METHOD FOR PREPARING METAL POWDER

Abstract

Provided is a method for preparing metal powder; a metal nitrate or metal sulfate is combined with ammonia water to produce an ammonia-containing complex metal salt solution; the said solution is then quantitatively jet-mixed with the solution containing the hydroxylamine compounds, and reacted under intense stirring; a dispersant solution is added during the reaction process, and after the reaction is complete, the solution is separated by centrifugation to yield the metal power. The method of the present invention can effectively control the reaction rate during the production process, and well control the nucleation rate and dispersity, with the produced metal powder having very good crystallinity, sphericity, tap property and dispersity.

Claims

1. A method for preparing metal powder, characterized in that: the method comprises the following steps: (1) preparation of an ammonia-containing complex metal salt solution: dissolving a metal nitrate solid or metal sulfate solid or an equivalent amount of metal nitrate or metal sulfate liquid into deionized water, adding ammonia water, keeping a molar ratio of [NH.sub.3]:[metal ion]=1:0.5-5 in the solution, stirring sufficiently before adding an acidic additive in an amount of 0.01%-10% by mass of the prepared ammonia-containing complex metal salt solution, and meanwhile heating this solution to 30 C.-90 C.; (2) preparation of a solution containing hydroxylamine compounds: this solution is prepared by adding an equivalent amount of hydroxylamine compound solid to deionized water; according to the metal content in the above step, keeping a molar ratio of [metal ion]:[hydroxylamine]=1:0.1-10 in the solution, stirring sufficiently before adding a pH regulator to regulate the pH in 2.5-9.5, and meanwhile heating this solution to 30 C.-90 C.; and (3) injecting to mix the ammonia-containing complex metal salt solution and the solution containing the hydroxylamine compounds to allow a reduction reaction to happen under vigorous stirring, and centrifugating after completion of the reaction to obtain spherical and nearly spherical metal powder with different particle size.

2. The preparation method according to claim 1, characterized in that: for the preparation of the ammonia-containing complex metal salt solution in Step (1), according to the requirement that the metal ion content in the prepared ammonia-containing complex metal salt solution is 10-500 g/L, adding 1%-30% by mass of ammonia water to get sufficiently stirred with the solution of this metal nitrate or sulfate, then adding an acidic additive, and meanwhile heating this solution to 30 C.-90 C. for later use.

3. The preparation method according to claim 1, characterized in that: for the preparation of the ammonia-containing complex metal salt solution in Step (1), the acidic additive is selected from an organic acid or the metal salt thereof or the mixture thereof.

4. The preparation method according to claim 3, characterized in that: for the preparation of the ammonia-containing complex metal salt solution in Step (1), the organic acid or the metal salt thereof is selected from saturated fatty acids and the metal salts thereof, as well as unsaturated fatty acids and the metal salts thereof; the saturated fatty acids and the metal salts thereof are selected from C.sub.nH.sub.2n+1COOH and the metal salts thereof, wherein n=1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 or the combination thereof, and the metal salts are selected from sodium or potassium salts; the unsaturated fatty acids and the metal salts thereof are selected from C.sub.nH.sub.2nCOOH and the metal salts thereof, wherein n=10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or the combination thereof, and the metal salts are selected from sodium or potassium salts.

5. The preparation method according to any of claims 1-4, characterized in that: the hydroxylamine compound in Step (2) is selected from hydroxylamine, hydroxylamine sulfate and hydroxylamine nitrate, or the mixture thereof.

6. The preparation method according to any of claims 1-4, characterized in that: the pH regulator in Step (2) is selected from inorganic bases and inorganic acids or the salts thereof.

7. The preparation method according to claim 6, characterized in that: the pH regulator added in Step (2) is selected from sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, nitric acid or ammonium nitrate, hydrochloric acid or ammonium chloride, sulfuric acid or ammonium sulfate solution, or the combination thereof.

8. The preparation method according to claim 1, characterized in that: in Step (3), using the pressure generated by a pump or compressed air to inject and mix quantitatively via a micropore the ammonia-containing complex metal salt solution and the hydroxylamine solution prepared in the above steps, with the injection flow rate of the two solutions controlled in the range of 0.2-50 L/min, reacting under vigorous stirring at a stirring speed of 10-500 rpm, and centrifugating after completion of the reaction to obtain all kinds of spherical and nearly spherical metal powder.

9. The preparation method according to claim 1 or 8, characterized in that: in Step (3), adding a dispersant solution at a temperature of 30 C.-90 C. dropwise quantitatively in the course of reaction at a dropping rate of 0.2-10 L/min and an amount of 0.1-5 L.

