JPS5964703A - Fine acicular metal powder - Google Patents

Abstract

PURPOSE:To manufacture the titled fine acicular metal powder or stable quality at a low cost, by electrolyzing Al or an Al alloy having the surface coated with an anodically oxidized film in an aqueous phase containing one or more of metal ions to precipitate said metal ion in fine pores inside the coating film, and then removing said anodically oxidized film by dissolution. CONSTITUTION:Al or an Al alloy having the surface coated with an anodically oxidized film is electrolyzed as an anode in an aqueous solution of one or more of water-soluble metal compounds as an electrolyte. After the electrolysis, said metal is precipitated in the fine pores of the anodically oxidized film on the surface. Thereafter, the surface is treated with an aqueous phosphoric acid solution having the excellent ability to dissolve an anodically oxidized film, e.g. one of concentration of 1-10% and a liquid temp. above 50 deg.C, to dissolve said anodically oxidized film. Thus, the acicular powder of said metal is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fine metal powder, and more particularly to a fine metal powder produced by electrolytic deposition using ultra-fine pores in an anodic oxide film formed on the surface of Ae or its alloy. Regarding fine metal powder.

Fine metal powders are mainly produced and used for powder metallurgy or pigments, but these metal powders have an average particle size of several μ to several 100 tt, the size of the so-called sub-sieve or sieve region, and these The powder is produced by pulverization, atomization, electrolysis, and other physical and chemical methods.

On the other hand, in recent years so-called ultrafine powders with particle sizes on the angstrom level have been manufactured, and these ultrafine powders have been found to have useful properties different from conventional metal powders, and their uses are expanding. It is expanding.

That is, magnetic powder (Fe) for high-density magnetic recording media.

Co, Ni, and their alloys), pigments for conductive/resistance paints (Ag, Ni, Cu, etc.), fillers for conductive combs/resins, surface chemical reaction elements (catalysts, electrode plates for batteries, low-temperature sintering, etc.) (Ag, Ni, PL, PA, etc.) Particulate filter (Ni, etc.), Combustion aid (A1.Ni), Dispersion-strengthened alloy (Ni, etc.),
Examples include light-receiving paint (AIJ) for infrared and other radiation detectors.

These ultrafine powders are manufactured by several chemical methods in addition to physical methods such as the so-called in-air evaporation method in which metals are evaporated in a low-pressure inert gas. Chemical methods include reducing metal compounds at high temperatures, chemically precipitating ultrafine particles of metal J'+nj and reducing them by heating, and atomizing an aqueous solution of salt containing metal ions and freezing it. Inui J:, by '+lj method? a
A method of thermally decomposing salts containing metal ions using low gas plasma has been proposed, and some of them have been industrialized. The medium evaporation method requires a large amount of energy and large vacuum equipment to evaporate the metal, and has the drawback of low productivity and high costs.-18
In chemical methods, the preparation of the raw material compounds is expensive, but in both cases a thermal reduction step is unavoidable, which causes grain growth of the produced fine particles during heating, resulting in poor particle size stability. There is.

An object of the present invention is to develop a method for producing angstrom-sized ultrafine powder of metal or alloy at a stable quality and at low cost, and in particular, a method for producing ultrafine powder with excellent magnetic properties.

The present inventors have discovered the first (and fourth) finding that micropores with extremely uniform pore diameters and depths are densely present in the anodic oxide film formed on the surface of metals, particularly A/ or its alloys. As a result of extensive research, we have arrived at the present invention.

Gold fa2:! /r- "lti solution Ino T comes out, followed] - note No. 11 frame 1 brightening film ;) i4t :I+<
This invention relates to fine sword-shaped metal powder produced by melting and removing the powder.

The process of the invention is carried out by a two-step 'fIL decomposition reaction in the aqueous phase and an oxide dissolution reaction.

First culm: Step of forming an anodic oxide film on the surface of Al or A/' alloy (-subsequent electrolytic treatment) Second culm: "5. Wandering in the film"! 7. Separate fine particles of metal or alloy inside the inner hole. The egg that comes out in the corner is 1゛ (
The process of selectively dissolving and removing the oxidized film on the frame (film dissolving process) will be described below with reference to each of the above steps.

