JP3678783B2 - Ultrafine particle fusion product and production method thereof - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a fusion of ultrafine metal particles and a method for producing the same.
[0002]
[Prior art]
Compound particles such as metal particles and metal oxide particles exhibit characteristics different from normal particles (for example, 1 μm or more) when the particles are made ultrafine so that the particle size is 100 nm or less. 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, and therefore the influence of surface energy on the properties of the particles cannot be ignored.
[0003]
Ultrafine particles such as those mentioned above are suitable for discovering new surface phenomena and grasping their outlines, and ultrafine particles have a lower melting point and sintering temperature compared to bulk, and their properties are applied to various fields. Since there is a possibility of application, research on the physical properties of ultrafine particles themselves, research on how to use ultrafine particles, and the like are underway.
[0004]
Conventional ultrafine particles are produced by, for example, the following physical methods and chemical methods. In other words, physical ultrafine particles are produced by evaporating metals, etc. in an inert gas, cooling and condensing by collision with the gas, and generating ultrafine particles. Sputtering method to be used, metal vapor synthesis method to obtain ultrafine particles by heating metal under vacuum and co-evaporating evaporated metal atoms with organic solvent below the freezing point of organic solvent, metal on oil Examples include a vacuum evaporation method on a fluid oil to be deposited.
[0005]
In addition, chemical ultrafine particles can be produced using a liquid phase using a colloidal method in which a noble metal salt is reduced under reflux conditions in alcohol coexisting with a polymer surfactant, or hydrolysis of a metal alkoxide. An alkoxide method, a coprecipitation method in which a precipitant is added to a mixed solution of metal salts to obtain precipitated particles, and a method for producing chemical ultrafine particles using a gas phase include a thermal decomposition reaction of a metal carbonyl compound or the like. Pyrolysis method of organometallic compounds to obtain ultrafine metal particles, reduction, oxidation or nitridation method of metal chlorides to obtain ultrafine particles by reducing, oxidizing or nitriding metal chlorides in a reactive gas stream, oxides and hydrates Examples include a reduction in hydrogen method in which heating is performed in a hydrogen stream and a solvent evaporation method in which a metal salt solution is sprayed from a nozzle and dried in hot air.
[0006]
[Problems to be solved by the invention]
By the way, research and development on conventional ultrafine particles are mainly related to an aggregate of ultrafine particles (ultrafine powder), and studies on various operations and controls on single ultrafine particles have not been sufficiently performed. This is due to the above-described conventional method for producing ultrafine particles, and many of the conventional production methods are suitable for producing ultrafine particles as an aggregate, but it is difficult to obtain ultrafine particles as a single particle. there were.
[0007]
As described above, since various studies on various operations and controls for single ultrafine particles have not been sufficiently conducted, application of single ultrafine particles based on them has not been specifically promoted. For example, it is anticipated that it will be possible to produce ultrafine products, substances having properties different from bulk, etc. by realizing the fusion of single ultrafine particles under controlled conditions.
[0008]
The present invention was made, for example, in order to enable application development from a single ultrafine particle, and provides an ultrafine particle fusion product capable of controlling the fusion state and the like and having high operability, and a method for producing the same. The purpose is that.
[0009]
[Means and Actions for Solving the Problems]
The first ultrafine particle fusion in the present invention is a fusion of metallic ultrafine particles composed of Al ultrafine particles having a particle diameter of 5 to 10 nm , and is fused by surface diffusion of constituent atoms of the metallic ultrafine particles. The cluster of constituent atoms having a diameter of 3 nm or less exists at the fusion interface.
[0010]
The second ultrafine particle fusion is a fusion of metal ultrafine particles composed of Al ultrafine particles having a particle diameter of 10 to 30 nm , and the crystal planes and crystal orientations of the metal ultrafine particles are the same. It is characterized by fusion in a state where the atomic arrangement of the metal ultrafine particles is changed.
[0011]
The method for producing an ultrafine particle fusion product of the present invention comprises irradiating at least two metal ultrafine particles with an electron beam of 1 × 10 ¹⁹ e / cm ² · sec or more in a vacuum atmosphere, so that the at least two metal ultrafine particles are It is characterized by fusing together.
