RU2561614C1 - Method of producing ultra-dispersed titanium carbide powder - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: water solution of titanyl sulphate is neutralized to pH 10-12 by solution of ammonia/sodium hydroxide in the presence of soot to get the powder. The latter is compacted and processed by microwave radiation at the frequency of 2450-3000 MHz and power of 700-1200 W in argon flow at the rate of 7-8 l/h in three steps: at first step - at the rate of 15°C/min to 500°C, at second step - at the rate of 10°C/min to 700°C, and at third step - at the rate of 5°C/min to 1300°C and with holding for 60-70 min.

EFFECT: ultrafine powder of titanium carbide with particle size of about 250 nm.

2 cl, 3 dwg, 1 tbl, 2 ex

Description

The invention relates to the field of powder metallurgy, in particular to methods for producing ultrafine powder materials based on titanium carbide, which are widely used in the manufacture of hard alloys and cutting tools. Titanium carbide is one of the most effective materials used as a wear-resistant coating, this is due primarily to its high wear resistance, hardness at high and low temperatures, good chemical stability and the ability to not collapse under the influence of mechanical and thermal loads.

A known method of producing titanium carbide by passing titanium oxide powder and a reactive gas as a carbon source through a plasma flame, in which, by changing the amount of gas supplied, it is possible to change the quality of the obtained titanium carbide powder (Application WO 2014002695, IPC C01B 31/30, 2014 .).

The disadvantage of this method is the expensive equipment and large losses in the process of obtaining the final product.

Closest to the proposed method is a method for producing nanodispersed titanium carbide, in which ball mills are used to grind titanium dioxide with Shwinigan carbon in ethanol and a microwave oven for firing in argon protective medium (Patent CN 100484872, IPC C01B 31/30, 2006 ., prototype).

The disadvantage of this method is the long and energy-intensive stage of mixing the starting reagents (from 12 to 18 hours).

The authors were faced with the task of developing a simple and reliable method for producing ultrafine titanium carbide powder with a particle size of less than 300 nm, which is a precursor for the manufacture of hard alloys, cutting tools and wear-resistant coatings.

The problem is solved in the proposed method for producing ultrafine titanium carbide powder, including mixing an oxygen-containing titanium compound with a carbon source, compressing the obtained powder and subsequent microwave treatment in argon medium, in which an aqueous solution of titanyl sulfate is neutralized to pH 10-12 with ammonia hydroxide solution ( sodium) in the presence of soot, followed by microwave irradiation with a frequency of 2450-3000 MHz at a power of 700-1200 W in an argon current at a speed 7-8 liters / hour in three steps: at 15 ° C / min to 500 ° C; at a rate of 10 ° C / min up to 700 ° C and at a speed of 5 ° C / min up to 1300 ° C with holding at the final stage for 60-70 min.

Moreover, the carbon black content corresponds to TiO ₂ : C = 1: 3 (in terms of oxide).

Currently, from the patent and scientific literature there is no known method for producing titanium carbide with obtaining an intermediate product (precursor) by liquid-phase precipitation from an aqueous solution of titanyl sulfate, followed by microwave irradiation, subject to the proposed process parameters.

In the course of studies conducted by the authors of the proposed technical solution, X-ray phase analysis revealed that the precursor, consisting of titanyl hydroxide and acetylene black, is X-ray amorphous. According to electron microscopy, the morphology of the obtained TiO (OH) ₂ || 3C precursor is a mechanical mixture of spherical particles of titanyl hydroxide and acetylene black (Figure 1). According to the results of the specific surface area, which was determined by the BET method in automatic mode on an automated sorption installation TriStar 3020 manufactured by Micromeritics (USA), it was found that the precursor has a high surface activity (Table 1). The specific surface area of the precursor was 285.17 m ² / g, of which it increased by 107.29 m ² / g due to the high microporosity of titanyl hydroxide. The high surface activity of the precursor ensures the subsequent carbidization to obtain ultrafine single-phase titanium carbide.

As a result of studies of the heat treatment process, all intermediate phases from the TiO (OH) ₂ || 3C precursor to titanium carbide were recorded. During the thermolysis of freshly precipitated titanyl hydroxide, evaporation of free and hydrated moisture occurs with the formation of the oxide phase of the tetragonal modification of the anatase structure (Figure 2). With increasing temperature above 850-900 ° C, the beginning of the formation of the titanium oxide phase of the tetragonal modification of the rutile structure was also recorded (Figure 2). At the final stage of carbidization at a temperature of 1300 ° C, single-phase cubic modification titanium carbide was obtained (Figure 2).

The particle morphology of the obtained product, cubic modification of titanium carbide (TiC), is shown in FIG. As can be seen, a product with an average particle size of ~ 250 nm was obtained and residual microporosity was observed on some particles, which is confirmed by the results of the specific surface area (Table 1, Sample 3). The lattice parameters for titanium carbide are a = 4.3213 (7) Å. The use of microwave radiation for carbidization of the precursor contributes to a significant decrease in the average particle size of titanium carbide by 500 nm without partial melting and sintering, and to a deeper carbonization of the carbide.

Thus, the proposed method allows to obtain ultrafine powders of titanium carbide with an average particle size of ~ 250 nm, with a specific surface area of ~ 10 m ² / g, which can be widely used in the preparation of hard alloys, cutting tools and wear-resistant coatings.

The proposed method is as follows.

