JPH07138098A - Production of tic whisker - Google Patents

Abstract

PURPOSE:To produce TiC whiskers of high bonded carbon content in high productivity by performing carbonization continuously in the production process according to the solid phase reaction method. CONSTITUTION:100 pts.wt. of titanium source comprising titanium dioxide and/or alkali metal titanate are mixed with 100 to 200 pts. wt. of carbon source and 1 to 30 pts.wt. of the whisker formation catalyst selected from chlorides of Fe, Ni and Co. The mixture is heated at 1,500 to 1,700 deg.C in an inert atmosphere to form TiC whiskers of at least 0.4300nm average lattice constant. Successively, the starting materials containing the TiC whiskers are heated at 1,800 to 2,000 deg.C in an inert atmosphere to effect carbonization.

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 TiC whiskers having a high amount of bonded carbon and exhibiting excellent hardness and strength characteristics.

[0002]

2. Description of the Related Art Whiskers composed of needle-like crystals of TiC have material properties such as high mechanical strength, heat resistance, and chemical stability, and have excellent hardness. It has attracted attention as a composite material for tools and as a cermet material. In particular, TiC whiskers are expected to serve as a composite reinforcing material for iron-based alloy cutting tools because they have the property of being less likely to react with iron.

Conventionally, the production methods for obtaining TiC whiskers are roughly classified into those by the gas phase reaction method and those by the solid phase reaction method. Among them, the gas phase reaction method includes a method of reacting titanium halide with carbon monoxide (JP-A-58-60700) or a mixed gas of titanium tetrachloride, aromatic hydrocarbons and hydrogen with a transition metal. Method for carrying out gas phase reaction in a system containing benzene (JP-A-3-208897)
Etc. are known. In all of these methods, a vapor or gaseous raw material component is introduced onto a heating substrate to generate TiC whiskers, but at this time, it is necessary to use a flammable hydrogen gas that easily leaks as a carrier gas. However, there is a drawback in that there is a high operational risk.

On the other hand, as a manufacturing technique using the solid-phase reaction method, 50 to 200 parts by weight of carbonaceous material and 100 parts by weight of titanium source material composed of titanium dioxide or / and an alkali metal titanate and iron, nickel or There is a method (JP-A-4-193800) in which 1 to 30 parts by weight of a produced catalyst selected from cobalt chloride is mixed and heated and reacted in an inert atmosphere in a temperature range of 1400 to 1700 ° C. This method is advantageous as an industrial production technique because it can produce TiC whiskers safely and efficiently, but it has a compositional problem that the quality of TiC whiskers to be obtained, especially the amount of bound carbon is small. The TiC whiskers having a small amount of bonded carbon have insufficient hardness and strength, so that the material function as the composite reinforcing material cannot be imparted.

As a method of manufacturing TiC whiskers which solves this problem, the average lattice constant of TiC crystals is 0.43 nm.
The above mixture containing TiC whiskers and carbon powder was press-molded at a surface pressure of 50 to 100 kg / cm ² , and the molded body was heated to 1700 to 2000 under a reduced pressure of 10 Torr in a heating furnace kept in an inert gas atmosphere. A method of heat treatment at a temperature of ° C has been developed by the present applicant (Japanese Patent Laid-Open No. 5-221718).
Issue).

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
According to the method described in Japanese Patent Publication No. 8, a high-quality TiC whisker having a carbon bond content of more than 19% by weight can be produced by using a safe solid-phase reaction method. However, since this method is a post-treatment process in which a mixture of once-produced TiC whiskers and carbon powder is press-molded and reheated, the production process requires a treatment step different from the TiC whisker production step. There are disadvantages that are disadvantageous in terms of efficiency and cost.

An object of the present invention is to provide a method for producing TiC whiskers of high quality having a high amount of bonded carbon by a continuous carbonization treatment in a production process by a solid phase reaction method with high productivity. Especially.

[0008]

In order to achieve the above object, a method for producing a TiC whisker according to the present invention comprises a carbonaceous material based on 100 parts by weight of a titanium source material composed of titanium dioxide or / and an alkali metal titanate. Raw material 100-
200 parts by weight, 1 to 30 parts by weight of a produced catalyst selected from chlorides of Fe, Ni and Co are mixed, and heat reaction is performed in a temperature range of 1500 to 1700 ° C. in an inert gas atmosphere to obtain an average lattice constant. Is at least 0.4300 nm
The TiC whiskers of No. 1 are produced, and subsequently, the carbonization treatment by heating is carried out in the temperature range of 1800 to 2000 ° C. in an inert atmosphere.

As the Ti source which is the main raw material of the present invention, powdery titanium dioxide (TiO ₂ ) or powdered or whiskered alkali metal titanate such as K ₂ O.6TiO ₂ or Na ₂ O.6TiO ₂ is used. Salts are used and used individually or in a mixture. Examples of carbonaceous powders used as carbonaceous materials include amorphous carbon powders, graphite powders, powdered activated carbon, carbon black, and the like. However, originally carbon black having a fine particle size and a large specific surface area can be applied. preferable.

