CN105502398A - Method for synthesizing tantalum carbide superfine powder through molten salt assisted magnesiothermic reduction - Google Patents

Abstract

The invention discloses a method for synthesizing tantalum carbide superfine powder through molten salt assisted magnesiothermic reduction. The method includes: using tantalum oxide and carbon black as raw materials, NaCl, KCl and KF as molten salts and magnesium powder as a reductant; weighing the raw materials proportionally; mixing the raw materials well, and filling a graphite crucible with a mixture of the raw materials; performing low-temperature carbothermic reduction in a flowing argon atmosphere to prepare the tantalum carbide superfine powder. The method is simple in process, easy in preparation condition control and low in cost. The tantalum carbide superfine powder prepared by the method can be applied to producing modifiers of ultrahigh-temperature tantalum carbide ceramic and hard alloys.

Description

A method for synthesizing tantalum carbide ultrafine powder with molten salt-assisted magnesia thermal reduction

technical field

The invention belongs to the technical field of inorganic non-metallic materials, and in particular relates to a method for synthesizing superfine tantalum carbide powders through magnesia thermal reduction assisted by molten salt.

Background technique

Tantalum carbide (TaC) is an important high-temperature structural material with high strength, corrosion resistance and good chemical stability. Its melting point is as high as 3880°C. Ablation resistance, high hardness and other characteristics can be used as high temperature resistant materials and cemented carbide additives. At present, domestic reports on the preparation of tantalum carbide powder mainly use tantalum oxide and tantalum powder as the tantalum source and carbon black as the carbon source to prepare tantalum carbide through high-temperature carbonization. The synthesis temperature is relatively high, and the product needs to be regrinded. Obtain tantalum carbide powder.

The molten salt assisted synthesis method utilizes the solubility of the reactants in the molten liquid salt to achieve atomic-scale mixing of the reactants in the liquid phase, and the reactants have a faster diffusion rate in the liquid medium, thus reducing the Synthesis temperature; at the same time, the distribution ratio of each component of the synthesis product is accurate, the composition is uniform, and there is no segregation. There is almost no agglomeration phenomenon in the washed product, and the prepared powder has a small particle size, which is beneficial to the preparation of nanometer powder and ultrafine powder.

At present, there are no documents or published invention patents on the low-temperature preparation of tantalum carbide ultrafine powders using molten salt as a medium, tantalum oxide and carbon black as raw materials, and Mg powder as a reducing agent.

Contents of the invention

The purpose of the present invention is to provide a method for synthesizing tantalum carbide ultrafine powder with molten salt-assisted magnesia thermal reduction, which has short process flow, convenient operation, easy realization and energy saving.

The method for synthesizing tantalum carbide ultrafine powder with molten salt _- assisted magnesia reduction of the present invention is to use _Ta2O5 and carbon black as raw materials, and Mg powder as a reducing agent to synthesize tantalum carbide powder, and the reaction equation is:

Ta ₂ O ₅ +5Mg+2C=2TaC+5MgO(1)

MgO+2HCl= _MgCl2 +H2O( ₂ )

The steps of the inventive method are as follows:

(1) According to the molar ratio of Ta ₂ O ₅ powder: Mg powder: carbon black is 1:5-6:2, mix evenly to obtain the mixture 1; wherein the Mg powder is the reducing agent;

(2) Weigh the molten salts NaCl, KCl, and KF according to the molar ratio of 1:1:0.1, and mix them evenly to obtain salt mixture 2;

(3) Weigh the mixture 1 and the salt mixture 2 according to the mass ratio of 1:3-5, and mix them evenly to obtain the mixed powder 3;

(4) Put the mixed powder 3 in a graphite crucible and cover it, then put the crucible into a tube furnace, and then pass in flowing argon as a protective atmosphere, and raise the temperature to 1150~ 1260°C, keep warm for 2-6 hours, take it out after cooling to room temperature, place it in a solution containing 1-2 mol/L hydrochloric acid and stir it magnetically for 4-8 hours, dissolve the MgO impurities generated by the reaction, and then use deionized water to clean and remove the molten salt. The powder is separated by centrifugation, and the TaC superfine powder is obtained by drying, and the particle size is less than 3 microns.

The particle size of Ta ₂ O ₅ described in the present invention is less than 0.5 μm, the purity of Ta ₂ O ₅ is greater than 99.5% (weight percent); the purity of carbon black is greater than 98.5% (weight percent); the particle size of magnesium powder is less than 0.074mm, and the purity of magnesium powder is greater than 98.5 % (percentage by weight).

The beneficial effects of the present invention are as follows:

1. The preparation process is simple, without complicated process equipment and process.

2. The present invention utilizes the advantages of the molten salt method and adopts magnesia thermal reduction of tantalum oxide, which not only reduces the synthesis temperature, but also controls the particle size of the tantalum carbide powder.

3. The preparation temperature is low, the powder particle size is small, and the purity is high, and the mass percentage of TaC phase in the prepared powder is greater than 95%.

