JP2007277054A - Fullerene particle for thermal spray - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: fullerene particles which are easily supplied, more suitable for thermal spray, and useful for forming a uniform carbon film; a method for producing the same; the carbon film formed by thermal spray using the fullerene particles as a raw material; and a method for producing the carbon film. <P>SOLUTION: The fullerene particles are characterized in that the lower limit of the particle diameter is ≥50 μm and the upper limit is ≤800 μm, and the packing density is ≥0.7 g/cm<SP>3</SP>. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fullerene particle used for thermal spraying, a method for producing the same, a carbon film characterized in that the fullerene particles are used as a raw material and deposited by a thermal spraying method, and a method for producing the same.

It has already been proposed to produce a film containing fullerene using a thermal spraying method, and Patent Document 1 proposes to create a coating film in which nanocarbons including fullerene are dispersed by a thermal spraying method. .
Japanese Patent Laid-Open No. 2005-29873

  However, Patent Document 1 is merely a method of dispersing powdered nanocarbon itself on the surface of a metal or resin matrix in order to make nanocarbon exhibit a “ball-bearing function”, creating a fullerene thick film, A smooth carbon film obtained by reacting fullerenes could not be obtained.

  Further, although spraying by fullerene partially proceeds, there is a problem that it is difficult to form a film uniformly on the entire surface of the sprayed part.

  The present invention has been made in view of the above-mentioned points, and it is easy to supply powder, and fullerene granules suitable for thermal spraying for producing a uniform carbon film, a manufacturing method thereof, and the fullerene granules. It is an object of the present invention to provide a carbon film characterized in that a film is formed by a thermal spraying method and a manufacturing method thereof.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found a fullerene particle having a specific range of particle diameters and packing density, which is optimal as a spraying fullerene, and by using this, fullerene can be obtained. It has been found that a carbon film as a raw material can be obtained more efficiently.

A first aspect of the present invention provides a fullerene granule having a lower limit of particle size of 50 μm or more, an upper limit of 800 μm or less, and a packing density of 0.7 g / cm ³ or more. The problem is solved.

  According to a second aspect of the present invention, there is provided a method for producing fullerene granules according to the first aspect of the present invention, wherein fullerene is molded, pulverized, and classified by a sieve to solve the above problem. Is.

  According to a third aspect of the present invention, there is provided a carbon film characterized in that the fullerene particles according to the first aspect of the present invention are used as raw materials and are formed by thermal spraying to solve the above-mentioned problems. .

  According to a fourth aspect of the present invention, there is provided a carbon film manufacturing method characterized in that the fullerene particles according to the first aspect of the present invention are used as raw materials and a film is formed by a thermal spraying method to solve the above-mentioned problem. Is.

  By utilizing the present invention, it is possible to produce fullerene granules that are easy to supply powder and that are more suitable for thermal spraying to form a uniform carbon film. Moreover, if this fullerene granule is utilized, the thermal spraying which used fullerene as a raw material efficiently can be performed, and a uniform carbon film can be created over a wide range.

  Further, by mixing with other metals and ceramics, it becomes possible to create a composite film or functionally gradient material of metal, ceramics and carbon.

  Such an operation and gain of the present invention will be made clear from the best mode for carrying out the invention described below.

  The fullerene granules of the present invention, a method for producing the same, and a carbon film characterized by using the fullerene granules as a raw material to form a film by a thermal spraying method and a method for producing the same will be described in detail below.

<Fullerene>
Fullerene is a carbon cluster in which carbon atoms form a hollow closed shell structure, and the number of carbon atoms forming the closed shell structure is usually an even number of 60 to 130. Specific examples of fullerene include C ₆₀ , C ₇₀ , C ₇₆ , C ₇₈ , C ₈₂ , C ₈₄ , C ₉₀ , C ₉₄ , C ₉₆ , and higher-order carbon clusters having more carbon than these. Can be mentioned. In the present invention, each of these fullerenes and a mixture of the above fullerenes can be used as appropriate, and the number of carbons is not particularly limited, but from the viewpoint of easy production, etc., a mixture of fullerenes. , or it is preferable to use _{C 60.}

  Fullerene is usually a powdery aggregate obtained by sublimation or crystallization from a solution, but fullerene suitable as a raw material for the carbon film of the present invention is a particle having a specific particle size and packing density. It is necessary.

