Structure, sliding member, and methods for manufacturing these

Abstract

The present invention has a step for immersing an iron oxide in a fullerene-containing benzotriazole solution, the immersion being carried out until the fullerene concentration of the benzotriazole solution decreases to a level lower than that before the immersion, whereby a structure having fullerene on an iron oxide surface is obtained. In the present invention, a sliding body in which the iron oxide surface having fullerene in the structure is positioned on a sliding surface thereof is used.

Description

Structure and sliding member, and manufacturing method thereof

[0001] The present invention relates to a structure, a sliding member, and a method for manufacturing the same.

[0002] It is known that the presence of fullerene on the surface improves the sliding properties and releasability.

[0003] For example, Patent Document 1 discloses a processed part or the like in which nanometer-order fullerenes are present on the processed surface (new metal surface) at a coverage of 1.0 area % or more and 90.0 area % or less, and further states that fullerenes once adsorbed on the new surface do not easily detach.

[0004] Furthermore, Patent Document 2 discloses that a coating containing fullerenes is formed on the surface of an object such as a mold coated with a carbon film containing at least one type of nanocarbon selected from the group consisting of carbon nanocoils, carbon nanotubes, and carbon nanofilaments by applying an alcohol containing fullerenes with a brush to the surface of the object. Patent Document 2 also discloses that while fullerenes are effective in improving surface properties, they have the disadvantage of easily falling off from the mold surface, but that according to this invention, fullerenes can be trapped between nanocarbons extending fibrously from the surface, thereby preventing fullerenes from falling off from the mold surface.

[0005] International Publication No. 2020 / 090964 International Publication No. 2010 / 067786

[0006] As described above, fullerenes have been applied to specific surfaces, but no fullerenes have been applied directly to the surface of an iron member on which a passive film or the like has been formed (i.e., an iron oxide surface).

[0007] An object of the present invention is to provide a structure and a sliding member that solve the above problems, as well as a method for manufacturing the same.

[0008] In order to solve the above problems, the present invention provides the following means. [1] A structure comprising iron oxide and fullerenes, wherein the fullerenes are adsorbed onto the surface of the iron oxide. [2] The structure according to the preceding item [1], wherein the adsorption is chemical adsorption. [3] The structure according to the preceding item [1] or [2], wherein the iron oxide is magnetite. [4] The structure according to any one of the preceding items [1] to [3], wherein the fullerenes cover the entire surface of the iron oxide. [5] The structure according to any one of the preceding items [1] to [4], further comprising metallic iron, wherein the iron oxide is a film formed on the metallic iron surface. [6] A sliding member arranged such that the fullerene-bearing iron oxide surface of the structure according to any one of the preceding items [1] to [5] serves as a sliding surface. [7] A method for producing a structure according to any one of the preceding items [1] to [5], comprising the step of immersing iron oxide in a benzotriazole solution containing fullerenes, wherein the immersion is continued until the fullerene concentration in the benzotriazole solution decreases compared to before the immersion. [8] The method for producing a structure according to the preceding item [7], wherein the benzotriazole solution further contains alcohol. [9] The method for producing a structure according to the preceding item [7] or [8], wherein the immersion is continued until the fullerene concentration in the benzotriazole solution decreases compared to before the immersion and then stops changing.

[10] The method for producing a structure according to any one of the preceding items [7] to [9], further comprising, after the immersion, washing the structure with alcohol and drying it.

[11] The method for producing a slide member, comprising obtaining a structure by the method according to any one of the preceding items [7] to

[10] , and disposing the fullerene-containing iron oxide surface of the structure on a slide surface.

[0009] According to the present invention, the sliding properties of the iron oxide surface can be improved.

[0010] Hereinafter, embodiments of the present invention will be described in detail. Note that the embodiments shown below are specifically described to provide a better understanding of the gist of the invention, and do not limit the present invention unless otherwise specified. Furthermore, in this specification, the use of "to" to indicate a range of numerical values ​​means that the numerical values ​​before and after it are included as the lower and upper limits, unless otherwise specified.