10. The preparation method according to claim 9, characterized in that: for the preparation of the dispersant solution, dissolving into deionized water one or more kinds of acidic polyhydroxy compounds or the salt compounds thereof or the mixture thereof at a content, of 20-100 g/L; and then stirring sufficiently before adding an amino acid or the polypeptide compound thereof at an amount of 0%-10% by mass of the prepared dispersant solution.

11. The preparation method according to claim 10, characterized in that: the added amino acid or the polypeptide compound thereof is selected from methionine, glutamic acid, alanine, gelatin or the combination thereof.

12. The preparation method according to claim 10, characterized in that: the acidic polyhydroxy compounds or the salt compounds thereof are selected from one or more kinds of triethyl hexyl phosphate, sodium lauryl sulfate, methyl amyl alcohol, cellulose derivatives, polyacrylamide, guar gum, polyethylene glycol, fatty acid polyglycol ester, vitamins, and the sodium or potassium salt thereof.

13. The preparation method according to claim 1, characterized in that: the metal includes copper, silver and tin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is a flow diagram of the method of the present invention.

[0029] FIG. 2 is a schematic diagram of the particle size detection of the metal powder prepared by the method of the present invention.

[0030] FIG. 3 is an electronic microscopic image of the spherical silver powder prepared by the method of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] In order to further understand the present invention, a preferred solution of the present invention will be described below with reference to specific examples. However, it should be understood that the description is used to further illustrate the features and advantages of the present invention, instead of limiting the claims thereof.

Example 1

[0032] (1) Preparation of an ammonia-containing complex silver solution: Dissolving a silver nitrate or sulfate solid or an equivalent amount of silver nitrate or sulfate liquid into deionized water, adding ammonia water, keeping a molar ratio of [NH.sub.3]:[silver ion]=1:0.5-5 in the solution, stirring sufficiently before adding an organic acid and the metal salts thereof at an amount of 0.01% to 10% by mass of the prepared ammonia-containing complex metal salt solution, and meanwhile heating this ammonia-containing complex silver solution to 50 C.-85 C.;

[0033] (2) preparation of a solution containing hydroxylamine compounds: this solution is prepared by adding an equivalent amount of hydroxylamine sulfate to deionized water; according to the silver content in the ammonia-containing complex silver solution, keeping a molar ratio of [silver ion]:[hydroxylamine]=1:0.1-5 in the solution, stirring sufficiently before adding an acidic or basic pH regulator to regulate the pH in 2.5-9.5, and meanwhile heating this reducing agent solution to 50 C.-85 C.;

[0034] (3) preparation of a dispersant solution: dissolving into deionized water one or more kinds of acidic polyhydroxy compounds or the salt compounds thereof or the mixture thereof at a content of 20-100 g/L, and heating the solution to 30 C.-90 C.;

[0035] (4) using a metering pump to inject and mix the ammonia-containing complex silver solution and the solution containing the hydroxylamine compounds quantitatively through a micropore, having reduction reaction under vigorous stirring, meanwhile adding the dispersant solution dropwise quantitatively at a dropping rate of 0.2-10 L/min, and centrifugating after completion of the reaction to obtain silver powder with different particle size.

Example 2

[0036] Preparing 300 mL silver nitrate solution containing 400 g/L silver in a 2000 mL jar, adding 200 mL ammonia water at a concentration of 20% by mass to obtain a silver-ammonia solution, adding 0.7 g acetic acid as an additive, and heating up to 65 C. for later use;

[0037] preparing a hydroxylamine-containing solution in another 2000 mL jar: dissolving 50 g hydroxylamine sulfate and 50 g hydroxylamine nitrate in 500 mL deionized water, adding potassium carbonate to regulate the pH in 6.5-8.0, and heating up to 50 C.;

[0038] preparing a dispersant solution in a 500 mL jar: dissolving 15 g fatty acid polyglycol ester and guar gum in 300 mL deionized water, adding 1.5 g methionine, and heating up to 55 C.;

[0039] injecting and mixing the above two prepared silver-ammonia solution and hydroxylamine reducing agent solution quantitatively in a 5000 mL jar by a metering pump through a micropore at a controlled flow rate of 250 mL/min, beginning to stir at a stirring rate of 20 rpm, adding the dispersant solution dropwise in the course of reaction at a controlled dropping rate of 200 mL/min, and centrifugating after completion of the reaction to obtain spherical or nearly spherical silver powder at an average particle size of 0.1-10 um.