[0012]
That is, the present invention does not require any special temperature control by simultaneously irradiating two metal ultrafine particles with an electron beam of 1 × 10 ¹⁹ e / cm ² · sec (2 A / cm ² ) or more in a vacuum atmosphere. Based on finding that it is possible to fuse metal ultrafine particles without melting them on a room temperature stage, and that the fusion state can be controlled according to the initial particle size of the metal ultrafine particles. Is.
[0013]
Examples of the metal ultrafine particles used as the starting material of the ultrafine particle fusion of the present invention include Al ultrafine particles having a particle size of about 5 to 30 nm. If the particle size of the metal ultrafine particles as a starting material is more than 30 nm, can not be irradiated with ^{1 × 10 19 e / cm 2} · sec or more electron beam to induce fusion events, also is the particle diameter 5nm It is difficult to produce the ultrafine metal particles of less than 1. When such two metal ultrafine particles are simultaneously irradiated with an electron beam in a vacuum atmosphere, a metal ultrafine particle fusion is formed, and the fusion state of the metal ultrafine particle fusion is determined by the particle size of the metal ultrafine particles as a starting material. Depending on.
[0014]
The first ultrafine particle fusion of the present invention is a metal ultrafine particle fusion obtained by irradiating the above-mentioned metal ultrafine particles with an electron beam, and particularly uses a small-diameter Al ultrafine particle as a starting material. That is, when the particle diameter of the starting ultrafine Al particle is particularly small, specifically when the particle diameter is in the range of 5 to 10 nm, surface diffusion of constituent atoms of the Al ultrafine particle occurs due to electron beam irradiation. A cluster of constituent atoms with a diameter of 3 nm or less is generated. Then, the Al ultrafine particles are fused through the generated cluster having a diameter of 3 nm or less.
[0015]
In such a first ultrafine particle fusion, a cluster of constituent atoms with a diameter of 3 nm or less exists at the fusion interface, so that the fusion interface is rich in toughness against external forces, functional materials, etc. Has applicability to
[0016]
The second ultrafine particle fusion of the present invention is a metal ultrafine particle fusion obtained by irradiating the above-mentioned metal ultrafine particles with an electron beam, and uses a relatively large-diameter Al ultrafine particle as a starting material. Is. That is, when the particle size of the Al ultrafine particles that are the starting material is relatively large, specifically when the particle size is in the range of 10 to 30 nm, when the Al ultrafine particles begin to approach each other by electron beam irradiation In addition, the atomic arrangement of the Al ultrafine particles changes so that the interface energy is minimized by combining the crystal plane and crystal orientation. Then, necking occurs from the contact where the crystal plane and the crystal orientation are the same, and a fusion product is generated. This fused body initially maintains the original ultrafine particle shape, and the integration is eventually completed as the electron beam irradiation time elapses.
[0017]
Such a second ultrafine particle fusion body can be a fusion body having a fusion interface having an epitaxial relationship with the same crystal plane and crystal orientation while maintaining the original ultrafine particle shape. It has the advantage of being high, and has applicability to structural members and the like.
[0018]
In the production method of the present invention, the intensity of the electron beam applied to the metal ultrafine particles is 1 × 10 ¹⁹ e / cm ² · sec (2 A / cm ² ) or more. If the intensity of the irradiated electron beam is less than 1 × 10 ¹⁹ e / cm ² · sec, the metal ultrafine particles cannot be activated to the extent that they can be fused together. In other words, an electron beam having an intensity of 1 × 10 ¹⁹ e / cm ² · sec or more brings about a local heating effect and an atomic displacement induction (knock-on) effect of the ultrafine metal particles, and thereby the ultrafine particle fusion is formed. Can be generated.
[0019]
Further, the electron beam irradiation to the ultrafine metal particles is performed in a vacuum atmosphere, and specifically, the electron beam irradiation is preferably performed in a vacuum atmosphere of 10 ⁻⁵ Pa or less. When the vacuum atmosphere at the time of electron beam irradiation exceeds 10 ⁻⁵ Pa, a compound with impurity atoms in the residual gas is generated, and the interface strength may be reduced . Here, in the present invention, the fusion of metal ultrafine particles not in a molten state is generated on a room temperature stage by electron beam irradiation of 1 × 10 ¹⁹ e / cm ² · sec or more in a vacuum atmosphere. Can do. In general, since it is difficult to irradiate an electron beam under controlled heating conditions, it is significant to enable generation of a metal ultrafine particle fusion by irradiating an electron beam on a room temperature stage. Therefore, it is possible to save energy without forming lattice defects such as residual strain and misfit dislocations in the vicinity of the interface.
