JPH08218163A - Superfine particle fused body and its production - Google Patents

Abstract

PURPOSE: To control the fused state, etc., to make a single superfine particle widely applicable and to provide a superfine-particle fused body enhanced in operability. CONSTITUTION: Metallic superfine particles 1 and 2 such as an Al superfine particle are fused together by the surface diffusion of the atoms constituting the superfine particles 1 and 2, and a cluster 3 of the constituent atoms having <=3nm diameter is present at the fused interface. Otherwise, the superfine particles are fused together with their atom arrangements changed so that the crystal faces and crystal orientations are identical with each other. These fused bodies are obtained by irradiating the two superfine particles with an electron beam of >=1×10<19> e/cm<2> .sec in a vacuum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fusion of ultrafine metal particles and a method for producing the same.

[0002]

2. Description of the Related Art When compound particles such as metal particles and metal oxide particles are made into ultrafine particles with a particle size of 100 nm or less, characteristics different from ordinary particles (for example, 1 μm or more) appear. This is because the number of atoms existing on the surface increases with respect to the total number of atoms, that is, the specific surface area increases, so that the influence of surface energy on the characteristics of the particles cannot be ignored.

The ultrafine particles as described above are suitable for discovering new surface phenomena and grasping the outline thereof, and in the ultrafine particles, the melting point and the sintering temperature are lowered as compared with the bulk, and their properties are Since it may be applied to various fields, researches on physical properties of ultrafine particles themselves and researches on methods of using ultrafine particles are underway.

Conventional ultrafine particles are produced, for example, by a physical method or a chemical method as shown below. That is, as a method for physically producing ultrafine particles, a metal evaporation method in an inert gas, a gas evaporation method in which ultrafine particles are generated by cooling and condensing by collision with a gas, and a sputtering phenomenon as an evaporation source are used. Sputtering method used, metal vapor synthesis method that heats metal under vacuum, co-evaporates evaporated metal atoms with organic solvent on the substrate cooled below freezing point of organic solvent to obtain ultrafine particles, metal on oil An example is a vacuum evaporation method over fluid oil for vapor deposition.

Further, as a chemical method for producing ultrafine particles using a liquid phase, a colloid method of reducing a noble metal salt under reflux conditions in an alcohol in the presence of a polymer surfactant, hydrolysis of a metal alkoxide The alkoxide method utilizing the metal salt, the coprecipitation method in which a precipitating agent is added to a mixed solution of metal salts to obtain precipitated particles, and the method for producing chemical ultrafine particles using a gas phase further includes heat treatment of a metal carbonyl compound or the like. Thermal decomposition method of organometallic compounds to obtain ultrafine metal particles by decomposition reaction, reduction / oxidation / nitridation method of metal chlorides to obtain ultrafine particles by reducing / oxidizing or nitriding metal chloride in a reaction gas stream, oxide / Examples include a reduction method in hydrogen in which a hydrate is heated and reduced in a hydrogen stream, and a solvent evaporation method in which a metal salt solution is sprayed from a nozzle and dried with hot air.

[0006]

By the way, the conventional research and development on ultrafine particles are mainly related to an aggregate of ultrafine particles (ultrafine powder), and research on various operations and control on ultrafine particles alone is sufficient. Has not been done. This is also due to the conventional method for producing ultrafine particles described above, and although many of the conventional production methods are suitable for producing ultrafine particles as an aggregate, it is difficult to obtain ultrafine particles as a single particle. there were.

[0007] As described above, since various studies and controls on ultrafine particles alone have not been conducted so far, the application of ultrafine particles based on them has not been specifically advanced. For example, it is expected that by realizing fusion of ultrafine particles alone under controlled conditions, it is possible to produce an ultrafine product or a substance having a property different from that of bulk.

The present invention has been made, for example, to enable the application and development of ultrafine particles from a single body, and it is possible to control the fusion state and the like, and to have a high operability, and a method for producing the same. Is intended to provide.

[0009]

The first ultrafine particle fusion body according to the present invention is a fusion body of ultrafine metal particles, which are fused by surface diffusion of constituent atoms of the ultrafine metal particles. The clusters of the constituent atoms having a diameter of 3 nm or less are present at the fusion interface.

The second ultrafine particle fusion body is a fusion body of the ultrafine metal particles, and the atomic arrangement of the ultrafine metal particles is changed so that the crystal planes and the crystal orientations of the ultrafine metal particles are the same. It is characterized by the fact that they are fused in the same state.

The method for producing an ultrafine particle fusion product of the present invention comprises:
It is characterized by irradiating an electron beam of ¹⁹ e / cm ² · sec or more to fuse the at least two ultrafine metal particles.

