JPH03170310A - Production of amorphous carbon material - Google Patents

Abstract

PURPOSE:To obtain an amorphous carbon material having improved gaseously transmissible property by subjecting a carbonaceous material to a specific treatment, heating and baking the produced aqua-mesophase or amphiphilic carbonaceous mesophase in an inert atmosphere and, as necessary, heat-treating the product at a high temperature. CONSTITUTION:A carbonaceous material having an H2 content of >=2wt.% and produced by the heat-treatment of a raw material such as coal tar pitch is treated with an acid or oxidizing agent such as HNO3, H2SO4, mixture of HNO3 and H2SO4, H2O2 or KMnO4 and the oxidation product is filtered, washed with water and dried. The dried material is dissolved in water, a basic aqueous solution or an organic solvent, the solution is filtered to remove insoluble components and the dissolved components are precipitated again and filtered to obtain an aqua-mesophase or amphiphilic carbonaceous mesophase. The mesophase is heated in a non-oxidizing atmosphere to >=600 deg.C at a heating rate of <=30 deg.C/h in the case of the treatment with an acid or an oxidizing agent containing HNO3 or at an arbitrary heating rate otherwise to effect the carbonization and baking of the mesophase. As necessary, the carbonized product is heated at a high temperature (>=2000 deg.C) to obtain the objective amorphous carbon material having isotropic fine structure.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an amorphous carbon material, particularly a crucible,
This invention relates to a method for producing an amorphous carbon material having an isotropic structure that is suitable for use in metallurgical jigs such as boat materials, mechanical jigs such as mechanical seals and bearings, semiconductor jigs, gas-impermeable materials, etc. .

[Background of the invention]

Carbonaceous mesophase, which is generated during the transition stage of heat treatment of pitch and other heavy bituminous materials to carbon, has a structure in which compounds mainly composed of planar condensed polycyclic aromatics are oriented and stacked during the process. Therefore, graphitizable carbon with developed graphite crystals can be obtained by graphitizing this carbonaceous mesophase at a high temperature.

On the other hand, glassy carbon is known as a carbon material in which graphite crystals are not developed. For example, phenolic resin,
Thermosetting resins such as furan resins and vinylidene resins, cellulose, etc. have three-dimensional molecular bonds, so during the heat treatment process before carbonization, the growth of aromatic planes and their layered structure are restricted by this structure. Because it prevents
Even when graphitized at high temperatures, non-graphitizable carbon is obtained in which hardly any developed graphite crystals are observed. This non-graphitizable carbon has a hard and isotropic structure,
It is called glassy carbon because its properties are similar to glass, with its fractured surface exhibiting a glossy glass-like appearance and extremely low gas permeability.

In addition to the above properties, glassy carbon has excellent properties such as light weight, chemical resistance, electrical conductivity, thermal conductivity, lubricity, and heat resistance, so it is suitable for metallurgical and mechanical applications such as crucibles and boat materials. It is used in many industrial H materials such as seals, bearings, and other machinery, semiconductor jigs, and gas-impermeable materials.

Furthermore, isotropic carbon materials having an isotropic structure are known. This can be molded using pulverized carbon material as an aggregate, either as a one-component material if it has self-sintering properties, or as a binary material with the addition of a binder if it does not have self-sintering properties. After that, it is obtained by firing. Such isotropic carbon can be obtained by increasing the filling oddness by adjusting the viscosity of the aggregate (Japanese Patent Publication No. 63-23124), or by using aggregate with a high shrinkage rate during heat treatment (Japanese Patent Publication No. 57/1989).
-25484), and by further increasing the density by hot pressing, etc., it becomes highly hard and dense, and an amorphous carbon material having the same properties as the above-mentioned glassy carbon can be obtained. The amorphous carbon material obtained in this way can be used in many industrial applications such as mechanical parts such as mechanical seal bearings, electrode materials for electrical discharge machining, reactor parts for nuclear reactors, semiconductor jigs, casting dies, and mold materials for hot presses. It is being used for various purposes.

However, since the glassy carbon uses thermosetting resins, cellulose, etc. as raw materials in its manufacture, it essentially has the following drawbacks.

That is, the reaction in the carbonization firing process is accompanied by the generation of a large amount of decomposed gas and water, so the recovery rate is low, and the reaction is accompanied by large shrinkage, which tends to cause cracks and fractures. To solve this problem, we applied brush, spray, and
A so-called multi-coating method has been devised, in which the operation of applying and curing a thin layer of resin using a centrifugal method or the like is repeated (No. 11 Patent No. 412,380). We also crush thermosetting resin,
There is also a method in which a molded body is produced as an aggregate and carbonized and fired (Japanese Patent No. 420682).

