JP2525161B2 - Glass-like carbon composite material and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a glassy carbon composite material. More specifically, the present invention relates to a composite material containing glassy carbon as a main component and having high wear resistance and a small friction coefficient, which is excellent as a material for precision processed parts.

[Summary] The present invention, in a composite material containing glassy carbon as a main component, by mixing specific ceramic ultrafine particles as a reinforcing component, the friction resistance with the mating material in sliding contact is small and the mating material is damaged. In addition, the present invention provides a glassy carbon composite material having excellent wear resistance and durability.

[Conventional technology]

At present, various devices for recording and reproducing by using a sheet or film having a magnetic layer or paper as a recording medium are commercially available. These recording / reproducing devices include a large number of components that constantly or temporarily slide in contact with a recording medium. Examples of this type of component include a flexible disk head slider, a hard disk flying slider, a thermal printing head, and a magnetic head. These parts are required to have characteristics of excellent durability and not damaging a recording medium which is in sliding contact with the parts. Also,
These parts, especially magnetic heads, require ultra-precision machining of several microns to several tens of microns, and require precise machining characteristics of the material.

As materials for such components, silicon dioxide, alumina, silicon carbide, hard glass, alumina-based ceramics, ferrite, calcium titanate, barium titanate, and the like are generally used. However, these materials are suitable for precision parts, but have high hardness and poor slidability with the recording medium, and thus may damage the recording medium.

A graphite material is known as a material having extremely good slidability, but has a high abrasion property, and it is difficult to maintain a stable shape over a long period of time. In addition, sufficient densities cannot be obtained due to the constituent particles, and thus they are not suitable for use as precision parts.

Therefore, the present inventors have conducted various studies in order to solve the above-mentioned drawbacks, and have found that glassy carbon can solve the above-mentioned drawbacks, and filed a patent application earlier. This application is disclosed in JP-A-59-8432.
It is disclosed as Japanese Patent Laid-Open No. 5 and Japanese Patent Laid-Open No. 59-144019.

Glassy carbon is a material with moderate lubricity,
When sliding with a mating material, the glassy carbon itself has a property of being worn first before the mating material is damaged.

[Problems to be solved by the invention]

However, as a result of further tests, it was found that the glass-like carbon alone may cause insufficient wear resistance due to the roughness and hardness of the surface of the mating material.

The present invention has a low frictional resistance with a mating material, does not damage the mating material, without applying a lubricant to the surface of the mating material in sliding contact and without providing a protective film on the surface of the mating material. It is an object of the present invention to provide a composite material capable of producing a sliding contact part having excellent wear resistance and durability.

[Means for solving problems]

The glassy carbon composite material of the present invention contains glassy carbon as a main component, does not contain graphite and carbon fiber, and has ultrafine metal oxide particles, ultrafine metal nitride particles, and metal carbide particles having an average particle diameter of 1 μm or less as a reinforcing component. It is characterized by containing one or more kinds of ultrafine particles selected from ultrafine particles and metal boride ultrafine particles.

As the ultrafine particles, alumina ultrafine particles, silicon carbide ultrafine particles, titanium carbide ultrafine particles, and silicon oxide ultrafine particles are particularly suitable.

Examples of the glassy carbon that is the main component of the glassy carbon composite material of the present invention include glassy carbon obtained by carbonizing a thermosetting resin such as a furan resin and a phenolic resin, and a glassy carbon that can be heat-cured such as a phenolic resin. Glassy carbon obtained by carbonizing a resin modified by polymerization or co-condensation is used.

In particular, nonporous glassy carbon obtained from a thermosetting resin which can contain 20% or more of water in the state of an initial condensate, that is, JP-A-60-171208, JP-A-60-17
1209, JP 60171210, JP 60-17
It is desirable to use the glassy carbon disclosed in Japanese Patent No. 1211.

These glassy carbons are materials in an amorphous state, have moderate lubricity, and when the recording medium slides,
It is a material that wears itself before the surface film of the recording medium is damaged.

