JPS60174807A - Refining method of fine particle - Google Patents

Abstract

PURPOSE:To refine the fine particles of the metal or metallic nitride obtd. by bringing metallic halide into reaction with a reducing gas in a vapor phase while preventing sintering and oxidation by washing said particles by using a solvent in an inert gaseous atmosphere. CONSTITUTION:Metallic halide such as FeCl2 in a gaseous or fine particulate state is brought into reaction with a reducing gas such as ammonia, hydrogen substantially in a vapor phase. The fine particles of the metal and/or metallic nitride such as metallic iron, iron nitride or the like obtd. by such vapor phase reaction are cleansed by water or solvent such as ethanol in an inert gaseous atomsphere of nitrogen, helium, argon, etc. Said solvents are preferably preliminarily removed of the dissolved oxygen by a method for blowing nitrogen, etc. The impurities consisting of unreacted halide and by-product, etc. are dissolved away by such washing and the above-mentioned fine particles are refined while oxidation and sintering are prevented.

Description

[Detailed description of the invention] The present invention relates to a novel method for purifying microparticles.

In recent years, a so-called gas phase reaction method in which a metal halide gas is reacted with a reducing gas such as hydrogen or ammonia has been attracting attention as a method for producing iron nitride fine particles or metal fine particles.

This method of producing fine particles through gas phase reaction is highly productive;
This manufacturing method has many excellent features, such as easy control of particle size and the ability to produce alloy fine particles and nitride fine particles of various compositions by controlling the composition of the raw material halide. However, this method has the problem that unreacted halides and by-products are contained in the fine particles produced, and when the particle size of the product is reduced, the content of unreacted halides increases. Ta.

(Unreacted halides and by-products mixed into the product not only reduce the purity of the fine particles produced, but also
It has an adverse effect such as promoting the oxidation of the generated fine particles, and it has been desired to develop a method for removing it. Methods for removing unreacted substances and byproducts in this product include, for example, high-temperature gas-solid separation at a temperature at which the halide vaporizes to remove the metal halide as a gas, and metal halides such as water and alcohol. A method has been proposed in which unreacted halides and by-products are dissolved and removed by washing the product using a solvent that dissolves the halides and by-products.

However, gas-solid separation at high temperatures has the disadvantage that the products are fine particles, and sintering between the fine particles tends to proceed due to the high surface activity. However, this method cannot be said to be suitable for practical use because it has the disadvantage that the product is oxidized during cleaning.

The present inventor has recently investigated a method for removing and refining the impurities contained in fine particles produced by such a gas phase reaction method while preventing sintering and oxidation. The present invention was achieved by discovering that purification can be achieved while preventing oxidation and sintering by using a solvent that dissolves halides and by-products and washing in an inert gas atmosphere.

The fine particles that are the object of the present invention are obtained by a so-called gas phase reaction in which a metal halogenide is reacted in a gaseous or fine particle state with a reducing gas such as ammonia or hydrogen in substantially the gas phase. Fe, Co, Ni, Cu
, Ad, Ga, Cr, ■, Sn, Ti.

Single element or alloy of Si, Mn, Zn, etc.
They are fine particles of metal or nitride.

The solvent used for cleaning is one that dissolves unreacted halides such as the metal halides mentioned above and by-products such as ammonium halides produced when reacting with ammonia. For example, water, alcohols such as ethanol, methanol, etc. Can be mentioned.

In washing, the solvent may be used as is, but it is preferable to remove dissolved oxygen in the solvent in advance. Examples of methods for removing dissolved oxygen include a method in which inert gas is blown into the solvent to replace the dissolved oxygen with nitrogen, a method in which the solvent is placed in a vacuum chamber, and dissolved oxygen is removed. Any inert gas may be used as long as it does not react with these metals, and nitrogen, helium, argon, etc. are preferably used.

Cleaning of fine particles is carried out in an inert gas atmosphere, and this method involves placing the peripheral powder in a solvent in a glove box whose interior has been replaced with an inert gas, stirring, and then purifying it by operations such as filtration and decantation. There is a method of separating the powder and a solvent containing impurities, a method of putting the solvent and peripheral flour into a stirring tank purged with inert gas, stirring, and then draining under a nitrogen atmosphere.

During washing, there is no particular restriction on the temperature of the solvent.
It is stored inside.

The present invention will be explained below with reference to Examples.

Example 1 Commercially available raw material pe: C12.
F c C12 obtained by dehydrating n1120 at 250° C. for 2 hours in a nitrogen stream was used.

