JP2008069062A - Titanium carbide or precursor of titanium carbide and mixture of carbon and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new precursor which can be manufactured simply without passing through complicated synthesis processes, and can be converted to titanium carbide or a mixture of titanium carbide and carbon by calcinating. <P>SOLUTION: The precursor of titanium carbide or a mixture of titanium carbide and carbon is characterized by comprising reaction products of an alcoxide of titanium or titanium chloride and phenol or a phenol compound. The precursor can be manufactured by mixing an alcoxide of titanium or titanium chloride and phenol or a phenol compound, to thereby form a solution or slurry, or by mixing an alcoxide of titanium or titanium chloride and phenol or a phenol compound in an organic solvent, to thereby form a solution or slurry. The titanium carbide or the mixture of the titanium carbide and carbon can be manufactured by calcinating the solid precursor which is prepared by drying the solution or slurry, to thereby effect a carbonization reaction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a novel precursor that can be easily produced without going through complicated synthesis steps, and changes to titanium carbide or a mixture of titanium carbide and carbon by firing, and a method for producing the same.

Titanium carbide (TiC) has features of a high melting point, high hardness, and chemical stability, and is used as a raw material for cutting tools, heat resistant high strength materials, and the like. In general, there are three main industrial production methods for titanium carbide powder: a menstral method, a metal method, and an oxide method (Non-Patent Document 1).

The Menstral method is also called McKenna method or special infiltration method, and heat treatment is performed by mixing excess carbon with titanium metal powder or alloy powder together with iron powder, nickel powder, etc.
This is a method obtained by precipitating titanium carbide in the molten metal, cooling it, and then dissolving and removing metal components other than titanium carbide by acid treatment with hydrochloric acid or the like. This method has a feature that a single crystal titanium carbide powder can be obtained, but generally becomes a coarse powder of about 100 μm, and when a fine titanium carbide powder is required, mechanical grinding by a ball mill or the like is required. .

The metal method is a method of obtaining a titanium carbide powder by mixing a predetermined amount of a carbon powder with a powder of metal titanium or titanium hydride, and heating and carbonizing the powder. In this method, a finer powder is more easily obtained than in the menstrual method. However, when a fine powder is required, it is necessary to pulverize the raw metal titanium powder or titanium hydride powder. Also, titanium metal powder is expensive,
Due to its high reactivity, it may ignite or explode, requiring caution when handling. When titanium hydride powder is used as a raw material, a large amount of hydrogen gas is generated by the reaction, which requires careful operation.

The oxide method is a method in which a predetermined amount of carbon powder is mixed with titanium oxide powder and heated to obtain titanium carbide powder by a reduction carbonization reaction. In this method, titanium oxide which is cheaper than titanium metal can be used as a raw material, and a fine powder can be easily obtained. However, since this involves a reduction reaction, it is necessary to heat at a higher temperature than the metal method.

Recently, by mixing and grinding metal titanium powder and carbon powder in a powerful ball mill without external heating, an abrupt combustion reaction is generated between titanium and carbon due to enormous mechanical energy such as impact and friction. A mechanochemical synthesis method has been reported. However, in general, the mechanochemical reaction takes a long time. Therefore, a method of mixing calcium or magnesium powder with a raw material in order to complete the reaction in a shorter time is disclosed (Patent Document 1). However, in this method, calcium oxide or magnesium oxide is mixed in the titanium carbide powder produced as a by-product, and these must be removed by acid treatment.

In order to produce a fine carbide powder, an organic compound is used as a raw material, and a synthesis technique by a gas phase reaction or a liquid phase reaction is progressing. A process using a gas phase reaction has a feature that high-purity and fine powder can be easily obtained, but has a problem of low productivity. On the other hand, as a process applying liquid phase reaction, for example, finely powdered carbon is dispersed in titanium alkoxide, and then hydrolyzed to produce a precipitate, and this precipitate is used as a precursor to cause a reduction carbonization reaction. A method of converting into titanium carbide powder by heat treatment is disclosed (Patent Document 2). However, this technique requires that finely divided carbon be uniformly dispersed in the alkoxide,
Therefore, it may be necessary to surface-treat the surface of finely powdered carbon to a state having a hydrophilic group.