  The term “fullerene granules” as used herein refers to an aggregate of particles in which fullerene molecules are formed into one particle after undergoing molding, crushing, and classification steps. Specifically, when observed with a microscope, it refers to particles in which fullerene molecules are gathered in a particulate form, and after passing through a process such as sieving, which is applied with physical forces such as various classifications used industrially However, it means that the particle state is maintained.

  The lower limit of the particle size of the fullerene granules is 50 μm, preferably 100 μm, and the upper limit is 800 μm, preferably 600 μm.

  The method for obtaining the upper and lower limits of the particle size is to determine the particle size distribution according to the particle size distribution measuring method defined in JIS K1474 “Activated Carbon Test Method” (hereinafter simply referred to as “JIS K1474”), and pass 95% by mass or more. The upper limit of the opening value is determined as the lower limit, and the opening passing 5% by mass or less is defined as the lower limit.

  When the lower limit of the particle size is smaller than 50 μm, there are many fullerenes that are burned or sublimated by heat during spraying, and the film formation does not proceed uniformly. In addition, since the particles are light, they are not fixed by thermal spraying, so that the film formation does not proceed. Furthermore, there is a disadvantage that the tube is clogged when the particles are conveyed during spraying. On the other hand, if the particle diameter is too larger than the upper limit, it becomes difficult to pass through the pipe during the conveyance of the particles, the fluid supply is not constant, and it becomes difficult to form a uniform film.

The packing density is determined according to JIS K1474. The lower limit of the packing density is 0.7 g / cm ³ or more, preferably 0.8 g / cm ³ or more. If the packing density is lower than the lower limit, the strength is not sufficient, it will collapse when transporting the particles during spraying, it will break when spraying the flame, the plasma or when it collides with the substrate, and the film formation will not progress, or Even if the film formation proceeds, there is a disadvantage that it is not uniform.

The upper limit of the packing density is not particularly limited, but the density of the C ₆₀ complete crystal does not exceed 1.73 g / cm ³ and there is a space between the grains, so that it is 1.5 g / cm ³ or less, preferably 1 .2 g / cm ³ or less.

  Since fullerene can be molded by itself, a granule may be prepared with only 100% fullerene, but a small amount of binder may be added. A binder is 30 mass% or less, Preferably it is 10 mass% or less. When there is too much binder, the plastic deformation ability of fullerene during thermal spraying cannot be utilized, and film formation does not proceed. Examples of the binder include, but are not particularly limited to, waxes such as coal tar, pitch, sugar tightness, sap, starch, thermosetting resin, and carnauba wax.

  Also, when forming particles by adding metal and ceramic powder when forming fullerene, it becomes possible to create a composite film of metal, ceramic and amorphous carbon, or a functionally gradient material (FGM). In addition, when powder that easily generates carbides such as Ti and Si is added, fullerene reacts during spraying, and a composite film of metal carbide and amorphous carbon can be formed.

<Method for producing fullerene granules>
The fullerene granules used in the present invention are obtained by molding, crushing, and classifying. As a forming method, any method may be used as long as the particles having the packing density of the present invention are obtained. For example, various molding machines such as a compression molding machine, a roller-type compressor, an extrusion molding machine, and an injection molding machine can be used. In particular, a roller type compressor is suitable for mass production and is preferable.

The molding pressure is usually 4.904 × 10 ^{5 to} 9.807 × 10 ⁸ Pa (0.005 to 10 t / cm ² ), preferably 9.807 × 10 ^{6 to} 9.807 × 10 ⁸ Pa (0 0.1 to 10 t / cm ² ). Moreover, in the case of a roller-type compressor in which molding pressure is difficult to obtain, the roll diameter is preferably 50 to 2000 mm, the effective width of the roll is 10 to 1000 mm, and the applied pressure of the roller is preferably 100 to 5000 kN.