The ultrafine particles mentioned here are particles having a particle size of 1 μm or less, and preferably particles having a particle size of 0.1 μm or less. As a method for producing these ultrafine particles, there are a gas evaporation method, a plasma evaporation method, a gas phase chemical reaction method and the like as a method utilizing a gas phase reaction, and a precipitation method and a melt spray pyrolysis as a method utilizing a liquid phase reaction. The law is known. The present invention does not have a problem in its manufacturing method.

The particle size of the ultrafine particles differs depending on the use of the glassy carbon composite, but in order not to impair the homogeneity of the glassy carbon and for the homogeneity and stability of the liquid pre-curing precursor and the mixed dispersion, Ultrafine particles having a particle size of 0.1 μm or less are desirable.

Examples of such ultrafine particles include silica ultrafine particles (Aerosil 130, primary particle size: about 16 nm), aluminum oxide ultrafine particles (aluminum oxide C, primary particle size: about 20 nm), titanium oxide manufactured by Nippon Aerosil Co., Ltd. Ultrafine particles (titanium oxide P25, primary particle size about 21n
m) etc. can be used.

The content of the ultrafine particles is desirably in the range of 0.005 to 0.2 in volume ratio to glassy carbon, and more preferably 0.005 to 0.1.
The range of is desirable. In this range, precision workability,
Excellent in wear resistance and friction coefficient. When the content of the ultrafine particles is small, the effect of mixing cannot be obtained. On the other hand, if the amount is too large, the precision workability decreases, and the friction coefficient increases.

A second invention of the present invention is a method for producing the above-mentioned glassy carbon composite material, wherein the curing precursor of the thermosetting resin which can contain 20% or more of water in the state of the initial condensate has an average particle diameter of One or more ultrafine particles selected from alumina ultrafine particles of 1 μm or less, titanium oxide ultrafine particles, silicon oxide ultrafine particles, and silicon carbide ultrafine particles are mixed, the resin is cured, and the temperature is kept at 800 ° C. or higher in an inert atmosphere. It is characterized in that it is carbonized and baked at a temperature.

Further, as the thermosetting resin, a resin which can contain 20% by weight or more of water in an initial condensate state before curing is desirable.

In the production method of the present invention, a composite material of ultrafine particles and a curing precursor of a thermosetting resin is molded by a commonly used method such as casting, compression, extrusion or injection, and then heat treatment in an inert atmosphere. To do. It is desirable to disperse the ultrafine particles in the initial condensate of the thermosetting resin. Further, the ultrafine particles can be subjected to a pretreatment in the same manner as in the method for producing a fiber reinforced plastic (FRP). As such pretreatment, surface treatment of ultrafine particles,
A surfactant is added to highly disperse the ultrafine particles, physical high shearing force is dispersed, and the like, and it is used to increase the reliability of the glassy carbon composite material finally produced.

[Work]

The glassy carbon composite material of the present invention is a material in which the ultrafine inorganic particles are dispersed in glassy carbon to improve the wear resistance while maintaining the low friction property of the glassy carbon. Therefore, by using this composite material, it is possible to manufacture a sliding contact part having low friction resistance with a mating material, not damaging the mating material, and having excellent wear resistance and durability.

The mating material differs depending on the application of the sliding contact part. For example, when the sliding parts are used for a magnetic head, a floppy disk head slider, or a hard disk flying slider, the mating material is a floppy disk, a hard disk, a magnetic tape, or the like. The material is paper or a polymer sheet, and is steel such as SUJ2 when used as a ball retainer for a bearing. As described above, the mating member may have any shape such as a flat surface, a curved surface, or a thread shape, and the shape may be unchanged or flexible.

When this material is used, for example, in a sliding contact part with a recording medium, a lubricant is not used between the recording medium and
It has advantages that the lubricity can be maintained for a long time, the surface of the recording medium is not damaged, and the material itself is less worn.

In addition, static electricity is not generated due to the conductivity of the glassy carbon, and there is an effect that dust hardly adheres to a portion in contact with the disk recording medium and the recording medium itself.

