JPH08109010A - Production nitride powder - Google Patents

Abstract

PURPOSE: To form a nitride powder maintaining the initial shapes of the starting powder particles without sintering between the particles during the nitriding. CONSTITUTION: After coating film containing a surfactant comprising oleic, linolic or linolenic acids or their salts or alkylamines is formed on the surface of the starting powder particles, the starting particles are introduced together with crushing medium 14 comprising particles of zirconia, alumina, silica and soda ash glass into a rotary heater 1. As the heater 1 is rotated, they are heated in a nitriding gas atmosphere to effect nitriding. The powder particles can be prevented from sintering each other by dispersing action of the coating film of surfactant and by crushing action of the crushing medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a nitride powder, and more particularly to a nitride powder suitable for a nitride fine ceramics raw material powder, a magnetic toner raw material powder, and a magnetic recording material raw material powder. The present invention relates to a method for producing powder.

[0002]

2. Description of the Related Art Conventionally, metal nitride powder obtained by nitriding powder of metal, metal oxide, metal chloride, etc. has been used as a raw material for fine ceramics, magnetic toner, magnetic recording materials and the like. There is. As a method for producing this metal nitride, various methods have been proposed and carried out, for example,
Regarding the iron nitride powder, a method of supplying iron powder into a plasma arc in a nitriding atmosphere or a method of evaporating iron by a plasma arc into iron vapor and supplying nitrogen gas thereto, a grain size of 0. Ultra-fine particles of iron nitride having a size of about 01 μm are manufactured. Further, a method of producing fine powder of metal nitride by reacting vapor of metal vapor or metal chloride with ammonia gas in a reducing gas atmosphere is also adopted. Furthermore, a method of producing a nitride of the raw material powder by introducing the raw material powder into a high temperature nitriding atmosphere using a calcining device such as a rotary kiln is also practiced.

However, in the above method, in the method of reacting a metal vapor and a nitriding gas like the plasma method, nitride powder is produced in a beaded state,
Further, in the method of firing using a rotary kiln, there is a problem that raw material powders are sintered during the nitriding reaction and large particles are generated. Therefore, the applicants of the present invention previously disclosed in Japanese Patent Application No. 5-61465 a high temperature nitriding atmosphere while introducing a pulverizing medium together with the raw material powder into a rotary heating furnace and stirring them strongly by rotation. Proposes a method for producing a metal nitride single particle without sintering of powder particles by simultaneously crushing and crushing the nitriding reaction.

[0004]

However, in the method for producing nitride particles described in the above-mentioned Japanese Patent Application No. 5-61465, the sintered powder produced during the progress of the nitriding reaction is forced by a grinding medium. Since it is a method of crushing and crushing to separate the sintered powder, the crushing medium does not affect the raw material powder by contamination and is formed of a material having excellent thermal and mechanical strength. In view of the crushing and crushing efficiency, a material having a relatively large specific gravity is preferable.
Therefore, the type of grinding medium that can be used is limited, and an expensive one may have to be used. Also,
When using a grinding medium with high specific gravity, the sintered powder may be crushed and crushed more than necessary, and even powder that has not been sintered may be destroyed. Yield of nitride single particles with different particle size (particles that exist independently and can be easily dispersed in each single particle), or a large amount of fine powder Are generated and adhere to the furnace wall of the heating furnace, and the reaction efficiency is decreasing.

Therefore, it is an object of the present invention to provide a method for producing a nitride powder in which the powders do not sinter during the nitriding reaction and the initial shape of the raw material powder is maintained.

[0006]

Means and Action for Solving the Problems The present inventors have
As a result of earnest research to achieve the above object relating to the method for producing a nitride powder, after forming a coating film containing a surfactant on the surface of the raw material powder, it was introduced into a rotary heating furnace together with a crushing medium, It was found that by heating in a nitriding gas atmosphere while rotating a rotary heating furnace to perform a nitriding reaction, it is possible to produce a nitride powder that does not sinter each other and maintains the initial particle size. The present invention has been completed.
The surfactant is preferably at least one of oleic acid, linoleic acid, linolenic acid or salts thereof, and alkylamines. The crushing medium is preferably made of at least one of zirconia, alumina, silica and soda ash glass.