[0011] (Structure) The structure of this embodiment has at least a surface portion or surface layer portion made of iron oxide and contains iron oxide and fullerenes. Preferably, the structure of this embodiment has at least a surface portion or surface layer portion made of iron oxide, and the fullerenes are adsorbed to the surface of the iron oxide. The adsorption may be, for example, physical adsorption or chemical adsorption. However, from the viewpoint of the difficulty of fullerenes being desorbed from the iron oxide surface, chemical adsorption, which forms a chemical bond that is irreversible, is preferable to physical adsorption, which is reversible.

[0012] The iron oxide may be, for example, FeO or Fe ３ O ４ (Magnetite), Fe ２ O ３ From the viewpoint of ease of adsorption of fullerenes, which will be described later, those with a higher oxidation number of iron are more preferable, and magnetite is more preferable from the viewpoint of wide range of uses such as formation of a passive film.

[0013] The fullerene is C ６０ , C ７０ , higher fullerenes, fullerene derivatives, or mixtures thereof. Among fullerenes, C ６０ or C ７０ is preferred, and C ６０ When the fullerene is a mixture, C ６０ is preferably contained in an amount of 50% by mass or more.

[0014] The more the amount of fullerene adsorbed, the better. ２ The maximum number of fullerene molecules per ６ pieces / μm ２ This corresponds to a state in which fullerenes cover the entire surface of the iron oxide, that is, a state in which fullerene molecules are closely packed and arranged in a single layer on the surface. In addition, the lower limit of the amount of adsorption is set to 1 particle / μm from the viewpoint of reducing the coefficient of friction. ２ More than 10 is preferable. ２ pieces / μm ２More than 10 is preferable, and taking into consideration the long-term stability such as the desorption of adsorbed molecules, ４ pieces / μm ２ More preferably, 10 ５ pieces / μm ２ The above is particularly preferred.

[0015] The iron oxide may be a film formed on the surface of metallic iron. In this case, the structure of this embodiment includes not only iron oxide and fullerenes but also metallic iron constituting a part of the structural member. Furthermore, the film is preferably a passive film from the viewpoint of protecting the metallic iron portion.

[0016] (Sliding member) The sliding member of this embodiment has the structure and is arranged so that the iron oxide surface containing fullerenes of the structure serves as a sliding surface. Of a pair of sliding members forming a sliding part, one may be the sliding member of this embodiment, but from the viewpoint of reducing frictional resistance, it is preferable that both are the sliding members of this embodiment. In addition, lubricating oil, lubricating grease, or the like may be applied to the sliding surface.

[0017] (Method for Manufacturing a Structure) The method for manufacturing a structure of this embodiment includes a step of immersing iron oxide in a benzotriazole solution containing fullerenes, and the immersion is continued until the fullerene concentration in the benzotriazole solution decreases compared to before the immersion. This decrease in concentration occurs because fullerenes are adsorbed onto the iron oxide surface. In other words, it can be considered that fullerenes equivalent to the decrease in fullerene concentration are adsorbed onto the iron oxide surface.

[0018] The immersion may be performed by spraying or applying the benzotriazole solution so that the surface of the iron oxide is covered with the benzotriazole solution. However, from the viewpoint of facilitating the determination of the fullerene concentration, which will be described later, it is preferable to submerge the entire iron oxide in the benzotriazole solution.

[0019] The amount of fullerene contained in the benzotriazole solution may be an amount sufficient to compensate for the amount of adsorption of fullerene, and is preferably 1.1 times or more of the adsorption amount, and from the viewpoint of enabling multiple immersion, is more preferably 10 times or more, and even more preferably 100 times or more. In either case, the amount of fullerene in the benzotriazole solution in which a saturated concentration of fullerene is dissolved is the upper limit. However, from the viewpoint of increasing the analytical accuracy of the amount of decrease in the fullerene concentration, it is preferably 1.1 to 100 times the adsorption amount, and more preferably 1.1 to 20 times.

