JP2004091859A - Method for manufacturing fine metal particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily manufacture nano-scale fine metal particles having uniform particle size at a low cost on an industrial scale. <P>SOLUTION: Metal powder as a raw-material consisting of one or more metallic elements is subjected to a first pulverizing step where grinding and/or shearing is applied and a second pulverizing step where impact stress is applied. <P>COPYRIGHT: (C)2004,JPO

Description

【００５３】
【発明の効果】
本発明によれば、磨砕及び／又はせん断が加わる第１粉砕工程によって原料金属粉末をナノ一次粒子に粉砕した上で、凝集したナノ一次粒子を衝撃応力が加わる第２粉砕工程によって解砕しているので、工業的規模で安価且つ簡便に、平均粒径が略１５０ｎｍ以下の、粒径の揃ったナノスケールの金属微粒子を製造することが可能となる。
【図面の簡単な説明】
【図１】実施例−１のＳｉ微粒子の粒度分布図である。
【図２】実施例−１のＳｉ微粒子の電子顕微鏡写真である。
【図３】実施例−２のＳｉ微粒子の粒度分布図である。
【図４】実施例−２のＳｉ微粒子の電子顕微鏡写真である。
【図５】比較例−１のＳｉ微粒子の粒度分布図である。
【図６】比較例−１のＳｉ微粒子の電子顕微鏡写真である。
【図７】比較例−３のＳｉ微粒子の粒度分布図である。
【図８】比較例−３のＳｉ微粒子の電子顕微鏡写真である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for miniaturizing metal powder, and more particularly to a method for producing a large amount of nano-sized metal fine particles by mechanical pulverization.
[0002]
[Prior art]
Conventionally, methods for obtaining metal fine particles include a gas phase method (CVD, sputtering, laser ablation), a mechanochemical method, a solution method (sol-gel method, coprecipitation method, electroless plating method), a method by mechanical pulverization, and the like. No.
[0003]
Among these, the technique of making metal powder fine by mechanical pulverization is widely used industrially because a large amount of metal fine particles can be produced easily at low cost.
[0004]
[Problems to be solved by the invention]
However, in the conventional method for producing metal fine particles by mechanical pulverization, fine metal particles (nano-primary particles) temporarily generated by pulverization are attracted to each other by electrostatic attraction and aggregate, so that various sizes of metal particles are obtained. Lumps (agglomerates) are formed. For this reason, the finally obtained metal fine particles have an average particle size and a particle size distribution larger than those of the nano primary particles, and there is a limit in miniaturization and homogenization. Therefore, it is difficult to obtain sufficiently fine and uniform fine metal particles having an average particle size and a particle size distribution of a certain value or less even when the conditions of the grinding (such as the grinding time and the strength of the grinding force) are adjusted. is there.
[0005]
For example, T. D. Shen, et al. J. et al. Mater. Res. 10 [1] 139-148 (1995) reports a method for producing Si fine particles by pulverizing Si particles with a high-energy mill. The average particle diameter of the obtained Si particles is approximately 0.5 μm ( (About 500 nm) is the limit, and its particle size distribution is also very large.
[0006]
On the other hand, it is possible to obtain finer metal particles with a uniform particle size by using the above-described methods such as the gas phase method, the mechanochemical method, and the solution method, but these methods are costly and require a large amount. Production was also difficult and unsuitable for industrial production.
[0007]
In view of the above background, there has been a strong demand for a technology capable of producing nanoscale metal fine particles having a uniform particle size easily and inexpensively on an industrial scale.
[0008]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method capable of producing nanoscale metal fine particles having a uniform particle size on an industrial scale at low cost and easily.
[0009]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, by performing two types of pulverization processing that satisfies specific conditions on a metal powder as a raw material, inexpensively and easily on an industrial scale, The inventors have found that nanoscale metal fine particles having an average particle size of about 150 nm or less and having a uniform particle size can be produced, and the present invention has been completed.
