JPH0645124A - Ferromagnetic carbon material and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide novel ferromagnetic carbon material excellent magnetic characteristics. CONSTITUTION:The title ferromagnetic carbon material is composed of ferromagnetic carbon material consisting of an ungraphitized carbide containing paramagnetic metal or metal compound powder, and the ferromagnetic carbon material is manufactured by removing the paramagnetic metal or metal compound powder from the above-mentioned ferromagnetic carbon material. The carbon- containing substance, in which paramagnetic metal or metal compound powder is added, is thermally decomposed in an atmosphere containing the gas which can be reacted with hydrogen, and ferromagnetic containing the paramagnetic metal or metal compound powder, having the characteristics in which ungraphitized carbide is grown, is manufactured. From the ferromagnetic carbon material containing powder of the paramagnetic metal or metal compound produced by the above-mentioned method, the powder of paramagnetic metal or metal compound is extracted and removed in an acidic solution to manufacture a ferromagnetic material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferromagnetic carbon material and a method for producing the same.

[0002]

2. Description of the Related Art Heretofore, simple substances, alloys, oxides, etc. of transition metals such as iron, cobalt and nickel have been used as ferromagnetic materials. These ferromagnetic materials have many merits such as a large magnetic susceptibility, a large coercive force and a remanent magnetization value, but on the other hand, they have some disadvantages. The disadvantage (1) is that since it is a heavy metal element, it has a large specific gravity and is inconvenient for transportation to outer space. The reason (2) is that elements other than iron are unevenly distributed on the earth as resources, and there is concern that resources will be depleted in the future. Since (3) is a metal element, it has a high hardness and is unlikely to be a soft material. In the case (4), there is a case where it is desired to demagnetize and dispose of it when it is no longer needed, but that requires a large amount of energy. The reason (5) is that metallic ferromagnetic materials have poor compatibility with living organisms and are toxic when dissolved in blood.
That is, it is difficult to embed it in a living body or disperse it in the blood in a fine powder state and use it for magnetic imaging. On the other hand, the carbon ferromagnet has few such problems. The present inventor has previously proposed a method for obtaining a ferromagnetic carbon material by thermally decomposing a carbon-containing substance and converting it into an ungraphitized carbide (Japanese Patent Application No. Hei 3).
-109779, 109780, 198795, 235
569). However, the magnetic properties of the carbide obtained by this method have not been satisfactory yet.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel ferromagnetic carbon material having excellent magnetic properties and a method for producing the same.

[0004]

The present inventor has completed the present invention as a result of intensive studies to solve the above-mentioned problems. That is, according to the present invention, a ferromagnetic carbon material made of an ungraphitized carbide containing a powder of paramagnetic metal or metal compound and a powder of paramagnetic metal or metal compound are removed from the ferromagnetic carbon material. Provided is a ferromagnetic carbon material. Further, according to the present invention,
A paramagnetic metal characterized in that a carbon-containing substance to which a powder of a paramagnetic metal or a metal compound is added is thermally decomposed in an atmosphere containing a gas capable of reacting with hydrogen to generate an ungraphitized carbide. Or a method for producing a ferromagnetic carbon material containing a powder of a metal compound and a ferromagnetic carbon material containing a powder of a paramagnetic metal or metal compound obtained by this method A method for manufacturing a ferromagnetic material is provided, in which powder is extracted and removed with an acidic solution.

In the production of the ferromagnetic carbon material of the present invention, SP containing a carbon-containing substance which is thermally decomposed to have an unsaturated valence
When generating a ferromagnetic carbon atom having a 2-sigma unpaired electron, a powder of a metal or a metal compound having a paramagnetic property is present, and the electron spin vector of the generated carbon atom is changed by the action of the paramagnetic metal atom. , And induce it to be parallel to the electron spin vector of the paramagnetic metal atom,
As a result, a carbide having excellent magnetic properties is obtained. The spin induction phenomenon of a carbon atom by a paramagnetic metal atom, which occurs during the thermal decomposition of a carbon-containing substance in the presence of such a paramagnetic metal atom, was first found by the present inventors.

Metals having paramagnetism are conventionally known, for example, Ti, Cu, Mg, Gd, Zr, Nb and M.
Simple metals and alloys of transition metals such as o and Pd are included. Examples of the paramagnetic metal compound include oxides, hydroxides and sulfides of the above transition metals.