[0020]
The ultrafine metal particles having a particle size of about 5 to 30 nm used as a starting material in the present invention can be produced, for example, as follows. Here, Al ultrafine particles will be described as an example.
[0021]
That is, metastable metal oxide particles such as θ-Al ₂ O ₃ particles are irradiated with an electron beam having an intensity of 1 × 10 ¹⁹ e / cm ² · sec or more in a vacuum atmosphere. An electron beam having an intensity of 1 × 10 ¹⁹ e / cm ² · sec or more brings about a local heating effect of metastable metal oxide particles and a displacement effect of oxygen atoms. These by, with consists of a constituent metals of a stable phase α-Al ₂ O ₃ and Al ₂ O ₃ Al, the small diameter of the super fine particles generated from θ-Al ₂ O ₃ particles as the starting material. The ultrafine Al particles obtained in this way are pure metal ultrafine particles having a particle size of about 5 to 30 nm that do not have a surface oxide, and any of them can be separated as a simple substance. Therefore, it can be used as ultrafine metal particles as a starting material of the present invention. However, the present invention is not limited to the above-described method, and various manufacturing methods can be applied as long as ultrafine metal particles that can be operated as a single ultrafine particle are obtained.
[0022]
【Example】
Examples of the present invention will be described below.
[0023]
Example 1
First, spherical θ-Al ₂ O ₃ particles (purity = 99.8%) having a particle size of about 100 nm were prepared, dispersed in alcohol, and then coated on a carbon support film and dried. Next, the carbon support film on which the spherical θ-Al ₂ O ₃ particles were placed was placed on a room temperature stage placed in a vacuum chamber of a 200 kV TEM device (manufactured by JEOL Ltd., JEM-2010 (trade name)).
[0024]
Next, after the vacuum chamber was evacuated to a vacuum of 1 × 10 ⁻⁵ Pa, 1.3 × 10 ²⁰ e / cm ² was applied to θ-Al ₂ O ₃ particles having a particle size of 100 nm arranged on the carbon support film. -Irradiated with an electron beam (irradiation diameter = 250 nm) of sec (20 A / cm ² ). 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.
[0025]
An Al ultrafine particle fusion was produced using the Al ultrafine particles described above. Specifically, the carbon support film having the generated Al ultrafine particles is maintained in a state (including the degree of vacuum) arranged in the vacuum chamber of the TEM apparatus, and the diameter is selected from the Al ultrafine particles on the carbon support film. Two adjacent Al ultrafine particles of about 5 nm were selected. The two Al ultrafine particles were simultaneously irradiated with an electron beam of 1.3 × 10 ²⁰ e / cm ² · sec (20 A / cm ² ).
[0026]
While irradiating with an electron beam, the state of two Al ultrafine particles was observed in situ. The observation result will be described with reference to the schematic diagram of FIG. First, when about 30 seconds passed from the start of electron beam irradiation, surface diffusion of constituent atoms was observed from each of the two Al ultrafine particles 1 and 2, as shown in FIG. Due to the surface diffusion of the constituent atoms, small-diameter Al atom clusters 3 start to be formed on the surfaces of the Al ultrafine particles 1 and 2. Furthermore, when the electron beam is continuously irradiated, the two Al ultrafine particles 1 and 2 approach each other, and the Al atomic cluster 3 formed on the surface thereof, specifically, the Al cluster 3 having a diameter of about 2 nm is formed by two Al superfine particles. After filling the space between the fine particles 1 and 200 seconds after the start of the electron beam irradiation, the Al ultrafine particles 1 and 2 are fused through the Al atom cluster 3 as shown in FIG. .