The raw material powder used in the present invention is a powder composed of a metal, an alloy, an intermetallic compound, and a metal compound such as an oxide or a chloride thereof, and is specifically used as an ordinary magnetic material. Metals and alloys such as iron, cobalt, nickel, manganese, and chromium, or intermetallic compounds containing them, and various metals and alloys such as aluminum, titanium, silicon and neodymium, rare earth metals such as samarium, or the like. An intermetallic compound containing is mentioned. Here, according to the present invention, since the initial shape of the raw material powder is maintained after the nitriding reaction for the reason described below, the particle diameter of these raw material powders is appropriately selected depending on the use of the produced nitride powder. It is possible to

Prior to the nitriding reaction, the surface of the raw material powder is coated with a film containing a surfactant. This surfactant-containing coating improves the dispersibility of the raw material powders and prevents sintering of the raw material powders during the nitriding reaction. Therefore, as the above-mentioned surfactant, if it decomposes and evaporates before reaching the nitriding reaction temperature and completely disappears from the surface of the raw material powder, the effect of preventing sintering of the powder particles cannot be obtained. It is preferable that the compound has a relatively high decomposition temperature.

Examples of the above-mentioned surfactants include fatty acid monocarboxylic acid salts, N-acryloylglutamates, alkylbenzene sulfonates, naphthalene sulfonate-formaldehyde condensates, sulfosuccinic acid dialkyl esters, sulfuric acid alkyl salts and alkyl polyoxysulfates. Anionic surfactants such as ethylene salt and alkyl phosphate,
Cationic surfactants such as alkylamine salts, alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, glycerin fatty acid esters, sorbitan acid esters, sucrose fatty acid esters, polyoxyethylene alkylphenyl ethers, polyoxyethylene Polyoxypropylene block copolymer, polyethylene glycol fatty acid ester, polyoxyethylene sorbitan fatty acid ester, fatty acid alkanolamide, N, N-dimethyl-N-alkylaminoacetic acid betaine, 2-alkyl-
An amphoteric surfactant such as 1-hydroxyethyl-1-carboxymethylimidazolinium betaine can be mentioned. When the raw material powder is made of a substance containing iron, oleic acid, linoleic acid, linolenic acid or salts thereof having high affinity with iron oxide or metallic iron, or alkylamines are preferable as the surfactant.

Then, the raw material powder or a dispersion solution of the raw material powder is added to a coating solution in which these surfactants are dissolved in a suitable solvent, and the mixture is thoroughly stirred and solid-liquid separated to separate solid components. By washing and drying, a raw material powder having a surfactant-containing coating film on its surface can be obtained.

The film thickness of the surfactant-containing coating is not particularly limited, but it is necessary that it is present on the surface of the raw material powder during the progress of the nitriding reaction. The remaining amount of decomposition of the surfactant-containing coating depends on the film thickness at the beginning of film formation, the reaction temperature and the reaction time. Therefore, by previously obtaining the relationship between the remaining amount of the surfactant-containing coating and the film thickness at the time of film formation, the reaction temperature, and the reaction time, the above film thickness control becomes possible. Specifically, carbide or hydrocarbon or C which is a decomposition component of the surfactant in the gas generated by the reaction.
A gas such as Ox is analyzed with a mass spectrometer over time, and it can be determined that the surfactant-containing coating has disappeared when the analysis value becomes a predetermined value (for example, 0.1 vol%) or less. Therefore, it is possible to set the film thickness at the beginning of film formation suitable for the reaction temperature and reaction time in the actual production process by changing the film thickness and reaction temperature and measuring the time until the film disappears. The film thickness at the beginning of film formation can be adjusted by the surfactant concentration of the coating solution. Further, by adding an amount of a binder and a film stabilizer to the coating solution in an amount that does not affect the dispersing action of the surfactant, the film-forming property and film stability of the film containing the surfactant are improved. Can be made.

The disintegration medium introduced into the rotary heating furnace together with these raw material powders is made of a material having a high specific gravity as in the prior art because the dispersibility of the powder is improved by the surface active agent-containing coating. It is not necessary to form the particles, and it is possible to sufficiently prevent the sintering of the powder particles even if they are made of a material having a low specific gravity. For example, zirconia particles, alumina particles,
Ceramic particles such as silica particles and soda ash glass particles can be preferably used. Further, these ceramic particles can be mixed and used. The crushing medium made of these materials having a low specific gravity hardly breaks or deforms the raw material powder even if it is introduced into the rotary heating furnace together with the raw material powder. It will be easier.