However, in actual production, according to the knowledge of the present inventors, these operations are quite complicated, and in both methods, the carbonization and firing steps are heated up to, for example, 500°C. 1℃/hr, 59C/hr up to 900℃
hr (British Patent No. 956,452, British Patent No. 1,024,97
Since it is necessary to strictly control the temperature increase at a very slow rate such as No. 1), there is a problem that it requires complicated conditions and a large amount of time. Also, in terms of raw materials,
Since the conventional method uses a composite resin, it cannot necessarily be said that it is advantageous for single production in terms of cost.

Regarding isotropic carbon, with conventional isotropic carbon, it is difficult to adjust the viscosity after the carbon material is finely pulverized, and the amount of binder added is relatively large, and the volatile content adjustment process is required separately. It becomes necessary. Furthermore, the use of hot press is expensive and the process is complicated, and when impregnation treatment is performed for densification, the number of steps increases further.
As a result, costs increase.

[Summary of the invention]

As a result of repeated research to solve the above problems, the present inventors have found that pitch, mesophase-containing pitch, carbonaceous mesophase, raw coke, etc., which are advantageous as industrial raw materials, can be easily carbonized. By using a carbonaceous material that provides graphitizable carbon as a raw material and heat-treating the mesophase obtained by subjecting this carbonaceous material to a specific acid treatment and re-precipitation, an amorphous lateral material with good properties can be produced. It was discovered that a carbon material with a strong structure can be obtained. moreover,
It has been found that when the above acid treatment is a treatment with an acid containing nitric acid, it is important to strictly control the temperature increase rate in the heat treatment process in order to obtain a good amorphous carbon material.

The present invention has been made based on the above findings, and more specifically, carbonaceous material treated with acid or oxidized is dissolved in water, basic aqueous solution & or organic solvent, and then dissolved. The aqua mesophase or amphiphilic carbonaceous mesophase obtained by redepositing the components is treated in an inert atmosphere at 30° C./11 in the case where the acid treatment or oxidation treatment is a treatment with an acid containing nitric acid. ``At the following heating rate, otherwise unrestricted heating rate, 6
An amorphous carbon material having a substantially isotropic microstructure is obtained by carbonizing or firing to a temperature of 00°C or higher, or further heat-treating at a high temperature of 2000°C or higher as necessary. It is.

The reason why a carbon material having an amorphous structure can be obtained by the above-mentioned method is not necessarily clear, but it can be considered as follows. In other words, the above-mentioned raw material carbonaceous material is generally composed of oriented and laminated polycyclic polynuclear aromatic compounds, and therefore its structure exhibits anisotropy, but aqua mesophase or amphiphilic carbonaceous mesophase In the manufacturing process, the orientation is isotropic as the carbon material is first dissolved and dispersed in a solution and then precipitated. It is thought that a so-called amorphous carbon material exhibiting a similar structure is produced.

In addition, in the present invention, since the materials are once in a uniform solution state during the manufacturing process, it is extremely easy to mix metals, metal oxides, ceramics, carbon materials, etc. into the solution, and the materials are uniformly dissolved. It is also possible to easily produce amorphous carbon dispersed in .

[Specific description of the invention]

As the carbonaceous material used in the present invention, pitch produced by heat treatment of pitch, which is a heavy bituminous substance, mesoface pitch, carbonaceous mesoface, raw coke, etc. can be used. Mesophase and/or raw coke may preferably be used.

The pitches used as raw materials for these carbonaceous materials include coal tar pitch, coal-based pitch of coal wave compounds, petroleum distillation residue oil, naphtha tar pitch produced as a by-product during the thermal decomposition of naphtha, and fluid catalytic cracking of naphtha. Petroleum-based pitch such as FCC decant oil produced by the CFCC method),
Pitch Jrj obtained by thermal decomposition of synthetic polymers such as PVC
, are cited as specific examples, and any type is not particularly limited as long as it provides graphitizable carbon through carbonization treatment. To obtain carbonaceous mesophase, these pitches are heat treated at about 350 to 500°C. Through this heat treatment, carbonaceous mesophase (including raw coke) is brought to life. The generation of carbonaceous mesophase can be easily detected by observing the heat-treated product under a polarizing microscope. That is, the carbonaceous mesophase can be identified as an optically anisotropic phase that is generated in a pitch that is an optically isotropic phase. At this time, the morphology of the carbonaceous mesophase can be either mesophase spherules that are formed during the slow stage of heat treatment, that is, the initial stage of the carbonization process, or so-called bulk mesophase that is formed by the growth of these spherules and coalescence with each other. good.

