JP2019070186A - Carbon metal composite molding and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material capable of exhibiting excellent strength, which is suitable for use as, for example, an electronic component of an aircraft or an automobile, a structural material, or the like. SOLUTION: The carbon-metal composite molded body of a flaky carbon material having a graphene skeleton and metal particles has a relative density of 90% or more and contains 25% by volume or less of carbon. Characterized carbon metal composite molded body. The metal particles in the carbon-metal composite molded body of the present invention preferably have an average aspect ratio of 2 or more. [Selection diagram] FIG. 10

Description

The present invention relates to a carbon metal composite molded body and a method for producing the same. More particularly, the present invention relates to a carbon-metal composite molded article that can be suitably used for electronic components of aircrafts and automobiles, structural materials, and the like, and a method of manufacturing the same.

Carbon materials are lightweight and have excellent properties such as high strength, high thermal conductivity, high electrical conductivity, etc., and are attracting attention as composite materials with other materials. For example, a carbon-metal composite molded body in which a carbon material is complexed with a metal (for example, a light metal such as Al, Mg, Ti, etc. used for electronic parts of aircrafts and automobiles, structural materials, etc.) is lightweight and excellent strength It is expected to have excellent thermal and electrical conductivity and current capacity.
As carbon materials, those having a graphene skeleton have been extensively studied because of their unique structures and physical properties.

As a conventional carbon metal composite molded body, a sintered body of graphene / metal nanocomposite powder containing a base metal and graphene as a composite of a carbon material having a graphene skeleton with a light metal or another metal (for example, a patent Reference 1) is disclosed. In addition, a method for producing a thermoelectric nanocomposite (see, for example, Patent Document 2) including the step of embedding several layers of graphene oxide nanosheets as a three-dimensional network structure inside a protective matrix material such as tetragonal ZrO ₂ ceramics is disclosed. It is done. Furthermore, a high thermal conductivity composite material in which a fibrous carbon material having a graphene tube is present in a plurality of layers in a base material made of a metal and / or ceramic pulse electric current and pressure sintered body (for example, Patent Document 3) 4), a nanocomplex of a metal and / or an oxide thereof and graphene oxide (see, for example, Patent Document 5).

For example, FLG (several layers of graphene: a Few layers of graphene) / Al or Al alloy composite material prepared by a ball mill method (see, for example, non-patent documents 1 and 2), powder metallurgy method (See, for example, Non-Patent Documents 3 and 4). Furthermore, a reduced graphite oxide / Al composite material is prepared by a composite powder assembly process (see, for example, Non-Patent Document 5).

JP, 2011-225993, A Unexamined-Japanese-Patent No. 2015-107881 JP 2008-285745 A Patent No. 5288441 gazette JP, 2016-193431, A

Gang Li, Bowen Xiong, Journal of Alloys and Compounds 697 (2017) 31-36 S. E. Shin, D. H. Bae, Composites: Part A-Appl. S 78 (2015) 42-47 Xin Gao, Hongyan Yue, Erjun Guo, Hong Zhang, Xuanyu Lin, Longhui Yao, Bao Wang, Materials and Design 94 (2016) 54-60 S. E. Shin, H. J. Choi, J. H. Shin, D. H. Bae, Carbon 82 (2015) 143-151 Zan Li, Qiang Guo, Zhiqiang Li, Genlian Fan, Ding-Bang Xiong, Yishi Su, Jie Zhang, Di Zhang, Nano Lett. 15 (2015) 8077-8083

Although the thing mentioned above as a carbon metal composite molded object which compounded the carbon material which has a graphene frame to light metal etc. is known, in order to fully exhibit the outstanding characteristic of the carbon material which has a graphene frame, it is a device There was room.
In addition, since the material of patent document 2 is ceramics, it was not able to fully apply the processing method used for metal. In addition, the ball mill method described in Non-Patent Documents 1 and 2 has a problem that the carbon material is damaged by balls.

This invention is made in view of the said present condition, for example, when it is used as an electronic component of aircraft and a motor vehicle, a structural material, etc., it aims at providing the forming object which can exhibit the outstanding intensity suitable. .

The present inventors have variously studied molded articles capable of exhibiting excellent strength when used as electronic parts for aircrafts and automobiles, structural materials, etc., and a carbon metal composite in which a lightweight carbon material and metal particles are compounded. Focusing on the molded body, a compact carbon metal composite molded body was formed in which a flaky carbon material having a specific ratio or less was compounded. Furthermore, the present inventors found that this carbon metal composite molded body is excellent in strength isotropically in which the flaky carbon material is three-dimensionally arranged along the grain boundaries between the metal particles, and is derived from metal. The plastic deformation ability is sufficiently maintained, and can be suitably deformed by applying pressure, whereby the metal particles in the compact after deformation become high in average aspect ratio, and strength in a specific direction is obtained. The present invention has been made in view of the finding that it will be a very excellent one, and in light of the fact that the above problems can be solved wonderfully.

That is, the present invention is a carbon metal composite molded article of a flaky carbon material having a graphene skeleton and metal particles, wherein the molded article has a relative density of 90% or more and contains 25% by volume or less of carbon. A carbon metal composite molded body characterized by

The metal particles in the carbon metal composite molded article of the present invention preferably have an average aspect ratio of 2 or more.

The carbon metal composite molded body of the present invention is excellent in strength because it is a dense body in which a flaky carbon material having a graphene skeleton and a metal are complexed at a specific ratio or less, and in particular, the metal particles in the molded body have a high aspect ratio. Those having a ratio are very excellent in strength in a specific direction.