As a technique for producing a precursor having a more uniform chemical composition, a method using a liquid material as a raw material has been developed. For example, there are a method of synthesizing a precursor using titanium butoxide and furfuryl alcohol (Non-patent Document 2) and a method of synthesizing a precursor using titanium tetraisopropoxide and an ester compound (Non-patent Document 3). It has been reported. However, these synthesis methods require time-consuming reflux and distillation steps.

Also disclosed is a method in which titanium chloride aqueous solution and water-soluble organic compound are used as raw materials, titanium chloride is converted into titanium hydroxide by hydrolysis reaction or neutralization reaction, and converted to titanium carbide powder by drying and heating. (Patent Document 3). In this method, titanium hydroxide can be produced as fine particles in an aqueous solution, while the organic compound serving as a carbon source is solidified by drying. Therefore, even if the fine particles of titanium hydroxide are uniformly dispersed in the aqueous solution, the dispersion of titanium hydroxide and the organic compound may become non-uniform due to an agglomeration phenomenon or the like at the drying stage.

JP 2002-187711 A Japanese Patent Laid-Open No. 61-232212 JP-A-5-170418 Hiroshi Doi: Advanced Technology of Fine Particles Volume II, Applied Technology (2002), 46-49. Z. Jiang and W. E. Rhine: Chem. Mater., 3 (1991), 1132-1137. K. Thorne et al .: J. Mater. Sci., 27 (1992), 4406-4414.

An object of this invention is to provide the novel precursor which can be simply manufactured without going through a complicated synthesis process and changes into titanium carbide or a mixture of titanium carbide and carbon by firing.

As a result of examining the titanium carbide synthesis process in detail, the inventor obtained a reaction product by mixing titanium alkoxide or titanium chloride, and phenol or a phenol compound, and calcined using the product as a precursor. It has been found that titanium carbide or a mixture of titanium carbide and carbon can be produced by causing a carbonization reaction.

That is, the precursor in the present invention is characterized by comprising a reaction product of titanium alkoxide or titanium chloride and phenol or a phenol compound. The precursor production method according to the present invention is characterized in that a solution or slurry is produced by mixing titanium alkoxide or titanium chloride, and phenol or a phenol compound.

In the present invention, titanium alkoxide or titanium chloride, and phenol or a phenol compound are used as raw materials. Moreover, in order for the reaction which arises by mixing to advance uniformly in the whole liquid mixture, it is desirable to mix these in an organic solvent. Here, as a method of mixing in an organic solvent, not only a method of mixing an alkoxide or titanium chloride of titanium and a phenol or a phenol compound in an organic solvent, but also an alkoxide or titanium chloride of titanium diluted in an organic solvent, and Alternatively, a method of mixing a diluted phenol or phenol compound in an organic solvent may be used.

Here, about the alkoxide of titanium, the kind of alkoxyl group is not ask | required. It may be an alkoxide subjected to a treatment such as chelation with ethyl acetoacetate. As titanium chloride, titanium tetrachloride is preferable. Moreover, although a kind is not ask | required as a phenol compound, a liquid resol type phenol resin oligomer is suitable. Even a solid phenol resin or another phenol compound can be used as long as it is soluble in a solvent.

The organic solvent is not particularly limited as long as it is uniformly mixed with the alkoxide or titanium chloride to be used and phenol or a phenol compound, and among them, lower alcohols such as methanol, ethanol, isopropyl alcohol are preferable. However, it is desirable to contain as little water as possible so that hydrolysis of titanium alkoxide or titanium chloride does not occur.

Titanium alkoxide is produced by reacting titanium or titanium chloride as a raw material with alcohol. Therefore, in order to obtain a single alkoxide, a step of separating and purifying unreacted alcohol is necessary. However, in the present invention, an alkoxide diluted with an alcohol can also be used. Therefore, it is advantageous in terms of cost to use an alkoxide from which unreacted alcohol has not been separated and purified.