(1) When electrolytic treatment A/ or its alloy is used as an anode and subjected to direct current or alternating current electrolysis in a branched bath, an oxide film having corrosion resistance, abrasion resistance, and decorative properties will be formed on the surface. As is well known, acid baths include various types of shaftless baths, IJ゛((
Snoring prison, or these /lll, acids are used. (
The hot water electrode oxide film has a porous layer with densely packed micropores, and a fine 71
It consists of a double layer structure with a few fine barrier layers between the bottom of the 'li1 hole and the metal surface. The micropores in the porous layer have a diameter on the order of angstroms, are regularly arranged in the direction perpendicular to the metal surface, and are open at the top. The pore size of the refinement varies depending on the type of electrolytic bath, bath temperature, etc., but under certain conditions, phosphoric acid is the largest, and sulfuric acid is the smallest. The thickness of the porous layer, that is, the depth of the pores, varies depending on the purity of l', alloy composition, electrolytic conditions, etc., but is generally pure Aj? For alloys containing heavy metals, it is thick. Also, depending on the electrolysis time, porous T'r,
There is a maximum point in the thickness of the layer, and once the film is formed, it dissolves in the electrolytic bath and becomes tri <.

The composition of the coating is mainly amorphous anhydrous A403 for both the barrier layer and the porous layer, but depending on the electrolytic conditions, a part of crystallized Al2O3 is formed, and the other parts in contact with the electrolytic bath contain 1 to 3 water. It has changed to Japanese food.

The primary 7ij llI'i' treatment solution for forming a positive (1mega) oxide film having micropores suitable for the purpose of the present invention includes:
Wj acid, chromic acid, phosphoric acid, etc., or oxalic acid,
Sulfamic acid, tartaric acid, maleiro? Aliphatic carbon 1+, ';2 syn'! , aromatic sulfonic acid a2'
Examples include 1st class acid (;q acid, or a mixed acid thereof; however, from the viewpoint of uniformly forming the necessary porous layer, sulfuric acid,
Chromic acid, phosphoric acid, and oxalic acid are suitable for use in electrolytic baths. In particular, sulfuric acid electrolytic baths form small pores, are inexpensive, and require little electrolytic power, making them economical and therefore most advantageously applied to the present invention. .

By the way, is it currently 1? Or, many of the alloy products are coated with a pre-bath (C) co-existing oxide film.
The haze of this kalpa/combined bath is 1 o ~ 30 wt, @
H2SO4, valley? #L is held at a predetermined temperature within the range of 15 to 25 °C, and electrolyzed at a current density of O''~3 A/on2 and an electrolytic voltage of 15 to 20 V.The bath temperature rises due to heat generation as the electrolysis progresses, and therefore This leads to the dissolution of the film once formed, and the skin 11%y formed with a high bath appearance is soft (with poor abrasion resistance and corrosion resistance = +! +4), so it is essential to forcibly cool the bath using a cooling means. So, the power required for this cooling is 11, and the power IQT' power 11 is -1.

However, in the present invention, since the micropores in the film are used, there is no mental strength to harden the film and impart 1iil J'[) property, and therefore, the bath 7□: +
The increase in i't is controlled by 15L from another point of view. Regarding this point, the present inventors have conducted extensive research and found that the bath temperature of the sulfuric acid type iQ.r bath suitable for the present invention is in the range of 130 to 80°C. When the bath temperature exceeds this -1 limit, the melting angle of the film formed is too fast to form a film of the required thickness uniformly.On the other hand, when the bath temperature exceeds this limit, If it is less than 100%, the film formed is hard and the dissolving power of the film after metal particles are deposited in the micropores is slow, and the removal is insufficient, so the effect of this invention cannot be fully demonstrated. What is further noteworthy is that the higher the temperature of the secondary electrolytic bath, the better the magnetic properties (coercive force, saturation magnetization, residual magnetization) of the ferromagnetic metal fine powder obtained by the secondary electrolytic treatment.

As described above, since the present invention uses high bath temperature electrolysis, it is different from the usual positive (1
'i,, rl' The bath cooling energy is small in the entire process, and since the electrolysis is performed at a low voltage, the electrolytic gravity (i) can be reduced by a large degree.

