CN101857196A - A kind of preparation method of nanometer chromium carbide/vanadium composite powder - Google Patents

Abstract

A preparation method of nano-chromium carbide/vanadium composite powder, said preparation method comprising the following steps: taking 4.20-10.90 g of powdery chromium salt, 3.70 g-7.70 g of ammonium vanadate, and 2.20 g of carbonaceous reducing agent according to the weight ratio ~8.40g, put them in deionized water or distilled water, and stir evenly to obtain a solution or a mixed solution; place the solution or mixed solution obtained in step a in a drying oven, and heat it at 100-200°C for 1- 3h, dry at 50-100°C for 1-5h, and finally obtain a precursor powder containing a chromium source, a vanadium source and a carbon source; place the precursor powder obtained in step b in a high-temperature reaction furnace, in vacuum, argon or Under the protection condition of hydrogen atmosphere, the carbonization reduction is carried out at 800-1100°C for 0.5-2 hours, and the nano-chromium carbide/vanadium composite powder with an average particle size of <100nm and uniform particle size distribution is obtained. The method has the characteristics of low reaction temperature, short reaction time, low production cost, simple process, etc., and is suitable for industrial production of nano-chromium carbide/vanadium composite powder.

Description

A kind of preparation method of nanometer chromium carbide/vanadium composite powder

technical field

The invention provides a method for preparing nanometer chromium carbide/vanadium composite powder, which belongs to the field of nanometer metal carbide preparation.

Background technique

The transition metal carbide, chromium carbide (vanadium), has a high melting point, hardness and high temperature strength, as well as good electrical and thermal conductivity. These excellent properties ensure its wide application in metallurgy, electronics, catalysts and high-temperature coating materials.

Among them, chromium carbide (vanadium) plays an important role as a grain inhibitor in the fields of cemented carbide and cermets. What is needed in industrial applications is chromium carbide (vanadium) powder with fine particle size and single phase composition. For example, when preparing ultra-fine cemented carbide, the particle size of WC powder should be less than 200nm, and high-pressure and low-temperature HIP sintering technology should be used for sintering. Also add chromium carbide (vanadium) grain growth inhibitor. If chromium carbide (vanadium) with a powder particle size of 2 to 5 μm is used as a grain growth inhibitor, it will be difficult to inhibit the particle size due to the small surface area, low surface activation energy, and slow atomic migration speed of the coarse chromium carbide (vanadium) powder. The grain growth of WC makes it difficult to further improve the performance of ultra-fine cemented carbide. Therefore, there is an urgent need for nano-chromium carbide (vanadium) powder in fields such as high-performance ultrafine cemented carbide.

In addition, vanadium carbide makes the alloy show the best hardness and wear resistance, and chromium carbide is the most effective for improving the bending strength and oxidation resistance; the alloy added with vanadium carbide and chromium carbide, the segregation of grain growth inhibitor is greater than Cemented carbide with vanadium carbide added alone has better grain suppression effect. However, at present, the combined addition of vanadium carbide and chromium carbide is mostly a method of mechanical mixing, which cannot fully disperse the powder, which is not conducive to the effect of grain suppression. Therefore, it is necessary to synthesize nano-chromium carbide/vanadium composite powder.

However, the preparation of chromium carbide (vanadium) powder usually adopts the mixed high-temperature reduction carbonization method of carbon black and chromium (vanadium) oxide. This method reaction temperature is higher, and production cost is higher. In addition, the particle size of the reaction product is relatively coarse, generally between 2 and 5 μm, and the free carbon content in the powder is high, which cannot meet the application of chromium carbide (vanadium) powder in modern industry.

In addition, in 2004, Wu Enxi and others proposed a preparation method of nano-chromium carbide powder in the patent CN1724349A: dissolve Cr ₂ O ₃ in an organic solution with a solution concentration of 10% to 20%; the solution is dried in a centrifugal spray dryer. Spray drying to obtain a mixed powder containing chromium complexes and free organic matter, and the powder shape is porous and loose hollow spheres. The powder is roasted at 500-600°C in a protective atmosphere to obtain a uniformly mixed powder of Cr ₂ O ₃ and atomic-level free C. At 850-1000°C, H ₂ /CH ₄ can be carbonized for 40-90 minutes. The nanometer chromium carbide powder with an average grain size of 0.1 micron and a grain size of 20-60 nanometers is prepared. This method has many advantages, such as lower reaction temperature, shorter reaction time, etc.; but there are also some disadvantages, such as complicated process and carbonization with H ₂ or H ₂ /CH ₄ , which increases the production cost.

In 2005, Wu Chengyi and others proposed a method for preparing nano-vanadium carbide powder in patent CN1569624A: dissolving ammonium metavanadate powder in distilled water to prepare ammonium metavanadate aqueous solution, and then spraying the solution at 120-130 °C Convert to V ₂ O ₅ precursor powder, then roast the V ₂ O ₅ precursor powder in the air at 450-550°C to convert it into dry nano-scale V ₂ O ₅ microcrystalline powder, and then shear the carbon , drying, carbonization of the mixture, carbonization, shearing and crushing, and vacuum drying to obtain nano-scale vanadium carbide powder. The main problem of this method is that the process is more complicated and the production cost is higher.

