JPS61111923A - Particle containing iron carbide production and use thereof - Google Patents

Abstract

PURPOSE:To produce a particle containing specific iron carbide and useful as a magnetic material, by contacting iron oxyhydroxide or iron oxide with a carbon-containing reducing and carbonizing agent after or without contacting the iron compound with a carbon-free reducing agent. CONSTITUTION:A particle having an average aspect ratio of >=1.0 and <3.0 and an average particle diameter of 0.1-5mum and giving an excellent magnetic material can be produced by contacting an iron oxyhydroxide (e.g. alpha-, beta- or gamma-FeOOH) or iron oxide (e.g. alpha- or gamma-Fe2O3) having an average aspect ratio of 1.0 and <3.0 and an average particle diameter of 0.1-5mum with a carbon- containing reducing and carbonizing agent (e.g. CO, CH3OH, 1-5C aliphatic hydrocarbon, etc.) or its mixture with a carbon-free reducing agent (preferably at 250-400 deg.C) after or without contacting the iron compound with a carbon-free reducing agent (e.g. H2) (preferably at 200-700 deg.C).

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to particles containing iron carbide, their production method and uses.

(Prior Art) Acicular γ-iron oxide is currently used in large quantities as a magnetic recording material. However, if the average axial ratio is 1.0 or more
．． γ-iron oxide with a value less than 0 has low magnetic properties such as coercive force,
It is not currently used as a magnetic recording material. However, such iron oxides or iron oxides or iron oxyhydroxides used as raw materials are easy to produce, and it is expected that the bulk particles produced from them will have a high packing density when made into a paint.

Spherical iron carbide is also known as a magnetic recording material (US Pat. No. 8, No. 3,572,993).

However, the manufacturing method is extremely difficult, as it involves reacting steam aggregates of carbonyl iron with Co or a mixed gas of Co and H2, and the average particle size is
It is extremely small (OO5~0.1μ) and is difficult to handle because it is difficult to disperse and is not currently produced.

(Problems to be Solved by the Invention) The purpose of the present invention is to create particles with a relatively large coercive force and a magnetic material made of the particles by using a raw material iron compound that has a relatively large average particle size, is easy to handle, and is easy to manufacture. The purpose is to provide materials.

(Means for Solving the Problems) The present invention relates to particles containing iron carbide with an average axial ratio of 1.0 or more and less than 3.0 and an average particle diameter of more than 0.1 μm and less than 5 μmIl.

The particles of the present invention are produced by contacting (a) iron oxyhydroxide or iron oxide with an average axial ratio of 1.0 or more and less than 3.0 and an average particle size of more than 0.1 μ- and less than 5 μ-III, and a reducing agent that does not contain carbon; It can be produced by contacting (b) a carbon-containing reducing carbonizing agent or a mixture thereof with a carbon-free reducing agent after or without contacting.

In the present invention, iron oxyhydroxide is α-FeOOH (dacite), β-FeOOH (7kanesite) or γ
-FeOOH (levidocrocite) is preferable, and iron oxides include α-Fez03 (hematite), γ-Fe:03
(W ghemite) or F ego, (v gnetite)
is preferred.

As the above a-F e2o 2 or 7-Fe2O, for example, a-FeOOH, β-FeOOH or γ-F
Those obtained by heating e00H to about 200 to 350°C and dehydrating them, or further heating and dehydrating e00H to about 350 to 90°C.
Acicular a Fe heated to 00°C to make the crystal denser
All kinds of materials such as 2Ox and γ-Fe20z can be used.

β-FeOOH is preferably treated with an alkaline aqueous solution (see Japanese Patent Application No. 10400/1983).

The aforementioned Fe1on can be produced by contacting an iron oxide or iron oxyhydroxide other than Fe1on with a carbon-containing reducing carbonizing agent, a carbon-free reducing agent, or a mixture thereof.