The reaction was carried out using the distribution method. The reactor has an outer diameter of 45 mm.
A quartz tube with a diameter of 80 cIrL and a length of 80 cIrL was used.This quartz tube is a triple tube from the gas inlet side, and the innermost tube contains raw material FeC4, and the tube on the alumina boat side contains ammonia. It is designed to mix and react all at once in the reaction section.Two 23cm long electric furnaces are used for heating.
The electric furnaces are used in series, and the electric furnace on the gas inlet side is the raw material F.
For the evaporation of e C (J 2 ), the electric furnace on the gas outlet side was used to heat the reaction section to a predetermined reaction temperature.

A specific example of synthesis will be described. First, FeC1 was dehydrated in advance.
Approximately 6 g of 2 was placed in an alumina boat and heated to 800°C in the evaporation section. Next, the generated F e C 4 vapor was supplied to the reaction section using high-purity nitrogen gas, mixed with ammonia at 880° C., and reacted.

The molar ratio of FeC4 to ammonia in the reaction section was about 45 times excess ammonia.

The product powder obtained at a production rate of about 0.2-7 min was collected with an electrostatic collector attached to the outlet of the reaction tube.

When the recovered product was analyzed by X-ray diffraction, it was found to contain unreacted iron chloride and by-product ammonium chloride in addition to iron nitride and metallic iron.

Next, in order to remove unreacted iron chloride and by-product ammonium chloride in the product, the product was placed in a glove box whose interior was replaced with nitrogen. The glove box contains water that has been blown with nitrogen for about 1 hour to remove dissolved oxygen, and this water and the product are placed in a beaker at a ratio of ]:]OO, and after stirring at room temperature for 1 hour, decane is added. Water and product were separated by the cation method. After repeating the above washing operation three times, the separated purified powder was vacuum dried.

When the vacuum-dried product was analyzed again by X-ray diffraction,
The peaks for unreacted chloride and by-product ammonium chloride disappeared, leaving only the peaks for iron nitride and metallic iron.

Comparative Example 1 Using a powder containing unreacted iron chloride and by-product ammonium chloride obtained by the method of Example 1, it was placed in water in the atmosphere,
After stirring for 1 hour, the resulting powder turned red. When the product after separation from water was analyzed by X-ray diffraction, a peak of iron hydroxide was obtained.

Example 2 A gas phase reaction was carried out under the same conditions as in Example J, except that the same reaction apparatus as in Example 1 was used, and the reducing gas was replaced with hydrogen, to obtain a powdered product.

When the product was analyzed by X-ray diffraction, peaks of metallic iron and unreacted iron chloride were observed.

In a glove box purged with nitrogen, 10 ml of this product was dispersed in 11 ml of water from which dissolved oxygen had been removed, stirred for 1 hour, and then poured into an aqueous solution. When the P-separated product was vacuum-dried and then subjected to X-ray analysis, peel containing only metallic iron appeared. - Comparative Example 2 When the powder containing unreacted iron chloride obtained in Example 2 was dispersed in water in the air and stirred for 1 hour, the resulting powder turned red. After water was separated, X-ray analysis revealed that iron hydroxide was produced.

Example 3 1 g of the product powder containing unreacted iron chloride obtained in Example 2
was dispersed in 200% ethanol from which dissolved oxygen had been removed in a nitrogen-substituted glove box, stirred for 1 hour, then separated from the oven, and the residue was vacuum-dried.

When X-ray analysis was performed after drying, only the peak of metallic iron was obtained.

Example 4 Product powder J containing unreacted chloride obtained in Example 2
The solution was dispersed in 100 g of water from which dissolved oxygen had not been specifically removed in a nitrogen-substituted glove box, and after stirring for 1 hour, the mixture was separated from the door, and the residue was vacuum-dried. When X-ray analysis was performed after drying, only the peak of metallic iron was found, and the peaks of iron hydroxide and iron oxide were only traces.

Written amendment to the procedure (Shirakai Q August 7, 1980 Director General of the Patent Office Manabu Shiga, Indication of the case 1983 Patent Application No. 29632 2 Name of the invention Method for purifying fine particles 3 Person making the amendment 7r゛、＼、Mei 1111, page 7, line 4, it says "...at a ratio of 1:100..." instead of "...at a ratio of 100:1..."
"..." I corrected myself.

Claims (1)

[Claims] (1) Metal and/or metal nitridation obtained by a gas phase reaction method in which a metal halide is reacted in gaseous or fine particle form with a reducing gas such as ammonia or hydrogen substantially in the gas phase. In refining fine particles of matter,
The fine particles are washed in an inert gas atmosphere using a solvent that dissolves unreacted halides and by-products, and impurities consisting of unreacted halides and by-products in the fine particles are dissolved and removed. Characteristic method for purifying fine particles.