CN103011241A - Rare-earth praseodymium lamellar crystal and preparation method for same - Google Patents

Abstract

The invention relates to a rare earth praseodymium flaky crystal and a preparation method thereof. The praseodymium content in the praseodymium lamella is 68% to 85% (mass fraction). The particle size is 15μm-40μm, the thickness is less than 1μm, and the aspect ratio, that is, the particle size/thickness ratio is greater than 20. When preparing, mix the praseodymium salt solution containing mineralizer and phosphorus compound and the precipitant aqueous solution to obtain a suspension or gel, dry the suspension or gel by evaporation, and treat it at 850-1400°C by molten salt method for 2 A solid product was obtained in -6 hours, and then washed with water, filtered and dried to obtain rare earth praseodymium flaky crystals. The praseodymium flake crystal has a large aspect ratio, good dispersibility, and smooth surface. It is a black flake crystal. After adding a small amount of cerium, the praseodymium flake crystal has a red luster. It is suitable as a matrix for pearlescent pigments and can be widely used in plastics, coatings, Inks, cosmetics and glazes.

Description

A kind of rare earth praseodymium flake crystal and preparation method thereof

technical field

The invention belongs to the field of preparation of inorganic powder materials, and relates to a rare earth praseodymium flaky crystal and a preparation method thereof.

Background technique

Pearlescent pigment is a kind of pigment with pearl-like soft color, which is formed by coating a flake-shaped substrate (such as mica flakes) with a metal oxide with a high refractive index (such as iron oxide, titanium oxide). As a substitute for mica, several flaky oxide powders have been synthesized, such as flaky titanium oxide, flaky aluminum oxide, flaky iron oxide, and aluminum-doped flaky iron oxide. There are not many types of substrates that can be used for pearlescent pigments, and even fewer rare earth elements are introduced into the substrate. Only Chinese patent ZL200810003686.4 proposes the preparation of neodymium oxide substrates by molten salt method. It shows different colors under natural light, it is purple under natural light, it is light blue under fluorescent light, and it is pink under incandescent light.

Contents of the invention

The purpose of the present invention is to provide a rare earth praseodymium flake crystal and a preparation method thereof, increase the types of substrates used for pearlescent pigments, and expand the application field of rare earth; it has a larger diameter-thickness ratio than conventional praseodymium oxide, and the smooth surface is not easy Forming twins and crystal agglomeration, it has good acid resistance, alkali resistance and weather resistance.

Technical solution of the present invention: a rare earth praseodymium flaky crystal, wherein the mass percentage of praseodymium is 68% to 85%, the mass percentage of oxygen is 15% to 23.5%, and the mass percentage of sulfur is 0 ~ 8.5%.

The grain size of the praseodymium flakes is 15 μm to 40 μm, the thickness is less than 1 μm, and the aspect ratio, that is, the grain size/thickness ratio is greater than 20.

Praseodymium lamellae are black, with pearlescent luster, smooth surface, not easy to form twins and crystal agglomeration, suitable for the matrix of pearlescent pigments.

After adding cerium chloride at a mass ratio of 0-10%, the praseodymium platelets show red luster.

A method for preparing rare earth praseodymium flaky crystals, adding a precipitant aqueous solution dropwise to a mixed solution of praseodymium salt, mineralizer, and phosphorus compound to obtain a suspension or gel, and drying the suspension or gel by evaporation, Then heat-treat the dried product in a resistance furnace at 850-1400 DEG C for 2-6 hours, then wash with water, filter and dry to obtain the rare earth praseodymium flake crystal.

In the present invention, the water-soluble praseodymium salt can be various water-soluble praseodymium salts, and the water-soluble precipitation agent can be alkali or alkali metal carbonate, and its consumption is equivalent to that of the water-soluble praseodymium salt.

In the present invention, the mineralizer and the phosphorus compound can be added together into the aqueous solution of praseodymium salt, and can also be added together into the aqueous solution of precipitating agent. The mineralizer is one or more of alkali metal chlorides and alkali metal sulfates. The amount used is 2-6 times the molar amount of the water-soluble praseodymium salt. The phosphorus compound is one or more of water-soluble compounds of phosphoric acid, phosphate, condensed phosphoric acid, and condensed phosphate, and the dosage is 1-5% of the mass of the praseodymium compound based on phosphorus pentoxide.

In order to obtain better rare earth praseodymium flaky crystals, the present invention uses precursors and molten salts to be mixed and heated, and melted at a high temperature to prepare rare earth praseodymium flaky crystals.