However, the above-mentioned Fe30- can be converted to 91 by this manufacturing method.
It is not limited to things that have been created. As a special case, a carbon-containing reducing carbonizing agent or a mixture thereof with a carbon-free reducing agent may be added to iron oxyhydroxide or Fe50.
In the case of producing Fe)On by contacting with iron oxides other than the above, the same contact conditions except for time can be used as compared with the contact conditions in the production method of the present invention described below.

In that case, it is possible to continue the contact under the same conditions following the production of Fe30- to produce the desired particles of the present invention.

In the present invention, iron oxyhydroxide or iron oxide has an average axial ratio of 1.0 or more and less than 3.0, and an average particle size (long sleeve).
is more than 0.1 μm and less than 5 μm. As will be described later, the produced particles have an average axial ratio and an average particle diameter of
This is because, although it is slightly smaller than those of these raw materials, there is almost no difference, and such particles are generally suitable for the particles of the present invention in general.

In addition, the iron oxyhydroxide or iron oxide used in the present invention is
As long as the main component is iron oxyhydroxide or iron oxide, small amounts of copper, magnesium, mandium, dibutyl, cobalt oxides, carbonates; silicon oxides; potassium salts, sodium salts, etc. are added. It may be something.

The above-mentioned needle-like iron oxyhydroxide is obtained from Japanese Patent Application No. 58-217530.
As described in the above, when the pH of the surface is 5 or more, acicular particles having a high coercive force can be obtained, which is preferable. pH
is less than 5, it is preferable to bring it into contact with an aqueous alkali solution (eg, sodium hydroxide, potassium hydroxide, ammonium hydroxide) to bring the pH to 5 or more. It is also possible to use acicular iron oxide treated with alkali. The alkaline treatment is carried out, for example, by bringing the object to be treated into contact with an alkaline aqueous solution (for example, an aqueous solution with a pH of 8 or more, preferably 10 or more) such as sodium hydroxide, potassium hydroxide, or ammonium hydroxide for 30 minutes or more if necessary. This can be carried out by stirring for 1 hour, cracking and drying.

Note that acicular iron oxyhydroxide or iron oxide coated with Co can also be used. To deposit Co, acicular iron oxyhydroxide or iron oxide is added to an aqueous solution of Co salt (e.g., diluted groove wL with a concentration of 0.1 to 10%) and stirred at room temperature or under heating. It is preferable to make the mixture alkaline with an alkaline aqueous solution and, if necessary, stir for 30 minutes to 1 hour and dry the mixture.

The raw material is coated with an anti-sintering agent such as a silicon compound, a boron compound, an aluminum compound, an aliphatic carboxylic acid or its salt, a phosphorus compound or a titanium compound, as described in Japanese Patent Application No. 58-250163. It can also be used.

In the present invention, representative examples of the reducing agent that does not contain carbon include N2, NH2NH2, and the like.

Further, as the carbon-containing reducing carbonizing agent, at least one of the following compounds can be used.

■CO ■Aliphatic, linear or cyclic, saturated or unsaturated hydrocarbons, such as methane, propane, butane, cyclohexane, methylcyclohexane, acetylene, ethylene,
Propylene, butanoene, isoprene, dunn gas, etc.

(2) Aromatic hydrocarbons, such as benzene, toluene, xylene, and their furkyl and alkenyl derivatives at temperatures below 15 oC.

(A) Aliphatic alcohols such as methanol, ethanol, propanol, cyclohexanol.

■ Boiling of esters such as methyl formate, ethyl acetate, etc., 4
Ester below 150℃.

(2) Ethers, such as lower alkyl ethers and vinyl ethers, having a boiling point of 150°C or less.

■Aldehydes, such as formaldehyde, acetaldehyde, etc., whose boiling point is below +50'C.

(2) Ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, etc., having a boiling point of 150'C or less.

Particularly preferred carbon-containing reducing carbonizing agents are CO%CH,
OH, HCOOCH, is a saturated or unsaturated aliphatic hydrocarbon having 1 to 5 carbon atoms.