That is, according to the present invention, two ultrafine metal particles are simultaneously subjected to 1 × 10 ¹⁹ e / cm ² · sec (2 A / cm ² ) in a vacuum atmosphere.
By irradiating the above electron beam, it is possible to fuse ultrafine metal particles without melting each other on a room temperature stage that does not require special temperature control.
It is based on the finding that the fusion state can be controlled according to the initial particle diameter of the ultrafine metal particles and the like.

Examples of the ultrafine metal particles used as a starting material for the ultrafine particle fusion product of the present invention include Al ultrafine particles having a particle size of about 5 to 30 nm. If the particle size of the ultrafine metal particles as the starting material exceeds 30 nm, 1 × 10 ¹⁹ e / cm ² · sec
Irradiation with the above electron beams cannot induce the fusion phenomenon, and it is difficult to prepare ultrafine metal particles with a particle size of less than 5 nm. When such two ultrafine metal particles are simultaneously irradiated with an electron beam in a vacuum atmosphere, a ultrafine metal particle fusion product is generated, and the fusion state of the ultrafine metal particle fusion product is the particle size of the ultrafine metal particles as a starting material. According to.

The first ultrafine particle fusion product of the present invention is a metal ultrafine particle fusion product obtained by irradiating the above-mentioned metal ultrafine particles with an electron beam, in which a metal ultrafine particle having a particularly small diameter is used as a starting material. Is. That is, when the particle size of the starting metal ultrafine particles is particularly small, specifically, when the particle size is in the range of 5 to 10 nm, surface diffusion of the constituent atoms of the ultrafine metal particles occurs by electron beam irradiation. , Clusters of constituent atoms with a diameter of 3 nm or less are generated. Then, the ultrafine metal particles are fused with each other through the generated clusters having a diameter of 3 nm or less.

Since such a first ultrafine particle fusion material has clusters of constituent atoms having a diameter of 3 nm or less at the fusion interface, it has the advantage that the fusion interface is rich in toughness against external force, and functions. It has the potential to be applied to functional materials.

Further, the second ultrafine particle fusion body of the present invention comprises:
An ultrafine metal particle fusion product obtained by irradiating the ultrafine metal particles described above with an electron beam, wherein ultrafine metal particles having a relatively large diameter are used as a starting material. That is, when the particle size of the starting material ultrafine metal particles is relatively large, specifically, the particle size is in the range of 10 to 30 nm, when the ultrafine metal particles start to approach each other by electron beam irradiation. In addition, the atomic arrangement of the ultrafine metal particles is changed so that the interfacial energy becomes minimum by matching the crystal planes and crystal orientations. Then, necking occurs from a contact having the same crystal plane and crystal orientation to generate a fusion body. Initially, this fusion maintains the original ultrafine particle shape, and eventually the integration is completed as the irradiation time of the electron beam elapses.

Such a second ultrafine particle fusion product can be a fusion product having a fusion interface having an epitaxial relationship in which the crystal planes and crystal orientations are the same while maintaining the original ultrafine particle shape. It has advantages such as high interfacial strength, and has applicability to structural members and the like.

In the manufacturing method of the present invention, the intensity of the electron beam with which the ultrafine metal particles are irradiated is 1 × 10 ¹⁹ e / cm ² · sec (2 A / cm
² ) At least. Irradiation electron beam intensity is 1 × 10 ¹⁹ e / cm ²
-If it is less than sec, the ultrafine metal particles cannot be activated enough to fuse with each other. In other words, 1 × 10
An electron beam with an intensity of ¹⁹ e / cm ² · sec or more brings about the local heating effect and atomic displacement induction (knock-on) effect of ultrafine metal particles, and it is possible to generate ultrafine particle fusion by these. Become.

Further, the electron beam irradiation to the ultrafine metal particles is carried out in a vacuum atmosphere, and specifically, the electron beam irradiation is preferably carried out in a vacuum atmosphere of 10 ⁻⁵ Pa or less. If the vacuum atmosphere at the time of electron beam irradiation exceeds 10 ⁻⁵ Pa, a compound with impurity atoms in the residual gas may be generated, which may reduce the interface strength. Here, in the present invention, 1 × 10 6 in a vacuum atmosphere is used. ¹⁹ e / cm ²
By irradiating the electron beam for sec or more, it is possible to generate a fusion body of ultrafine metal particles that have not passed through a molten state on a room temperature stage. In general, it is difficult to irradiate an electron beam under controlled heating conditions.Therefore, it is significant to enable the generation of ultrafine metal particle fusion particles by irradiating an electron beam on a room temperature stage, and at the same time, melting Since it is possible to generate a fusion body without forming a lattice defect such as residual strain or misfit dislocation in the vicinity of the interface, energy can be saved.