The glassy carbon composite material of the present invention is specifically,
It can be used for sliding contact parts such as head sliders for flexible disks, floating sliders for hard disks, thermal printing heads, magnetic heads, ball retainers for bearings, rings for high-speed twisting, vane pump blades, and various bobbins and guides. These parts may be entirely composed only of the glassy carbon composite material of the present invention, or only the sliding contact portion with a mating material such as a recording medium may be composed of the glassy carbon composite material of the present invention. Good.

Furthermore, the glassy carbon composite material of the present invention can be used for fuel cell separators, machine parts, various jigs, and the like.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following examples are merely examples, and do not limit the technical scope of the present invention. Further, "parts" in the examples all mean "parts by weight".

(Example 1) Furfuryl alcohol (manufactured by Kao Quaker Co., Ltd.) 100
5 parts of 0.011 N-HCl aqueous solution was added to the parts, and the mixture was reacted at 96 ° C. for 6 hours and then dehydrated under reduced pressure to obtain a thermosetting resin. To this thermosetting resin, 2% by weight of alumina ultrafine particles (aluminum oxide C manufactured by Nippon Aerosil Co., Ltd.) having an average primary particle size of about 20 nm was added, and dispersed and mixed by a ball mill.
To 100 parts of the obtained furfuryl alcohol initial condensate resin, 1.5 parts of a 70% aqueous paratoluenesulfonic acid solution was added and sufficiently stirred. This was poured into a strip-shaped mold having a thickness of 3 mm and degassed under reduced pressure. Then, it was heated at 50-60 ° C for 3 hours and further at 90 ° C for 5 days. The strip-shaped composite cured resin obtained in this manner was put into a tubular furnace and heated at 10 ° C / h in a nitrogen stream.
The temperature was raised to 1200 ° C. at a heating rate of r, and the temperature was maintained for 2 hours and then cooled.

The bending strength of this sample is 1050 kg / cm ² , and the bending strength of glassy carbon that does not contain alumina ultrafine particles is 1000 kg.
Slightly increased compared to / cm ² .

The density of glassy carbon as the main component is 1.5 g / cm ³ ,
The apparent specific gravity of the alumina ultrafine particles mixed in this was 75 g /
Is. The residual carbon rate of the resin used, that is, the weight ratio before and after firing is about 50%. In this embodiment, 100 parts of resin is mixed with 2 parts of alumina ultrafine particles and the mixture is cured and baked, so that 50 parts of glassy carbon contains 2 parts of alumina ultrafine particles, and considering the specific gravity of alumina of about 3.9, the volume is The ratio is 50 / 1.5 to 2 / 3.9, that is, the volume of alumina is 1.45 with respect to the volume of glassy carbon of 100. Similarly, when 4 parts, 8 parts, or 25 parts of alumina ultrafine particles are mixed with 100 parts of resin, the volume ratio is 3.08, respectively.
6.15 and 19.2.

The exact volume ratio can be determined by heat treating the composite material in air and removing the carbon content and quantifying the resulting alumina residue. The value of the volume ratio calculated from the weight ratio almost agrees with this exact volume ratio as long as the resin having a residual carbon ratio of 50% is used.

(Example 2) Alumina ultrafine particles were added to the thermosetting resin obtained in Example 1.
0.7, 1, 2, 4, 8, 15 and 20% by weight were added and dispersed and mixed by a sand mill. After this, as in Example 1, 12
It was baked at 00 ° C.

When the obtained sample was measured by X-ray diffraction, it was an alumina fine particle-glassy carbon composite material in which alumina fine particles were uniformly dispersed in glassy carbon. The bending strengths of these samples were 1,000, 10 and 10 respectively for the amounts of 0.7, 1, 2, 4, 8, 15, 20 wt% alumina fine particles mixed.
It was 20,1050,1080,1080,1060,1010 kg / cm ² .

(Example 3) In the thermosetting resin obtained in Example 1, 2% by weight and 5% of ultrafine titanium oxide (titanium oxide P25 manufactured by Nippon Ahirozil Co., Ltd.) having an average primary particle diameter of 21 nm was used. The mixture was added at a weight percentage and dispersed and mixed by a sand mill.
After this, it was fired at 1200 ° C. as in Example 1.