To obtain an intermediate product (precursor) of a mixture of a freshly precipitated precipitate of titanyl hydroxide and a carbon carrier (acetylene carbon black), an acidic aqueous solution of titanyl sulfate and a solution of ammonia hydroxide (sodium) are used. Precipitation is carried out with constant stirring to a pH of 10-12. The calculated amount of carbon is introduced into the initial solution of titanyl sulfate before the precipitation stage. The resulting precipitates are washed from impurities, filtered and dried in an oven at T = 120 ° C. Next, the obtained precursor is subjected to heat treatment in a microwave muffle furnace in a stream of inert medium (Ar). The heating is carried out in three stages with a heating rate of 15 ° C / min to 500 ° C, 10 ° C / min to 700 ° C and 5 ° C / min to 1300 ° C with holding at the final stage for 60-70 min. Heat treatment of the precursor is carried out in a microwave muffle furnace "Microwave lab assistant" of the company "NPO" Ural-Hephaestus "(power 0.70-1.20 kW and operating frequency 2450-3000 MHz) in an inert gas medium, mainly using argon. Before the heat treatment, the dried precursors are pressed into tablets (⌀10 mm, h = 10 mm), placed in a quartz crucible, closed with a quartz lid and installed in the working part of the microwave oven muffle.

Example 1

Take 175 ml of an acidic aqueous solution of titanyl sulfate (TiOSO ₄ ) with a titanium content of 17 g / l. Next, carbon black calculated on titanium oxide is introduced into it in a ratio of TiO ₂ : C = 1 ÷ 3 in the amount of 2.25 g and precipitation is carried out with ammonium hydroxide (NH ₄ OH, 12%) with constant stirring to a pH of 10. As a result get a precipitate of titanyl hydroxide on soot. Next, the precipitate is washed by decantation to a neutral medium of pH 6, filtered and dried in an oven at a temperature of 120 ° C.

The resulting precursor, TiO (OH) ₂ / 3C, is a mechanical mixture of particles of titanyl hydroxide and carbon black with an average particle size of ~ 150 nm and a specific surface area of 285.17 m ² / g, of which 107.29 m ² / g is microporosity (Table 1, Sample 2).

The resulting precursor is pressed into a ⌀10 mm tablet and placed in a quartz crucible, which in turn is placed in a muffle of a microwave oven. Next, heat treatment is carried out in an argon stream at a speed of 7 l / h. The heating is carried out in three stages with a heating rate of 15 ° C / min to 500 ° C, 10 ° C / min to 700 ° C and 5 ° C / min to 1300 ° C with holding at a temperature of 1300 ° C for 70 min.

The result is ~ 3.75 g of the product, an ultrafine cubic modification titanium carbide powder (Fig. 3a) with an average particle size of ~ 250 nm and a lattice parameter of a = 4.3213 (7) Å. The specific surface area of the sample was 9.50 m ² / g (Table 1, Sample 3).

Example 2

Take 200 ml of an acidic aqueous solution of titanyl sulfate (TiOSO ₄ ) with a titanium content of 15 g / l. Next, carbon black calculated on titanium oxide is introduced into it in the ratio of TiO ₂ : C = 1 ÷ 3 in the amount of 2.25 g and precipitation is carried out with ammonium hydroxide (NH ₄ OH, 12%) with constant stirring to a pH of 12. As a result get a precipitate of titanyl hydroxide on soot. Next, the precipitate is washed by decantation to a neutral medium of pH 6, filtered and dried in an oven at a temperature of 110 ° C.

The resulting precursor is pressed into a ⌀10 mm tablet and placed in a quartz crucible, which in turn is placed in a muffle of a microwave oven. Next, heat treatment is carried out in an argon stream at a speed of 8 l / h at a temperature of 1300 ° C. Heating is carried out in three stages with a heating rate of 15 ° C / min to 500 ° C, 10 ° C / min to 700 ° C and 5 ° C / min to 1300 ° C with holding at a temperature of 1300 ° C for 60 minutes.

The result is ~ 3.75 g of the product — an ultrafine cubic modification titanium carbide powder with an average particle size of ~ 250 nm. The specific surface area of the sample was 9.50 m ² / g.

Thus, the authors propose a simple and reliable method for producing ultrafine titanium carbide powder with a particle size of ~ 250 nm with a highly developed surface activity.

Table 1 Specific surface area No. Connections Specific surface area S _beats , m ² / g microporosity, m ² / g one Acetylene carbon black 18.10 2 TiO (OH) ₂ / 3C 285.17 107.29 3 TiC, mic., 1300 ° C, 60 min 9.5 0.48

Claims (2)

1. A method of producing an ultrafine titanium carbide powder, comprising mixing an oxygen-containing titanium compound with a carbon source, compressing the obtained powder and subsequent microwave treatment in argon, characterized in that they neutralize to a pH of 10-12 an aqueous solution of titanyl sulfate with ammonia / sodium hydroxide solution in the presence of soot to obtain a powder, and the processing of the powder with microwave radiation is carried out with a frequency of 2450-3000 MHz at a power of 700-1200 W in argon flow at a speed of 7-8 l / h s in three stages, the first stage at a speed of 15 ° C / min up to 500 ° C, the second at a speed of 10 ° C / min up to 700 ° C and the third at a speed of 5 ° C / min up to 1300 ° C and with exposure for 60-70 minutes 2. The method according to claim 1, characterized in that the carbon black is used in terms of oxide at a ratio of TiO ₂ : C = 1: 3.

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