JPS58213606A - Preparation of titanium nitride powder - Google Patents

Abstract

PURPOSE:To prepare TiN powder having high purity and uniform and fine particle size, at a low cost, by heating a mixture of TiO2 and a reducing agent in a nitrogen-containing atmosphere selecting the kinds of the raw materials, the mixing condition of the raw materials, and the reduction and nitriding condition, etc. CONSTITUTION:Anatase-type titanium oxide powder is mixed with amporphous carbon powder as a reducing agent, and thoroughly pulverized and mixed under wet condition. The mixture is dried and heated at 1,800-2,000 deg.C in a nitrogen- containing atmosphere to effect the simultaneous reduction and nitriding. The process affords the preparation of TiN powder having low oxygen content and carbon content, high nitrogen content, high purity, and uniform and fine particle size, at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing highly pure, uniformly grained, fine titanium nitride powder that has a low oxygen content, a low carbon content, and a high nitrogen content.

In recent years, the demand for titanium nitride powder as a slag powder member for powder metallurgy, abrasive materials, and other uses has been increasing.

Conventionally, methods for producing titanium nitride powder include mixing titanium oxide with a carbon source as a reducing agent and heating it in a nitrogen-containing atmosphere to reduce and nitride it; Alternatively, the most common method was known to produce titanium hydride powder by heating it in a nitrogen-containing atmosphere while controlling the large amount of heat generated by the nitriding reaction.

However, with the former method, titanium nitride powder has a strong property of dissolving oxygen, making it difficult to produce powder with a low oxygen content, and also because some of the added carbon also dissolves in titanium nitride. However, there is a problem in that it is not easy to reduce the amount of residual carbon.In particular, increasing the amount of carbon added to reduce the amount of oxygen contained will further increase the amount of residual carbon. Since it is extremely difficult to reduce the amount of oxygen and the amount of residual carbon at the same time, the content of oxygen and carbon as impurities is low.
Moreover, it has been difficult to produce high-purity titanium nitride powder whose nitrogen content is close to the theoretical value. It has also been reported that in this case, it is effective to further increase the heating temperature in order to reduce the amount of oxygen contained.
Heating and holding at temperatures above ℃ is not preferable in terms of equipment or energy economy, and it is particularly difficult to mass produce.Moreover, the higher the heating temperature, the coarser the powder particles become, and the larger the particles become. As the powder solidifies as the sintering progresses, post-processing such as pulverization becomes difficult, and it is extremely difficult to produce powder with a size of, for example, 1 μm or less.

Thus, the production of titanium nitride powder using titanium oxide as a raw material is rarely applied industrially, especially due to purity issues, that is, high oxygen and carbon content, and therefore low nitrogen content. is the current situation.

On the other hand, according to the latter method, i.e., the method of nitriding high-purity metallic titanium powder or titanium hydride powder, high-purity, i.e., low oxygen, low carbon, and high nitrogen It is possible to produce titanium nitride powder with a high content, and most of the commercially available titanium nitride powders that are currently mass-produced are produced by this method. However, in this method, since a pulverized powder with an angular particle size is used as the raw material powder, titanium metal powder or titanium hydride powder, the particle shape of this raw material remains in the titanium nitride powder product, which affects its powder properties. Moreover, when the raw material powder is pulverized, the oxygen content increases, so it generally remains coarse, and for this reason, the titanium nitride powder obtained also has a particle size of several μm.
Since the particles became coarser, it was necessary to crush them again as a post-treatment. Therefore, the titanium nitride powder obtained by this method has a grain shape with sharp edges.

The average particle size was coarse and had a wide particle size distribution.

From the above-mentioned viewpoint, the present inventors conducted repeated research through trial and error in order to find a method of producing uniformly fine, high-purity titanium nitride powder at low cost without going through complicated processing steps. result.