In the step (,) of the present invention, the carbon-free reducing agent can be used diluted or undiluted, and examples of the diluent include N2, CO2, fulvon, helium, and the like. Further, the dilution rate can be arbitrarily selected, and it is preferable to dilute, for example, about 1.1 to 10 times (volume ratio). Contact conditions such as contact temperature, contact time, flow rate, etc.
For example, the manufacturing history of acicular iron oxyhydroxide or acicular iron oxide,
It varies depending on the average axial ratio, average particle size, specific surface area, etc.
It is best to choose as appropriate. The preferred contact temperature is about 200
~700°C, more preferably about 300-400°C, and the preferred contact time is about 0.5-6 hours. The preferred flow rate is about 1 to 10100 OS, T per gram of raw iron compound.
.

It is 87 minutes. In addition, the contact pressure includes the diluent,
A pressure of 1 to 2 atmospheres is commonly used, but there is no particular restriction.

Also in the step (b) of the present invention, a carbon-containing reducing carbonizing agent or a mixture of this and a carbon-free reducing agent can be used diluted or undiluted. When a mixture is used, the mixing ratio can be selected as appropriate, but it is usually preferable that the volume ratio of the carbon-containing reducing carbonizing agent to the carbon-free reducing agent be Ilo, 05 to 115. Contact conditions can be similarly selected as appropriate;
The preferred contact temperature is about 250 to 400°C, more preferably about 300 to 400°C, and the preferred contact time is about 0.5 to 6 hours when step (a) is performed, and about 6 hours when step (a) is not performed. It is 1 to 12 hours. A preferred flow rate is about 1-10100 OS, T, P/min per gram of raw iron compound. The contact pressure, including the diluent, is usually 1 to 2 atmospheres, but is not particularly limited.

When observed with an electron microscope, the particles obtained in the present invention are uniform particles on average and have the same shape as the raw material iron oxyhydroxide or iron oxide particles. - Exists as particles. In addition, the obtained particles contained carbon according to elemental analysis, and furthermore, X#11
The diffraction pattern reveals that it contains iron carbide. The X#i diffraction pattern has a lattice spacing of 2.28.2.
20.2.08.2.05 and 1.92A. Such a pattern corresponds to Fe5C2, and the iron carbide of the present invention usually consists mainly of Fe, C2, but FezC,
Fe2oC5 (Fe2.2C), Fe, C, etc. may coexist. Therefore, the iron carbide contained in the particles of the present invention is appropriately expressed as Fe and C (2≦x3).

In addition, when carbonization is incomplete, the particles obtained according to the invention also contain iron oxides, mainly Fe and O.

Generally, for iron oxide, Fed, Fe50. and γ
-F ex Os are structurally related, and the oxygen atoms in all three have a cubic close-packed structure, and the actually existing Fe and O vary in these widths. The above iron oxide is suitably denoted by Fe0y (1<y≦1.5).

In addition, the obtained particles contain iron carbide or iron oxide in some cases, but referring to the elemental analysis values of C, H and N,
Usually, it contains more carbon than the amount of carbon calculated from the chemical formula of iron carbide, which is confirmed by the X-ray diffraction pattern. It is unclear whether such excess carbon exists in combination with iron or as free carbon. In this sense, elemental carbon may be present in the particles obtained. Therefore,
The obtained particles have an average axial ratio of 1.
0 or more and less than 3.0, particles consisting essentially of iron carbide or particles consisting of iron carbide, iron oxide and/or elemental carbon.

Therefore, the content of iron carbide and iron oxide in the obtained particles can be determined by determining the chemical formulas of iron carbide and iron oxide using the respective main components Fe, C2 and Fe, O, detected by X, 11 diffraction analysis. , which can be further determined by elemental analysis and scorching bulking. The content of iron carbide is preferably 20% by weight or more, more preferably 50% by weight or more. Further, iron oxide is preferably 70% by weight or less, and more preferably 40% by weight or less.