[0010]
That is, the gist of the present invention is characterized in that a raw material powder composed of one or more metal elements is subjected to a first pulverizing step in which grinding and / or shearing is applied and a second pulverizing step in which impact stress is applied. In the method for producing metal fine particles.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail.
The present invention relates to a pulverization process comprising two types of processes, a first pulverization process in which grinding and / or shear is applied to a raw metal powder composed of one or more metal elements, and a second pulverization process in which impact stress is applied. To produce metal fine particles.
[0012]
-Raw metal powder:
The raw metal powder is a powder composed of one or more metal elements. The kind of the metal element is not particularly limited, but is selected from the group consisting of elements belonging to Group Ia, Group IIa, transition metals (Groups IIIa to VIIIa), Group Ib, Group IIb, Group IIIb, Group IVb and Group Vb. Elements are preferable, and among them, elements belonging to transition metals, groups Ib, IIb, IIIb, IVb, and Vb are more preferable. Specifically, Ca, K, Mg, Ti, V, Mn, Fe, Si, Co, Ni, Cu, Zn, Al, Ga, Ge, Sb, Sn, Bi, Pb, Ag, Au, and In are more. Preferably, Mg, Ti, Ni, Cu, Fe, Si, Al, Ge, Sb, Sn, and Ag are more preferable, and Si and Cu are particularly preferable. Also, there is no particular limitation on the number and combination of types of metal elements, even a single metal element powder arbitrarily selected from the above element group, two or more metals selected in any combination from the above element group A mixed powder of elements (a mixture of powders of individual metal elements) may be used. The average particle size of the raw metal powder is usually 100 μm or less, preferably 50 μm or less, more preferably 20 μm or less. The lower limit is not particularly limited, but is usually 0.2 μm or more, preferably 0.4 μm or more.
[0013]
・ Pulverization processing:
In the conventional method of producing metal fine particles by mechanical pulverization, as described above, fine metal particles (nano-primary particles) temporarily generated by pulverization are attracted to each other by electrostatic attraction and aggregate, so that they are actually aggregated. The resulting product is a powder containing an aggregate of nano-primary particles (an aggregate of a plurality of nano-primary particles; an aggregate of nano-primary particles). Therefore, it is difficult to obtain extremely fine and uniform metal fine particles having an average particle size and a particle size distribution equal to or less than a certain value even when the grinding conditions (such as the grinding time and the strength of the force applied during the grinding) are adjusted. Met.
[0014]
Therefore, in the present invention, in addition to the first pulverizing step (the same step as the conventional mechanical pulverization) to which grinding and / or shearing is applied, the first pulverizing step is different from the first pulverizing step in that impact stress is applied. 2. Perform a grinding step. After the raw metal powder is pulverized to nano-primary particles by the first pulverization step, the aggregates of the nano-primary particles contained in the product are pulverized by the second pulverization step to obtain a nano-size having a nearly uniform particle size distribution. Can be obtained. Therefore, while the first pulverizing step needs to be a strong pulverizing treatment to bring the raw material metal powder to the nano primary particles, the second pulverizing step needs to separate the aggregated nano primary particles into pieces. A sufficiently weak grinding treatment is desirable.
[0015]
The type of the first pulverizing step is not particularly limited as long as it is a pulverizing step to which grinding and / or shearing is applied. Here, grinding refers to an operation of grinding an object by mechanical processing to make it finer, and shearing refers to an operation of cutting an object in a horizontal direction with respect to the object by mechanical processing. By the grinding and / or shearing, a compressive / shear stress is applied to the raw metal powder, and the raw metal powder is reliably ground to the nano primary particles. In addition, as long as it is accompanied by the compressive / shear stress, an impact stress described later may be simultaneously applied.
[0016]
The grinding and / or shearing in this step is preferably performed under the condition that a certain strong force is applied to the raw metal powder so that the raw metal powder is surely pulverized to the nano primary particles. Specifically, it is carried out under such conditions that the compression / shear stress (compression / shear force) applied to the raw metal powder is preferably 1 G to 500 G, more preferably 10 G to 500 G (G: gravitational acceleration).