(A) A transmission electron microscope (TEM) image of graphene oxide (GO) prepared in advance by the modified Hamers method is shown. (B) It is a selected-area electron diffraction (SAED) pattern of GO acquired from the position shown by the square shown to (a). (C) It is a diffraction intensity in alignment with a (1-210) axis from a (1-210) axis about a pattern shown in (b). (A) pure Al powder, (b) GO / Al composite powder having a GO content of 0.16% by mass, (c) GO / Al composite powder having a GO content of 0.66% by mass, (d) GO content It is a field emission-type scanning electron microscope (FE-SEM) image which shows 1.62 mass% GO / Al composite powder. (A) It is a TEM image of GO content 0.66 mass% GO / Al composite powder. (B) It is a TEM image of GO content 0.66 mass% GO / Al composite powder. Fig. 6 shows Raman spectra of a green body obtained by GO, pulse current pressure sintering (PCPS), and a green body after PCPS and hot extrusion (HE). (A) TEM image of 0.4 vol% rGO / Al composite compact. (B) HR (high resolution) TEM-EDS mapping of the rGO / Al boundary obtained from the position of the square indicated by the broken line in (a). (C) HRTEM image for 0.4 vol% rGO / Al composite compact, upper left inset is SAED pattern of Al ₂ O ₃ layer obtained from the filled circle part. Also, the lower right inset is the EDS spectrum of carbon line scanned on a line marked by a short line. (D) HRTEM image for a 0.4 vol% rGO / Al composite compact, the lower left inset is the SAED pattern of the Al matrix taken from the filled circle portion. Also, the upper right inset is the EDS spectrum of carbon line scanned on a line marked with a short line. (A) It is a graph which shows the weight with respect to the temperature of GO in a thermogravimetric analysis. (B) It is a narrow scan spectrum of C1s domain by XPS measurement of GO after GO and PCPS, respectively. (A) Electron beam of pure Al, 0.2 vol% FLG / Al composite compact, 0.4 vol% FLG / Al composite compact, 0.6 vol% FLG / Al composite compact after PCPS Inverse pole figure (IPF) map in backscattering analysis (EBSD analysis) is shown. (B) It is a graph which shows the average particle diameter with respect to the volume ratio of rGO. (A) A lower magnification FE-SEM image of a cross-sectional view of a 0.4 vol% FLG / Al composite molded body obtained by PCPS. (B) Higher magnification FE-SEM image of a cross-sectional view of a 0.4 vol% FLG / Al composite compact obtained with PCPS. 5 is a backscattered electron image and elemental mapping in an electron beam microanalyzer (EPMA) analysis of a cross-sectional view of a 0.4 vol% FLG / Al composite compact obtained by PCPS. (A) IPF map for cross-sectional view of 0.4 vol% FLG / Al composite compact after PCPS and HE. (B) IPF map in EBSD analysis of longitudinal section of 0.4 vol% FLG / Al composite compact after PCPS and HE. (A) TEM image of a hot extruded 0.4 vol% FLG / Al composite compact. (B) HRTEM image of a hot extruded 0.4 vol% FLG / Al composite compact, the upper left inset is the EDS spectrum of the Al ₂ O ₃ layer. Also, the lower left inset is the SAED pattern of the Al matrix obtained from the filled white circle. In addition, the lower right inset is the EDS spectrum of carbon line scanned on a line marked by a short line. (C) TEM image of a hot extruded 0.4 vol% FLG / Al composite compact. (D) HRTEM image of a hot extruded 0.4 vol% FLG / Al composite compact, the upper left inset is the fast Fourier of the electron beam diffraction pattern of the Al matrix taken from the filled circle It is a transform (FFT) pattern. Also, the lower right inset is the EDS spectrum of carbon line scanned on a line marked by a short line. 1 shows a typical nominal tensile stress-tensile strain curve of a 0.4 vol% FLG / Al composite compact and pure Al.

The present invention will be described in detail below.
In addition, what combined two or more of each preferable form of this invention described below is also a preferable form of this invention.

<Carbon-metal composite molded body>
The carbon metal composite molded body of the present invention is a carbon metal composite molded body of a flaky carbon material having a graphene skeleton (hereinafter, also simply referred to as a carbon material) and metal particles, and has a relative density of 90% or more And 25% by volume or less of carbon. The carbon-metal composite molded body according to the present invention is a dense body in which a carbon material at a specific ratio or less is complexed to metal particles, and for example, it is molded such as pellets obtained by sintering a carbon material and metal particles. The body, or the one that is deformed by applying pressure to it may be mentioned. A pellet-like compact or the like obtained by sintering has a carbon material arranged three-dimensionally along the grain boundaries between metal particles, and is isotropically excellent in strength, and has plasticity peculiar to metal, A plastic deformation can be suitably performed, and by applying pressure to this to deform it, etc., it is possible to form a molded body which is extremely excellent in strength in a specific direction.
The shape and size of the molded product are not particularly limited, and examples thereof include films, sheets, fibers, columns, cubes, and spheres, as well as pellets.

The carbon-metal composite molded article according to the present invention preferably has a relative density of 92% or more, more preferably 94% or more, still more preferably 96% or more, particularly preferably 99% or more preferable. Thereby, the strength of the carbon metal composite molded body of the present invention can be made more excellent.
The upper limit of the relative density is not particularly limited, and may be 100%.
The relative density can be measured by the Archimedes method.

The carbon-metal composite molded body of the present invention preferably contains 10 vol% or less of carbon, more preferably 5 vol% or less, still more preferably 3 vol% or less, and 2 vol% or less The content is more preferably 1% by volume or less, and particularly preferably 0.8% by volume or less. Thereby, in the carbon metal composite molded body of the present invention, the aggregation of the carbon material is more sufficiently prevented, and the effect of the present invention can be remarkably exhibited despite the small carbon content.