Further, the average axial ratio and average particle diameter of the particles obtained are slightly smaller than those of iron oxyhydroxide or iron oxide as raw materials, but there is almost no difference. Therefore, the average axial ratio of the particles obtained by this manufacturing method is usually 1.0 or more and less than 3.0,
The average particle size (long axis) is more than 0.1μ apex and less than 5μm.

The iron carbide-containing particles of the present invention can be used as a magnetic material for magnetic recording, as is clear from the direct characteristics, but are not limited to this. Since it is used as a catalyst etc. for the synthesis of 'Il'b.

(Effects of the Invention) According to the method of the present invention, particles having a relatively large coercive force can be produced using a raw material iron compound that is easy to produce.

(Example) A detailed explanation will be given below with reference to examples.

In the examples, various characteristics etc. were determined by the following methods.

(1) Magnetic properties Unless otherwise specified, it is determined by the following method.

A sample filling rate of 0 was measured using a space meter using a Hall element.
．． 2, the coercive force (Ha.

Oe), saturation magnetization g (, s, e, m, u) and residual magnetization sensitivity (σY·, e, +++, u) are measured.

(2) Elemental analysis of C, H and N Elemental analysis is performed using MT2C) INCOR manufactured by Yanagimoto Seiko Co., Ltd.
This is carried out in a conventional manner using a DERYanaco at 900''C by passing oxygen (helium carrier) through.

(3) How to determine the composition The chemical formulas of iron oxide and iron carbide were determined by XM diffraction analysis, and were determined from the elemental analysis value of C and the weight increase due to the heat treatment described below. For example, Fe50° is Ichikawa's 1,0
F(!,,O,, which is equivalent to 35 times, and also F e5 C
The calculation is performed assuming that 2 changes to Fe20J, which is equivalent to 1.317 times its weight. Heat treatment (to reduce the weight increase, place the sample in a platinum crucible and heat it in a Matsufuru furnace for 60 minutes.
After heat treatment at 0°C for 1 hour, α~Fe2 was determined by X-ray diffraction.
After confirming the presence of O, the weight increase due to heat treatment is determined according to a conventional method.

To be more specific, if the composition ratios of Fe5C2, Fe, O, and elemental carbon are X, y, and 2% by weight, respectively, and the carbon analysis value and increase in heat treatment due to heat treatment are A and 8% by weight, respectively, then X% Y and 2 can be determined from the following three-dimensional equation.

x + y + z = 100 1.317x+ 1.035y” 100+ Bz +
0.079x = A Example 1 2 g of dacite particles with an average particle diameter of 0.6 μm) and an average axial ratio of 2 were placed in a porcelain boat, inserted into a tube furnace, and the air was replaced with nitrogen. After that, the temperature was raised to 300'C, and at that temperature, H2 was contacted at a flow rate of 100+ol/min for 2 hours.

Subsequently, at that temperature, CO was contacted at a flow rate of 100+nl/min for 1 hour, and then allowed to cool to room temperature to obtain a black powder.

The X-ray diffraction pattern of the product is ^STM X-Ray1
〕omder I)uta Filp 20-509
It matched with Fe5Cz Iron Carbide.

The results are shown in Tables 1 and 2.

Examples 2 to 5 Black powder was obtained in the same manner as in Example 1 using the raw materials and contact conditions listed in Table 1. The results are shown in Tables 1 and 2.

Table 1 Table 2 Example 6 2 g of dacite particles with an average particle diameter of 0.6 μm (long and thin) and an average axial ratio of 2 were placed in a porcelain boat, inserted into a tube furnace, and nitrogen was flowed to replace the air. After that, the temperature was raised to 300°C, and at that temperature, CO was contacted at a flow rate of 100 ml/min for 2.5 hours, and then the mixture was allowed to cool to room temperature to obtain a black powder. The conditions and results are shown in Tables 3 and 4.