[0017]
The apparatus used in this step is not particularly limited as long as it is a pulverizer capable of performing grinding and / or shearing. However, grinding and / or shearing under conditions such that compressive / shear stress having a strength within the above range is applied to the raw metal powder. It is preferably a pulverizer capable of performing shearing. Examples of usable pulverizers include a roll pulverizer, a medium pulverizer, an air-flow pulverizer, and a shear / grinding pulverizer. Specific examples of the roll-type pulverizer include a roll rotating type and a roller rolling type. Medium-type pulverizers are roughly classified into container-driven type and medium-stirring type. Rolling mills, vibrating mills, planetary mills, and centrifugal fluidized bed mills are examples of the former, and tower types are examples of the latter. , Stirred bed type, flow tube type and annular type. Specific examples of the air flow type pulverizer include a collision type and a particle grinding type. Specific examples of the shearing / milling type pulverizer include a compression shearing type, a high-speed rotary shearing type, and a high-speed rotary grinding type. Among the above examples, a shearing / grinding type pulverizer is preferable, and a compression shearing type pulverizer is particularly preferable.
[0018]
In the case of using a pulverizer that performs pulverization by rotational motion, in order to keep the compressive / shear stress applied to the raw metal powder within the above range, usually 100 rpm or more, preferably 1000 rpm or more, and usually 20,000 rpm or less, preferably Pulverization is preferably performed at a rotation speed of 3000 rpm or less.
[0019]
This step is generally carried out for 10 minutes or more, preferably 30 minutes or more, more preferably 1 hour or more, and usually 5 hours or less, preferably 3 hours or less, more preferably 2 hours or less.
[0020]
The type of the second pulverizing step is not particularly limited as long as it is a pulverizing step to which an impact stress is applied. Here, the impact stress is a force given by impact of a hammer or the like rotating at high speed on a solid. In the present step, the purpose is to disintegrate the aggregates of the nano primary particles by selectively applying a relatively weak impact stress. Therefore, it is preferable to avoid the above-mentioned compressive / shear stress as much as possible. Although the strength of the impact stress applied in this step is not particularly limited, it is preferable that the strength is such that the aggregate of the nano primary particles can be broken.
[0021]
The apparatus used in this step is not particularly limited as long as it can apply an impact stress to the raw metal powder, but is preferably a pulverizer capable of applying an impact stress in the above range. Examples of the crusher that can be used include a high-speed rotary impact crusher, and specific examples thereof include a hammer type, a rotating disk type, an axial flow type, and an annular type.
[0022]
In order to realize this step, it is preferable to carry out pulverization at a rotation speed of usually 100 rpm or more, preferably 5000 rpm or more, and usually 20,000 rpm or less.
[0023]
This step is carried out usually for 5 seconds or more, preferably 10 seconds or more, more preferably 15 seconds or more, and usually for 1 hour or less, preferably 30 minutes or less, more preferably 10 minutes or less.
[0024]
The first and second pulverization steps may be performed using a single type of pulverization method or a pulverizer, or may be performed by arbitrarily combining two or more types of pulverization methods or pulverizers. Good. Further, each pulverizing step may be performed in one stage, or may be performed in a plurality of stages. In the latter case, the grinding may be carried out in a plurality of stages under the same grinding conditions. However, if the conditions specified above are satisfied, different grinding conditions may be set for each stage. In addition, any of the pulverization steps can be performed by applying not only a pulverizer but also a kneader, a granulator, or the like.
[0025]
・ Pre-processing, post-processing, intermediate processing:
In each of the first pulverizing step and the second pulverizing step, various kinds of processing may be performed as necessary as pre-processing, intermediate processing, and post-processing. Examples of such treatment include heat treatment, cooling treatment, material addition treatment, aggregation inhibitor addition treatment, drying treatment, classification treatment, sizing treatment and the like. Further, for the purpose of the first pulverizing step, as a pre-treatment, an intermediate treatment, and a post-treatment of the first pulverizing step, a light pulverizing treatment with impact stress corresponding to the condition of the second pulverizing step may be performed. .