The shape of the crushing medium is not particularly limited, but the diameter is 0.2 to 30 mm, preferably 0.5 to.
Small spheres of 10 mm can be used alone or in combination of small spheres having different diameters. Further, the shape is not limited to the spherical shape, and may be a rod shape having the same size. Furthermore, spherical and rod-shaped ones may be used in combination. Further, the mixing ratio of the raw material powder and the crushing medium, the type of the raw material powder, the shape of the crushing medium and its usage, that is, the spherical crushing medium alone, or the spherical and rod-like crushing medium Although it depends on the combination or the like, in any case, since the dispersibility of the powder is improved by the surfactant-containing film, the amount of the crushing medium can be reduced as compared with the conventional case. This is to maintain the initial shape of the raw material powder,
It is a further advantage. Specifically, in terms of weight ratio, raw material powder 1
00 is introduced into the rotary heating furnace at a ratio of 10 to 1000, preferably 30 to 400 of the raw material powder.

The raw material powder and the crushing medium are introduced into a rotary heating furnace for nitriding. As a rotary heating furnace, the applicants of the present invention previously filed Japanese Patent Application No. 5-593.
The device described in No. 10 can be preferably used. That is, as shown in FIG. 1, the manufacturing apparatus 1 includes a cylindrical reaction container 2, a heating furnace 3 arranged so as to surround the reaction container 2, and a rotary drive device 4 for rotating the reaction container 2. The reactive gas or carrier gas filled in the gas cylinder 7 is introduced from the gas supply port 5 of the reaction container 2 into the reaction container 2 through the supply pipe 8 and is connected to the exhaust port 6. Exhausted through the exhaust pipe 9,
Then, it passes through the air-cooled trap 10, the oil trap 11, and the water trap 12, and is purified and discharged to the outside of the system.

In the nitriding reaction, the raw material powder 13 on which the surfactant-containing coating is formed is housed together with the crushing medium 14 in the space defined by the partition wall 15 inside the reaction vessel 2, and the reaction vessel 2 is rotated. It is performed by heating for a predetermined time in a nitriding atmosphere. As for the reaction conditions, although the surfactant-containing coating is formed on the surface of the raw material powder, the film thickness is usually not so thick as to affect the permeability of the nitriding gas. It may be the same as the nitriding reaction in the case of not being formed. For example, a reducing gas such as hydrogen gas,
A carrier gas composed of an inert gas such as nitrogen gas or argon gas or a mixed gas thereof and a nitriding gas such as ammonia gas are mixed in a volume ratio of 1: 100 to 100: 1 as carrier gas: nitriding gas. In a nitriding atmosphere consisting of a proportion of 200 to 1000 ° C., preferably 40
0 to 800 ° C., 0.5 to 10 hours, preferably 2 to 8
A nitride powder is obtained by heating for a time. At this time, the dispersibility of the raw material powder is improved by the surfactant-containing film formed on the surface of the raw material powder, and the raw material powder and the nitride powder produced during the reaction are constantly crushed by the crushing medium. As a result, the particles are prevented from sintering together.

[0016]

EXAMPLES Next, the method for producing a nitride powder according to the present invention will be described in more detail based on examples. [Example 1] 50 g of spherical tetrairon trioxide fine particles having an average particle size of about 0.2 µm were added to 500 ml of a 10% aqueous solution of sodium oleate prepared in advance in a water bath maintained at 95 ° C. The solution containing iron trioxide fine particles was kept for 1 hour while stirring with a motor stirrer to obtain a dispersion solution. The pH of the dispersion solution was adjusted to 4 by adding 0.1N hydrochloric acid, the iron oxide fine particles having the oleic acid monomolecular film formed on the surface were aggregated, and the obtained aggregate was filtered with a filter paper, and the temperature was adjusted. The electrolyte adhering to the surface was removed by washing with 1 liter of deionized water at 20 ° C, and then the temperature was adjusted to 10
It dried at 0 degreeC and obtained the dry powder. 52 g of the powder thus obtained was used as zirconia beads 15 having an average particle diameter of 1 mm.
1 g of hydrogen gas and 1 g of ammonia gas in the reaction vessel of the rotary heating furnace shown in FIG.
While supplying a mixed gas at a flow rate of 1 liter per minute, the temperature was raised to 500 ° C. over 2 hours, and then at 500 ° C.
After holding for a while, it was allowed to cool. After cooling, the zirconia beads were sieved to obtain 38 g of iron nitride powder. When this iron nitride powder was observed with a scanning electron microscope, it was spherical, and sintering of the particles was not observed, and they were independent spherical nitride fine particles. Also, image processing device L manufactured by Nireco Co., Ltd.
The average particle size obtained using UZEXIII is 0.18μ
It was m. Regarding the magnetic characteristics, the magnetization in a magnetic field of 10 kOe was 145 emu / g.