From the viewpoint of exhibiting sufficient strength by carbon, the carbon metal composite molded body of the present invention preferably has a carbon content of 0.01% by volume or more, and more preferably 0.1% by volume or more More preferably, it is 0.2% by volume or more, and particularly preferably 0.3% by volume or more.
The carbon content can be measured by the method of the example.

The carbon metal composite molded body of the present invention is, for example, (1) GO as a graphene oxide (GO) / aluminum (Al) composite molded body after pulse current pressure sintering (PCPS) described later. (2) Furthermore, an Al ₂ O ₃ layer is present at the grain boundaries, and GO is dispersed among the Al ₂ O ₃ layers. In addition, it is thought that it will become a suitable form suitably, if metals, such as Al, Mg, and Ti with which the particle | grain surface is oxidized easily, are used as a metal of a metal particle, and PCPS is performed.
That is, it is preferable that the carbon metal composite molded body of the present invention has a laminated structure in which a metal layer, a metal oxide layer, a carbon material layer, a metal oxide layer, and a metal layer are laminated in this order. It is one of the
In the above laminated structure, another layer may be inserted between the layers, but it is preferable that the layers be in direct contact with each other.
This form can be confirmed by TEM observation shown in the examples.

(Flake-like carbon material with graphene skeleton)
The flaky carbon material having a graphene skeleton is not particularly limited as long as it has carbon (C) bonded by sp ² bond and has a layered structure in which the carbon is flaky (planar). Specifically, the carbon material may have a structure consisting of only a layer (single layer) in which carbon atoms bonded by sp ² bonds are arranged in a plane, and two or more layers of the layers are stacked. It may have a structure. The carbon material preferably has, for example, a single-layer structure composed of only one layer, or a stacked structure of about 2 to 100 layers.

It is preferable that the said carbon material is what has carbon combined with oxygen (O). For example, the carbon material is more preferably graphite oxide. More preferably, it is graphene oxide in which oxygen is bonded to carbon of graphene.
Generally, graphene refers to a sheet consisting of one layer in which carbon atoms bonded by sp ² bonds are arranged in a plane, and a stack of a large number of graphene sheets is referred to as graphite. Not only the sheet | seat which consists of one layer but the thing which has a structure which laminated | stacked about 2-100 layers is also contained.

The carbon material is, for example, preferably heated and reduced at the time of compounding to form a reduced graphite oxide in the carbon metal composite molded body of the present invention.
The carbon material may further have functional groups such as a carboxyl group, a hydroxyl group, a sulfur-containing group, and an alicyclic epoxy group.

Among the above-mentioned carbon materials, those having a laminated structure of about 2 to 50 layers are preferable, those having a laminated structure of about 2 to 15 layers are more preferable, and those having a laminated structure of about 2 to 9 layers are more preferable. . In the present specification, one having a stacked structure of about 2 to 9 layers is also referred to as FLG (a few layers of graphene). Note that FLG may be several layers of graphene oxide or may be several layers of reduced graphene oxide.
The number of stacked layers of sheets in which carbon atoms bonded by such sp ² bonds are arranged in a plane is expressed as a peak number of strength against distance in a cross-sectional view of a TEM image described later.

The specific surface area of the carbon material is preferably 1 m ² / g or more, and more preferably 10 m ² / g or more. A carbon material having such a specific surface area can exhibit higher dispersibility when complexed with metal particles. The upper limit of the specific surface area is not particularly limited, but can be, for example, 2000 m ² / g or less.
The specific surface area can be measured by a specific surface area measuring device by a nitrogen adsorption BET method.

The carbon material preferably has an average particle size of 1000 μm or less. Further, the average particle diameter is preferably 5 nm or more.
The average particle size can be measured by a particle size distribution measuring apparatus.
The particles having an average particle diameter in the range as described above are, for example, a method of pulverizing the particles with a ball mill or the like, dispersing the obtained coarse particles in a dispersing agent to obtain a desired particle diameter, and drying. The coarse particles can be sieved or the like to separate the particle size, and the preparation conditions can be optimized at the stage of producing the particles to obtain particles having a desired particle size.

The carbon material can be obtained by treating graphite with a known oxidizing agent, for example, treated with potassium permanganate according to the Modified Hummers Method, and if necessary, ultrasonicated in a solvent It can be suitably obtained by performing solid-liquid separation treatment such as treatment or centrifugation.

(Metal particles)
Examples of the metal particles according to the present invention include simple metals, alloys, and compounds (such as oxides), but simple metals and / or alloys are preferable. As a result, the carbon material can be uniformly dispersed in the carbon-metal composite molded article of the present invention without aggregation, and the excellent effect of the strength of the obtained molded article can be made more remarkable. . The metal constituting the metal particle according to the present invention is, for example, more preferably aluminum, silicon, titanium, nickel, copper, iron, zirconium, silver, tin, or an alloy composed of two or more of these metals, among which Aluminum, titanium, nickel, copper, iron, silver, tin, and alloys composed of two or more of these metals are more preferable. Among them, aluminum is particularly preferred. The metal particles may further contain silicon or zirconium as an additive. Moreover, it is preferable that the metal which comprises the metal particle which concerns on this invention is crystalline.
Further, from the viewpoint of making the specific strength excellent, the metal preferably has a specific gravity of 5 or less.

It is preferable that the average grain size of the metal particles in the carbon metal composite molded body of the present invention is 4 μm or more. Thereby, the effect excellent in strength can be made more remarkable. The average grain size is more preferably 5 μm or more, still more preferably 6 μm or more, and particularly preferably 7 μm or more.
The upper limit of the average grain size is not particularly limited, but is usually 50 μm or less.
Average grain size can be measured by EBSD according to the method of the embodiment.