[0026]
The aggregation inhibitor is not particularly limited, and examples thereof include metal salts and metal halides.
Examples of the metal salt include a sulfate, a nitrate, an ammonium salt, an acetate, and the like. Among them, those that can be easily removed by solvent removal or heat treatment are preferable.
Examples of the metal halide include a chlorinated compound, a brominated compound, and an iodized compound, and a chlorinated compound is preferable because it is more easily available and easily handled.
[0027]
Among them,
I. Being solid at 25 ° C., and
II. (1) Gas or sublimation temperature is 400K or more and 2500K or less, or
{Circle around (2)} those which are water-soluble and have a solubility w in water at 25 ° C. (the ratio of mass (g) in 100 g of saturated aqueous solution) of 10% by weight or more and 100% by weight or less.
[0028]
Specifically, NaCl, LiCl, KCl, NaBr, LiBr, KBr, MgCl, MgBr, BaCl ₂ , BaBr ₂ , AgCl, ZnCl ₂ , AlCl ₃ , CuCl ₂ , SnCl, MnCl, FeCl ₃ , NiCl ₂ , FeBr ₂ , CuBr, SnBr _{2 and the} like.
[0029]
Among them, NaCl and LiCl are preferable in that they can be easily removed with water. After the treatment, the aggregation inhibitor can be removed by solvent washing, heat treatment, or the like.
[0030]
-The resulting metal powder:
The nano primary particles obtained by the present invention have an average particle size of usually at least 10 nm, preferably at least 50 nm, and usually at most 200 nm, preferably at most 150 nm, and have a narrow particle size distribution and uniform particle size. ing. In the present specification, the narrow particle size distribution means that, for example, the particle sizes corresponding to 25%, 50%, and 75% of the total particles are D ²⁵ , D ⁵⁰ , and D ⁷⁵ , respectively, and W = (D ⁷⁵ −D when calculating the ^{25) / D 50,} W is 0.1 or more, preferably, 0.1 or more and usually 1.6 or less, preferably refers to a range of 1.0 or less.
[0031]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples as long as the gist is not exceeded.
[0032]
[Example-1]
40 g of Si powder having an average particle size of 6 μm was used as a raw metal powder, and as a first pulverization step, a multi-ring medium type ultra-fine pulverizer (Micros MIC-0 manufactured by Nara Machinery Co., Ltd.) was used for 3 hours at 2000 revolutions. For dry grinding (nitrogen flow rate 100 cc / min.). As a result, Si particles (nano primary particles) having an average particle size of 0.35 μm were obtained.
[0033]
Subsequently, the Si particles were continuously pulverized (rotational speed: 16000 rpm) for about 10 seconds by a sample mill (manufactured by Nara Machinery Co., Ltd.) as a second pulverization step. Further, Si fine particles were obtained through a 250 μm partition net.
[0034]
The obtained Si fine particles were dispersed in water, and subjected to ultrasonic treatment for 10 minutes using a laser diffraction particle size distribution analyzer (model SALD-2000J manufactured by Shimadzu Corporation). The particle size was measured under the condition of seconds. A particle size distribution diagram of the obtained Si fine particles of Example-1 is shown in FIG. 1 (horizontal axis: Particle size (particle diameter), bar graph vertical axis: Volume fraction (volume fraction), line graph vertical axis: Cumulative volume percentage) (Cumulative volume ratio)). The average particle size of the Si fine particles was 130 nm, and had a narrow particle size distribution. FIG. 2 shows an electron micrograph of the Si fine particles of Example 1, taken using a scanning electron microscope (FE-SEM; Model S-4700, manufactured by Hitachi). As a result of observation, no aggregate of the nano primary particles was observed.