When the obtained sample was measured by X-ray diffraction, it was a titanium carbide / glassy carbon composite in which titanium carbide ultrafine particles were uniformly dispersed in glassy carbon. The flexural strengths of these samples were 1020 and 1050 kg / cm ² , respectively, for a mixture amount of 2% by weight and 5% by weight.

(Example 4) 2 parts by weight and 5 parts by weight of the alumina ultrafine particles used in Example 1 were mixed with 100 parts of a mixture of spherical semi-cured phenol resin powder (Bellpearl manufactured by Kanebo Co., Ltd.) and novolac resin powder, and heated. It was heat-molded by a press machine to obtain a strip-shaped composite cured resin. This composite cured resin was heated to 1200 ° C. at a temperature rising rate of 10 ° C./Hr in a nitrogen stream, held at this temperature for 2 hours, and then cooled.

The bending strengths of the obtained samples were 1050 and 1060 kg / cm ² with respect to the mixing amounts of 2 parts by weight and 5 parts by weight, respectively.

(Example 5) 500 parts of furfuryl alcohol and 480 parts of 92% paraformaldehyde were dissolved by stirring at 80 ° C, and a mixed solution of 520 parts of phenol, 8.8 parts of sodium hydroxide and 45 of water was added dropwise under stirring. After completion of dropping, the mixture was reacted at 80 ° C. for 3 hours. Thereafter, a mixed solution of 80 parts of phenol, 8.8 parts of sodium hydroxide and 45 parts of water was further added, and the mixture was reacted at 80 ° C. for 4.5 hours. After cooling to 30 ° C., it was neutralized with 70% paratoluenesulfonic acid. The neutralized product was dehydrated under reduced pressure to remove 150 parts of water, and 500 parts of furfuryl alcohol was added. The viscosity of the obtained resin was 680 cps at 25 ° C. The amount of water that this resin could contain was 38%.

Alumina ultra fine particles are added to this thermosetting resin initial condensate.
It was added at a ratio of 5% by weight and 5% by weight, and dispersed and mixed by a sand mill. After that, it was fired at 1200 ° C. in the same manner as in Example 1.

The flexural strengths of the obtained samples were 1070 and 1090 kg / cm ² with respect to the mixed amounts of 2% by weight and 5% by weight, respectively.

(Comparative Example 1) In order to compare with Examples 1 to 5, an alumina-based ceramic (trade name "Neoceram" manufactured by Nippon Electric Glass Co., Ltd.) was used as Comparative Example 1 in the test described below.

(Comparative Example 2) Similarly, calcium titanate (Sumitomo Special Metal Co., Ltd.)
The product, trade name "TC-105") was used as Comparative Example 2.

Comparative Example 3 In the same manner as in Example 1, a composite material was prepared in which 0.3% by volume of alumina ultrafine particles were dispersed in glassy carbon.

Comparative Example 4 By the same method as in Example 1, a composite material was prepared in which 25% by volume of ultrafine alumina particles were dispersed in glassy carbon.

(Test Examples and Test Results) The samples obtained in the above Examples 1 to 5 and Comparative Examples 1 to 4 were processed to measure the friction coefficient and the wear amount.

(I) Measurement of friction coefficient FIG. 1 shows the shape of the test piece used for the measurement of the friction coefficient. These test pieces were obtained by using the samples obtained in the above Examples 1 to 5 and Comparative Examples 1 to 4 in a length a of 4.0 mm and a width b of 6.0 m.
Cut out a rectangular parallelepiped with m and height h of 3.0 mm, and gradually polish the sliding surface A from rough polishing to final fine polishing, and finally emery paper # 15000.
The mirror finish was done. Furthermore, the sliding contact surface A of this rectangular parallelepiped
Chamfer the ridges surrounding it with low-number emery paper, and then gradually use high-number emery paper to finally obtain a radius of 0.2.
A test piece for measuring the coefficient of friction was provided with a roundness of ~ 0.3 mm.