The catalyst produced is selected from the chlorides of Fe, Ni and Co. Even with such transition metal compounds, other than chlorides, the effect of promoting the formation of TiC whiskers is poor. In addition, chlorides of alkali metals such as NaCl and KCl can be added to the raw material system as a powdering suppressing agent, if necessary. This component has an action of suppressing the generation of powdered TiC during the heating reaction, and has a function of relatively improving the production yield of TiC whiskers.

The above raw material components are 100 to 200 parts by weight of carbonaceous material, 1 to 100 parts by weight of titanium source material, and 1 to 1 parts of produced catalyst.
Mix at a compounding ratio of 30 parts by weight. The amount of carbon material is 10
If the amount is less than 0 parts by weight, the carbon component remaining after the heat reaction treatment is insufficient, and it becomes difficult to increase the amount of bonded carbon smoothly in the stage of the heat carbonization treatment. A large amount remains and the removal and separation process becomes complicated. On the other hand, if the mixing ratio of the produced catalyst is less than 1 part by weight, the catalytic effect is not exhibited, and if the mixing ratio exceeds 30 parts by weight, it becomes unnecessary from the viewpoint of the effect and rather remains as an impurity. A suitable catalyst amount is in the range of 5 to 18 parts by weight. When the powder suppressor is added, it is preferable to set the addition amount in the range of 10 to 100 parts by weight per 100 parts by weight of the titanium source raw material, and if the amount is less than this range, there is no effect and the compounding above is unnecessary. .

The raw material mixture is stirred and mixed so as to be uniform, and then charged into a reaction vessel with a lid made of a heat resistant material such as graphite and sealed. In filling the raw material at this time, if it is lightly packed in a container so that the bulk density of the raw material is 0.2 g / cc or less, it is advantageous for the production of TiC whiskers. Then, the closed reaction vessel is placed in a heating furnace maintained in an atmosphere of an inert gas such as Ar gas to perform a heating reaction treatment.

The temperature during the heating reaction is 1500 to 1700.
The TiC whiskers having an average lattice constant of at least 0.4300 nm are formed in the raw material system by setting the temperature in the range of ° C. If the heating temperature is less than 1500 ° C, the average lattice constant is 0.43
TiC whiskers of 00 nm or more do not form smoothly,
If the temperature exceeds 00 ° C., the whiskers may have poor properties. In addition, it is a preferable condition that the rate of temperature increase during heating is in the range of 2 to 10 ° C./min.

Then, the raw material system containing TiC whiskers is subsequently carbonized by heating in a temperature range of 1800 to 2000 ° C. in an inert gas atmosphere. This process produces Ti
This is a step for increasing the amount of carbon bonds to C whiskers to improve the material strength performance, and the treatment operation can be continuously performed in the same heating furnace. At this time, the heating temperature is 1
If it is less than 800 ° C, the carbon bonding effect does not occur smoothly, and 2
If the temperature exceeds 000 ° C., the TiC whiskers may be deformed in properties such as thickening or granulating.

The product after the heating and carbonization treatment is taken out from the cooled reaction vessel and subjected to a post-treatment for removing unreacted carbonaceous material components. As a method of the post-treatment, for example, a method of burning and removing a carbonaceous material component in air may be applied, but in this case, there is a disadvantage that TiC is converted into oxidized TiO ₂ . Treated products with organic solvents (toluene, light oil,
Apply a liquid phase separation method in which a non-hydrophilic carbon component is separated into an organic solvent phase and a hydrophilic TiC component is separated into an aqueous phase by pouring it into a two-phase liquid consisting of kerosene) and water and shaking vigorously. However, since the hydrophilicity of TiC whiskers decreases as the amount of carbon bound increases, the TiC whiskers are easily trapped at the two-liquid interface and the recovery rate decreases. The most preferable residual carbon component separating means for the present invention is a wet classification in which a treated product is dispersed in water containing a small amount of a nonionic surfactant and separated using the difference in the Stokes diameter between the TiC whiskers and the carbon component. Is the law.

The TiC whiskers obtained in the above process are gray fine needle-like crystals having a diameter of 1 to 3 μm and a length of 5 to 50.
It has an aspect property of μm, has a small amount of particulates and the like, and has a high amount of bonded carbon exceeding 19% by weight.

[0017]

According to the phase diagram of the Ti-C system, when the C / Ti atomic ratio is 0.5 or less, the liquid phase is formed at a temperature of 1650 ° C or higher. Although this liquid phase state effectively acts to promote carbonization, the needle-like crystals are melted and deformed and the whiskers are converted into particles. In addition, even in the case where the granules are not completely granulated, the whiskers are fused and sintered with each other, resulting in lumps and deterioration in quality. By the way, there is a fixed relationship between the lattice constants of C / Ti atoms and TiC crystals, and the average lattice constant of TiC whiskers corresponding to a C / Ti ratio of 0.5 is 0.4300 nm. Both the C / Ti ratio and the average lattice constant increase in the temperature rising process of the heat treatment, and when the liquid phase forming temperature of 1645 ° C. is reached, the C / Ti ratios of the TiC whiskers are all 0.5 or more.