The reaction by mixing the titanium alkoxide or titanium chloride and the phenol or the phenol compound in the present invention proceeds spontaneously only by mixing without heating, and does not require time-consuming refluxing or distillation operations. This reaction is considered to be the condensation of phenol or a phenol compound with alkoxide or titanium chloride. Therefore, it occurs rapidly without the addition of water because it is not based on hydrolysis of alkoxide or titanium chloride.

It is desirable to sufficiently stir during mixing. Mixing immediately results in a yellow to red solution, or a yellow product is formed with the alcohol decomposed from the alkoxide. When titanium alkoxide or titanium chloride and a phenol compound are mixed in an organic solvent, the product becomes yellow particles, and the entire mixture becomes a yellow or red slurry. Since such particles can be directly deposited by mixing, the powder can be prepared as a precursor powder without going through a pulverizing step by appropriately selecting the mixing conditions.

This slurry can be obtained as a precursor powder through a step of removing the solvent, such as filtration and drying. The unreacted liquid component is removed by decantation, etc.
More preferably, it is washed with alcohol and then dried. Here, the method for removing the solvent does not matter. Heat drying, vacuum drying, freeze drying, etc. can be selected. The spray drying method is particularly suitable for mass production. Further, the mixed solution or slurry is dried on a desired substrate, and
It is also possible to form a titanium carbide coating on the substrate by firing under appropriate conditions as described below to cause a carbonization reaction.

By firing the precursor of the present invention to cause a carbonization reaction, the precursor can be converted into titanium carbide or a mixture of titanium carbide and carbon in accordance with the C / Ti ratio depending on the mixing ratio of the raw materials. Depending on the type of raw material, when obtaining titanium carbide, the mixing ratio C / Ti is 0.5.
It is desirable to be within a range of ˜5.

Here, C / Ti represents the ratio of the number of moles of carbon after firing of phenol or a phenol compound to the number of moles of titanium alkoxide of titanium or titanium chloride of titanium chloride. As a preliminary experiment, a simple substance of phenol or a phenol compound is fired until it is completely carbonized, and the residual carbon ratio is obtained from the weight ratio before and after that. The number of moles of carbon after firing can be calculated by converting the weight to the number of moles in consideration of the residual carbon ratio from the blending amount of phenol or phenol compound used as a raw material. When the mixing ratio C / Ti is less than 0.5, the amount of titanium alkoxide or titanium chloride that does not contribute to the reaction increases, resulting in a low yield of the precursor, and when the mixing ratio C / Ti is larger than 5. Provides a mixture of titanium carbide and carbon.

The mixture of titanium carbide and carbon of the present invention can be used as a raw material for TiC—Mo ₂ C (dimolybdenum carbide) —Ni (nickel) cermet, for example. TiC-Mo ₂
C-Ni-based cermets are generally produced by mixing and sintering TiC, Mo ₂ C carbide powder and metal Ni powder, but instead of Mo ₂ C powder, metal molybdenum powder and carbon powder are used. Also by mixing together with other raw material powders and sintering, molybdenum carbonization reaction occurs during the sintering process, and a similar cermet can be produced. Therefore, by applying the manufacturing method of the present invention, a mixture of titanium carbide and carbon containing a carbon amount corresponding to the blending amount of the molybdenum powder is prepared, and each metal powder of molybdenum and nickel is mixed with this. By sintering, a TiC—Mo ₂ C—Ni-based cermet can be produced.