The heat treatment conditions for producing carbonaceous mesofaces are determined by the elemental composition of the carbonaceous mesofaces separated from the heat-treated pitch. In particular, it is preferable that the hydrogen content be 2% by weight or more. This is because it is involved in the amount of functional groups (carboxyl group, sulfonic acid group, hydroxyl group, etc.) introduced in the next step, treatment with an acid such as nitric acid, sulfuric acid, or a mixed acid of nitric acid and sulfuric acid. Therefore, it is important to avoid excessive heat treatment so that the hydrogen content does not fall below 5% in semi-coke in which pitches are completely solidified under strict heat treatment conditions.

Separation of carbonaceous mesophase from heat-treated pitch can be carried out by sedimentation methods and/or solvent fractionation methods. That is, when the heat-treated pitch is allowed to stand still in a molten state, the carbonaceous mesophase settles downward, so only this portion is collected. In addition, heat-treated pitch is dissolved and dispersed in an organic solvent such as quinoline or pyridine as a solvent, or an aromatic oil containing a large amount of aromatic compounds such as anthracene oil or creosote oil.
It can be carried out as an insoluble component of these solvents.

The carbonaceous H material obtained as above was mixed with nitric acid, sulfuric acid,
By treating with a mixture of nitric acid and sulfuric acid, an acid such as fuming sulfuric acid, or an oxidizing agent such as hydrogen peroxide or potassium dichromate, carboxyl groups, sulfonic acid groups, Introducing a hydrophilic functional group such as a hydroxyl group. In the present invention, the term acid treatment means a treatment that includes both the above-mentioned acid and treatment with an oxidizing agent.

At this time, the inventor has discovered that the carbonaceous material treated with the acid or oxidizing agent becomes soluble in the basic aqueous solution (PreprinL of" 18thBi
annual Conr. of' Carbon,
p. 405 (1987), Japanese Unexamined Patent Publication No. 64-9288). That is, when a basic aqueous solution is added to the acid-treated product described above so as to maintain a constant pH, the acid-treated carbonaceous material becomes soluble. Furthermore, by adding an acid aqueous solution to this soluble component, that is, by adjusting the pH of the soluble component to 3 or less, preferably 1 or less, the solubilized carbonaceous material is redeposited as a carbonaceous component. (The carbonaceous component thus precipitated is called "aqua mesoface").

On the other hand, it is known that the above-mentioned acid-treated carbonaceous material is also soluble in organic solvents (Japanese Unexamined Patent Publication No. 64-9288), and after dissolving it in an organic solvent, evaporation etc. Remove the solvent to obtain a carbonaceous fraction (the carbonaceous component obtained in this way is called "amphiphilic carbonaceous mesophase")
.

The above-mentioned aqua mesophase or amphiphilic carbonaceous mesophase has a relatively large shrinkage during drying, and only particles with a particle size of 2 to 3 particles can be obtained by normal drying.

However, in the present invention, by adjusting drying speed, humidity, controlling surface tension, etc.
It is possible to control one or more arbitrary particle shapes. Surface tension can be controlled, for example, by adding additives such as alcohol, formalin, ammonia, and DMF.

Next, the aqua mesophase or amphiphilic carbonaceous mesophase is treated in a non-oxidizing atmosphere with a heating rate of 30°C/hr or less in the case of treatment with an acid containing nitric acid, or in other cases. is carbonized and fired at an elevated temperature of not limited to 600° C. or higher, preferably 1000° C. or higher, and further heat-treated at a high temperature of 2000° C. or higher if necessary. If the heating temperature is lower than 600° C., sufficient carbonization will not occur, and therefore it will be difficult to impart the desired properties as an amorphous carbon material.

At this time, it is particularly important to limit the temperature increase rate to 30°C/hr or less for items that have been acid-treated using an acid containing nitric acid.
In the temperature range of 50 to 300°C, if carbonization is performed rapidly at a heating rate exceeding 30°C/hr, for example at a rate of 100°C/hr or more, expansion and foaming accompanied by the generation of a large amount of gas will occur. However, this is because a carbon material with a dense structure cannot be obtained.