[0020] Such a range of the fullerene amount is usually easily achieved by setting the fullerene concentration in the benzotriazole solution to preferably 10 ppm by mass to 500 ppm by mass, more preferably 30 ppm by mass to 100 ppm by mass.

[0021] Since benzotriazole is a solid at room temperature, it may be used by heating it to or above its melting point (about 100°C). However, from the viewpoint of ease of handling, an alcohol may be added to the benzotriazole to make it a liquid at a temperature that is easy to handle, such as room temperature, to form a mixed solvent. From the viewpoint of availability, the alcohol is preferably at least one selected from methanol, ethanol, 1-propanol, and 2-propanol. For example, adding ethanol in a mass ratio of 1:1 to 1:1 with respect to benzotriazole allows it to be sufficiently handled as a liquid at room temperature, and adding 1:1 to 3:1 allows it to be handled as a liquid even at lower temperatures.

[0022] When iron oxide is immersed in a benzotriazole solution containing fullerenes, the fullerenes are adsorbed onto the surface of the iron oxide, resulting in a decrease in the fullerene concentration in the solution. The immersion may be terminated when a desired amount of fullerenes is adsorbed, but from the viewpoint of maximizing the amount of adsorbed fullerenes, it is preferable to continue the immersion until the fullerene concentration in the benzotriazole solution decreases compared to before the immersion and then no longer changes.

[0023] After the immersion, the structure may be stored by applying or immersing it in machine oil, as with general machine parts, but from the viewpoint of ease of handling, it is preferable to wash the structure with alcohol and then dry it. From the viewpoint of ease of availability, the alcohol is preferably at least one selected from methanol, ethanol, 1-propanol, and 2-propanol.

[0024] Fullerenes are adsorbed onto the iron oxide surface of the structure obtained in this way. Even when this structure is washed with a good solvent for fullerenes, such as toluene, almost no fullerenes are eluted, and it is believed that most of the adsorbed fullerenes are chemically adsorbed. In chemical adsorption, it is thought that iron oxide and fullerenes are bonded via oxygen atoms.

[0025] (Method for manufacturing a sliding member) In the sliding member of this embodiment, the iron oxide surface having the fullerenes of the structures is arranged on the sliding surface. A plurality of the structures may be arranged according to the shape of the sliding surface, or the sliding member may be formed by forming an oxide film on the surface of an iron member having the shape of the sliding member and adsorbing fullerenes onto the surface.

[0026] Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to a specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

[0027] The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0028] Solution: A solution of benzotriazole and ethanol in a mass ratio of 1:1 (hereinafter referred to as "mixed solvent") was prepared.

[0029] As a benzotriazole solution containing fullerene, a solution (hereinafter referred to as "immersion liquid") was prepared by adding fullerene to a mixed solvent so that the fullerene concentration was 56.9 ppm by mass.

[0030] Measurement Method: (Measurement of Fullerene Concentration) Using a high performance liquid chromatograph (Shimadzu Corporation, Prominence-i LC-2030C 3D), the fullerene concentration in the sample was quantified using a solution such as an immersion liquid under the following conditions.

[0031] Column: YMC-Pack ODS-AM (150 mm x 4.6 mm) manufactured by YMC Co., Ltd. Developing solvent: 1:1 (volume ratio) mixture of toluene and methanol Detection: absorbance (wavelength 309 nm) If dilution was necessary, the sample was diluted in advance with the above-mentioned developing solvent. A calibration curve was also created using the fullerene used in sample preparation.

[0032] When oxidized fullerenes were contained in the sample, they were converted into unoxidized fullerenes and added to the fullerene concentration to avoid mistaking oxidized fullerenes generated by the side reaction between iron oxides and fullerenes for adsorbed fullerenes.

[0033] (Measurement of Total Adsorption Amount) The fullerene concentration in the immersion liquid before immersion and the fullerene concentration in the immersion liquid after immersion were measured, and the total adsorption amount of fullerene was calculated from the difference between the two fullerene concentrations using the following formula (1).