The atmosphere for firing the precursor of the present invention is preferably an inert atmosphere such as argon (Ar). In an oxidizing atmosphere, the carbonization reaction is inhibited, and titanium oxide is formed instead of titanium carbide. Here, calcination refers to an operation in which an organic precursor is converted into an inorganic substance by heating and further causes a carbonization reaction of titanium. The conversion reaction from organic to inorganic in this precursor starts from about 200 ° C. and usually ends at 500 to 800 ° C. Therefore, although heating at 500 ° C. or higher is necessary as the firing temperature condition, it can be arbitrarily selected according to the characteristics of the target titanium carbide powder. The reaction formed by the carbide is completed in a shorter time as the temperature is higher, but the powder particles are likely to become coarser as the temperature is higher. Generally, 1200-1600 degreeC is preferable. After raising the temperature to the set temperature so that the reaction is completed in the entire sample to be processed at one time, it is desirable to hold for about 5 minutes to 2 hours depending on the processing amount.

5.7 g of liquid phenol resin oligomer (Dainippon Ink and Chemicals, J-325
: 60% resin component, remaining methyl alcohol solvent) was added to 40 g of ethanol and diluted. Meanwhile, 30 g of titanium tetraisopropoxide was added to 300 g of ethanol for dilution. While diluting this titanium tetraisopropoxide dilute with a magnetic stirrer, the dilute solution of the aforementioned phenol resin oligomer was added dropwise to form a mixed solution.
In this case, the mixing ratio of carbon and titanium corresponds to C / Ti = 1.

As a result, the particles immediately precipitated in the mixed solution as the solution was dropped, and the mixed solution became a yellow slurry. The slurry was allowed to stand to settle the precipitate, and then decantation was performed to drain off the supernatant. Further, the precipitate was washed by adding ethanol and stirring and repeating the same decantation twice. Decant once again and deposit 5
A yellow powder was obtained by drying at 0 to 60 ° C.

A scanning electron micrograph of this powder is shown in FIG. From this photograph, it can be seen that the powder is a fine powder having a primary particle diameter of approximately 100 nm or less, although there is aggregation and partial particle bonding. The X-ray diffraction pattern of this powder is shown in FIG. In the X-ray diffraction pattern, no clear crystalline diffraction peak is observed, and this powder is considered to have an amorphous structure.

Using this powder as a precursor, the temperature was raised to 1400 ° C. at 10 ° C./min in an argon atmosphere.
Held for hours. The X-ray diffraction pattern of this powder is shown in Fig. 2-b). The X-ray diffraction pattern shows a clear cubic TiC phase diffraction peak.

Titanium tetraisopropoxide and a phenol resin oligomer were weighed so that the mixing ratio was C / Ti = 3, C / Ti = 6, and C / Ti = 10, and each precursor was obtained by the same operation as in Example 1. A body powder was prepared. Furthermore, each precursor powder was 1400 in an argon atmosphere.
The temperature was increased to 10 ° C. at a rate of 10 ° C./min, and a baking treatment was performed for 1 hour. The analysis result of the carbon content in each calcined powder is shown in FIG.

When the mixing ratio is C / Ti = 1 and C / Ti = 3, the carbon amount is 20 of the stoichiometric composition.
It can be seen that a nearly single-phase titanium carbide powder is obtained near wt%. In contrast, C
In the case of / Ti = 6 and C / Ti = 10, the higher the C / Ti ratio, the greater the carbon content.
It can be seen that a mixed powder of titanium carbide and carbon is obtained.

11 g of the same liquid phenol resin oligomer as in Example 1 was added to 40 g of ethanol and diluted. On the other hand, 5 g of titanium tetrachloride was diluted with 300 g of ethanol. While stirring the diluted solution of titanium tetrachloride with a magnetic stirrer, the diluted solution of the phenol resin oligomer described above was added dropwise to form a mixed solution. In this case, the mixing ratio of carbon and titanium corresponds to C / Ti = 12.

As a result, particles were immediately deposited in the mixed solution as it was dropped, and the mixed solution became a yellow-red slurry. The slurry was allowed to stand to settle the precipitate, and then decantation was performed to drain off the supernatant. Further, the precipitate was washed by adding ethanol and stirring and repeating the same decantation twice. Decantation was performed once again, and the precipitate was dried at 50 to 60 ° C. to obtain a yellow powder.