Compared with the conventional praseodymium oxide, the rare earth praseodymium flaky crystal prepared by the invention has larger particle size, uniform and small thickness, and larger diameter-thickness ratio. Rare earth praseodymium flaky crystals with a particle size of 15 μm to 45 μm, a thickness of less than 1 μm, and an aspect ratio, that is, a flaky particle with a particle size/thickness ratio greater than 20. The rare earth praseodymium flaky crystal is black in color, has a smooth surface, is not easy to form twin crystals and crystal agglomeration, and is suitable as a matrix of pearlescent pigments. Pearlescent pigments with better pearl luster can be obtained after being coated with metal oxides with high refractive index. This pearlescent pigment is suitable for use in plastics, coatings, inks, cosmetics and glazes.

Detailed ways

Example 1

The water bath was heated to 80° C., and 0.5 moles of praseodymium chloride and 2 moles of sodium chloride were dissolved in 250 ml of deionized water to obtain a sodium chloride-containing praseodymium chloride solution. Dissolve 1.5 moles of sodium hydroxide and 1.5 grams of trisodium phosphate dodecahydrate in 200 ml of deionized water to obtain an aqueous solution of sodium hydroxide containing phosphorus compounds. While stirring, mix the above two aqueous solutions, and continue stirring for 30 minutes after mixing to obtain a suspension or sol, which is evaporated to dryness, and the resulting solid is heated at 1100° C. for 4 hours. Add deionized water to the heat-treated product to dissolve free sodium chloride. The insoluble solid was filtered off, washed with deionized water, and finally dried, thereby obtaining the desired rare earth praseodymium flaky crystal.

The obtained rare earth praseodymium flaky crystal is tested by X-ray diffractometer, and there is only one spectrum compound peak in the diffraction pattern. The results of optical microscope and electron microscope observation show that the rare earth praseodymium flake crystals have a particle size of 15-35 μm and a thickness of 0.5 μm, and no twins have occurred. Rare earth praseodymium platelet crystals produce smooth streamlines when dispersed in water by stirring.

Example 2

The water bath was heated to 80°C, and 0.5 mole of praseodymium chloride was dissolved in 250 ml of deionized water to obtain an aqueous solution of praseodymium chloride. Dissolve 1.5 moles of sodium hydroxide in 200 ml of deionized water to obtain an aqueous sodium hydroxide solution. While stirring, mix the above two aqueous solutions, and continue stirring for 30 minutes after mixing to obtain a suspension, which is evaporated to dryness, and the dried powder is mixed with 142 grams of sodium sulfate, 174 grams of potassium sulfate, and 2 grams of dodecahydrate. Trisodium phosphate was placed in a ball mill jar, and ball milled in a planetary ball mill for 4 hours to make the mixture uniform, and the obtained solid was heated at 1100° C. for 4 hours. Add deionized water to the heat-treated product to dissolve free sodium chloride. The insoluble solid was filtered off, washed with deionized water, and finally dried, thereby obtaining the desired rare earth praseodymium flaky crystal.

The results show that the rare earth praseodymium flaky crystals prepared by this method have a particle size of 15-25 μm, a thickness of 0.3 μm, and good dispersion. Compared with the implementation of Experiment 1, the sulfuric acid composite molten salt has a better dissolving ability, which makes the shape of the flaky crystals more regular and the particle size distribution more uniform.

Example 3

The water bath was heated to 80° C., and 0.5 mole of praseodymium chloride, 1 mole of sodium chloride and 1 mole of potassium chloride were dissolved in 250 ml of deionized water to obtain a chloride-containing praseodymium chloride solution. Dissolve 0.75 moles of sodium carbonate and 2 grams of trisodium phosphate dodecahydrate in 200 ml of deionized water to obtain an aqueous sodium hydroxide solution of phosphorus-containing compounds. While stirring, mix the above two aqueous solutions, and continue stirring for 30 minutes after mixing to obtain a suspension or sol, which is evaporated to dryness, and the resulting solid is heated at 1100° C. for 4 hours. Add deionized water to the heat-treated product to dissolve free sodium chloride. The insoluble solid was filtered off, washed with deionized water, and finally dried, thereby obtaining the desired rare earth praseodymium flaky crystal.

The results show that the rare earth praseodymium flake crystals have a particle size of 15-25 μm, a thickness of about 0.4 μm, regular shape and good dispersion.

Example 4

The heat treatment temperature in Example 2 was changed to 1200° C., and the rest of the ingredients, formula and preparation process were the same.

The results show that the particle size distribution of rare earth praseodymium flaky crystals becomes wider due to the increase of firing temperature, the particle size is 15-45μm, and the shape is not very regular.

Example 5

The heat preservation time among the embodiment 2 is changed into 6 hours, and all the other ingredients, formula and preparation process are identical.

The results show that due to the prolongation of the holding time, the thickness of rare earth praseodymium flaky crystals increases to 0.9 μm, the shape is more regular, and the dispersion is good.

Example 6

The quality of sodium sulfate and potassium sulfate in embodiment 2 is changed into 284 grams and 348 grams respectively, and all the other ingredients, formula and preparation process are identical.