[0035]
[Example-2]
The same raw material metal powder as in Example-1 was subjected to the same first pulverization step as in Example-1, and Si particles (nano primary particles) obtained were further subjected to a second pulverization step. Using the same sample mill as in Example 1, dry grinding was performed in a batch system for 30 minutes to obtain Si fine particles.
[0036]
FIG. 3 shows a particle size distribution chart of the Si fine particles of Example-2 measured under the same conditions as in Example-1 (horizontal axis: Particle size (particle diameter), bar graph vertical axis: Volume fraction (volume fraction)) , Line graph vertical axis: Cumulative volume percentage (cumulative volume percentage)). The average particle size of the Si fine particles was 140 nm, and had a narrow particle size distribution. FIG. 4 shows an electron micrograph of the Si fine particles of Example-2, taken under the same conditions as in Example-1. As a result of observation, no aggregate of the nano primary particles was observed.
[0037]
[Example-3]
Si particles (nano-primary particles) obtained by subjecting the same raw metal powder as in Example-1 to the first pulverizing step as in Example-1 except that the treatment time was set to 1 hour, In the second pulverization step, dry pulverization was performed continuously for 10 seconds using the same sample mill as in Example 1 to obtain Si fine particles.
[0038]
When the particle size distribution of the Si fine particles of Example-3 was measured under the same conditions as in Example-1, the average particle size of the Si fine particles was 130 nm. An electron micrograph of the Si fine particles of Example 3 was taken under the same conditions as in Example 1, and no aggregate of nano primary particles was observed.
[0039]
[Example-4]
Si particles (nano primary particles) obtained by subjecting the same raw metal powder as in Example-1 to the first pulverizing step as in Example-1 except that the treatment time was set to 6 hours, The same second pulverization step as in Example-3 was performed to obtain Si fine particles.
[0040]
When the particle size distribution of the Si fine particles of Example-4 was measured under the same conditions as in Example-1, the average particle size of the Si fine particles was 115 nm. An electron micrograph of the Si fine particles of Example-4 was taken under the same conditions as in Example-1, and no aggregate of nano primary particles was observed.
[0041]
[Comparative Example-1]
Si particles obtained by subjecting the same raw metal powder as in Example-1 to the same first pulverization step as in Example-1 were used.
[0042]
FIG. 5 shows a particle size distribution diagram of the Si particles of Comparative Example 1 measured under the same conditions as in Example-1 (horizontal axis: Particle size (particle diameter), bar graph vertical axis: Volume fraction (volume fraction)) , Line graph vertical axis: Cumulative volume percentage (cumulative volume percentage))
. The average particle size of the Si fine particles was 350 nm. FIG. 6 shows an electron micrograph of the Si fine particles of Comparative Example 1, taken under the same conditions as in Example-1. As a result of observation, aggregated particles were observed.
[0043]
[Comparative Example-2]
50 g of Si powder having an average particle diameter of 6 μm was used as a raw metal powder, and wet pulverization (ethyl) was performed at 2,000 rpm for 3 hours using the same multi-ring medium type ultra-fine pulverizer as in Example 1 as a first pulverization step. (Alcohol: 200 ml) to obtain Si particles.
[0044]
When the particle size distribution of the Si particles of Comparative Example 2 was measured under the same conditions as in Example 1, the average particle size of the Si particles was 0.8 μm. An electron micrograph of the Si fine particles of Comparative Example 2 was taken under the same conditions as in Example 1, and aggregated particles were observed.
[0045]
[Comparative Example-3]
Using Si having an average particle diameter of 6 μm as a raw metal powder, the first pulverizing step is not performed, and as the second pulverizing step, the Si powder is dry-pulverized by continuous pulverization using a sample mill (nitrogen flow rate 100 cc / min.). did.
[0046]
FIG. 7 shows a particle size distribution diagram of the Si particles of Comparative Example-3 measured under the same conditions as in Example-1 (horizontal axis: Particle size (particle diameter), bar graph vertical axis: Volume fraction (volume fraction)) , Line graph vertical axis: Cumulative volume percentage (cumulative volume percentage))
. The average particle size of the Si particles was 500 nm. FIG. 8 shows an electron micrograph of the Si fine particles of Comparative Example-3, taken under the same conditions as in Example-1. As a result of observation, aggregated particles were observed.