(2) Secondary? The secondary electrolytic treatment for electrolytic T1 precipitation of the Aj? T or l? Gold alloy 7: J-based water-soluble gold alloy; an aqueous solution of the compound 1) 'J alone or mixed and DC, AC, AC/DC superposition between the aqueous 'lit solution and the pre-bath or other suitable 11 frames. This is done by electrolyzing by passing a current such as Precipitated metals include Fe, Co, and Ni.

]) a , P L + F r 1M n , Cr +
M o + W + V + N b + T a
, B 1 + Ti, Zr + Y + La + Ce
, Sm, Znl Cu + Ag! Most of the metallic elements such as Au + are targeted.

-1] Water-soluble compounds of the metals include sulfur salts, nitrates, phosphorus:'jR salts, pyrophosphates, cyanates, halides, metal salts, etc., acetates, and tartaric compounds. 1 or 2 plates selected from the group consisting of organic compounds such as dredging salts and sulfamates are applied. In these metal salts, there is selectivity in the electrolytic current depending on the f, tli Wi, and valence of metals in these metal salts. be. For example, in the case of 181.1 of 1JNi, Co,
AC electrolysis is suitable, and in the case of Fe (ferric iron), no metal is deposited in either AC or DC electrolysis in 1X, and the AC type of ferrous salt ifJ? In this case, oxidation (Fe-+Fe) during electrolysis causes Fe(OH) to precipitate.
In order to generate precipitation retardation 1 of 3 and reduce Fe flux, it is preferable to add a small amount of an antioxidant such as hydroquinone to the electrolytic solution.

Generally, it is effective to add boric acid and glycerin to the electrolytic bath for secondary electrolytic treatment. The former addition has the effect of buffering the pH of the electrolytic bath and complexing the metal ions, while the latter addition has the effect of increasing the viscosity of the electrolytic bath and homogenizing the electrolytic deposition. Glycols and sugars can also be used as additives.

The necessary addition F1i varies depending on the metal salt to be electrolyzed and is determined by experiment, but for example, in the case of Fe, NrrCo, boric acid is 25 to 40.9 as H3B03 in the bath, glycerin is 10 to 30.9 in the bath. Add to a concentration of /l.

In secondary electrolytic treatment, compounds of two or more metals are
)97, alloys of these metals can be electrolytically deposited. In this case, it is necessary to select the type of salt, bath composition, etc. for effective electrolytic deposition. N1-C.

In this case, the precipitation positions are close to each other, but in Fe-Ni and Fe-
In Ni--Co, etc., since the deposition potential of Fe is far apart, it is necessary to bring them close by selecting a salt seed, a complexing agent, etc. The conditions for electrolytically depositing these two or more metals simultaneously by secondary electrolytic treatment are the same as those for alloy plating that has already been put into practical use.

The electrolytic bath temperature of the secondary electrolytic treatment depends on the type of metal compound, lI-,
Under a constant electrolytic voltage, the higher the bath temperature, the more metal deposited bars 1 will be formed, although this will vary depending on factors such as 1 degree. For example, when alternating current electrolysis is carried out using a cobalt sulfate aqueous solution (pH=4.3) as an electrolytic bath, the metal deposition ();- reaches about 150 times the value when the bath temperature is 20°C at a bath temperature of 50°C. However, in general, when the bath temperature exceeds -75°C, the metal deposition efficiency is saturated, and on the other hand, the energy loss for maintaining the high bath temperature increases. Therefore, the bath temperature is 2 as a double millet treatment condition.
It is desirable to maintain the temperature within the range of 0-760°C.

(3) Film dissolution treatment 11, self-Sagoyama'iQ' (dokoro) 21 ni (man put out ii; ](]Also Q-]fn gold plate 111 and α, understand・2 and 1.r The operation to do is to remove the film and the
1:H:l: i Niji:] 1L chemical reaction of alloy 1. ig,
・111. Based on the i′ first river. l! 'I
,! l! The property of forming fine pores as shown in (-σl oxidized skin II. The chemical activity of the film differs depending on A/1.In the present invention, as described above, the primary 'mountain IQ' (treatment) -
'1i! This year, I raised -r, 11.2, alkali silicon/l; +'easy to oxidize A/' oxide and +1'C.