Example 3

[0040] Formulating 300 mL silver nitrate solution containing 400 g/L silver in a 2000 mL jar, adding 200 mL ammonia water at a concentration of 20% by mass to obtain a silver-ammonia solution, adding 0.2 g formic acid as an additive and 0.5 g potassium laurate, and heating up to 65 C. for later use;

[0041] formulating a hydroxylamine-containing solution in another 2000 mL jar: dissolving 50 g hydroxylamine and 50 g hydroxylamine nitrate in 500 mL deionized water, adding potassium hydroxide to regulate the pH in 6.5-8.5, and heating up to 35 C.;

[0042] preparing a dispersant solution in a 500 mL jar: dissolving 15 g sodium lauryl sulfate in 300 mL deionized water, adding 1.5 g gelatin, and heating up to 55 C.;

[0043] injecting and mixing the above two prepared silver-ammonia solution and hydroxylamine reducing agent solution quantitatively in a 5000 mL jar by a metering pump through a micropore at a controlled flow rate of 250 mL/min, beginning to stir at a stirring rate of 20 rpm, adding the dispersant solution dropwise in the course of reaction at a controlled dropping rate of 200 mL/min, and centrifugating after completion of the reaction to obtain spherical or nearly spherical silver powder at an average particle size of 0.1-10 um.

Example 4

[0044] Formulating 650 mL copper sulfate solution containing 300 g/L copper in a 2000 mL jar, adding 350 mL ammonia water at a concentration of 20% by mass to obtain a copper-ammonia solution, adding 0.5 g potassium laurate, and heating up to 65 C.;

[0045] formulating a hydroxylamine-containing reducing agent solution in another 2000 mL jar: dissolving 150 g hydroxylamine in 1000 mL deionized water, adding 0.2 g sodium carbonate to regulate the pH in 6.5-8.5, and heating up to 35 C.;

[0046] preparing a dispersant solution in a 500 mL jar: dissolving 25 g triethyl hexyl phosphate in 250 mL deionized water, adding 1 g alanine and glutamic acid, and heating up to 55 C.;

[0047] injecting and mixing the above two prepared copper-ammonia solution and hydroxylamine solution quantitatively in a 5000 mL jar by a metering pump through a micropore at a controlled flow rate of 500 ml/min, beginning to stir at a stirring rate of 100 rpm, adding the dispersant solution dropwise in the course of reaction at a controlled dropping rate of 200 mL/min, and centrifugating after completion of the reaction to obtain spherical or nearly spherical copper powder.

Example 5: Mass Production

[0048] Adding 250 kg silver nitrate solid in a 2000 L preparation tank, adding 500 L deionized water, sufficiently stirring to dissolve before adding 250 L ammonia water at a concentration of 15% by mass to obtain a silver-ammonia solution, adding 200 g formic acid as an additive and 500 g potassium laurate, and heating up to 65 C. for later use;

[0049] adding 800 L deionized water in another 2000 L preparation tank, then adding 100 kg hydroxylamine and 50 kg hydroxylamine nitrate to get sufficiently dissolved, adding 500 g potassium hydroxide to regulate the pH in 6.5-8.5, and heating up to 35 C.;

[0050] dissolving 5 kg sodium dodecyl sulfate in 100 L deionized water in a 500 L preparation tank, adding 150 g gelatin, and heating up to 55 C.;

[0051] injecting and mixing the above two prepared silver-ammonia solution and hydroxylamine reducing agent solution quantitatively in a reaction tank by a metering pump through a micropore at a controlled flow rate of 5 L/min, beginning to stir at a stirring rate of 120 rpm, adding the dispersant solution dropwise in the course of reaction at a controlled dropping rate of 2 L/min, and centrifugating after completion of the reaction to obtain spherical or nearly spherical silver powder at an average particle size of 0.1-10 um.

TABLE-US-00001 Property Unit Index value Tap density g/cm.sup.3 5.7-6.2 Specific surface area m.sup.2/g 0.5-0.7 Particle size PSD D100 um 3.5-6.5 distribution PSD D90 um 2.0-4.0 PSD D50 um 1.0-2.5 PSD D10 um 0.7-1.5 Heat loss @ 110 C. % <0.1 Heat loss @ 538 C. % <0.4

TABLE-US-00002 Property Unit Index value Tap density g/cm.sup.3 4.7-5.5 Specific surface area m.sup.2/g 1.3-2.2 Particle size PSD D100 um 2.7-4.5 distribution PSD D90 um 1.4-2.5 PSD D50 um 0.9-1.4 PSD D10 um 0.6-1.0 Heat loss @ 110 C. % <0.1 Heat loss @ 538 C. % <0.9

[0052] The technical contents and technical features of the present invention have been disclosed as above. However, those skilled in the art may still make various substitutions and modifications based on the teachings and disclosures of the present invention without departing from the spirit of the present invention. Therefore, the scope of protection of the present invention should not be limited to the contents disclosed in the examples, but should include a variety of replacement and modification without departing from the present invention, and is covered by the claims of the present patent application.