Example 2 3 g of oleic acid was added to 86 g of dehydrated kerosene heated to 80 ° C., and mixed and dissolved in a solution of 30 g of spherical iron fine particles having an average particle size of about 0.5 μm.
Was added, and the mixture was held for 3 hours while stirring with a motor stirrer to obtain a dispersion solution. The dispersion solution is subjected to solid-liquid separation by a centrifuge, and after cooling, the solid content is 8 at a temperature of 80 ° C. by a vacuum dryer.
After drying for an hour, a dry powder was obtained. 30 g of the oleic acid-coated powder thus obtained was housed together with 100 g of zirconia beads having an average particle diameter of 3 mm in the reaction container of the rotary heating furnace shown in FIG. While supplying the mixed gas at a flow rate of 1 liter per minute, the temperature was raised to 500 ° C. over 2 hours, the temperature was further maintained at 500 ° C. for 5 hours, and then allowed to cool. After cooling, the zirconia beads were sieved to obtain 28 g of iron nitride powder. When this iron nitride powder was observed with a scanning electron microscope, it was spherical, and sintering of the particles was not observed, and they were independent spherical nitride fine particles. Further, the average particle size obtained by using an image processing device LUZEXIII manufactured by Nireco Co., Ltd. was 0.6 μm. Regarding the magnetic characteristics,
The magnetization in a magnetic field of 10 kOe was 150 emu / g.

Example 3 To 120 g of dehydrated kerosene, 20 g of amine (polybutenyl succinimide tetraethylenepentamine) was added, and further 30 g of spherical iron powder was added and heated to 120 ° C. in a nitrogen atmosphere and stirred with a motor stirrer. After stirring for 30 minutes, the mixture was cooled, solid-liquid separated, and dried at 80 ° C. for 8 hours by a vacuum dryer to obtain a dry powder. 40 g of the amine-coated iron powder thus obtained had an average particle size of 1
mm alumina beads 30 g and average diameter 3 mm alumina beads 50 g were housed in the reaction vessel of the rotary heating furnace shown in FIG. 1, and a mixed gas of a ratio of volume ratio of nitrogen gas 1 to ammonia gas 4 was set for each. While supplying at a flow rate of 1 liter / minute, the temperature was raised to 600 ° C over 2 hours, and then 6
After holding at 00 ° C. for 4 hours and 30 minutes, it was allowed to cool. After cooling, the alumina beads were sieved to obtain 32 g of iron nitride powder. When this iron nitride powder was observed with a scanning electron microscope, it was spherical, and sintering of the particles was not observed, and they were independent spherical nitride fine particles. Further, the average particle size obtained by using an image processing device LUZEXIII manufactured by Nireco Co., Ltd. was 0.6 μm. Regarding the magnetic characteristics, the magnetization in a magnetic field of 10 kOe was 160 emu / g.

Example 4 Using the same method as in Example 1, 50 g of octahedral tetrairon tetraoxide fine particles having an average particle size of 0.33 μm was used as the iron raw material, and oleic acid of 2.5 g was used as the coating raw material. A coating is formed on the surface of iron trioxide, and 30 g of zirconia beads having an average particle size of 1 mm and an average particle size of 3 m are used as a crushing medium.
20 g of zirconia beads of m.
g together with g in the reaction vessel of the rotary heating furnace shown in FIG. 1 and supplying a mixed gas of hydrogen gas to hydrogen gas at a ratio of 1 to 1 at a flow rate of 1 liter per minute to 450 ° C. Temperature rises over 30 minutes, then 450 ° C
It was kept for 6 hours and then left to cool. After cooling, the zirconia beads were sieved to obtain 45 g of iron nitride powder. When the shape of this iron nitride powder was confirmed by a scanning electron microscope, it was found to be an octahedron which was almost the same as the raw material. Also, the average particle size obtained using the image processing device LUZEXIII manufactured by Nireco Co., Ltd.
It was 0.35 μm. Further, the composition of the compound obtained by the powder X-ray diffraction method was Fe ₄ N. Regarding the magnetic characteristics, the magnetization in a magnetic field of 10 kOe is 135
It was emu / g.