The results show that due to the increase of the amount of molten salt, the particle size of rare earth praseodymium flake crystals decreases and the distribution is not uniform,

Example 7

Heating to 80° C., dissolving 0.45 moles of praseodymium chloride, 0.05 moles of cerium chloride and 2 moles of sodium chloride in 250 ml of deionized water to obtain a sodium chloride-containing praseodymium chloride solution. Dissolve 1.5 moles of sodium hydroxide and 1.5 grams of trisodium phosphate dodecahydrate in 200 ml of deionized water to obtain an aqueous solution of sodium hydroxide containing phosphorus compounds. While stirring, mix the above two aqueous solutions, and continue stirring for 30 minutes after mixing to obtain a suspension or sol, which is evaporated to dryness, and the resulting solid is heated at 1100° C. for 4 hours. Add deionized water to the heat-treated product to dissolve free sodium chloride. The insoluble solid was filtered off, washed with deionized water, and finally dried.

The color of the obtained praseodymium flaky crystals turns red, and the obtained rare earth praseodymium flaky crystals are tested by an X-ray diffractometer, and there is only one spectrum compound peak in the diffraction pattern. The results of observation with optical microscope and electron microscope show that the rare earth praseodymium flake crystals have a particle size of 15-40 μm, a thickness of 0.6 μm, and a uniform distribution.

Claims (9)

1. praseodymium tabular crystal, it is characterized in that: wherein the quality percentage composition of praseodymium is 68%～85%, and the quality percentage composition of oxygen is 15%～23.5%, and the quality percentage composition of sulphur is 0～8.5%.

2. described a kind of praseodymium tabular crystal according to claim 1, it is characterized in that: praseodymium platelet particle diameter is 15 μ m～40 μ m, thickness is less than 1 μ m, aspect ratio, namely particle diameter/Thickness Ratio is greater than 20.

3. described a kind of praseodymium tabular crystal according to claim 1, it is characterized in that: the praseodymium platelet is black, has nacreous lustre, and smooth surface is difficult for forming twin and crystal is reunited, and is fit to do the matrix of pearly pigment.

4. described a kind of praseodymium tabular crystal according to claim 1 is characterized in that: after adding mass ratio and being 0～10% Cerium II Chloride, and the praseodymium platelet gloss that takes on a red color.

5. the preparation method of a praseodymium tabular crystal, it is characterized in that: the precipitation agent aqueous solution is added drop-wise in the mixed solution of praseodymium salt, mineralizer, phosphorus compound, obtain a kind of suspensoid or gel, by this suspensoid of evaporation drying or gel, with molten-salt growth method 850-1400 ℃ lower after processing cooling in 2-6 hour a solid product, after wash again, filter and the dry praseodymium tabular crystal that obtains.

6. the preparation method of described a kind of praseodymium tabular crystal according to claim 5, it is characterized in that: the described precipitation agent aqueous solution is the aqueous solution a kind of in alkali, alkaline carbonate, the oxalate, the amount of its consumption and water-soluble praseodymium salt is suitable.

7. the preparation method of described a kind of praseodymium tabular crystal according to claim 5, it is characterized in that: mineralizer is one or more in alkali metal chloride and the alkali metal sulfates in the mixed solution of described praseodymium salt, mineralizer, phosphorus compound, the mineralizer consumption be water-soluble praseodymium salt molar weight 2-6 doubly.

8. the preparation method of described a kind of praseodymium tabular crystal according to claim 5, it is characterized in that: phosphorus compound is one or more in the water-soluble cpds of phosphoric acid, phosphoric acid salt, condensed phosphoric acid and condensed phosphate in the mixed solution of described praseodymium salt, mineralizer, phosphorus compound, and the phosphorus compound consumption is counted 1～5% of praseodymium compound quality with Vanadium Pentoxide in FLAKES.

9. the preparation method of described a kind of praseodymium tabular crystal according to claim 5, it is characterized in that: better implementation condition is: heating in water bath to 80 ℃, 0.5 mole of praseodymium chloride and 2 mole nacls are dissolved in the 250ml deionized water, obtain the praseodymium chloride solution of sodium chloride-containing; Dissolving 1.5 molar sodium hydroxides and 1.5 restrain ten phosphate dihydrate trisodiums in the 200ml deionized water, obtain the aqueous sodium hydroxide solution of P contained compound; In situation about stirring, mix above-mentioned two kinds of aqueous solution, mix complete continuation and stirred 30 minutes, get a suspensoid or colloidal sol, be evaporated to drying regime, the gained solid was heated 4 hours under 1100 ℃; Add deionized water in the product that heat treated is crossed to dissolve free sodium-chlor, leach insoluble solid, use again deionized water wash, final drying obtains desired praseodymium tabular crystal thus, and praseodymium tabular crystal particle diameter is 15～35 μ m, thickness is 0.5 μ m, do not produce twin, in water the time, the praseodymium tabular crystal produces smooth streamline by dispersed with stirring.