[0034] Total adsorption amount (pieces / μm ２ ) = K × (C ０ -C １ ) × V １ / (S × M) ... (1) where K is a constant, 6.02 × 10 ９ C ０ C: fullerene concentration in the immersion liquid before immersion (ppm by mass) １ V: fullerene concentration in the immersion liquid after immersion (ppm by mass) １ : Volume of immersion liquid (ml) S: Surface area of ​​the iron oxide portion of the structure (cm ２ M: molecular weight of fullerene used, e.g., C ６０ If so, 720

[0035] (Measurement of physical adsorption amount and chemical adsorption amount) 1 part by mass of a sample of the structure obtained in each example was immersed in 2 parts by mass of toluene and stirred for about 30 minutes. The physical adsorption amount was calculated from the concentration of fullerene in toluene after this immersion using the following formula (2).

[0036] Physical adsorption amount (pieces / μm ２ ) = K × C ２ ×V ２ / (S × M) ... (2) where K is a constant, 6.02 × 10 ９ C ２ V: concentration of fullerene in toluene after immersion in toluene (ppm by mass) ２ : Volume of toluene (ml) S: Surface area of ​​the iron oxide portion of the structure (cm ２ M: molecular weight of fullerene used, e.g., C ６０ If so, 720

[0037] Further, the difference between the total adsorption amount and the physical adsorption amount was defined as the chemical adsorption amount, as shown in the following formula (3).

[0038] Chemical adsorption amount (pieces / μm ２ ) = Aa - Ap (3) where, Aa: total adsorption amount (pieces / μm ２ ) Ap: Physical adsorption amount (pieces / μm ２ )

[0039] (Measurement of Friction Coefficient) Using the structure as a sample, a ball-on-disk friction tester was used to measure the average friction coefficient of the structure sliding surface in a range of 180 to 220 sliding cycles (sliding distance equivalent to 4.5 m to 5.5 m) under the conditions of a ball (material SUJ2, diameter 6 mm), lubricant (Diana Fresia P-46, manufactured by Idemitsu Kosan Co., Ltd.), a load of 45 N, a circular orbit of 8 mm diameter, and a rotation speed of 30 rpm (linear velocity 13 mm / sec).

[0040] Example 1: 0.500 g of iron oxide (II) powder (FeO, specific surface area 100 cm) was used as iron oxide. ２ / g, surface area 50cm ２) was used, 10 g of immersion solution was added to it, and it was immersed while shaking for about 30 minutes. Thereafter, the iron oxide powder was removed from the immersion solution, washed with ethanol, air-dried, and then dried on a hot plate at 50°C to obtain a structure. The obtained structure was used as a sample to measure the total adsorption amount, physical adsorption amount, and chemical adsorption amount. The results are shown in Table 1.

[0041] Example 2: 0.425 g of iron (III) oxide powder (Fe) was used instead of iron (II) oxide powder. ２ O ３ , specific surface area 118cm ２ / g, surface area 50cm ２ The same operations and measurements were carried out as in Example 1, except that the same ion exchange resin as in Example 1 was used. The results are shown in Table 1.

[0042] Comparative Example 1: 0.655 g of iron powder (Fe, specific surface area 76 cm) was used instead of iron (II) oxide powder. ２ / g, surface area 50cm ２ The same operations and measurements were carried out as in Example 1, except that the same ion exchange resin as in Example 1 was used. The results are shown in Table 1.

[0043] Comparative Example 2: The same procedures and measurements were carried out as in Example 1, except that ethanol was used instead of the mixed solvent. The results are shown in Table 1.

[0044] Comparative Example 3: The same operations and measurements were carried out as in Example 1, except that a mixed solvent (i.e., fullerene concentration 0) was used instead of the immersion liquid. The results are shown in Table 1.

