The method of obtaining powders of refractory compounds based on titanium

 

(57) Abstract:

The invention relates to the field of powder metallurgy and concerns a method for obtaining powders of refractory compounds on the basis of a carbide or nitride of titanium compounds that can be used for the production of cutting tools, metal fittings, etc. In the method of producing titanium carbide, oxycarbide titanium, titanium nitride, oxynitride titanium or oxycarbonate titanium, including the production of particles of oxide compounds of titanium with adsorbed on the surface of the amorphous carbon and the subsequent carbothermic recovery, in an aqueous solution of titanium sulfate type acetylene carbon black at a ratio of Ti+4: Csootnot less than 1:0.5, and then in continuous active stirring add at the rate of 1-2 cm3/min aqueous ammonia, defend the formed pulp within 10-20 min, decanted solution, the precipitate is filtered, washed with water and dried at a temperature of 200-220C. the Method allows to obtain ultrafine powders of refractory compounds of titanium technologically simple and safe method with the possibility of strict control over the amount of carbon. 2 C.p. f-crystals.

soedinenii on the basis of a carbide or nitride compounds of titanium, which can be used for the production of cutting tools, metal fittings, etc.

The known method of producing powders of carbides of transition metals, in particular titanium, which is mixed oxides with carbon powder, reagent is heated in the reaction chamber under the pressure of the inert gas to a temperature of 1200 - 2000oC, maintaining a pressure sufficient to prevent significant losses of oxides or carbon reagent (U.S. Patent 5338523, l, C 01 B 35/56, 1994).

The disadvantage of this method is the inability to obtain ultrafine powder of the final product due to the formation of large irregular particle size, as well as undesirable discontinuities in the carbothermic reduction process. In addition, when carrying out the reaction between the reagents as a by-product is carbon monoxide, which must be removed to complete the reaction.

The closest technical solution known to the present invention is a method of obtaining powder of carbide, nitride or carbonitride of titanium, comprising two stages. In the first stage, the source of titanium dioxide is covered with amorphous carbon for schino is applied to particles of titanium dioxide with periodic thermogravimetric analysis. In the second stage, carry out the heating of the coated carbon particles in an inert atmosphere to obtain a titanium carbide or nitrogen atmosphere to nitride or carbonitride of titanium at temperatures of 1200 - 1600oC, you get a final product of desired purity with a particle size of 0.05-0.2 m (U.S. Patent 5417952, l. C 01 B 21/076, 1995).

The disadvantages of this method is primarily attributable to the conduct of the process in the gas phase, since in this case can not control the amount of carbon and may receive its surplus and, therefore, the uneven distribution deposited on the surface of particles of titanium dioxide of carbon, which can lead to uneven size and composition of the particles of the final product. In addition, the use of hydrocarbon gas complicates the process and makes it unsafe.

Thus, the authors task was to develop a technologically simple and secure way of receiving ultradispersed powders of a wide range of refractory compounds of titanium with the possibility of strict control over the amount of carbon that is deposited on the surface of the source of an oxide compound of titanium, forming the amorphous coating is a, titanium nitride, oxynitride titanium or oxycarbonate titanium, including the production of particles of oxide compounds of titanium with adsorbed on the surface of the amorphous carbon and the subsequent carbothermic recovery, in which an aqueous solution of titanium sulfate type acetylene carbon black at a ratio of Ti+4: Csootnot less than 1:0.5, and then in continuous active stirring add at the rate of 1 - 2 cm3/min aqueous ammonia, defend the formed pulp for 10 - 20 min, decanted solution, the precipitate is filtered, washed with water and dried at a temperature of 200 - 220oC.

At the present time of patent and technical literature is not a method of obtaining ultrafine powders on the basis of a carbide or nitride of titanium compounds in which before carbothermic recovery receive an amorphous carbon coating on the particles of oxide compounds of titanium, a titanium hydroxide by deposition of titanium oxide from a solution of titanium sulfate aqueous ammonia solution in the presence of acetylene black in the amount of Ti+4: Csootnot less than 1:0,5.

Obtaining a homogeneous ultrafine powders Eugenie carbon coating on the surface of particles of titanium hydroxide) in the liquid phase in the presence of acetylene black. This is due to the following reasons. When drying the titanium hydroxide can be roughly divided into three States associated with temperature control. At temperatures up to 200oC hydroxide loses water, forming amorphous fine particles are divided into local microregions, which is a separate group (associates), a size of the order of size of anatase (-phase). Upon further heating appears-phase (anatase) and associates (the group) to reduce its volume. The heat treatment of the beginning of the polymorphic transformation at a temperature of 850oC in the dispersion system, new particle-phase rutile), which is almost an order of magnitude larger still preserved crystals of anatase and have a characteristic melted form at boundaries. Thus, in the heating process there is a strong growth of crystals TiO2am---> TiO2Anat---> TiO2rutile. With respect to subsequent carbothermic restore preferably at the stage of formation of particles of amorphous TiO2to prevent the formation of large groups of associates. This is important because carbothermic restoration flows on the surface of the oxide particles with the further diffusion of atossa recovery of oxides soot on the surface of the original oxide phase recovered microlayer with the advent of lower oxides of titanium or moreover, the refractory carbide or nitride phase interferes with the process of further sintering products, thus practically does not change the particle size of the original titanium oxide.