The carbon-containing substance may be any substance as long as it can be carbonized by thermal decomposition, including liquid or solid substances at room temperature, and both low molecular weight compounds and high molecular weight compounds. It can be used. But,
Materials that cannot be decomposed, such as diamond and graphite, cannot be used. The carbon-containing substance may contain an atom other than carbon such as an oxygen atom, a nitrogen atom, a sulfur atom, an alkali metal atom, etc., but since the silicon atom remains in the carbide, the carbon-containing substance is silicon. It is preferably free of atoms. The silicon content in the carbide is 10
It is less than or equal to% by weight, preferably zero%. Preferable specific examples of the carbon-containing substance include, for example, various pitches of petroleum or coal type; organic polymer substances such as polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyacrylate, polymethacrylate; pulp powder, wood Wood-based materials such as powder may be used.

In the present invention, a paramagnetic metal powder and / or a powder of a paramagnetic metal compound (hereinafter, also referred to as paramagnetic powder) is mixed with a carbon-containing substance, and the mixture is heat-treated to obtain the carbon-containing substance. The material is converted to ungraphitized carbide to obtain a ferromagnetic carbon material.

The average particle size of the paramagnetic powder is 0.1 to 500.
μm, preferably 10 to 150 μm. The amount of paramagnetic powder added is 100 parts by weight of the carbon-containing substance.
The proportion is 10 parts by weight or more, preferably 20 to 30 parts by weight.

The heat treatment temperature may be a temperature for the thermal decomposition reaction of the carbon-containing substance, and is generally 400 to 700 ° C, preferably 500 to 600 ° C. The heating atmosphere should just contain the gas which can react with hydrogen. In this case, examples of the gas capable of reacting with hydrogen include halogen and halogenated hydrocarbons, and these gases can be used alone or in a mixture. The heating atmosphere can contain an inert gas such as nitrogen, carbon dioxide, or argon. The oxygen concentration in the atmosphere is 0.1 vol% or less, preferably zero%. By heat-treating the mixture of the carbon-containing substance and the paramagnetic powder as described above, the carbon-containing substance is pyrolyzed, the hydrogen atoms contained therein are removed, and converted into ungraphitized carbide. When the hydrogen content in the carbide is 5% by weight or less, the presence of a gas capable of reacting with hydrogen is not particularly required, and the heating atmosphere can be vacuum (2 Pascal or less). The hydrogen atoms contained in the ungraphitized carbide finally obtained by the present invention are in a ratio of 1/100 atom or less, preferably 1/200 atom or less, per 1 carbon atom.

The ungraphitized carbide containing the paramagnetic powder obtained as described above is composed of carbon having SP2-sigma unpaired electrons and has ferromagnetism. As such, it is a ferromagnetic carbon material. It can be used. However, since this material contains a paramagnetic metal, it still has problems such as a high specific gravity and poor compatibility with living bodies. In order to obtain a ferromagnetic carbon material free from the problems caused by these paramagnetic metals, the paramagnetic metal contained therein may be removed.

There are various methods for removing the paramagnetic powder from the ferromagnetic carbon material containing the paramagnetic powder, but it is preferable to extract and remove the paramagnetic powder by using an acidic solution as an extract. Is. The acidic solution used as the extract is preferably an aqueous solution containing nitric acid and sulfuric acid and / or phosphoric acid. The nitric acid concentration in the aqueous solution is 5 to 30% by weight, preferably 10 to 20% by weight, and the concentration of sulfuric acid and / or phosphoric acid is 20 to 50% by weight, preferably 30 to
It is 40% by weight. The extraction treatment temperature is 20 to 80 ° C, preferably 50 to 60 ° C. According to such an extraction treatment, the paramagnetic metal contained in the ferromagnetic carbon material is efficiently extracted and removed from the ferromagnetic carbon material as metal ions.

[0013]