In the present invention, at least the average lattice constant once produced is 0.4300 nm (C / Ti ratio: 0.5).
The TiC whiskers (above) are heated and carbonized in the temperature range of 1800 to 2000 ° C. in the state where the residual carbonaceous material component is present, thereby effectively increasing the amount of bonded carbon without changing the properties of the whiskers. It becomes possible. Therefore, a TiC whisker having a high bond carbon amount and having a hardness and strength sufficient for composite strengthening of ceramics and metal materials can be efficiently produced by the continuous heat treatment step which is advantageous in terms of productivity.

[0019]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples.

Examples 1 to 4 and Comparative Examples 1 to 3 Reagent first-grade anatase type TiO ₂ powder [manufactured by Wako Pure Chemical Industries, Ltd.] was used as a Ti source material, and carbon black [Tokai] was used as a carbonaceous material for 100 parts by weight thereof. Carbon Co.,
100 parts by weight of the cast 5H] as N
Anhydrous Ni obtained by drying and dehydrating 100 parts by weight of aCl and special grade nickel chloride (NiCl ₂ .6H ₂ O) as a catalyst for formation.
Cl ₂ was blended by changing the addition amount and stirred and mixed in a juicer mixer until it became sufficiently uniform. The mixture was lightly packed into a graphite container with a screw lid so that the packing density was 0.2 g / cc or less, the lid was closed, and the mixture was set in a high-frequency furnace maintained in an Ar gas atmosphere and the heating rate was 2.5 to 5 ° C. The temperature was raised to a predetermined heating temperature by 1 / min, and the reaction was carried out at this temperature to form TiC whiskers.

The properties, average lattice constants, and amount of bonded carbon of the TiC whiskers produced in the above step were measured, and the results are shown in Table 1 in comparison with the varying conditions at the time of production. The lattice constant of the TiC whisker crystal was measured using an X-ray diffractometer, and the amount of bonded carbon was analyzed by elemental analysis using TiC.
The whiskers were calculated as Ti-C-0 solid solution.

[0022]

[Table 1]

Subsequent to the heat reaction treatment of the above TiC whiskers, the temperature of the furnace was raised to 2000 ° C. and heating was performed for 30 minutes to carry out carbonization treatment. The treated product was taken out of the reaction vessel, dispersed in a 0.1% solution of a nonionic surfactant, and wet-classified to separate and collect TiC whiskers. The properties of the obtained TiC whiskers are shown in Table 2.

From the results shown in Tables 1 and 2, the amount of bound carbon after the heating and carbonization treatment was clearly increased, and 19% by weight was obtained in each case.
You can see that it is above. However, in the comparative example in which the TiC whiskers having an average lattice constant of 0.4300 nm or less were heated and carbonized, the whisker morphology was deformed and the degree of conversion into particles was increased.

[0025]

[Table 2]

Examples 5 to 6 and Comparative Examples 4 to 5 The products containing the TiC whiskers produced in Example 1 were subsequently carbonized in the same furnace at different heating temperatures. The properties of the obtained TiC whiskers are shown in Table 3 in comparison with the heating carbonization temperature to which they are applied. From the results in Table 3, it is clear that the temperature of the heating carbonization treatment is appropriately in the range of 1800 to 2000 ° C.

[0027]

[Table 3]

[0028]

As described above, according to the present invention, the step of heat-reacting a specific raw material system to produce TiC whiskers and the step of subsequently carbonizing the raw material system containing the produced TiC whiskers are continuously performed. By operation, it becomes possible to produce a high-performance TiC whisker having an increased hardness and strength and an increased amount of bonded carbon. Therefore, it is useful as a means for producing a composite reinforcing material for ceramic materials and metal materials.

Claims (2)

[Claims] 1. A production catalyst 1 selected from 100 to 200 parts by weight of carbonaceous material and chlorides of Fe, Ni and Co based on 100 parts by weight of titanium source material composed of titanium dioxide or / and an alkali metal titanate. ˜30 parts by weight are mixed and subjected to a heat reaction treatment in a temperature range of 1500 to 1700 ° C. under an inert gas atmosphere to produce TiC whiskers having an average lattice constant of at least 0.4300 nm,
A method for producing a TiC whisker, characterized in that a raw material system containing TiC whiskers is subsequently subjected to a heat carbonization treatment in a temperature range of 1800 to 2000 ° C. in an inert gas atmosphere. 2. The method for producing a TiC whisker according to claim 1, wherein 10 to 100 parts by weight of a chloride of an alkali metal is added and mixed as a powdering suppressing agent to 100 parts by weight of the titanium source raw material.