Skin 1F; j #i As a decomposable liquid, the concentration of 1τ is about 1-10%, liquid! ! 1. ! The concentration of phosphoric acid in water at 50°C or above is approximately 0.
5 to lo, the liquid temperature is 3 Fl ℃ or higher [j'1) and the alkali is 2). (Withdrawal with J 1., Ba, alloy is 111
For gold i:r; systems, caustic alkalis are suitable, and for non-metallic systems such as S n + S e + Z n + old etc., a caustic alkali containing an inhibitor suitable for the precipitated metal is used ) 1 lysis solution is suitable. It is effective to add 1R inhibitor to prevent metal surface oxidation in the film solution, and add an alkaline 1T+I solution (1-I 1 dredging 5, for example, Na,... S i 0
3'! Adding l It,, O gives 14'l
Rukinsu, i-dama, and alloy drums are predominant.

Metals and alloys remaining in the solution after dissolution treatment 341j (; Wash n1, dry.Soluble) Minute v1 (1 to 1 Ill filtration, or 0.1 centrifugation Z)
':Yo! However, the purifying solution is even more effective when used with water, alcohol, ether, etc. as a solvent. Low temperature and reduced pressure drying is suitable for drying.

+ノ, 1; +14. : The precipitated metal after the melting treatment j-jjj, as shown in FIGS. 1 and 2 of the Examples described below, is
-: 0.2-: 'Jurn's feed body exhibits a shape in which it is tightly packed in the length direction.

d and 7 of each of these gold 1-like bodies? The electricity described above can be controlled by one processing event. In addition, each xiphoid outer comrade joint σ) can be easily applied with a weak suppressing force, and can also be ruptured in the radial direction if necessary. .

For such disintegration and crushing, impact type crushing (shock flow, crushing machine, etc. in which teeth or particles are bombarded with each other) is used.

The present invention will be explained below based on experimental examples and examples. The present invention is limited to this! It is not something that will be done.

Example (1) No divination i';■J...7'Lumiuno-'/i'+ (9g,
LJ Al, thickness 0, ], 111111 X I
ll 501n1nX length 100 mm) [iCl・
...-1 Industrial pure aluminum & (JIS A1]
00-Horizontal $24, +12 1.0 +nm X l1
15 +1111111. ×Length L 00 mm
)(2) Inner surface treatment for child Ino 11: Substrate A was immersed in a 5% NaOH aqueous solution at 10°C for 2 minutes, followed by: U() Section J-rNO,.

Washed and dried in '111 for 1 minute with water.

(3) - Next city, waste disposal; 1) Denkaku Ryoba: (a): ] 55% H2SOs, bath r! in
Keep the bath temperature constant at 20°C or 50°C at 20°C or 50°C. Direct current electrolysis was performed at a constant current density [time].

(4) Secondary electrolytic treatment; 11) 71,) 7 bath: ++1 old), 25 and 20% glycerin dissolved in an aqueous solution containing (',)' ・Fc SO4 ・71-120 5.0
Dissolve 5.0% of CoSO4H7Tl2O, adjust the pH to 3.5 with each lI2SO4, and use it as an electric bamboo bath for 1 minute. The bath temperature is 3 (keep it constant at 1℃)
11-It was. .

2) 7i, + 111 completion: Place the carbon plate on the opposite pole and keep the specified 111 flow 7haj-9 constant [I,
7 minutes Bunryuden 11+F (did.

(5) Film dissolution treatment, etc.; After the above-mentioned secondary 'li: solution, it becomes blackish brown due to I + ≦. The precipitated metal fine particles that had settled in the liquid were suctioned and filtered using TodlI paper 5C. Place in a vacuum desiccant using magnesium perchlorate as a desiccant and dry at room temperature.
Dry smoked for 1 hour.