[0047]
[Comparative Example-4]
Si particles obtained by subjecting the same raw metal powder as in Example-1 to the same first pulverization step as in Example-1 except that the treatment time was set to 1 hour were used.
[0048]
When the particle size distribution of the Si particles of Comparative Example-4 was measured under the same conditions as in Example-1, the average particle size of the Si particles was 0.9 μm. When an electron micrograph of the Si fine particles of Comparative Example-4 was taken under the same conditions as in Example-1, aggregated particles were observed. In this case, it is considered that the nano-primary particles are generated in a shorter time than the conventional pulverization time, but the average particle diameter is large due to aggregation.
[0049]
[Comparative Example-5]
Si particles obtained by subjecting the same raw metal powder as in Example-1 to the same first pulverization step as in Example-1 except that the treatment time was set to 6 hours were used.
[0050]
When the particle size distribution of the Si particles of Comparative Example-4 was measured under the same conditions as in Example-1, the average particle size of the Si particles was 130 nm and had a wide particle size distribution. An electron micrograph of the Si fine particles of Comparative Example-5 was taken under the same conditions as in Example-1, and aggregated particles were observed. Therefore, although sufficiently small particles can be obtained by the 6-hour treatment in the first pulverizing step, the particle size distribution is wide and the treatment time is extremely long, so that it is not suitable for industrial practice.
[0051]
Table 1 below shows the average particle size of the Si particles obtained in Example-1 to Example-4 and Comparative Example-1 to Comparative Example-5.
[0052]
[Table 1]

[0053]
【The invention's effect】
According to the present invention, the raw metal powder is pulverized into nano-primary particles by a first pulverization step in which grinding and / or shearing is applied, and then the aggregated nano-primary particles are pulverized in a second pulverization step in which impact stress is applied. Therefore, it is possible to produce nanoscale metal fine particles having an average particle diameter of about 150 nm or less and having a uniform particle diameter easily and inexpensively on an industrial scale.
[Brief description of the drawings]
FIG. 1 is a particle size distribution diagram of Si fine particles of Example-1.
FIG. 2 is an electron micrograph of Si fine particles of Example-1.
FIG. 3 is a particle size distribution diagram of Si fine particles of Example-2.
FIG. 4 is an electron micrograph of Si fine particles of Example-2.
FIG. 5 is a particle size distribution diagram of Si fine particles of Comparative Example-1.
FIG. 6 is an electron micrograph of Si fine particles of Comparative Example-1.
FIG. 7 is a particle size distribution diagram of Si fine particles of Comparative Example-3.
FIG. 8 is an electron micrograph of Si fine particles of Comparative Example-3.

Claims (5)

A method for producing metal fine particles, comprising subjecting a raw metal powder comprising one or more metal elements to a first pulverizing step in which grinding and / or shearing is applied and a second pulverizing step in which impact stress is applied. . The method for producing metal fine particles according to claim 1, wherein the first pulverizing step is performed under a condition where a compressive / shear stress (G: gravitational acceleration) of 10 G or more and 500 G or less is applied. The method according to claim 1 or 2, wherein the second pulverizing step is performed at a rotation speed of 100 rpm or more and 20000 rpm or less. The method for producing metal fine particles according to any one of claims 1 to 3, wherein an average particle size of the raw metal powder is 0.2 µm or more and 100 µm or less. A kind of a single metal element selected from the group consisting of elements belonging to Group Ia, Group IIa, transition metals (Groups IIIa to VIIIa), Group Ib, Group IIb, Group IIIb, Group IVb and Group Vb; The method for producing metal fine particles according to any one of claims 1 to 4, characterized in that the powder is a powder of (1) or a mixed powder of two or more metal elements.

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