The metal particles in the carbon metal composite molded article of the present invention preferably have an average aspect ratio of 2 or more. Such a carbon-metal composite molded article of the present invention is one in which carbon materials are arranged along a specific direction, and the strength in the direction is very excellent.
Such a carbon-metal composite molded article according to the present invention is, for example, a laminated structure in which a metal layer, a metal oxide layer, a carbon material layer, a metal oxide layer, and a metal layer are laminated in this order, a metal layer, a metal oxide layer, carbon Having at least one kind of laminated structure selected from the group consisting of a laminated structure in which a material layer and a metal layer are laminated in this order, and a laminated structure in which a metal layer, a carbon material layer and a metal layer are laminated in this order Is one of the preferred embodiments of the present invention.
In the above laminated structure, another layer may be inserted between the layers, but it is preferable that the layers be in direct contact with each other.
This structure can be confirmed by TEM observation shown in the examples.
When there is no metal oxide layer between the metal layer and the carbon material layer, the metal oxide may be mixed or not mixed in the metal layer (metal matrix).
Such a carbon-metal composite molded article of the present invention can be suitably obtained by applying pressure to the pellet-like molded article after PCPS to deform as described later.

The average aspect ratio of the carbon metal composite molded article of the present invention is more preferably 2.5 or more, and still more preferably 3 or more.
The upper limit of the average aspect ratio is not particularly limited, but is usually 10 or less.
The average aspect ratio can be determined by dividing the average diameter of particles calculated from the longitudinal drawing by the average diameter of particles calculated from the transverse drawing.

In the carbon metal composite molded body of the present invention, the content of the metal particles is preferably 75 to 99.99% by volume. The content of the metal particles is more preferably 90 to 99.9% by volume, still more preferably 95 to 99.8% by volume, and still more preferably 97 to 99.7% by volume. Still more preferably, it is 99% by volume or more, and particularly preferably 99.4% by volume or more.

The carbon metal composite molded body of the present invention may be a composite obtained by using one type of carbon material and one type of metal particle, or may be a type combined using two or more types. Moreover, although other components other than the carbon material and the metal particles may be included, the content of the other components is preferably 5% by volume or less, more preferably 1% by volume or less, 0 It is further preferable that the content be 1% by volume or less, and it is particularly preferable that the carbon metal composite molded body of the present invention does not contain other components.

The carbon-metal composite molded article of the present invention is applicable to various applications, but from the viewpoint of achieving weight reduction of materials, it is preferably used as, for example, electronic parts for aircraft and automobiles, structural materials, etc. .

<Manufacturing method of carbon metal composite molded body>
The carbon-metal composite molded body of the present invention can be produced by combining a carbon material and metal particles by heating, pressing or the like, but by sintering the carbon material and metal particles. Among them, sintering by pulse current pressure sintering (PCPS) is more preferable. In particular, pulse electric pressure and pressure sintering enables uniform sintering over the entire material, and even if the temperature in the sintering step is high enough to make it easy for the carbon material to move, sufficient aggregation thereof is achieved. A more precise compact can be produced while preventing, and the effect of excellent strength becomes remarkable. For example, the present invention is a method for producing a carbon-metal composite molded body using a flaky carbon material having a graphene skeleton and a metal particle, and the production method includes a flaky carbon material having a graphene skeleton and a metal particle And a step of sintering by pulse current pressure sintering.

The temperature in the sintering step is preferably 200 ° C. or more. Thereby, the compact obtained can be further densified. The temperature is more preferably 350 ° C. or more, still more preferably 500 ° C. or more. Further, from the viewpoint of preventing aggregation of the carbon material, the temperature is preferably 2000 ° C. or less, and more preferably 1500 ° C. or less.
The time for performing the sintering step is preferably 1 minute to 1 hour. More preferably, it is 2 minutes-30 minutes, More preferably, it is 3 minutes-20 minutes.
The heating of the carbon material may be performed in air, or may be performed in an inert gas atmosphere such as nitrogen, helium or argon. Moreover, the pressure conditions in a sintering process are not specifically limited, It can carry out under pressure conditions, normal pressure conditions, and pressure reduction conditions.

The production method of the present invention preferably further includes the step of mixing the carbon material and the metal particles before the sintering step. Moreover, it is more preferable to obtain the composite powder of a carbon material and metal particles by this mixing process.
The said mixing process can be performed by, for example, dripping the water dispersion of a carbon material in the water which metal particle disperse | distributed, filtering the composite powder of the obtained carbon material and metal particle, and drying. The water in which the metal particles are dispersed is preferably prepared by uniformly mixing the metal particles and the water and performing ultrasonic treatment or the like.

In the process of preparing a composite powder of metal particles and a carbon material by the above mixing process, ball mill mixing, use of a surface modifier, use of electrostatic interaction, etc. are used as a method for bonding metal particles and a carbon material. It can be mentioned. Among them, a method using electrostatic interaction is particularly preferable in terms of avoiding damage to graphene, mixing of impurities, and the like. Since it has an ether group or a carbonyl group and electrostatically interacts with the carbon material negatively charged in water, it is positively charged in water (the point at which the zeta potential in an aqueous solution at 25.degree. Preferred is a metal particle having an oxide coating at a point of pH> 7). Examples of such a metal include Al.

The production method of the present invention preferably further includes the step of applying pressure to the molded body obtained in the sintering step to deform it. According to the manufacturing method of the present invention, the metal particles in the molded product have a high aspect ratio, and the molded product can be made extremely excellent in the strength in a specific direction.
In the present specification, the step of applying pressure and deforming is not particularly limited, but is preferably a step of pressing the material and then stretching in at least one direction, for example, stretching the material into a film using a roller A rolling process, an extrusion process using a mold or the like, a process of forming into a film by a flat plate press, an injection molding process, a casting process, etc. may be mentioned.