(6) Results; Convergence of fine powder total bending R) according to the conditions of primary electric IQlf treatment and secondary electrolytic treatment, and the magnetic properties of the same fine metal powder are not shown in Table 1. In the table - Compare the results of secondary electric fTl bath temperature 2o℃ and 50℃ (experiment No. 1, 2 and 5゜6 and experiment No. 3)
．． 4 and 7.8), the higher the bath temperature is, the higher the primary electrolysis rate.
It is recognized that the lu force consumption [11] is significantly reduced, there is a large amount of metal 4 discharge (!;'' in the secondary electrolysis, and the magnetic q′, ? properties of the obtained goldfffj fine powder are also excellent.-Next As the electrolytic treatment solution, both Ilv acid and phosphoric acid can be effectively used, but in the case of phosphoric acid, a film will not be formed if the bath temperature is 30°C or higher, and if the current density is lower than IA/αnL2 or lower.
In this case, the conditions in Table 1 were the limit because burning occurred.

Example 2 (]) Base material; aluminum bamboo (419,99-A7
? j1fusa0. i 1n+11 X 1lJ125
+1m x length 250+Ill++) (2) Preliminary! i! Alcrine #1 at 60℃
100 (Okuno UiW, j',!; Kogyo?l-manufactured commercially available A
f Degreasing agent (trade name) After etching by immersing it in 3% aqueous DK for 3 minutes, it was dried in water 6 (compared to C: drying).

(3)-Next electrolytic treatment 1; 1)', [1 Bath decomposition: 15 tons of H2So4, bath temperature 715°C
was held constant.

2)? 'Lj Solution: Pure Al plate as counterplant; 3A/
d7112X 3.3 minutes,”! 5 A/dn
DC electrolysis was carried out at 'f x 2 minutes.

(4) Secondary frost thawing treatment; ■) Electrolytic bath: 1'1CD-=-Fe so, -711204,0% in the water temperature liquid in which Section 04 was dissolved.
+N15O.

・7H201,0 Bath ■・・・・・・tt u 2. (L section-
I 〃・7H,,03,0 section
The pH was adjusted to 3.7 with H to prepare a bath. obscene i/, ′, ffi′.

was held constant at: IO'C.

2) Electrolysis: carbon plate as sentence 1 (as 愼), 4 V
AC electrolysis was carried out for 75 minutes.

(,5) Film dissolution treatment, etc.; Melting solution S1... 2% NaOH aqueous solution S 2-IMI+ 02% Na2 S l
03' () l-I20 Water dissolution conditions 40°C
Same as.

(6) Results: Fe5O4 in the secondary electrolytic bath becomes monovalent during electrolysis and becomes Fe(
011) Set f6 t ll of 3. Ninchu'+'S h
ljNo, 11-12, and No, 1': U-1
As is clear from the comparison of /l, the addition of hydroquinone prevents oxidation without adversely affecting the magnetic properties of fine powder metals or alloys. 4) l! Eggplant) 11. By placing 75 pieces of free melon in between, it has the effect of not reducing the amount of precipitated metal.

As the film property 1'+'1' liquid, SL with only NaOH
It is recognized that S2 containing Na25in as a reinhibitor is superior in magnetic q and j properties without much deterioration even if the dissolution period becomes longer.

The magnetic properties of the fine powder obtained vary depending on the Ni/Fe ratio of the secondary electrolytic bath, and when this ratio is 1/4 (Ni20% - Fe80%), the coercive force is high, but is it saturated? Le conversion and residual magnetization are low, and this ratio is: Me2(NiCo%-re
4o%), the opposite is true.

Example 3 (1) Base A2; Aluminum plate (99,8 section Aj?
Board-II24, j9 size 5 ml x width 1.000
+III x length 2, 0 0 0 jnTII
) (2) Preliminary surface treatment: immersion in 5% NaOH aqueous solution at 5oC for 30 seconds for etching, followed by immersion for 2 to 3 minutes αJ
It was then desmatted and then washed with water.

(3) -Next electrolytic treatment' 1500 ++onX,
ljsu15.

0 +111+1 x depth 1500 +nm 'mountain iQ
(An aqueous solution of 15% 112so in I soda was prepared.

Industrial pure aluminum plate (JIsAllo.

-I124) as a counter rod at 50℃, 3 minutes, DC 5A
Immediately after the primary electrolytic treatment was carried out under the conditions of /dm2, it was washed with water.

(4) Secondary 111 electrolytic treatment; The electrolytic IQF4 bath method is the same as the primary electrolytic treatment.