A scanning electron micrograph of this powder is shown in FIG. From this photograph, it can be seen that although there is aggregation and partial particle bonding, the powder is a fine powder having a primary particle diameter of approximately 200 nm or less. The X-ray diffraction pattern of this powder is shown in FIG. The X-ray diffraction pattern shows a halo pattern unique to an amorphous substance.

Using this powder as a precursor, the temperature was raised to 1400 ° C. at 10 ° C./min in an argon atmosphere.
Held for hours. The X-ray diffraction pattern of this powder is shown in Fig. 5-b). The X-ray diffraction pattern shows a combination of a halo pattern and a clear diffraction peak of a cubic TiC phase. This halo pattern is thought to be due to amorphous carbon, indicating that a mixed powder of titanium carbide and carbon is produced.

The spectrum obtained by measuring each precursor powder produced in Examples 1 and 3 by FT-IR is shown in FIG. For reference, the spectrum of the phenol resin is also shown. The results of analyzing the vibration modes of the absorption bands in these spectra are summarized in Table 1.

From these absorption bands, it is considered that each precursor sample produced in the example contains an aromatic ring in the molecular structure. Moreover, the absorption considered to be based on a Ti-O bond was recognized.
[Comparative example]

10 g of ethyl silicate which is an alkoxide of silicon was diluted with 10 g of ethanol. To this solution, 3.4 g of the same liquid phenol resin oligomer as in Example 1 was added and stirring was continued at room temperature, but no precipitate was generated in the mixed solution after 48 hours. From this, the formation reaction by mixing the alkoxide of titanium and the phenol resin oligomer of the present invention is not a general reaction that occurs between any alkoxide and the phenol resin,
It can be seen that it occurs in certain types of alkoxides, such as titanium alkoxides.

The precursor production method of the present invention can be easily deposited in a very short reaction even at room temperature by mixing raw materials, and thus does not require complicated equipment and enormous energy for production of the precursor, so that mass production is possible. Is suitable. The precursor of the present invention can be obtained as a powder by stirring and mixing in an organic solvent. Furthermore, in the production method of the present invention, a titanium carbide powder having a fine particle diameter or a mixed powder of titanium carbide and carbon can be produced by appropriately selecting raw material mixing conditions, drying conditions, and firing conditions. Is possible.

The drawing substitute scanning electron micrograph of the precursor powder produced in Example 1 (scale is 100 nm). X-ray diffraction pattern of the precursor powder (a) produced in Example 1 and the powder (b) calcined at 1400 ° C. (◯ indicates the diffraction angle of the cubic TiC phase). 3 is a graph showing the carbon content of a 1400 ° C. fired powder produced in Example 2. FIG. The scanning substitute electron micrograph of the precursor powder produced in Example 3 (scale is 100 nm). X-ray diffraction pattern of the precursor powder (a) prepared in Example 3 and the powder (b) fired at 1400 ° C. (A mark indicates a diffraction angle of a cubic TiC phase). The FT-IR spectrum of the phenol resin (a), the precursor powder (b) produced in Example 1, and the precursor powder (c) produced in Example 3.

Claims (5)

A precursor of titanium carbide or a mixture of titanium carbide and carbon, characterized by comprising a reaction product of titanium alkoxide or titanium chloride and phenol or a phenol compound. The production of a titanium carbide or a precursor of a mixture of titanium carbide and carbon according to claim 1, characterized in that a solution or slurry is produced by mixing titanium alkoxide or titanium chloride and phenol or a phenol compound. Method. The titanium carbide or the mixture of titanium carbide and carbon according to claim 1, wherein a solution or slurry is produced by mixing titanium alkoxide or titanium chloride and phenol or a phenol compound in an organic solvent. A method for producing a precursor. A method for producing a solid precursor of titanium carbide or a mixture of titanium carbide and carbon, wherein the solution or slurry produced in the method according to claim 2 or 3 is dried. A method for producing titanium carbide or a mixture of titanium carbide and carbon, wherein the solid precursor produced by the method according to claim 4 is fired to cause a carbonization reaction.

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