Example 7 1 g of dacite particles with an average particle size of 0.6 μm (long sleeve) and an average axial ratio of 2 was placed in a porcelain boat, inserted into a tubular furnace, and after nitrogen was flushed and replaced, the temperature was raised to 300 ° C. At that temperature CO
was contacted at a flow rate of 300 ml per minute for 3 hours, and then allowed to cool to room temperature to obtain a black powder. The conditions and results are shown in Tables 3 and 4.

Example 8 3 g of α-FeOOH was dehydrated at 600°C for 1 hour to obtain αFe
2O3, reduced H2 at 400°C for 1 hour, and heated to 350°C.
γ-F 2203 particles were obtained by oxidation in air for 1 hour.

Next, the mixture was placed in 100 ml of 2% cobal sulfate (2% cobal sulfate), stirred, adjusted to pH 10 with an aqueous NaOH solution, stirred at 80° C. for 30 minutes, and dried to obtain Co-coated γ-Fe2O3. 2g of these particles were placed in a porcelain boat and inserted into a tube furnace.
After purging with nitrogen, the temperature was raised to 350° C., and at that temperature, CO was contacted at a flow rate of 100+al/min for 3 hours, and then allowed to cool to room temperature to obtain a black powder. The conditions and results are shown in Table 3 and Table tJfJ4.

Examples 9 to 12 and Reference Example 1 The raw iron compounds shown in Table 3 were brought into contact with the contact gases shown in the same table to obtain black products shown in Table 4.

Table 3 1 Example Raw material iron compound Contact gas 1 type Pongee Type Flow rate example (μm Ratio m17 min'(: br6 -Fe00HO062Co
100 2゜7 // /
／／／Co 300
3゜8 Co coating 0.31. Co 1
00 3゜Fe203 9 -Fe00HO,51,Co 300
3゜Table 4 Example 13 The powders obtained in Example 6, Example 12, and Reference Example 1 were each mixed with 5.25 g of vinyl chloride-vinyl acetate copolymer, dioctyl 7-talate +, and ooglau.
phosphoric acid
0.2 bit en
15.0 g of methyl isobutyl ketone (15 g, 20 g or 25 g, respectively) is added to a vehicle consisting of 15.0 g, and an iron ball 6 with a diameter of 15IIlf11 is placed inside the vehicle to give an internal volume of 200τ1.
Knead for 6 hours at 3 Or, p, +n in a No. 1 porcelain ball mill.

The resulting paint was applied onto a polyethylene terephthalate film using a doctor knife, and the state of crosstalk was observed. The results are shown in Table 5.

Table 5 ○: Uniformly kneaded.

×: Wires were mixed unevenly (relay parts were scattered).

Claims (7)

[Claims] (1) Average axial ratio of 1.0 or more and less than 3.0, average particle size of 0.
Particles containing iron carbide of more than 1 μm and less than 5 μm. (2) (a) After contacting iron oxyhydroxide or iron oxide with an average axial ratio of 1.0 or more and less than 3.0 and an average particle size of more than 0.1 μm and less than 5 μm with a reducing agent that does not contain carbon, or (b) contact with a reducing carbonizing agent containing carbon or a mixture of this and a reducing agent not containing carbon, with an average axial ratio of 1.0 or more and less than 3.0, and an average particle size; is 0.1
A method for producing particles containing iron carbide with a size exceeding 5 μm. (3) Iron oxyhydroxide is α-, β- or γ-FeO
OH, iron oxide is α- or γ-Fe_2O_3 or F
The manufacturing method according to claim 2, which is e_3O_4. (4) The manufacturing method according to claim 2, wherein the contact temperature in step (a) is 200 to 700°C, and the contact temperature in step (b) is 250 to 400°C. (5) The reducing carbonizing agent containing carbon is CO, CH_3OH
, HCOOCH_3 is a saturated or unsaturated aliphatic hydrocarbon having 1 to 5 carbon atoms. (6) The manufacturing method according to claim 2, wherein the carbon-free reducing agent is H_2. (7) Average axial ratio of 1.0 or more and less than 3.0, average particle size of 0.
A magnetic material consisting of particles containing iron carbide with a size of more than 1 μm and less than 5 μm.