  If the molding pressure is too low, the packing density within the range of this patent cannot be obtained, and the powder breaks down during transportation of particles during spraying, in the frame or plasma, resulting in a small particle size. Not proceed.

  Next, the obtained molded body is crushed. The crushing may be performed by any method as long as the particles having the particle diameter of the present invention are obtained, and various pulverizers such as a ball mill, a hammer mill, and a mixer are used.

  Next, classification is performed. Although various classification methods used industrially can be used for classification, classification by sieving is preferable because it is suitable for mass production. The classification is carried out using a mesh sieve having desired upper and lower openings defined in JIS Z8801-1 "Sieving sieve for test-Part 1: Metal steel sieve". For the operation of the sieve, a manual or automatic sieve shaker is used and shaken for 1 to 30 minutes.

<Spraying>
In the present invention, a carbon film is formed on an object by spraying particles of fullerene onto the object by a thermal spraying method. The thermal spraying method is not particularly limited as long as it is a commonly used thermal spraying method, but a method of forming a powder film at a higher speed is preferable. In the case of flame spraying, high-speed flame spraying (HVOF). Alternatively, plasma spraying under normal pressure or reduced pressure is preferable. Further, it is possible to use a cold spray that causes the powder to collide at a supersonic speed. The atmosphere is not problematic even under normal air, but in order to prevent oxidation and combustion of fullerene, a low oxidation atmosphere, an inert atmosphere, or a reduced pressure is preferable. Examples of the low-oxidation atmosphere include combustion exhaust gas, and examples of the inert atmosphere include argon, helium, and nitrogen.

When the produced carbon film is measured by Raman spectroscopy, a broad amorphous carbon peak is observed in the vicinity of 1200 to 1600 cm ⁻¹ . The peak derived from fullerene is not observed at all or is minute even if observed. That is, the carbon film obtained by the present invention is an amorphous carbon film made of substantially amorphous carbon.

  The film thickness varies depending on the particle size of the fullerene used as a raw material and the application of the film, but the lower limit is 0.5 μm, preferably 1 μm, more preferably 10 μm, and the upper limit is 1 mm, preferably 300 μm. This is appropriately adjusted according to the spraying amount of the fullerene granules.

  In thermal spraying, it has been generally considered that film formation proceeds only with a powder that is melted or semi-molten at high temperatures. However, by using a fullerene that is a molecular crystal and has plastic deformability, thermal spraying is possible even for a carbon material having no melting point. However, fullerenes sublime at high temperatures, react with fullerenes, carbonize, or burn if oxygen is present. Although the particles during thermal spraying are exposed to high temperatures instantaneously, even if the surface of the particles sublimates, carbonizes, or burns during that time, the large particles are used inside the particles. Deformable fullerene remains and film formation proceeds. In spraying, generally, a method of sucking up with a reduced pressure is used to supply granules, but fullerene having a small particle size may clog the supplied pipe. Further, when the particle size is large, the supply is not constant, and the film formation is nonuniform.

  Hereinafter, the present invention will be specifically described by way of examples. In addition, this invention is not limited to the form of the Example shown below, unless the summary is exceeded.

(Example)
Raw fullerene granules are mixed fullerene only (manufactured by Frontier Carbon Corporation nano arm _{mix, C} 60: _60% by _{weight, C} 70: 22 wt%, the other molecular weight high fullerenes: 18 mass% fullerene mixture) using However, no binder was used. When 10 kg of mixed fullerene was molded at a roll pressure of 175 kN using a roll type compressor (manufactured by Shinto Kogyo, compacting machine BCS25, roll diameter 228 mm, roll effective width 48 mm), the width was 48 mm and the length 30 A plate-like molded body of ˜200 mm was obtained. The molded body was pulverized with a mixer, and manually shaken for 5 minutes using 150 μm and 500 μm mesh sieves to obtain fullerene granules having a particle size of 150 to 500 μm. When the packing density was measured according to JIS K1474, it was 0.93 g / cm ³ .