Contrary to conventional wisdom, in the conventional manufacturing method of complexed titanium powder, which involves trapping and heating titanium oxide to which a reducing agent has been added in a nitrogen-containing atmosphere, selection of raw material types, setting of raw material mixing conditions, reduction, It has been found that titanium nitride powder with sufficiently satisfactory purity and particle size can be obtained by organically intertwining and managing the settings of nitriding conditions.

Therefore, the present invention has been made based on the above findings, and relates to a method for producing titanium nitride by adding a carbon source as a reducing agent to titanium oxide and heating the mixture in a nitrogen-containing atmosphere.

Anatase-type powder was used as titanium oxide, and a necessary and sufficient amount was added as a carbon source for titanium oxide reduction of amorphous carbon powder, thoroughly crushed and mixed in a wet process, and dried. By heating the mixed powder at a temperature of 1800 to 2000°C in a nitrogen-containing atmosphere,
Reduction and nitriding are carried out simultaneously, the oxygen content and residual carbon are as low as 0.5 or less, the nitrogen content is high in purity, and the particle size is 2 μm or less without essentially containing coarse particles of 2 μm or more. This method is characterized by obtaining uniformly fine titanium nitride powder having an average particle size of .

In the method of this invention, as mentioned above, anatase type titanium oxide is used and amorphous carbon powder is used as the carbon source.

There are two types of commercially available titanium oxide powder: one with a rutile crystal structure and one with an anatase crystal structure.

800 by heating anatase type titanium oxide powder
It is known that it converts to the rutile form at around 30°F (°C) even in the presence of a carbon source. ) powder and amorphous carbon powder (e.g. carden black), and it is known that amorphous carbon converts into graphite at temperatures above about 1300°C when heated, but anatase By combining titanium oxide and amorphous carbon,
The specific reason why the reduction/nitridation reaction is promoted so well is still not clear. However, in this way, anatase-type titanium oxide begins to crystallize into a rutile type at about 800°C, which is before the temperature at which reduction by carbon begins. Considering that graphitization begins even if complete crystal conversion does not occur at temperatures above approximately 1300°C, which is the temperature at which titanium oxide is produced, one reaction promotion effect is that when mixing such specific raw materials, heating It can be assumed that this is achieved by creating a mechanism that promotes the in-phase diffusion reaction during It is thought that this phenomenon occurred to a greater extent than in the case of other raw material combinations. This can be understood from the fact that the mixing conditions have a large influence, but with this invention, we were able to secure the effect of promoting the reaction with this best combination of raw materials, and the above effects were further improved by the mixing conditions of these raw materials. By increasing the
Together with 9, the reaction can be sufficiently promoted even at temperatures below 2000°C.

It can be seen that the reaction progresses uniformly and titanium nitride powder with uniform grains and fine particles is obtained.

The reason why we used a wet method for crushing and mixing the raw materials is because it is necessary to thoroughly mix the raw materials to promote the reaction, so a wet method is better than a dry method.

This is because a better mixing state can be obtained with the presence of the mixing promoting medium.

In addition, the heating temperature was set in the range of 1,800 to 2,000°C because the higher the heating temperature, the coarser the particles become, and when the temperature exceeds 2,000°C, the particle size becomes 2.0 μm or more, requiring re-grinding. On the other hand, if the temperature is lower than 1800° C., the amount of oxygen contained becomes high and high quality titanium nitride powder cannot be obtained.

The gas for the nitriding reaction in the method of this invention, that is, the atmosphere during heating, may be any atmosphere containing nitrogen as long as it does not inhibit the reduction and nitriding reactions, for example; It is also possible to conduct the process in an atmosphere sufficiently supplied with a mixed gas or ammonia gas.

Next, the present invention will be explained using examples and comparing with comparative examples.

Example First, commercially available anatase type titanium oxide powder near 7.1 weight fjkS was added with carbon black (22.9 weight), which was also commercially available. 7] with -ru (5 times the amount)? −
The mixture was placed in a Lumil and wet mixed by adding acetone for 24 hours. After drying the mixture, it was molded under pressure and heated to an elevated temperature without flowing nitrogen or gas.