1) Electrolytic bath: FeSO4.7H2043%, Nl5o
4.6H200.7%, 113B 04 2.5%
, Chrycerin 2, (NH4,)2 So, 1%, water (mixture solution), adjust the pH to 45 (02
This was adjusted to give an electrolytic bath.

2) 'r', solution; 14V constant voltage commercial AC IB solution was applied for 10 minutes using lead as wart countermeasure, and immediately after that, it was washed with water.

(5) Film dissolution IQ'f treatment, etc.; 1. After completion of I5 solution and washing with water, the base metal, which had a black color due to the precipitated metal, was hung in an empty cypress and Na2 was added from both sides.
5i03 ・9H, 50°C containing 01% NaO
The H aqueous solution was strongly sprayed from a nozzle for 1 minute to dissolve the positive 4ifiA oxide film formed by the secondary electrolytic treatment and at the same time suspend the precipitated metal in the Na OFI aqueous solution. .

This suspension (black color) was separated into solid precipitated metal particles and an aqueous NaOH solution using a centrifugal separation device II, and then washed and dried at a high temperature. The separated Na0II aqueous solution can be used after reconstitution.

(6) Results; Yield! ) 'j:'C has an average of 1.3,9/m2.
, 9, residual magnetization 7゜emO/fj, holding force 1,200
0e, and the particles are sufficiently durable to be used as magnetic fine particles.

Electron micrograph of fine powder metal produced by the present invention (
The appearance of a transmission electron microscope (H-700H) manufactured by Hitachi, Ltd. is shown in the photographs in FIGS. 1 and 2. This was exemplified in the case of Example No. 011 in Table 2, but the appearance was almost similar in other cases as well. Figure 1 shows the appearance immediately after the film dissolution treatment, showing an aggregate of fine needle-shaped precipitated metals.

Figure 2 shows the final appearance of the metal fine powder obtained by the method of the present invention after the precipitated metal in Figure 1 has been dismantled by a gentle plate-forming method. -500A, exhibiting a needle shape with a length of Q2 to 31tm.

The fine metal powder beam according to the present invention produced as described above] B Has a feeling characteristic? Ilp'l/I:, which has conventionally been widely used as magnetic powder for P-air recording tapes, such as l'F'' ++04, CrO2, Co-modified 11
In addition to being used without color loss as iron dioxide, etc., it is also used in various ultrafine powder applications as listed in (11) above.

[Brief explanation of the drawing]

The drawings are electron micrographs of Fe-/lPO-related N1g1 powder produced by the method of the present invention, and Figure 1 shows an aggregate of precipitated metal fine particles immediately after film dissolution treatment (magnification: 000x);
Similarly, Figure 3 shows the solution of the aggregate in Figure 1, (,/',"1
．． , 'l, li'ji'flj, 1llJj person 11rJ
lf1. l l! 'is1゛(・1be1 Zhu style 4 meeting?1 substitute person j1'''ll! '-1', 'r'5 book
-Ya-Procedure Written by Masaaki Ura (Method) Jθ March 1981≠Mr. Tsukio Wakasugi, Commissioner of the Japanese Patent Office 1 Matters 1. ! (Display of ``Shoji Ell 1957 Special Application No. 172525 2 Name of the invention Needle-like metal 1-suck powder 3 Relationship to the case of the person making the amendment Patent applicant address 7-13 Shiba Koen-chome, Minato-ku, Tokyo Name: Showa Light Metal Co., Ltd. Representative: Kenhiko Hayashi 4 Agent residence: 13-9-6 Shiba Daimon-chome, Minato-ku, Tokyo Subject of amendment: "Inventor" column in the application and "Brief description of drawings" in the specification Column 7. Contents of the amendment (2) Amended details of the specification", page 23, line 20, "Figure 3" is corrected to "Figure 2."

Claims (1)

[Claims] (1) Aj? with an anodic oxide film on the surface. Or Aj?
Electrolyzing the alloy in an aqueous phase containing metal ions of type 1 plate 1- to precipitate the metal in the micropores in the anodic oxide film, then dissolving the anodic oxide film in j decimal folds,
Acicular fine metal powder produced by removal.