Using these test pieces, the coefficient of friction was measured by the so-called “pin disk method”. That is, a test piece for measuring the friction coefficient was attached to the gimbal spring used in the floppy disk drive, and a load of about 20 g was applied from above to the friction disk and the floppy disk that was attached to the spindle and rotating plate rotating at an arbitrary speed. It was slid. At this time, the frictional force was obtained by a strain gauge attached to the arm of the apparatus, and the friction coefficient μ was calculated.

(Ii) Measurement of wear amount FIG. 2 shows the shape of the test piece used for measurement of wear amount.
These test specimens have a width w in the lateral direction on a sliding surface A of the specimen used for the measurement of the friction coefficient by a slicing machine.
The groove is formed with a depth d of 0.5 μm and a depth d of several μm.
The distance r from the end of this groove is 2.0 mm. The cross-sectional curve of the groove was determined using a precision roughness measuring instrument (HIPOSS ET-10 manufactured by Kosaka Laboratory Co., Ltd.), and the groove depth was measured. This test piece was attached to a gimbal spring and attached to the head portion of a floppy disk drive. A load of 20 g was applied to the test piece to cause friction sliding with the floppy disk, and the head was moved by one track per rotation of the floppy disk to wear the test piece.

The groove depth of the test piece was measured over time to determine the wear depth.

(Iii) Test Results The above test results are shown in Tables 1 to 6. Tables 1 to 5 show the test results of Examples 1 to 5, and Table 6 shows the test results of Comparative Examples 1 to 4. In these tables, "amount of ultrafine particles" indicates a volume part of ultrafine particles to 100 parts by volume of glassy carbon, and "A" in the "disc type" column indicates γ-Fe ₂ O.
₃ shows a coated disk, and "B" also shows a Co-Cr sputtered disk.

[Effects of the Invention] As described above, the glassy carbon composite material of the present invention is a material having excellent wear resistance, a small coefficient of friction, and capable of precision processing. It is also excellent in strength.

When sliding contact parts are manufactured using the glassy carbon composite material of the present invention, lubricating properties can be maintained for a long time without using a lubricant between the mating material and the surface of the mating material. An excellent effect can be obtained without damaging the material and with less wear of the material itself. In addition, since the glassy carbon as the main component has conductivity, static electricity is not generated, and there is an effect that dust hardly adheres to a partner material and a contact portion thereof.

Further, the glassy carbon composite material of the present invention can be used for fuel cell separators, mechanical parts, various jigs, and the like by utilizing its strength.

[Brief description of drawings]

FIG. 1 is a view showing the shape of a test piece used for measuring a friction coefficient. FIG. 2 is a view showing a shape of a test piece used for measuring a wear amount.

Claims (4)

(57) [Claims] 1. A glassy carbon as a main component (however,
(Does not include graphite and carbon fiber), and one or more ultrafine particles selected from metal oxide ultrafine particles, metal nitride ultrafine particles, metal carbide ultrafine particles, and metal boride ultrafine particles having an average particle size of 1 μm or less as a reinforcing component. Glassy carbon composite material containing. 2. The glass according to claim 1, wherein the ultrafine particles include one or more ultrafine particles selected from alumina ultrafine particles, silicon carbide ultrafine particles, titanium carbide ultrafine particles, and silicon oxide ultrafine particles. Shaped carbon composite material. 3. A volume ratio of ultrafine particles to glassy carbon is 0.005 to 0.2.
The glassy carbon composite material according to the item. 4. A curing precursor of a thermosetting resin which can contain 20% or more of water in the state of an initial condensate, an alumina ultrafine particle having an average particle size of 1 μm or less, a titanium oxide ultrafine particle, a silicon oxide ultrafine particle, and carbonization. A method for producing a glassy carbon composite material, which comprises mixing one or more kinds of ultrafine particles selected from ultrafine silicon particles, curing the resin, and carbonizing and firing at a temperature of 800 ° C. or higher in an inert atmosphere.