At a pressure in the step of deforming the addition of the pressure is not particularly limited, is preferably 0.1 kN / mm ² or more, more preferably 0.5 kN / mm ² or more, 1 kN / mm ² or more It is further preferred that
Also the pressure is preferably at 50 kN / mm ² or less, more preferably 10 kN / mm ² or less.

The temperature in the step of applying and deforming the pressure is preferably 200 ° C. or more. More preferably, it is 300 degreeC or more, More preferably, it is 400 degreeC or more. The temperature is preferably 2000 ° C. or less, more preferably 1000 ° C. or less, and still more preferably 700 ° C. or less.
The step of applying and deforming the pressure may be performed in air, or may be performed in an inert gas atmosphere such as nitrogen, helium, argon or the like.

Among the above-described steps of applying and deforming the pressure, the extrusion step and the rolling step are preferable. In particular, rolling is preferable in terms of excellent productivity.

Below, an extrusion process is demonstrated in detail as an example.
The extrusion load in the extrusion step is preferably 100 kN or more, more preferably 200 kN or more, and still more preferably 300 kN or more.
The extrusion load is preferably 1000 kN or less, more preferably 800 kN or less.

The extrusion speed in the extrusion step is preferably 0.01 m / h or more, more preferably 0.02 m / h or more, and still more preferably 0.04 m / h or more.
The extrusion speed is preferably 1 m / h or less, more preferably 0.5 m / h or less, and still more preferably 0.2 m / h or less.

The extrusion ratio in the extrusion step is preferably 1 or more, more preferably 5 or more, and still more preferably 10 or more.
The extrusion ratio is preferably 200 or less, more preferably 100 or less, and still more preferably 40 or less.
The extrusion ratio is a value obtained by dividing the cross-sectional area of the mold on the side pressing the material by the cross-sectional area of the mold on the side from which the material emerges in the cross section perpendicular to the extrusion direction of the material.

The extrusion step is preferably, for example, a step of hot extrusion. The preferred temperature range in the step of hot extrusion is the same as the preferred temperature range in the deformation step.

The carbon metal composite molded body of the present invention can be used in various forms, and can be suitably used, for example, as an electronic component of an aircraft or an automobile, a structural material, and the like.

EXAMPLES The present invention will be described in more detail by way of the following examples, but the present invention is not limited to these examples. In addition, unless there is particular notice, "part" shall mean "weight part" and "%" shall mean "mass%."

In the present specification, a shaped body having an average aspect ratio of 2 or more of metal particles is also referred to as a shaped body containing metal particles having a high average aspect ratio.

Various characteristic values were measured by the following methods.
(Transmission electron microscope (TEM) observation, limited field electron diffraction observation, HRTEM-EDS map)
It carried out using the high-resolution transmission electron microscope (HF-2000EDX) made from Hitachi High-Technologies Corporation.
(Field emission scanning electron microscope (FE-SEM) observation)
It carried out using the scanning electron microscope (JSM-6500F) made from JEOL.

(Microscopic Raman spectrum)
The incident laser light with a wavelength of 532 nm was measured using a SOLAR TII Nanofider (Tokyo Instruments, Inc.) having a 100 × objective lens.

(Backscattered electron image)
It measured using the atomic resolution analysis electron microscope (JEM-ARM200F) of JEOL Ltd. make.
(EPMA elemental mapping)
The measurement was performed using a field emission electron probe microanalyzer (JXA-8530F) manufactured by JEOL.

(Electron backscattering diffraction (EBSD), IPF map)
The crystal orientation analyzer (OIM Ver. 6) manufactured by TSL Solutions Inc. was used.

(Carbon content in molded body)
It measured using the carbon analyzer (TC-444, product made by LECO).

(Thermogravimetric analysis)
It measured using the differential thermal / thermogravimetry simultaneous measurement apparatus (SDT Q600).
(XPS measurement)
It was measured using a scanning X-ray photoelectron spectrometer (PHI5600, manufactured by ULVAC-PHI, Inc.).
(Maximum tensile strength [UTS], yield strength, elongation)
It measured using the Shimadzu Corporation precision universal testing machine (AUTOGRAPH AG-I 50KN).

Example 1
<Composition of FLG>
Charge 1 g of graphite (manufactured by Bay Carbon, product name: SP-1) and 25 mL of sulfuric acid at room temperature into a flask, put the flask in an ice bath, and gradually add 3.5 g of potassium permanganate so as to maintain 273 K (0 ° C.) It was thrown in.
Next, after stirring using a magnetic stirrer at 313 K (40 ° C.) for 2 hours, 200 mL of deionized water and 5 mL of 30% hydrogen peroxide water were charged in this order. The precipitate was washed with 150 mL of hydrochloric acid and collected by vacuum filtration.
The collected precipitate was dispersed in 200 mL of water, allowed to stand for one week, and then recovered again. Furthermore, 1 L of water was added to the recollected precipitate, and ultrasonication was performed. Finally, centrifugation was performed at 4000 rpm for 30 minutes to obtain FLG.

<Preparation of FLG / Al Composite Powder>
15 g of Al particles (manufactured by Ecka granule Japan, purity 99.85%, average particle diameter 5.5 μm) and 200 mL of water were charged into a beaker, and agitation and ultrasonication were performed for 2 hours in an ice bath. Next, 25 mL of FLG solution (4.95 × 10 ⁻⁴ g / mL) was added dropwise. Finally, the FLG / Al composite powder was recovered by filtration and vacuum dried at 343 K (70 ° C.) to obtain an FLG / Al composite powder having a FLG content of 0.08 mass%.