Essential to achieve this goal are the technical parameters of the process of obtaining particles of titanium hydroxide with adsorbed on their surface carbon. The ratio of titanium contained in the sulfuric acid solution, and added to a solution of acetylene soot causes the composition of the final product, which may vary from oxycarbide (in the event of a recovery in an inert atmosphere) and oxynitride (in the case of recovery in a stream of nitrogen) titanium carbide to and, respectively, nitride compounds, however, the compound obtained is characterized by a cubic NaCl-type lattice. To obtain a carbide or nitride of titanium compounds it is necessary to maintain a specified ratio in the range of 1: 2 > Ti+4: C 1:3. Further increase in the ratio does not affect the composition of the final product, but has a significant impact on the increase of its dispersion. While maintaining the ratio Ti+4: C 1: 2 final product is oxycarbon in the final product you receive impurity phase - titanium dioxide.

When the speed of adding an aqueous solution of ammonia is less than 1 cm3/min and time settling for less than 10 min is not achieved full deposition of particles of the hydroxide with adsorbed on their surface carbon. When the speed of adding more than 2 cm3/min and time advocate for more than 20 min, the formation of large particles of titanium hydroxide with subsequent increase of the crystalline particles of titanium dioxide in the charge.

When the drying temperature below 200oC remains hydrated moisture. When the drying temperature above 220oC possible crystallization of titanium dioxide.

The proposed method consists in the following.

To obtain an amorphous coating on the surface of particles of titanium hydroxide in an aqueous solution of titanium sulfate (concentration 64,7 g/l) add acetylene carbon black in an amount necessary to obtain the ratio Ti+4: C not less than 1:0,5; then, when continuous active stirring add at the rate of 1 - 2 cm3/min 30% aqueous ammonia solution, the resulting slurry assert within 10 - 20 min, decanted solution, the precipitate is filtered, washed with water and dried at a temperature of 200 - 220oC. the Obtained mixture, moderatore 1350oC in a stream of nitrogen. Control of the chemical composition of the obtained product of x-ray phase and chemical analyses, set the average particle size of the obtained product by known methods. Get a carbide, oxycarbide, nitride, oxynitride or oxycarbide titanium, consisting of ultrafine particles with a size of 0.36-0,7 m

The proposed solution is illustrated by the following examples.

Example 1. Take 500 ml of a solution of titanium sulfate concentration was 64.7 g/l, type of 14.57 g of acetylene black (gain ratio Ti+4:C=1:3), then with continuous stirring, add at the rate of 1 cm3/min 30% aqueous ammonia solution, defend for 10 min, the precipitate is filtered, washed with water and dried at a temperature of 200oC for 30 minutes followed by a carbothermic recovery at a temperature of 1200oC in vacuum 210-2mm RT. Art. Get ultra-fine powder of titanium carbide composition of TiC with a particle size of 0.5-0.8 m

Example 2. Take 500 ml of a solution of titanium sulfate concentration was 64.7 g/l, add 29,0 g acutiloba soot (gain ratio Ti+4:C=1:6), then with continuous stirring, add at the rate of 2 cm3/min 30% in the SUP>oC for 20 minutes followed by a carbothermic recovery at a temperature of 1350oC in a stream of nitrogen supplied at a speed of 2 cm3/s. Get ultra-fine powder of titanium nitride composition TiNi with a particle size of 0.3-0.5 m

Example 3. Take 500 ml of a solution of titanium sulfate concentration was 64.7 g/l was added 48 g of acetylene black (gain ratio Ti+4:C=1:1), then with continuous stirring, add at the rate of 2 cm3/min 30% aqueous ammonia solution, defend for 20 min, the precipitate is filtered, washed with water and dried at a temperature of 220oC for 20 minutes followed by a carbothermic recovery at a temperature of 1200oC in vacuum 210-2mm RT. Art. Get ultra-fine powder oxycarbide titanium composition TiC0,5O0,5with a particle size of 0.5-0.8 m

Thus, the proposed method allows to obtain ultrafine powders of refractory compounds of titanium.

1. The method of obtaining powders of refractory compounds based on titanium, including the production of particles of oxide compounds of titanium with adsorbed on their surface carbon and subsequent platonicheskoe recovery, characterized in that Poluchenie adding an aqueous solution of titanium sulfate acetylene black at a ratio of Ti+4: Csootnot less than 1 : 0.5 s and then adding with continuous stirring at a rate of 1 - 2 cm3/min of an aqueous solution of ammonia, by settling in for 10 - 20 min, decanting the solution, filtering the precipitate, washing with water and drying at a temperature of 200 - 220oC.

2. The method according to p. 1, characterized in that for obtaining powders of refractory compounds based on carbide of titanium compounds platonicheskoe recovery is carried out in an inert atmosphere.

3. The method according to p. 1, characterized in that for obtaining powders of refractory compounds based on nitride of titanium compounds platonicheskoe recovery is carried out in nitrogen atmosphere.

 

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1 tbl, 3 ex

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