JPH02204319A - Production of superfine powder of high-melting-point carbide - Google Patents

Abstract

PURPOSE:To easily produce the superfine powder of a high-melting-point carbide excellent in sinterability by hydrolyzing a transition-metal alkoxide in a suspension of carbon in alcohol under specified conditions, drying the formed gel, heating and then disintegrating the dry gel. CONSTITUTION:A carbon suspension, alcohol and a transition-metal alkoxide, alcohol and water are mixed, the pH of the mixture is controlled to a value close to the isoelectric point of the transition-metal oxide, and hydrolysis is carried out. The water is removed by heating, etc., to dry the product, and a metal oxide gel in which fine carbon grains are uniformly dispersed is obtained. The gel is heated (ordinarily at about 1250 deg.C) in vacuum or in an inert gas to obtain a granular carbide which is disintegrated for several minutes by an ultrasonic wave, etc., into fine powder. By this method, the superfine powder of a high-melting-point carbide such as ZrC, TiC and TaC having 4 about 1mu grain diameter is easily obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing ultrafine high melting point carbide powder with excellent sinterability.

[Conventional technology]

As a method for producing high melting point carbide powders such as zirconium carbide, titanium carbide, and tantalum carbide (ZrC, TiC, and TaC, respectively),
The main methods utilize the reactions of metals from group A to group A) and carbon, thermal carbon reduction of transition metal oxides, and reaction of transition metal chlorides with carbon. In these methods, a mixture of raw material powders is heated at high temperature to proceed with the reaction, and the produced carbide needs to be pulverized by a long-term pulverization process.

In addition to the above methods, methods such as (1) causing a gas phase reaction between a transition metal chloride and a hydrocarbon have been devised, but it is not easy to control the properties of the resulting powder, such as its composition and cohesiveness.

[The problem that the invention attempts to solve! Title]

When a long time grinding process is required as in conventional methods (1) to (2), impurities are mixed in during the process, which may cause a decrease in the strength of the sintered body obtained using the powder. In addition, in view of the fact that the gas phase synthesis method described in (2) requires advanced technology in controlling the process, the present invention provides a relatively convenient method for achieving high performance without requiring a long pulverization process. The object of the present invention is to provide a method for producing ultrafine melting point carbide powder.

[Means to solve the problem]

In the present invention, a transition metal alkoxide is hydrolyzed in an alcohol solution in which carbon is suspended near the isoelectric point of the metal oxide, and then dried to produce an oxide with carbon fine particles uniformly dispersed inside. A gel is produced, and the gel is further heat-treated in a vacuum or in an inert gas to produce a soft granular carbide, and by loosening the granular carbide, an ultrafine powder is produced.

(Function) FIG. 1 is a flowchart showing the method of the present invention. As described above, carbon suspension, alcohol and transition metal alkoxide, and alcohol and water are mixed, the pH is adjusted to near the isoelectric point of the oxide, and the mixture is hydrolyzed. After this, water is removed by a method such as heating. A metal oxide gel is obtained.The gel has a structure in which carbon is uniformly dispersed in an amorphous oxide, and has a density of about 40% of the theoretical value.Furthermore, the gel is heated in a vacuum or in an inert gas. A granular carbide is obtained by heating the granular carbide.
This is a mirror photo. The granular carbide is soft and can be easily loosened and made into a fine powder by a known method such as applying ultrasound for several minutes. FIG. 3 is a graph showing the particle size distribution of the fine powder. As is clear from the graph, the particle size is 1- or less, and the average particle size is about 0.4-
It is.

Here, the reason why the hydrolysis is performed near the isoelectric point is to obtain a homogeneous mixture by attaching the oxide gel to the carbon particles, and separation from the carbon tends to occur under conditions far outside the isoelectric point. This is because there is.

In addition, heat treatment was performed in vacuum or inert gas because
This is to achieve the low oxygen partial pressure necessary for the reaction between the oxide and carbon to proceed.

Furthermore, although the heating temperature varies depending on the type of transition metal, it is generally preferably 1,250'C or higher in order to obtain a carbide with good crystallinity and low oxygen content.

As described above, in the method according to the present invention, a soft granular carbide is obtained as an intermediate product, and ultrafine powder with a particle size of 1 or less can be obtained by simply exposing it to ultrasonic waves or the like for a short period of time.

Example I Titanium isopropoxide (TI(OCzllv)n)
Hydrolyze 0.1 mol of carbon powder in isopropyl alcohol containing 0.3 mol of carbon powder by adding isopropyl alcohol containing 2.5 mol of water little by little using a metering pump over a period of about 1 hour. did.

This was suction-dried with a water aspirator to remove alcohol, and then water was further removed in air at 60°C. 1!
) The resulting gel had a structure in which carbon was uniformly dispersed in an amorphous oxide, and the density was about 40% of the theoretical density value.

This was heated at 1250°C or higher in a vacuum of about 10-'Torr to obtain titanium carbide (TfC) granules.

However, a heating temperature of 1400°C was required to generate titanium carbide without solid solution of oxygen. The product was in the form of soft granules (FIG. 2) and could be easily crushed by exposure to ultrasound for several minutes to give a fine powder with an average particle size of 0.4-. Figure 3 shows the particle size distribution of the product powder.

Example 2 Zirconium n-propoxide (Zr (#tHff)
a) 0.1 mol was hydrolyzed in isopropyl alcohol in which 0.3 mol of carbon powder was suspended by adding isopropyl alcohol containing 1 mol of water little by little using a metering pump. Ultrafine powder of zirconium carbide (ZrC) was obtained by the same method as in Example 1. However, the heat treatment temperature was I400°C.

Example 3 Tantalum ethoxide (Ta(CJsO)s) 0.1
Hydrolysis was carried out by adding ethyl alcohol containing 1 mol of water little by little to a suspension of 0.35 mol of carbon powder in ethyl alcohol using a metering pump.

Ultrafine powder of carbonized tankard (TaC) was obtained by the same method as in Example 1. However, the heat treatment temperature was 140Q'C.

(Effects of the Invention) As described above, in the method of the present invention, the reaction itself is simple, and the obtained carbide is in the form of soft granules, so that fine powder of metal carbide can be obtained very easily.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram showing the flow of the production method of the present invention, FIG. 2 is a micrograph showing the particle structure of carbide granules produced by the method of the present invention, and FIG. 1 is a graph showing the measurement results of particle size distribution of ultrafine powder after ultrasonic crushing of carbide granules obtained by ultrasonic crushing. Tail 2 figure Irntr) Arrival, tI2I Ma, 3 concave kalpa and discharge (PL”)

Claims (2)

[Claims] 1. A transition metal alkoxide is hydrolyzed in an alcohol solution in which carbon is suspended near the isoelectric point of the transition metal oxide, and then dried to create an oxide gel in which carbon fine particles are uniformly dispersed. A method of producing ultrafine carbide powder by heating the gel in vacuum or in an inert gas to produce granular carbide, and loosening the granular carbide. 2. A transition metal alkoxide is hydrolyzed in an alcohol solution in which carbon is suspended near the isoelectric point of the transition metal oxide, and then dried to create an oxide gel in which carbon fine particles are uniformly dispersed. , A method for producing granular carbide by heat-treating the gel in vacuum or in an inert gas.