The amorphous carbon thus obtained is a non-graphitizable carbon that has a dense isotropic structure and does not develop graphite crystals even when heat treated at a high temperature of 2000° C. or higher. Therefore, it has gas impermeability, and products fired at 1000° C. or lower exhibit characteristics such as uniform pores being formed by loading.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

(Example 1) Raw coke obtained by a delayed coke force method was finely pulverized to have an average particle size of 10 μm. This elemental composition is carbon 9
5. 1 wt%, hydrogen 3.1 wt%, and nitrogen 0.6 wt%. 5 g of this was added little by little to a 300 ml Erlenmeyer flask containing 100 ml of a mixed acid of 96% sulfuric acid and 70% nitric acid in a 50:50 volume ratio. After adding the entire amount, it was heated for 4 hours in an oil bath preheated to 80°C.

Then, it was filtered through a glass finoletter (No. 4), thoroughly washed with water, and then dried. The yield was 140%. Disperse this in water and adjust the pH while stirring.
IN-NaOH was added until the concentration reached 10.

Next, pass through a Menplan filter (0.1 μm),
? I got the liquid. The amount of insoluble matter was 0.7% by weight based on the raw coke. IN-HCI was added to this to make the pH less than 1, and the precipitate was transferred to a glass finoletter (No.
4) I was disappointed. Fill this into a 30 x 50 x 10 mm container, fill it with water at the bottom, leave it in a dessicator covered with aluminum foil with many 1 mm holes on the top for 20 days, and then put it in a dryer at 120°C for 10 hours. Dry. The yield at this time was 133% by weight based on the raw material raw coke.
there were.

This was heated at 30°C/1 in a nitrogen gas stream using a tube furnace.
The sample was heated to 1000° C. at a heating rate of 1,000° C. and held for 1 hour for firing treatment. Further, the mixture was heated to 2800°C using a Tammann furnace under argon gas flow and held for 30 minutes. What was obtained was a granular material with a particle size of 20 to 30WIII1 or less,
The yield was 50.8% by weight based on raw coke. FIG. 1 is a transmission electron micrograph of the obtained amorphous carbon material, and FIG. 2 is an X-ray diffraction image. Graphite crystallites are randomly distributed, and no orientation is observed in the diffraction pattern.

Table 1 shows the characteristics of the amorphous carbon grain thus obtained.

table 1 Specific gravity is measured in accordance with JIS R7212.

(Example 2) About 15% of quinoline is added to 500g of coal tar pitch.
00ml was added and heated to about 90°C to dissolve it. The insoluble components were precipitated using a centrifugal sedimentation machine, and the supernatant was filtered through qualitative paper under reduced pressure.

The citrus liquor was distilled under reduced pressure to remove quinoline, yielding pitch containing no free carbon. This pitch of 300g is 500g
The mixture was placed in a ml glass solid cylindrical container, heated to 450° C. for 1 t while stirring in a nitrogen gas stream, and maintained at this temperature for 45 minutes. After the elapse of time, the mixture was immediately cooled to room temperature to obtain 273 g of heat-treated pitch. 600 ml of quinoline was added to 200 g of heat-treated pitch and heated to about 90° C. to dissolve and disperse. The insoluble components were sedimented using a centrifugal sedimentation machine, the supernatant was removed, fresh quinoline was added to the insoluble portion, and after heating to about 90°C, the insoluble components were sedimented using a centrifugal sedimentation machine. After repeating this operation five times, the insoluble components were thoroughly washed with benzene and then with acetone to remove quinoline, and the mixture was dried at about 70° C. to obtain 98 g of carbonaceous mesophase. Next, 50 g of this carbonaceous mesophase was added to 200 ml of quinoline, and about 25 g of
After heating to 0° C. and holding for 3 hours while refluxing the quinoline, insoluble components were precipitated using a centrifugal sedimentation machine, and the supernatant was removed. After adding quinoline to the insoluble components and heating to about 90° C., the insoluble components were sedimented using a centrifugal sedimentation machine, and the supernatant was removed.

After repeating this operation 8 times, the insoluble components were thoroughly washed with benzene and then with acetone to remove quinoline, and the mixture was heated to about 70°C.
was dried to obtain 44 g of carbonaceous membrane. The elemental composition of the carbonaceous mesophase prepared in this way was 2.3 wt% carbon Q, 3.4 wt% hydrogen, and 1.4 wt% nitrogen.
%Met.

After adding 5 g of this particle size of 0.35 W or less to a 300 ml Erlenmeyer flask containing 100 ml of 30% oleum, the flask was held in an oil bath preheated to 150° C. for 5 hours. After removing from the oil bath and cooling to room temperature, it was gradually transferred to 300 ml of water. Then, it was filtered through a glass filter (No. 4), washed with nitric acid of pH 1, and then dried.

The yield was 151.0% by weight.