Particle size 5 to 30 used as a starting material in the present invention
The ultrafine metal particles having a size of about nm can be produced, for example, as follows. Here, Al ultrafine particles will be described as an example.

That is, the metastable metal oxide particles such as θ-Al ₂ O ₃ particles are subjected to 1 × 10 ¹⁹ e / cm ² · sec in a vacuum atmosphere.
The electron beam having the above intensity is irradiated. 1 x 10 ¹⁹ e / cm
^The electron beam having an intensity of ² sec or more brings about a local heating effect of the metastable metal oxide particles and a displacement effect of oxygen atoms. By these, α-Al ₂ O ₃ and Al ₂ which are stable phases
Together consisting of O is a _third configuration metals Al, the small diameter of the super fine particles generated from theta-Al ₂ O ₃ particles as the starting material. The Al ultrafine particles thus obtained are pure metal ultrafine particles having a surface oxide-free particle size of about 5 to 30 nm, and any of them can be separated as a simple substance. Therefore, it can be used as ultrafine metal particles as the starting material of the present invention. However, not limited to the above-mentioned method, various manufacturing methods can be applied as long as the ultrafine metal particles that can be operated as a single ultrafine particle are obtained.

[0022]

Embodiments of the present invention will be described below.

Example 1 First, spherical θ-Al ₂ O ₃ particles having a particle size of about 100 nm (purity
= 99.8%), and after dispersing this in alcohol,
It was coated on a carbon support film and dried. Then, the carbon support film on which the spherical θ-Al ₂ O ₃ particles are arranged is
00kV TEM device (JEM-2010 (trade name) manufactured by JEOL Ltd.)
It was installed on a room temperature stage placed in the vacuum chamber of.

Next, after the vacuum chamber was evacuated to a vacuum degree of 1 × 10 ^-5 Pa, the particle size 1 on the carbon support film was reduced.
The θ-Al ₂ O ₃ particles of ^{00nm, 1.3 × 10 20 e /} cm 2 · sec (20
A / cm ² ) electron beam (irradiation diameter = 250 nm) was irradiated. Then, by this electron beam irradiation, Al ultrafine particles having a diameter of about 5 to 10 nm were generated from the θ-Al ₂ O ₃ particles.

An Al ultrafine particle fusion was produced using the Al ultrafine particles described above. Specifically, while maintaining the state (including the degree of vacuum) of the carbon support film having the generated Al ultrafine particles in the vacuum chamber of the TEM device, the diameter of the carbon ultrafine particles on the carbon support film is Close to about 5 nm
Two ultrafine Al particles were selected. Then, the two ultrafine Al particles were simultaneously irradiated with an electron beam of 1.3 × 10 ²⁰ e / cm ² · sec (20 A / cm ² ).

The state of the two Al ultrafine particles was observed in situ while irradiating the electron beam. The observation result will be described with reference to the schematic diagram of FIG. First,
About 30 seconds after the start of electron beam irradiation,
As shown in (a), surface diffusion of constituent atoms was observed from each of the two Al ultrafine particles 1 and 2. Due to the surface diffusion of these constituent atoms, the surface of each of the Al ultrafine particles 1 and 2 has a small diameter.
Al atom cluster 3 begins to be formed. Further, when the electron beam is continuously irradiated, the two Al ultrafine particles 1 and 2 approach each other, and the Al atom clusters 3 formed on their surfaces,
Specifically, an Al cluster 3 with a diameter of about 2 nm fills the space between the two Al ultrafine particles 1 and 2, and 2 from the start of electron beam irradiation.
After about 00 seconds, as shown in Fig. 1 (b),
The Al ultrafine particles 1 and 2 were fused with each other through the Al atom cluster 3.

In this way, two Al ultrafine particles 1, 2 are obtained.
As a result, Al ultrafine particle fusion body 4 was obtained by surface diffusion accompanied by electron beam irradiation. It is considered that this fusion is due to both the local heating effect by the irradiated electrons and the atomic displacement induction (knock-on) effect. The obtained Al ultrafine particle fusion body 4 has Al atom clusters 3 having a diameter of about 2 nm at the fusion interface as described above, and basically, the crystal structure and shape of the original Al ultrafine particles 1 and 2 are formed. , Plasticity was maintained.