[Embodiment 5] Dry powder having an oleic acid coating was prepared in the same manner as in Embodiment 2 by using spherical carbonyl iron fine particles having an average particle diameter of 1.8 μm as an iron raw material. 30 g of alumina beads having a particle diameter of 1 mm and 10 g of alumina beads having an average particle diameter of 3 mm were housed together with the dry powder in the reaction container of the rotary heating furnace shown in FIG. While supplying the mixed gas in the ratio of gas 1 at a flow rate of 1.5 liters per minute, the temperature was raised to 450 ° C. over 1 hour and 30 minutes, and the temperature was further maintained at 450 ° C. for 8 hours and then allowed to cool. When the shape of the obtained iron nitride powder was confirmed by a scanning electron microscope, it was found to have a spherical shape almost the same as that of the raw material. Also, the average particle size obtained using the image processing device LUZEXIII manufactured by Nireco Co., Ltd.
It was 2.2 μm. Further, the composition of the compound obtained by the powder X-ray diffraction method was Fe ₄ N. Regarding the magnetic characteristics, the magnetization in a magnetic field of 10 kOe is 156e.
It was mu / g. The total amount of carbon remaining in the iron nitride is 0.
It was 1% by weight or less, and it was confirmed that most of it evaporated and disappeared.

Comparative Example 1 A dry powder having an oleic acid coating was prepared in the same manner as in Example 2 by using spherical carbonyl iron fine particles having an average particle diameter of 1.8 μm as an iron raw material, and used as a crushing medium. Using 30 g of iron balls having an average particle size of 1 mm and 10 g of iron balls having an average particle size of 3 mm, together with the dry powder, FIG.
In a reaction vessel of a rotary heating furnace shown in Fig. 1 and supplying a mixed gas of a volume ratio of ammonia gas 6 to nitrogen gas 1 at a flow rate of 1.5 liters per minute to 450 ° C for 1 hour 30 The temperature was raised over a period of minutes, the temperature was further maintained at 450 ° C. for 8 hours, and then the mixture was allowed to cool. When the shape of the obtained iron nitride powder was observed with a scanning electron microscope, flat particles and ultrafine particles due to over-milling were confirmed. The average particle size obtained using an image processing device LUZEXIII manufactured by Nireco Co., Ltd. is 1.
3 μm, and the weight of fine powder of 0.1 μm or less is 2
It was 5%, and the entire particle size distribution was shifted to the fine particle side.

[0022]

As described above, according to the present invention,
The dispersibility of the raw material powder is improved by the surfactant-containing film formed on the surface of the raw material powder, and the raw material powder and the nitride powder produced during the reaction are constantly disintegrated by the disintegration medium. Therefore, sintering of the particles is prevented. Moreover, since the material having a low specific gravity can be used as the crushing medium, the raw material powder is less likely to be broken or deformed even when introduced into the rotary heating furnace together with the raw material powder, and the initial stage of the raw material powder can be reduced. The shape can be maintained and converted into a nitride, and the particle size of the generated nitride particles can be easily controlled.

[Brief description of drawings]

FIG. 1 is a diagram showing a rotary heating furnace used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rotary heating furnace 2 reaction container 3 heating furnace 4 rotation drive means 7 gas cylinder 8 gas supply pipe 9 gas exhaust pipe 13 raw material powder 14 crushing medium

Front page continuation (72) Inventor Takashi Shinko 8-10-16 Shimorenjaku, Mitaka-shi, Tokyo Within Nittetsu Mining Co., Ltd. (72) Inventor Isao Nakatani 1-2-1 Sengen, Tsukuba-shi, Ibaraki Science and Technology Agency (72) Inventor Katsuhito Nakatsuka 4-3-5-3, Moiwadai, Taihaku-ku, Sendai City, Miyagi Prefecture

Claims (3)

[Claims] 1. After forming a film containing a surfactant on the surface of the raw material powder, the raw material powder is introduced into a rotary heating furnace together with a crushing medium, and the rotary heating furnace is rotated under a nitriding gas atmosphere. A method for producing a nitride powder, which comprises heating and performing a nitriding reaction. 2. The method for producing a nitride powder according to claim 1, wherein the surfactant is at least one of oleic acid, linoleic acid, linolenic acid or salts thereof, or alkylamines. . 3. The method for producing a nitride powder according to claim 1, wherein the crushing medium comprises at least one of zirconia, alumina, silica and soda ash glass.