Add 2g of this to 100ml of dimethyl sulfoxide (DMSO)
After stirring thoroughly, the mesh size is 0. It was passed through a 5 μm Teflon Membrane Fino Letter. After heating the resin solution to evaporate DMSO, it was dried under reduced pressure to obtain amphiphilic carbonaceous mesophase.

At this time, the yield is 1 for the raw material carbonaceous mesophase.
It was 50.2% by weight, and no insoluble components were present.

This was heated at 300°C/h in a nitrogen gas stream using a tube furnace.
It was heated to 1000° C. at a heating rate of r and held for 1 hour for firing treatment. Further, the mixture was heated to 2800° C. using a Tammann furnace under argon gas flow and maintained for 1 hour. The yield was 46.0% by weight based on the carbonaceous mesophase. FIG. 3 is a transmission electron micrograph of the obtained amorphous carbon material, and FIG. 4 is an X-ray diffraction image.

Graphite crystallites exist randomly, and no orientation is observed in the diffraction pattern.

Table 1 shows the properties of the amorphous carbon material thus obtained.

(Example 3) 0.35 of the same carbonaceous mesophase used in Example 2
Add 5 g of particle size below 3 mm to a 300 ml Erlenmeyer flask.
After adding it to a solution containing 100 ml of 1% hydrogen peroxide solution, it was kept in an oil bath preheated to 100° C. for 3 hours. The mixture was taken out from the oil bath, cooled to room temperature, filtered through a glass filter (No. 4), and dried. The yield was 51.6% by weight.

This was dispersed in water, and while stirring, IN-NaOH was added until the pH reached 2. Next, it was passed through a membrane filter (0.5 μm) to obtain a filtrate. The amount of insoluble matter was 0.8% by weight based on the raw coke. IN to this
-HCI was added to make the pH less than 1, and the precipitate was filtered through a glass filter (NO, 4) and dried.The yield at this time was 41.8% by weight based on the raw material raw coke. Ta.

This was heated at 300°C/hr in a nitrogen gas stream using a tube furnace.
The sample was heated to 600° C. at a temperature increase rate of 100° C. and held for 1 hour for firing treatment. The properties of this heat-treated product are shown in Table 2.

Further, this fired product was heated to 600° C. in a carbon dioxide gas stream at a heating rate of 100° C./hr using a tubular furnace, and was maintained for 1 hour for activation treatment. The characteristics of this treated product are shown in Table 2.

2U Table 2 (Comparative Example 1) The acid-treated product obtained in Example 1 (not as Aqua Mesofes) was washed with water and dried in the same manner as in Example 1, and heated in a tube furnace in a nitrogen gas stream for 30 minutes. After heat treatment to 1000℃ at a heating rate of ℃/hr, heat treatment was carried out at 28℃ in a Tammann furnace.
It was treated at 00°C for 30 minutes. The yield was 48.6% by weight based on raw coke. This characteristic is shown in Table 3.

(Comparative Example 2) The same conditions as in Example 1 were used except that the temperature increase rate in Example 1 was changed to 50° C./hr. Table 3 shows the properties of the heat-treated product obtained.

table 3

[Brief explanation of the drawing]

FIG. 1 and FIG. 3 show Example 1 and Example 2, respectively.
FIGS. 2 and 4 are transmission electron micrographs showing the crystal structure of the amorphous carbon material obtained in
1 is an X-ray diffraction image photograph of the amorphous carbon materials obtained in Examples 1 and 2.

Claims (1)

[Claims] 1. Carbonaceous material treated with acid or oxidation,
After dissolving in water, a basic aqueous solution, or an organic solvent, the aqua mesophase or amphiphilic carbonaceous mesophase obtained by reprecipitating the dissolved components is subjected to the acid treatment or oxidation treatment using nitric acid in an inert atmosphere. In the case of treatment with an acid containing acid, carbonization or sintering is carried out to a temperature of 600 °C or more at a temperature increase rate of 30 °C / hr or less, and in other cases, at an unrestricted temperature increase rate, or further as necessary. 1. A method for producing an amorphous carbon material, the method comprising obtaining a carbon material having a substantially isotropic microstructure by heat-treating the carbon material at a high temperature of 2000° C. or higher. 2. The method according to claim 1, wherein the carbonaceous material has a hydrogen content of 2% by weight or more and is capable of providing graphitizable carbon by ordinary carbonization treatment. 3. The acid treatment or oxidation treatment according to claim 1, wherein the acid treatment or oxidation treatment is performed with an acid or an oxidizing agent such as nitric acid, sulfuric acid, a mixture of nitric acid and sulfuric acid, hydrogen peroxide, potassium permanganate, etc. Method.