EXAMPLES Next, the present invention will be described in more detail by way of examples. Example 1 1.0 g of polyvinyl chloride (PVC) is taken and 20 ml of tetrahydrofuran (THF) is added and dissolved. 50 mg of titanium powder crushed to 100 mesh or less
And stir vigorously. The metal / polymer dispersion thus obtained is poured into 50 ml of methanol, which is stirred with a magnetic stirrer, to precipitate the polymer. After drying, put in a magnetic boat and heat up at 10 ° C / min from 20 ° C to 260 ° C in a carbon tetrachloride atmosphere of 10 Pascal, and heat up from 260 ° C to 325 ° C at 2 ° C / min. The temperature was raised from 325 ° C to 390 ° C at a rate of 10 ° C / min, heated at 390 ° C for 60 minutes, and then rapidly cooled. Next, this is put in a glass tube, and further heated in a carbon tetrachloride atmosphere of 10 Pascal at 20 to 390 ° C. at 30 ° C./min and heated at 390 to 454 ° C. at 2 ° C./min. Then 45
0-520 ° C is heated to 1 ° C / min and heated to 520 ° C.
Hold for 60 minutes and then quench. A ferromagnetic carbide was obtained with a yield of 5.1% based on the original PVC. This has a maximum magnetic susceptibility of 16.2 emu / g (1.5 T) and a coercive force of 3.96.
It showed magnetic characteristics of mT and residual magnetization of 0.231 emu / g. The change of the magnetization value with respect to the applied magnetic field is shown in FIG. Figure 1
In, the horizontal axis represents the applied magnetic field strength and the vertical axis represents the magnetization value.

Example 2 As in Example 1, 50 mg of electrolytic copper powder was used to obtain 1.05 g of PVC containing copper powder. This was thermally decomposed according to the same atmosphere and the same temperature program as in Example 1 to obtain a ferromagnetic carbide with a yield of 5.2% based on the original PVC. This has a maximum magnetic susceptibility of 15.7 emu / g (1.5
T), coercive force 3.85 mT, remanent magnetization 0.220 emu
The magnetic property was / g.

Example 3 The same experiment as in Example 1 was carried out except that titanium oxide which had been partially reduced was used in place of the titanium powder, and a ferromagnetic carbide was obtained with a yield of 6% based on the original PVC. It was This one has a maximum magnetic susceptibility of 13.5 emu / g (1.5T),
The magnetic characteristics were a coercive force of 3.50 mT and a residual magnetization of 0.210 emu / g.

Example 4 30 mg of the carbide obtained in Example 1 was added to 150 g of nitric acid /
It was immersed in 10 ml of an acidic aqueous solution containing liter and 350 g / liter of sulfuric acid for 200 minutes at 55 ° C. and then dried by heating at 70 ° C. to obtain a carbide from which titanium was eluted and removed. This has a maximum magnetic susceptibility of 17.8 emu.
/ G (1.5T), coercive force 3.95 mT, residual magnetization 0.
The magnetic property was 232 emu / g.

Comparative Example 1 The same experiment as in Example 1 was carried out except that titanium powder was not used. The yield of ferromagnetic ungraphitized carbide obtained in this case was 1%, which had a maximum magnetic susceptibility of 13.2 emu / g (1.5 T) and a coercive force of 3.
The magnetic characteristics were 00 mT and a residual magnetization of 0.20 emu / g.

[0018]

According to the present invention, a carbide showing ferromagnetism can be produced relatively easily in high yield with the aid of a paramagnetic powder such as copper or titanium. Further, since the paramagnetic powder can be dissolved and removed with a water-soluble acid, the ferromagnetic carbide can be obtained in a pure state. According to the present invention, a ferromagnetic carbon material can be reliably produced in high yield from various carbon-containing substances as raw materials, and its industrial significance is great.

[Brief description of drawings]

1 shows a magnetic susceptibility curve measured from a ferromagnetic carbide obtained in Example 1. FIG. FIG. 1 (a) shows a magnetic field sweep performed from −1.5T to + 1.5T.
In (b), the magnetic field sweep is performed from −50 mT to +50 mT.

Claims (5)

[Claims] 1. A ferromagnetic carbon material comprising an ungraphitized carbide containing a powder of a paramagnetic metal or metal compound. 2. A ferromagnetic carbon material obtained by removing powder of a paramagnetic metal or metal compound from the ferromagnetic carbon material according to claim 1. 3. A non-graphitized carbide is produced by thermally decomposing a carbon-containing substance to which a powder of paramagnetic metal or metal compound is added in an atmosphere containing a gas capable of reacting with hydrogen. A method for producing a ferromagnetic carbon material containing powder of paramagnetic metal or metal compound. 4. The powder of the paramagnetic metal or metal compound is extracted and removed as a metal ion from the ferromagnetic carbon material containing the paramagnetic metal or metal compound obtained in claim 1 with an acidic solution. A method for producing a ferromagnetic carbon material, which is characterized by the above. 5. The method according to claim 4, wherein a mixed acid aqueous solution of nitric acid and phosphoric acid and / or sulfuric acid is used as the acidic solution.