<Production of molded body>
Pulse electric current pressure sintering device (discharge plasma sintering device) (Dr. Sinter S 511, Sumitomo Coal Mining Co., Ltd.) under the conditions of 50 MPa, 873 K (600 ° C.) (temperature raising rate: 1200 K / h) of FLG / Al composite powder Sintering) for 0.33 hours to obtain a PCPS sample (molded body) having a diameter of 15 mm and a length of 30 mm. Next, the obtained PCPS sample was subjected to an extrusion speed of 0.06 m / h and an extrusion ratio of 20 using a universal tester (UH-500 kN1, manufactured by Shimadzu Corporation) under the conditions of 500 kN and 773 K (500 ° C.) Hot extrusion was performed to obtain a molded article containing metal particles having a high average aspect ratio.

(Example 2)
In the same manner as in Example 1 except that in the above <Production of FLG / Al composite powder>, the amount of the dropped FLG solution was changed to 50 mL to obtain FLG / Al composite powder having a FLG content of 0.16% by mass. A molded body was obtained.

(Example 3)
In the same manner as in Example 1 except that in the above <Production of FLG / Al composite powder>, the amount of the dropped FLG solution was changed to 100 mL to obtain an FLG / Al composite powder having a FLG content of 0.33% by mass. A molded body was obtained.

(Example 4)
In the same manner as in Example 1 except that in the above <Production of FLG / Al composite powder>, the amount of the dropped FLG solution was changed to 200 mL to obtain an FLG / Al composite powder having a FLG content of 0.66% by mass. A molded body was obtained.

(Example 5)
In the same manner as in Example 1 except that in the above <Production of FLG / Al composite powder>, the amount of the dropped FLG solution was changed to 300 mL to obtain FLG / Al composite powder having a FLG content of 0.98% by mass. A molded body was obtained.

(Example 6)
In the same manner as in Example 1 except that in the above <Production of FLG / Al composite powder>, the amount of the dropped FLG solution was changed to 500 mL to obtain FLG / Al composite powder having a FLG content of 1.62% by mass. A molded body was obtained.

(Comparative example 1)
In <Production of FLG / Al Composite Powder>, the amount of the dropped FLG solution was changed to 0 mL, and a molded body was obtained in the same manner as Example 1, except that a pure Al powder was obtained.

(Evaluation)
FIG. 1 (a) shows a TEM image of GO (graphene oxide) previously prepared by the modified Hamers method. The GO is in the form of a sheet (flaky) in which the edge is slightly wound and folded (see the portion shown by the small filled circle in FIG. 1 (a)). In addition, some wrinkles are observed (marked by the dashed circle in FIG. 1 (a)), indicating the flexibility of the GO.

FIG. 1 (b) is a selected-area electron diffraction (SAED) pattern of GO obtained from the position of the open square shown in FIG. 1 (a). This diffraction pattern shows the typical six-fold symmetrical pattern expected for graphene.
FIG. 1 (c) is a diffraction intensity along the (1-210) axis to the (-2110) axis for the pattern shown in FIG. 1 (b). This GO may be a monolayer, as the {1100} inner peak appears stronger than the {2110} outer peak. In addition, it can be understood from TEM observation that this GO has a structure in which several layers of less than one layer or less than 10 layers are laminated. The number of layers will be discussed further later. Also, from dynamic light scattering (DLS) measurement, the average size of GO, which is estimated to be a round sheet, is 700 nm, which is much smaller than the size (5.5 μm) of the Al powder used in this example.

FIG. 2 (a) is an FE-SEM image showing pure Al powder. Fig. 2 (b), Fig. 2 (c) and Fig. 2 (d) show an FE having a GO content of 0.16% by mass, 0.66% by mass and 1.62% by mass, respectively. -SEM image. The black broken line in FIG. 2 (b) shows crumpled GO on the Al surface. The white arrows in FIG. 2 (d) indicate slight aggregation of GO sheets between Al particles.
In FIG. 2 (a)-(c) which shows GO / Al composite powder to GO content 0.66 mass%, GO cluster is hardly observed. However, at a GO content of 1.62% by mass, slight aggregation of GO is observed between Al particles (FIG. 2 (d)). One reason is that during powder mixing, the contact surface of the Al particles to the total surface area of the GO sheet is limited.

FIGS. 3 (a) and 3 (b) are TEM images of a GO content of 0.66 mass% GO / Al composite powder.
FIG. 3 (a) shows a structure in which Al particles are wrapped with a GO sheet. As described above, the size of the GO sheet and the size of the Al particles are significantly different. Therefore, Al particles are covered with several GO sheets. The black arrows in FIG. 3 (b) indicate GO sheets that crosslink between two Al particles. As shown in FIG. 3 (b), some of the GO sheets crosslink between the Al particles, so that the GO sheets overlap each other, stick together, form a network structure, and uniformly when viewed across the material It becomes dispersed and can fully exhibit characteristics such as strength.

GO content (% by mass) in composite powder (Examples 1 to 6) or pure Al (Comparative example 1) of Examples 1 to 6 and Comparative Example 1, and rGO / Al composite formed article (Example Relative density (%) after pulse current pressure sintering, relative density (%) after HE (hot extrusion), rGO content (volume%) of 1 to 6) or pure Al (comparative example 1) The grain size (μm) after PCPS and the grain size (μm) perpendicular to HE after HE are shown in Table 1 below. The rGO content (volume%) was determined using a density of 2.28 g / cm for rGO and a density of 2.7 g / cm for Al.

From the results of Table 1, it can be seen that the carbon-metal composite moldings of the examples and the moldings obtained by applying pressure thereto and deforming them have a sufficiently high relative density, and also have directionality by the application of pressure. It is understood that it is a thing. The carbon content in the molded body is considered to be the same as the carbon content in the composite.