The mixture was held at 1900° C. for 2 hours and then ground to obtain titanium nitride powder.

The analytical values and particle size of the titanium nitride powder thus obtained are shown in Table 1 as Test No. 1, along with the manufacturing conditions.

Table 1 also shows whether the titanium oxide used is anatase type or rutile type, whether the carbon source is carbon black or graphite, and whether the mixing conditions are such that carbide 2I-ru is added as a mixing promotion medium. Whether it is wet mixing or dry mixing, the heating temperature can be selected and varied.
The analytical values and particle sizes of titanium nitride powders produced under the combined conditions are also shown as test numbers 2 to 14, along with the production conditions.

The abbreviations in the table are A: Anatase type, R nilthyl type.

CB: Power-? Black.

G: graphite, W: Wet method, D: Dry method.

Yes: No mixing accelerating medium, No: No mixing accelerating medium, Average particle size is Fisher company 5
These are the measured values for ub-51eva 5izer.

In addition, in order to compare the particle shapes of the titanium nitride powder according to the present invention obtained by pressing in this manner and the commercially available titanium nitride powder (made from titanium hydride powder), scanning electron micrographs of each were taken as follows. It is shown in Figures 1 and 2.

As is clear from the results shown in Table 1, anatase type titanium oxide was used as the raw material.

It is clear that the reduction and nitriding reactions are most promoted in the combination of a carbon source and carbon black; If the condition of sufficient mixing is adopted, the oxygen content and residual carbon content will be as low as 0.5% by weight or less, and the nitrogen content will be close to the theoretical value (22.5% by weight). .5-
It is also clear from point b that it is possible to obtain titanium nitride powder with a high purity of 114 or higher.

Furthermore, as is clear from FIGS. 1 and 2, the particle shape and particle size distribution of the titanium nitride powder obtained by the method of the present invention are as follows.
Conventional methods or commercially available powders (e.g.

The powder had a rounded shape and an extremely uniform particle size, rather than the angular shape and particle size distributed over a wide range (such as powder made from nitrided titanium hydride powder). .

The amount of amorphous carbon added in the above example was approximately 98% of the theoretical amount calculated by formula %, but even if the amount added was increased, the amount of carbon contained would only increase.

A decrease in the amount of oxygen content is hardly expected, and the addition of the theoretical amount of about 98ts is due to various factors, such as the amount of oxygen content in the heated atmosphere, which decreases at temperatures below about 1300'0. The optimum amount to be added is determined by conditions such as the rate of temperature increase, and should not be set at a constant value of 1 L.

As described above, according to the present invention, fine titanium nitride powder with uniform particle size and high purity can be produced at a low cost without requiring special equipment or undergoing complicated processing steps. This brings about industrially useful effects such as further expanding its uses.

[Brief explanation of drawings]

Figure 1 is a grain shape photograph taken using a scanning electron microscope of titanium nitride powder obtained by the method of the present invention, and Figure 2 is a grain shape photograph taken using a scanning electron microscope of titanium nitride powder made using titanium hydride powder as a raw material, which is a conventional method. It is. Applicant E Ryokinzoku Co., Ltd. (and 1 other person) Agent
Wealth 1) Kazuo 23-

Claims (1)

[Claims] In a method of producing titanium nitride by adding a carbon source as a reducing agent to titanium oxide and heating it in a nitrogen-containing atmosphere, anatase-type titanium oxide powder is used as the titanium oxide, and amorphous carbon powder is used as the carbon source. , these were thoroughly ground and mixed in a wet method, and then dried, and the resulting mixed powder was heated to 1800 to 2
A method for producing nitrided and titanium powder with high purity and uniform grain size, characterized by simultaneously performing silica reduction and nitriding by heating at a temperature of 1,000°C.