obtained by shifting the absorption wavelength and the light emission wavelength into 460 nm and 613 nm, respectively (FIGS. 12a and 12b). This fluorescent material may be utilized as a fluorescent material with a wavelength conversion for a blue magneto-luminescent device in the blue region.

Example 30

Preparation of Yttrium Oxide from Yttrium Hydroxide

(27) The resulting product in Example 1 may be converted into yttrium oxide by heating. Two g of the yttrium hydroxide powder produced in Example 1 was put into a 10 ml-alumina crucible, and subjected to heat treatment at 400 C. in an electric furnace for 2 hrs. At this time, the heat treatment temperature may be controlled from 300 C. or more to less than 1,300 C. After the heat treatment, the to crucible was cooled down to room temperature to obtain yttrium oxide as a white solid. During the heat treatment, the weight was reduced by about 20%. The XRD pattern and SEM image of the yttrium oxide produced are represented in FIGS. 13 and 14, respectively.

Comparative Example 1

When Washing is Performed without Heat Treatment in Example 1

(28) The combustion process was performed in the same manner as in Example 1. However, the washing step was immediately performed without heat treatment after the combustion as follows. The white solid obtained after the combustion was washed five times with 10 ml of water, and then dried at room temperature. At this time, it was confirmed through XRD patterns that the powder obtained was a composite oxide, not a metal hydroxide. And then, it was demonstrated through the XRF result that sodium ions had been significantly reduced. The corresponding XRD and XRF results are illustrated in FIG. 15 and Table 2, respectively.

Comparative Example 2

When Preparation is Performed without Alkali Salt in Example 1

(29) Only yttrium nitrate (Y(NO.sub.3).sub.3.6H.sub.2O, 0.0095 mol) and urea (0.02 mol) were put into a 200 ml-alumina crucible, 50 ml of water added thereto, the mixture was stirred until the mixture became a transparent solution, and then the resulting product was transferred to an electric furnace pre-heated to 500 C. After water was evaporated, the combustion (oxidation) reaction started, lasted for several minutes, and then stopped. The combustion product was a white powder, and to was again subjected to heat treatment at 900 C. in an electric furnace for 2 hrs. The heat-treated powder was cooled down to room temperature, and then washed five times with 10 ml of water. The remaining solid was separated by a centrifuge, and then dried at room temperature to obtain a white solid. It was confirmed through the XRD pattern that the resulting product was yttrium oxide, not a hydrate (FIG. 16).

(30) When a yttrium hydrate-based compound according to the present invention is prepared, lanthanide or transition metal ions may be added together, and in this case, much stronger light emission may be obtained from the lanthanide or transition metal ions because a yttrium hydrate-based compound to be the resulting product acts as a host. Accordingly, a yttrium oxide (Example 30), which may be used as a host of a fluorescent material and formed by conversion of the oxide, has a high crystallinity, and thus may exhibit good functionality when used as a fluorescent material, a catalyst, a ceramic material and the like.

(31) Although the specific part of the present disclosure has been described in detail, it will be obvious to those skilled in the art that such a specific description is just one exemplary embodiment and the scope of the present disclosure is not limited thereby. Therefore, the substantial scope of the present disclosure will be defined by the appended claims and equivalents thereof.