[0027]
In this way, an Al ultrafine particle fusion 4 was obtained by surface diffusion accompanying electron beam irradiation on the two Al ultrafine particles 1 and 2. This fusion is believed to be due to both the local heating effect by the irradiated electrons and the knock-on effect. The obtained Al ultrafine particle fusion 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. The plasticity was maintained.
[0028]
Example 2
In the same manner as in Example 1, an Al ultrafine particle fusion was produced 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 a state (including the degree of vacuum) arranged in the vacuum chamber of the TEM apparatus, and is close to the Al ultrafine particles on the carbon support film 2 Two Al ultrafine particles were selected. These Al ultrafine particles are multiple twin grains with a diameter of about 15 nm. The two Al ultrafine 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.
[0029]
While irradiating with an electron beam, the state of two Al ultrafine particles was observed in situ. The observation result will be described with reference to the schematic diagram of FIG. First, before the electron beam irradiation, as shown in FIG. 2A, the two Al ultrafine particles 5 and 6 had different crystal orientations.
[0030]
From this state, when the two Al ultrafine particles 5 and 6 are irradiated with an electron beam, the two Al ultrafine particles 5 and 6 surrounded by the {111} plane start to approach each other, and as a result, there is no clear twin boundary. It was observed that the entire crystal changed from a polyhedron to a dome structure. Moreover, as shown in FIG. 2 (b), it was observed that both the {111} planes were parallel, that is, the entire particle constituent atoms were curved so as to have an epitaxy relationship. That is, when the two Al ultrafine particles 5 and 6 come close to each other, the atomic arrangement is changed so that the interface energy is minimized by actively aligning the crystal plane and orientation.
[0031]
Further, when the electron beam irradiation is continued, necking starts at the contact point, and after about 300 seconds have elapsed from the start of the electron beam irradiation, as shown in FIG. Generated. When the electron beam was further irradiated from this state, the solid fusion body 7 was fused and integrated after about 350 seconds from the start of irradiation.
[0032]
In this way, an Al ultrafine particle fusion 7 was obtained by rearrangement of atoms accompanying electron beam irradiation to the two Al ultrafine particles 5 and 6. This fusion is considered to be 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. 2C, the obtained Al ultrafine particle fusion body 7 was fused by forming an interface having an epitaxy relationship while maintaining the original particle shape (heptagon).
[0033]
As is clear from each of the above-described embodiments, according to the present invention, fusion control including crystal control of ultrafine particles can be realized by electron beam irradiation under a condition that is easy to control on a room temperature stage. It has great potential to develop into various manipulations by using electron beams.
[0034]
【The invention's effect】
As described above, according to the method for producing an ultrafine particle fusion of the present invention, an ultrafine particle fusion in which the fusion state and the like are controlled can be obtained under the condition of easy control on the room temperature stage. Such an ultrafine particle fusion product of the present invention has a control of fusion state, operability, etc., and thus greatly contributes to, for example, application development from single metal ultrafine particles.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a production process of an ultrafine particle fusion product in one example of the present invention.
FIG. 2 is a diagram schematically showing a production process of an ultrafine particle fusion product in another example of the present invention.
[Explanation of symbols]
1, 2 …… Al ultrafine particles 3 …… Al atomic clusters 4 …… Al ultrafine particle fusion 5 by surface diffusion 5, 6 …… Al ultrafine particles (multiple twin grains)
7 ... Al ultrafine particle fusion by atomic rearrangement

Claims (4)

A fusion of Al ultrafine particles having a particle size of 5 to 10 nm , which is fused by surface diffusion of constituent atoms of the Al ultrafine particles, and a cluster of the constituent atoms having a diameter of 3 nm or less exists at the fusion interface. An ultrafine particle fusion product characterized by A fusion of Al ultrafine fine particles having a particle size of 10 ~ 30 nm, the Al to the crystal surface and the crystal orientation of the super fine particles are fused in a state where atomic arrangement of the Al ultrafine particles is changed to be the same Ultrafine particle fusion characterized by Ultrafine particle fusion characterized in that at least two metal ultrafine 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 metal ultrafine particles. Body manufacturing method. In the method for producing an ultrafine particle fusion product according to claim 3 ,
A method for producing an ultrafine particle fusion product, wherein Al ultrafine particles having a diameter of 5 to 30 nm are used as the metal ultrafine particles.

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