Example 2 Similar to Example 1, an Al ultrafine particle fusion body was produced by using Al ultrafine particles produced by electron beam irradiation of θ-Al ₂ O ₃ particles. Specifically, the carbon support film having the generated Al ultrafine particles is maintained in the vacuum chamber of the TEM apparatus (including the degree of vacuum), and the carbon ultrafine particles on the carbon support film are brought close to each other. Two Al ultrafine particles were selected.
These ultrafine Al particles are multiple twin grains with a diameter of about 15 nm.
Then, these two ultrafine Al particles were simultaneously irradiated with an electron beam of 1.3 × 10 ²⁰ e / cm ² · sec (20 A / cm ² ) on a TEM room temperature stage.

The state of the two ultrafine Al particles was observed in situ while irradiating the electron beam. The observation result will be described with reference to the schematic diagram of FIG. First,
Before irradiation with an electron beam, as shown in FIG.
The Al ultrafine particles 5 and 6 had different crystal orientations.

When the two Al ultrafine particles 5 and 6 are irradiated with an electron beam from this state, the two Al ultrafine particles 5 and 6 surrounded by the {111} planes start to come close to each other, and as a result, clear twinning occurs. It was observed that the boundary disappeared and the whole crystal changed from a polyhedron to a dome structure. Moreover, FIG.
As shown in (b), it was observed that both {111} planes were parallel, that is, all the constituent atoms of the grain were curved so as to have an epitaxy relationship. That is, two Al ultrafine particles 5,
When 6 approaches each other, the orientation of atoms is positively aligned with the crystal plane to change the atomic arrangement so that the interface energy becomes minimum.

Further, when the electron beam irradiation is continued, necking starts at the contact point, and about 300 seconds after the start of electron beam irradiation, as shown in FIG. 2 (c), solids of Al ultrafine particles 5 and 6 are solid. Fusion 7 was produced. If you continue to irradiate the electron beam from this state, 3
After about 50 seconds, the solid fusion body 7 was fused and integrated.

In this way, the two ultrafine Al particles 5, 6 are formed.
Al ultrafine particle fusion body 7 was obtained by rearrangement of atoms accompanied with electron beam irradiation. It is considered that this fusion is due to both the local heating effect by the irradiated electrons and the atomic displacement induction (knock-on) effect, as in Example 1. In the state shown in FIG. 2 (c), the obtained Al ultrafine particle fusion body 7 maintained the initial grain shape (hexagonal shape) and was fused by forming an interface having an epitaxy relationship.

As is clear from the above-mentioned embodiments,
According to the present invention, fusion control including crystal control of ultrafine particles can be realized by electron beam irradiation under a condition of easy control on a room temperature stage. Therefore, it can be widely applied to various manipulations with an electron beam having a nanometer diameter. It has the potential.

[0034]

As described above, according to the method for producing an ultrafine particle fusion product of the present invention, an ultrafine particle fusion product in which the fusion state and the like are controlled can be obtained under the condition of being easily controlled on a room temperature stage. be able to. Since such an ultrafine particle fusion product of the present invention has control and operability of a fusion state, it greatly contributes to application development from a single metal ultrafine particle alone.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a process of producing an ultrafine particle fusion body in one example of the present invention.

FIG. 2 is a diagram schematically showing a process of producing an ultrafine particle fusion body in another example of the present invention.

[Explanation of symbols]

 1, 2 ... Al ultrafine particles 3 ... Al atomic clusters 4 ... Al ultrafine particle fusion by surface diffusion 5,6 ... Al ultrafine particles (multiple twin grains) 7 ... Al ultrafine particles by rearrangement of atoms Fusion

Claims (6)

[Claims] 1. A fusion of ultrafine metal particles, wherein the ultrafine metal particles are fused by surface diffusion of the atoms, and clusters of the atoms having a diameter of 3 nm or less are present at the fusion interface. Ultrafine particle fusion characterized by being 2. The ultrafine particle fusion body according to claim 1, wherein the metal ultrafine particles are Al ultrafine particles having a particle size of 5 to 10 nm. 3. A fusion of ultrafine metal particles, wherein the ultrafine metal particles are fused in a state in which the atomic arrangement of the ultrafine metal particles is changed so that the crystal planes and crystal orientations of the ultrafine metal particles are the same. Characteristic ultrafine particle fusion. 4. The ultrafine particle fusion body according to claim 3, wherein the metal ultrafine particles are Al ultrafine particles having a particle size of 10 to 30 nm. 5. The at least two ultrafine metal particles are irradiated with an electron beam of 1 × 10 ¹⁹ e / cm ² · sec or more in a vacuum atmosphere to fuse the at least two ultrafine metal particles. And a method for producing an ultrafine particle fusion product. 6. The method for producing an ultrafine particle fusion product according to claim 5, wherein Al ultrafine particles having a diameter of 5 to 30 nm are used as the metal ultrafine particles.