FIG. 4 shows Raman spectra of composite molded bodies obtained by GO and PCPS, and molded bodies after PCPS and HE. The D band at 1350 cm ⁻¹ is usually associated with the presence of lattice defects, and the G band at 1580 cm ⁻¹ corresponds to planar C—C symmetric stretching vibrations in the graphene sheet. It is reported that the I _D / I _G ratio increases when GO is reduced in the temperature range of 473 K to 1273 K (non-patent document: SHHuh. Thermal reduction of grapheme oxide: INTECH Open Access Publisher; 2011). After PCPS, the I _D / I _G ratio is slightly increased from 0.97 to 1.09, and it is considered that GO was reduced to rGO (reduced graphene oxide) during PCPS. Moreover, 2D band and D + G band were detected at 2600-3300 cm ⁻¹ . The 2D band reflects the aromatic carbon structure, and the D + G band is induced by lattice disorder of the graphitic material. The 2D band reappears in the composition after PCPS and the I _2D / I _{D + G} is improved, which is due to the recovery of the graphene double bond (conjugated structure).

FIG. 5 (a) is a TEM image of a 0.4 vol% rGO / Al composite compact. FIG.5 (b) is a HRTEM-EDS mapping of the rGO / Al boundary acquired from the square position shown with the broken line in (a). FIG.5 (c), FIG.5 (d) is a HRTEM image about 0.4 volume% rGO / Al composite compact.
FIG. 5 (b) is HRTEM-EDS mapping at grain boundaries obtained from the area in the white square in FIG. 5 (a). C corresponds to rGO. Al and O correspond to Al ₂ O ₃ .
As shown in FIG. 5 (c) and FIG. 5 (d), the rGO plate is sandwiched between the Al ₂ O ₃ layers which are amorphous of 5 nm or less in thickness and is in direct contact with the Al ₂ O ₃ layers. This is clear evidence that rGO is located at grain boundaries. When viewed as the whole rGO / Al composite compact, rGO can be evaluated as being uniformly dispersed in the material.

The upper left inset in FIG. 5 (c) is the SAED pattern of the Al ₂ O ₃ layer obtained from the portion of the filled circle, showing the halo pattern specific to the amorphous structure. The lower left inset in FIG. 5 (d) is the SAED pattern of the Al matrix taken from the portion of the filled circle, showing the diffraction spots according to the symmetry of the Al crystal.
The inset at the lower right of Fig. 5 (c) and the inset at the upper right of Fig. 5 (d) are EDS spectra of carbon line-scanned on a line marked with a short line (the horizontal axis is the line scan distance, vertical Characteristic X-ray intensity of carbon (axis), the number of graphene layers at grain boundaries can be determined. In the lower right inset of FIG. 5 (c), five peaks are shown, and the rGO platelets contain five layers of graphene. In the upper right inset in FIG. 5 (d), three peaks are shown, and the rGO platelets contain three layers of graphene. It is presumed that rGO platelets at grain boundaries are several layers of graphene (FLG) because platelets including 10 or more graphene layers are hardly observed.
From the above results, looking at FIG. 5 (a), FIG. 5 (a) shows that the flexible FLG is continuously present at the curved grain boundaries and fitted.

FIG. 6 (a) is a graph showing weight against temperature of GO in thermogravimetric analysis. FIG. 6 (b) is a narrow scan spectrum of the C1s region by XPS measurement of GO and GO after PCPS, respectively. FIG. 6 (a) shows that after PCPS at 600 ° C. for GO, there was a weight loss of about 40%. Further, in the C1s spectrum shown in FIG. 6B, after PCPS, peaks derived from C—O and COO disappear. From these results, it can be seen that GO was reduced after PCPS to form reduced rGO.

FIG. 7 (a) shows pure Al, 0.2 vol% FLG / Al composite compact, 0.4 vol% FLG / Al composite compact, 0.6 vol% FLG / Al composite compact after PCPS. An inverse pole figure (IPF) map in each electron backscattering analysis (EBSD) is shown. FIG. 7 (b) is a graph showing the particle diameter with respect to the volume ratio of rGO. The results shown in FIG. 7 (b) are also shown in Table 1 above.

FIG. 8 (a) is a lower magnification FE-SEM image of a cross-sectional view of a 0.4 vol% FLG / Al composite molded body obtained by PCPS. FIG. 8 (b) is a higher magnification FE-SEM image of a cross-sectional view of a 0.4 vol% FLG / Al composite compact obtained with PCPS.
The average grain size of the Al matrix in FIG. 8 is 4.8 μm.
Furthermore, the grain size after PCPS of the Al matrix is independent of the FLG concentration (rGO content) (Table 1). Grain boundaries containing FLG platelets, shown in FIG. 5, are observed as unbroken white outlines in FIG. These contours surround all particles with a substantially uniform thickness.

FIG. 9 is a reflection electron image and elemental mapping in EPMA analysis of a cross-sectional view of a 0.4 vol% FLG / Al composite compact obtained by PCPS. The line shown in “BSE” in FIG. 9 represents the grain boundary of Al particles, and the results of EPMA confirm that carbon (FLG) is uniformly dispersed in the grain boundary represented by this line. it can.

Therefore, FLG is uniformly dispersed at grain boundaries in the composite compact after PCPS to form a three-dimensional network along the grain boundaries. It was confirmed that the FLGs were uniformly distributed in the composite compact and that there was no significant aggregation.