  Using this fullerene granule as a raw material, DC arc plasma spraying was performed on the mild steel surface in an argon atmosphere. As the thermal spraying conditions, a vacuum chamber was used, argon substitution was performed, the pressure was 66.7 kPa (500 Torr), the plasma output was 34.85 kW (voltage 41 V, current 850 A), the argon flow rate was 80 L / min, and the torch distance was It was set to 130 mm and 20 reciprocating scans were performed at a speed of 500 cm / min. For powder supply, a powder supply apparatus was used under the conditions of 6.1 L / min of argon as a carrier gas and 5 g / min of fullerene input. As a result, it was confirmed that the fullerene granules were supplied without collapsing, and a carbon film was formed uniformly over the entire surface of the mild steel by thermal spraying.

About the surface of this mild steel, Raman spectroscopy apparatus: Nicolet Almega XR (manufactured by Thermo Electron Co., Ltd.), excitation wavelength: 532 nm, measurement time: 10 seconds × 6 times, resolution: about 10 cm ⁻¹ Measurements were made. As a result, a broad amorphous carbon peak was observed in the vicinity of 1200 to 1600 cm ⁻¹ , and it was confirmed that an amorphous carbon film was formed on the surface of the mild steel.

(Comparative Example 1)
As fullerene granules, fullerene was formed and crushed by the same method as in Example, and then classified using a 50 μm mesh sieve to obtain fullerene granules of 50 μm or less. Using this fullerene granule, thermal spraying was performed under the same conditions as in the examples. As a result, it was found that the tube was gradually clogged during the supply of fullerene particles, and the powder was not supplied uniformly. Moreover, the thermal spraying did not proceed only partially, and a uniform carbon film could not be formed on the entire surface.

(Comparative Example 2)
Fullerene granules were formed and crushed by the same method as in Example, and then classified using an 800 μm mesh sieve to obtain fullerene granules of 800 μm or more. Using this fullerene granule, thermal spraying was performed under the same conditions as in the examples. As a result, when fullerene granules were supplied, powder having a large particle size was sometimes clogged, and the powder was not supplied uniformly. Further, the plasma flame also pulsated and a stable flame could not be formed, and spraying did not proceed only partially, and a uniform carbon film could not be formed on the entire surface.

(Comparative Example 3)
Except for setting the roll pressing force to 90 kN, molding, crushing, and classification were performed in the same manner as in the examples, and fullerene granules having a particle size of 150 to 500 μm were obtained. The bulk density was 0.61 g / cm ³ .

  Using this fullerene granule, thermal spraying was performed under the same conditions as in the examples. As a result, thermal spraying progressed only partially, and a uniform carbon film could not be formed on the entire surface. Further, since the phenomenon of gradually clogging the supply pipe was observed when the thermal spraying was continued, it is considered that the fullerene particles were pulverized to a small particle size at the time of supply.

  Although the present invention has been described with reference to the most practical and preferred embodiments at the present time, the present invention is not limited to the embodiments disclosed herein. The fullerene particles that can be changed as appropriate without departing from the gist or concept of the invention that can be read from the claims and the entire specification, the method for producing the fullerene particles, and the use of the fullerene particles as a raw material Also, it should be understood that a carbon film formed by thermal spraying and a manufacturing method thereof are also included in the technical scope of the present invention.

Claims (4)

A fullerene granule having a lower limit of particle size of 50 μm or more, an upper limit of 800 μm or less, and a packing density of 0.7 g / cm ³ or more. The method for producing fullerene granules according to claim 1, wherein the fullerene is molded, crushed, and classified by a sieve. A carbon film formed by spraying using the fullerene particles according to claim 1 as a raw material. A method for producing a carbon film, wherein the fullerene particles according to claim 1 are used as a raw material, and a film is formed by a thermal spraying method.