4. The ultrafine tantalum carbide powder prepared by the present invention can be used as a modifier for preparing TaC series ultra-high temperature ceramics and hard alloys.

detailed description

The present invention will be further described below in conjunction with embodiment:

Example 1

Mix according to the molar ratio of _Ta2O5 powder: Mg powder: carbon black is 1:6: ₂ to obtain the mixture 1; Weigh and mix the molten salt NaC, KCl, KF according to the molar ratio of 1:1:0.1 Obtain the salt mixture 2 evenly; weigh the mixture 1 and the salt mixture 2 according to the mass ratio of 1:3 and mix them evenly to obtain the mixed powder 3; put the mixed powder 3 in a graphite crucible and cover it, then put the crucible into In a tube furnace, heat up to 1150°C at a heating rate of 3°C/min under a flowing argon atmosphere, keep it warm for 6 hours, and take it out after cooling to room temperature; place the product in a solution containing 2mol/L hydrochloric acid and stir it magnetically for 4h, then Wash with deionized water to remove the molten salt, separate the tantalum carbide powder from the solution with a centrifuge (8000 rpm), and dry at 110°C for 8 hours to obtain an ultrafine TaC powder with a particle size of less than 3 μm.

Example 2

Mix according to the molar ratio of _Ta2O5 powder: Mg powder: carbon black is 1:5.5: ₂ to obtain the mixture 1; the molten salt NaCl, KCl, KF are weighed and mixed according to the molar ratio of 1:1:0.1 Obtain the salt mixture 2 evenly; weigh the mixture 1 and the salt mixture 2 according to the mass ratio of 1:5 and mix them evenly to obtain the mixed powder 3; put the mixed powder 3 in a graphite crucible and cover it, then put the crucible into In a tube furnace, heat up to 1200°C at a rate of 10°C/min under a flowing argon atmosphere and keep warm for 4 hours, then take it out after cooling to room temperature; place the product in a solution containing 1.5mol/L hydrochloric acid and stir it magnetically for 4h, then Wash with deionized water to remove the molten salt, separate the tantalum carbide powder from the solution with a centrifuge (11,000 rpm), and dry at 110°C for 8 hours to obtain an ultrafine TaC powder with a particle size of less than 3 μm.

Example 3

Mix according to the molar ratio of _Ta2O5 powder: Mg powder: carbon black is 1:5.25: ₂ to obtain the mixture 1; the molten salt NaCl, KCl, KF are weighed and mixed according to the molar ratio of 1:1:0.1 Obtain the salt mixture 2 evenly; weigh the mixture 1 and the salt mixture 2 according to the mass ratio of 1:5 and mix them evenly to obtain the mixed powder 3; put the mixed powder 3 in a graphite crucible and cover it, then put the crucible into In a tube furnace, heat up to 1230°C at a rate of 15°C/min under a flowing argon atmosphere, keep it warm for 3 hours, and take it out after cooling to room temperature; place the product in a solution containing 1mol/L hydrochloric acid and stir it magnetically for 8h, then Wash with deionized water to remove the molten salt, separate the tantalum carbide powder from the solution with a centrifuge (9000 rpm), and dry at 110°C for 8 hours to obtain an ultrafine TaC powder with a particle size of less than 3 μm.

Example 4

Mix according to the molar ratio of _Ta2O5 powder: Mg powder: carbon black is 1:5.3: ₂ to obtain the mixture 1; the molten salt NaCl, KCl, KF are weighed and mixed according to the molar ratio of 1:1:0.1 Obtain the salt mixture 2 evenly; weigh the mixture 1 and the salt mixture 2 according to the mass ratio of 1:5 and mix them evenly to obtain the mixed powder 3; put the mixed powder 3 in a graphite crucible and cover it, then put the crucible into In a tube furnace, heat up to 1260°C at a rate of 5°C/min under flowing argon atmosphere, keep it warm for 2 hours, take it out after cooling to room temperature; place the product in a solution containing 2mol/L hydrochloric acid for 4h with magnetic stirring, and then Wash with deionized water to remove the molten salt, separate the tantalum carbide powder from the solution with a centrifuge (11,000 rpm), and dry at 110°C for 8 hours to obtain an ultrafine TaC powder with a particle size of less than 3 μm.

Claims (2)

1. a method for fused salt assisting magnesium thermal reduction synthesis tantalum carbide superfine powder, is characterized in that: described method steps is as follows:

(1) by Ta ₂o ₅powder: Mg powder: the mol ratio of carbon black is that 1:5 ~ 6:2 carries out proportioning, mixes and obtains compound 1; Wherein said Mg powder is reductive agent;

(2) fused salt NaCl, KCl, KF are weighed according to mol ratio 1:1:0.1, mix and obtain salt compound 2;

(3) compound 1 and salt compound 2 are weighed according to mass ratio 1:3 ~ 5, mix and obtain powder mix 3;

(4) powder mix 3 is placed in plumbago crucible to add a cover; again crucible is put into tube furnace; then the argon gas of flowing is passed into as protective atmosphere; be that 3 ~ 15 DEG C/min is warmed up to 1150 ~ 1260 DEG C by temperature rise rate; be incubated 2 ~ 6 hours; take out after being cooled to room temperature; be placed in containing 1 ~ 2mol/L hydrochloric acid soln magnetic agitation, 4 ~ 8h; the MgO impurity that solubilizing reaction generates; then washed with de-ionized water is used to remove fused salt; go out powder through centrifugation, dry i.e. obtained TaC superfine powder, its particle diameter is less than 3 microns.

2. the method for the fused salt assisting magnesium thermal reduction synthesis tantalum carbide superfine powder according to claims 1, is characterized in that: described Ta ₂o ₅granularity is less than 0.5 μm, Ta ₂o ₅purity is greater than 99.5%; Carbon black purity is greater than 98.5%; Magnesium Powder Particle Size is less than 0.074mm, and magnesium powder purity is greater than 98.5%.