FIG. 10 (a) shows an IPF map for a cross-sectional view (cross section perpendicular to the extrusion direction) of the 0.4 vol% FLG / Al composite compact after PCPS and HE. FIG. 10 (b) shows a reverse pole figure map in EBSD analysis of a longitudinal cross-sectional view (cross section parallel to the extrusion direction) of a 0.4 vol% FLG / Al composite compact after PCPS and HE. In FIG. 10 (b), ED indicates the extrusion direction, and TD indicates the transverse direction.
From FIGS. 10 (a) and 10 (b), it is understood that the three-dimensional network of the FLG is broken by the hot extrusion (HE), and the two-dimensional orientation is made in the extrusion direction. The average aspect ratio of the Al particles is four.
The combination of PCPS and HE is very effective for preparing fully compact FLG / Al composite compacts, all extruded samples have a relative density of 99.5% or more (Table 1) ).
The main Al particles are considered to be spindle-shaped and oriented along the extrusion direction and to exhibit strong tensile strength. The average grain size in the cross-sectional view of the extruded molded body is 2.2 μm (FIG. 10 (a)), which is smaller than the average grain size (4.6 μm) of the material after PCPS. Thus, it can be seen that the distance between two adjacent FLGs is reduced by 50% in the cross-sectional view.

FIG. 11 (a) is a TEM image of a hot extruded 0.4% by volume FLG / Al composite compact. FIG. 11 (b) is an HRTEM image of a hot extruded 0.4 vol% FLG / Al composite compact. FIG. 11 (c) is a TEM image of a hot extruded 0.4% by volume FLG / Al composite compact. Figure 11 (d) is an HRTEM image of a hot extruded 0.4 vol% FLG / Al composite compact.

The HRTEM observations shown in FIGS. 11 (a) and 11 (c) revealed that the individual FLG platelets were aligned in a direction parallel to the HE direction and integrated with the Al matrix. FIG. 11 (b) shows that FLG is in intimate contact with Al ₂ O ₃ on one side, but in direct contact with the Al matrix on the other side.
Figure 11 (d) shows that the FLG is in direct contact with the Al matrix on both sides.
It is inferred that the plastic flow of the Al matrix during the HE process breaks up the FLG network at grain boundaries and repositions the individual FLG platelets along the direction of plastic flow. Plastic flow may have contributed to stretching and flattening of the FLG plate. At the same time, the thin Al ₂ O ₃ layer on the Al powder surface was broken by plastic flow, which created a new surface of Al and brought the FLG and Al matrix into direct contact. It is clear from the Raman spectrum analysis shown in FIG. 4 that the quality of FLG after HE was maintained.

It was shown that the FLG / Al material was completely dense, most of the individual FLG platelets were aligned along the extrusion direction, little strain remained, and the FLG / Al was in direct contact at the interface .

Figure 11 (b) was taken from the position of the white square shown by the dashed line in Figure 11 (a); the upper left inset in Figure 11 (b) is the EDS spectrum of the Al ₂ O ₃ layer, Characteristic X-rays of O and Al elements can be confirmed. Also, the lower left inset is the SAED pattern of the Al matrix obtained from the filled white circle part, showing the diffraction spots according to the symmetry of the Al crystal. Further, the lower right inset is the EDS spectrum of carbon scanned on a line marked by a short line (horizontal axis: line scan distance, vertical axis: characteristic X-ray intensity of carbon). Nine peaks are confirmed from the EDS spectrum, and FLG in FIG. 11 (b) contains nine layers of graphene. The upper left inset in FIG. 11 (d) is a Fast Fourier Transform (FFT) pattern of the HRTEM image of the filled circle portion, showing the diffraction spots according to the symmetry of the Al crystal. Also, the lower right inset is the EDS spectrum of carbon line-scanned on a line marked by a short line (horizontal axis is line scan distance, vertical axis is characteristic X-ray intensity of carbon). Five peaks are confirmed from the EDS spectrum, and it is shown that FLG in FIG. 11 (d) contains five layers of graphene.
The number of peaks in the inset in FIG. 11B is nine.

Maximum tensile strength (UTS), yield strength, elongation of rGO / Al composite compacts (Examples 1 to 6) or pure Al (Comparative Example 1) after hot extrusion in Examples 1 to 6 and Comparative Example 1 Is shown in Table 2 below. FIG. 12 shows typical nominal tensile stress-tensile strain curves of 0.4 volume% FLG / Al composite compact (Example 4) and pure Al (Comparative Example 1).

The maximum tensile strength (UTS), yield strength, and elongation in Comparative Example 1 were measured to be 136.7 MPa, 110.3 MPa, and 24.3%, respectively. On the other hand, for example, UTS, yield strength and elongation of Example 4 were measured as 173.0 MPa, 146.2 MPa and 14.2%, respectively. Accordingly, in Example 4, the UTS significantly increased to 26.6% and the yield strength significantly increased to 32.5% relative to Comparative Example 1. Also in the other examples 1 to 3, 5 and 6, the UTS and the yield strength significantly increased relative to the comparative example 1.

Claims (5)

A carbon metal composite molded body of a flaky carbon material having a graphene skeleton and metal particles,
What is claimed is: 1. A carbon-metal composite molded body, wherein the molded body has a relative density of 90% or more and contains 25% by volume or less of carbon. The carbon metal composite molded article according to claim 1, wherein the metal particles in the molded article have an average aspect ratio of 2 or more. A method of producing a carbon-metal composite molded body using a flaky carbon material having a graphene skeleton and metal particles,
The method for producing a carbon metal composite formed body, comprising the step of sintering a flaky carbon material having a graphene skeleton and metal particles by pulse current pressure sintering. The method according to claim 3, wherein the metal particles are a single metal and / or an alloy of metal. The method for producing a carbon-metal composite molded body according to claim 3 or 4, further comprising the step of applying pressure to the molded body obtained in the sintering step to deform the molded body obtained in the sintering step.