[0045]

[0046] The results of Examples 1 and 2 and Comparative Examples 1 to 3 show that when benzotriazole and fullerenes are included in the immersion solution, fullerenes are chemically adsorbed to iron oxide. In Example 1, an increase in the total adsorption amount of fullerenes was observed when the immersion time was 30 minutes compared to 25 minutes, but in Example 2, there was almost no difference between the immersion times of 25 minutes and 30 minutes. This suggests that the upper limit of the adsorption amount was almost reached in Example 2.

[0047] Example 3: A 5 mm thick steel (SUJ2 material) test substrate with a 13 mm square mirror-finished surface on one side was immersed in an 11% by mass sodium hydroxide aqueous solution at 80°C for 3 minutes to form an iron oxide layer on the surface. Under these conditions, the iron oxide layer is thought to be a mixture of iron (II) and iron (III) oxides.

[0048] The test substrate on which the iron oxide layer was formed was washed with water and then with ethanol, and then immersed in 10 mL of an immersion solution for 35 minutes, with ultrasonic agitation for the first 5 minutes during immersion, and then allowed to stand.

[0049] The substrate was then removed from the immersion solution and washed by suspending it in ethanol. The ethanol on the substrate surface was then removed by spraying nitrogen gas onto the substrate, and the substrate was dried on a hot plate at 50°C for 10 minutes to obtain a structure. The coefficient of friction of the obtained structure was measured using the mirror-finished surface as the test surface. The results are shown in Table 2.

[0050] Comparative Example 4: The same operations and measurements were carried out as in Example 3, except that a mixed solvent (i.e., fullerene concentration 0) was used instead of the immersion liquid. The results are shown in Table 2.

[0051] Comparative Example 5: The same operations and measurements were carried out as in Example 3, except that the sample was not immersed in the aqueous sodium hydroxide solution. The results are shown in Table 2.

[0052]

[0053] In Example 3, the oxide layer was treated in a manner similar to that of Examples 1 and 2, and therefore it is believed that fullerenes were chemically adsorbed to the oxide layer. Also, as can be seen from Table 2, the friction coefficient in Example 3 was about 5% smaller than that in Comparative Examples 4 and 5. It is believed that the friction-reducing effect of fullerenes was not apparent in Comparative Example 4 because fullerenes were not adsorbed and in Comparative Example 5 because an iron oxide layer was not formed on the test surface of the substrate.

[0054] This application claims priority based on Japanese Patent Application No. 2021-168395 filed with the Japan Patent Office on October 13, 2021, and the entire contents of Japanese Patent Application No. 2021-168395 are incorporated by reference into this application.

[0055] The structure of the present invention can be usefully applied to slide members and the like.

Claims

1. A structure comprising an iron oxide and a fullerene, the fullerene being adsorbed on the surface of the iron oxide.

2. 2. The structure of claim 1, wherein the adsorption is chemical adsorption.

3. 3. The structure according to claim 1, wherein the iron oxide is magnetite.

4. 3. The structure according to claim 1, wherein the fullerenes cover the entire surface of the iron oxide.

5. The structure according to claim 1 or 2, further comprising metallic iron, wherein the iron oxide is a film formed on the surface of the metallic iron.

6. A sliding member in which the surface of the iron oxide having the fullerenes of the structure according to claim 1 is arranged to serve as a sliding surface.

7. A method for manufacturing the structure according to claim 1, comprising: immersing the iron oxide in a benzotriazole solution containing the fullerene; The immersion is continued until the concentration of the fullerene in the benzotriazole solution decreases compared to before the immersion. A method for producing a structure having fullerenes on the surface of an iron oxide.

8. The method for manufacturing a structure according to claim 7 , wherein the benzotriazole solution further contains alcohol.

9. The method for manufacturing a structure according to claim 7 or 8, wherein the immersion is continued until the concentration of the fullerene in the benzotriazole solution decreases compared to before the immersion and then stops changing.

10. The method for manufacturing a structure according to claim 7 or 8, further comprising the step of washing the structure with alcohol and drying it after the immersion.

11. A method for producing a sliding member, comprising obtaining a structure by the method according to claim 7 or 8, and disposing the iron oxide surface of the structure having the fullerenes on a sliding surface.