In 2005, Wu Enxi and others proposed the preparation method of vanadium carbide powder in the patent CN1607175A: first, dissolve V ₂ O ₅ in the organic acid solution, stir while heating, and obtain a clear and transparent solution at 60-80 ° C, the solution concentration is 10%-40%; then the powder is roasted at 500-600°C in a protective atmosphere to obtain a powder uniformly mixed with V ₂ O ₃ and atomic-level free C; and at 850-1000°C, H ₂ or H ₂ /CH ₄ carbonization for 40 to 90 minutes to obtain superfine vanadium carbide powder with an average particle size of 0.1 micron and a grain size of 20 to 60 nanometers. This method has many advantages, such as lower reaction temperature, shorter reaction time, etc.; but it also has disadvantages such as complex process and unfavorable industrial production.

In 2006, Hao Junjie and others provided a preparation method of nano-chromium carbide powder in patent CN100357187C. The method uses ammonium dichromate, hydrazine hydrate, nano-carbon black, and phenolic resin as raw materials, and the preparation process is as follows: synthesis of amorphous nano-Cr ₂ O ₃ →preparation of phenolic resin ethanol solution →ball milling (2-8h) →drying (1- 2h)→vacuum carbonization→ball milling (2-8h)→drying→sieving→product. This method has high innovation, and the synthesized powder has reached the nanoscale, but the process is complicated, the energy consumption is large, and the production cost is high, which is not conducive to industrial production.

Sadangi et al. from Rutger University in the United States prepared Cr ₃ C ₂ (V ₈ C ₇ ) powders with a particle size of 0.6 μm (0.5 μm) using the process of “spray drying → reduction decomposition → gas phase carbonization” (see RK Sadangi, LEMcCandlish, BHKear, P . Seegopaul. Synthesis and characterization of submicron vanadium and chromium carbide grain growth inhibitors. Advances in Powder Metallurgy & Particular Materials, 1998: P9-P15). The process is as follows: first prepare a precursor solution containing Cr(V), then spray dry it, then pyrolyze the spray-dried powder, and carry out gas phase carbonization of the pyrolyzed product with CH ₄ /H ₂ mixed gas. The main problem of this method is that the process is more complicated, and the particle size of the obtained chromium carbide (vanadium) powder is relatively large, which cannot satisfy the application of chromium carbide (vanadium) powder in modern industry.

Cintho et al. milled chromium powder and graphite powder with high-energy balls, followed by heat treatment in an argon atmosphere at 800°C for 2 hours, and finally obtained chromium carbide powder (Cr ₃ C ₂ and Cr ₇ C ₃ ) (see OMCintho, EAPFavilla, JDT Capocchi. Mechanical-thermal synthesis of chromium carbides [J]. Journal of Alloys and Compounds, 2007, 439(1-2): 189-195.). The main problem of this method is that the process is relatively complicated, and the particle size of the obtained chromium carbide powder is relatively large, which cannot meet the application of chromium carbide powder in modern industry.

Therefore, in order to save energy and reduce production costs, it is necessary to explore a low-cost, simple process for the preparation of nano-chromium carbide/vanadium composite powders, so as to better meet the needs of chromium carbide/vanadium composite powders in metallurgy, electronics, catalysts and Applications in high temperature coating materials and other fields.

Contents of the invention

The purpose of the present invention is to provide a new preparation method of nano-chromium carbide/vanadium composite powder, so as to meet the application of chromium carbide/vanadium composite powder in the fields of metallurgy, electronics, catalysts and high-temperature coating materials.

The preparation method of the present invention comprises the following steps:

a. Take 4.20-10.90g of powdered chromium salt, 3.70g-7.70g of ammonium vanadate, and 2.20g-8.40g of carbonaceous reducing agent by weight, put them in deionized water or distilled water, and stir evenly to prepare to obtain a solution or mixture;

b. Put the solution or mixed solution obtained in step a in a drying oven, heat at 100-200°C for 1-3 hours, and dry at 50-100°C for 1-5 hours, and finally obtain the chromium source, vanadium source and carbon Source precursor powder;

c. Place the precursor powder obtained in step b in a high-temperature reaction furnace, and carry out carbonization and reduction at 800-1100°C for 0.5-2 hours under the protection conditions of vacuum, argon or hydrogen atmosphere, and obtain an average particle size of < 100nm nano-chromium carbide/vanadium composite powder with uniform particle size distribution.

The powdery chromium salt in the present invention is any one of ammonium chromate or ammonium dichromate or a mixture thereof.

The powdery ammonium vanadate described in the present invention is any one of ammonium metavanadate or ammonium polyvanadate or a mixture thereof.

The carbonaceous reducing agent described in the present invention is any one of nano-carbon black, nano-activated carbon, glucose, starch or sucrose

The high-temperature reaction furnace in the present invention is any one of carbon tube furnace, tube furnace, induction furnace, microwave sintering furnace, rotary furnace, pusher kiln or tunnel kiln.

Compared with the existing method for preparing chromium carbide (vanadium) powder, the present invention has the following beneficial effects:

(1) Abundant raw materials and low price: the present invention uses chromium salt, ammonium vanadate and carbonaceous reducing agent as raw materials, which has abundant sources, low price and cost saving.

(2) Low reaction temperature, short reaction time, and energy saving: the preparation of nano-chromium carbide/vanadium composite powder by the precursor carbonization method greatly reduces the reaction temperature and shortens the reaction time. The preparation of nano-chromium carbide/vanadium composite powder, thus saving energy.

(3) The process is simple: the present invention can complete carbonization at one time, avoiding the pre-reduction of chromium salt and ammonium vanadate into low-priced oxides of chromium (vanadium), and then carbonizing, eliminating many processes, convenient operation, and suitable for industrialization Production.

(4) The composition is single, the particle size is uniform and fine: the particle size of the chromium carbide/vanadium composite powder produced by the reaction is less than 100nm, the particle size distribution range is narrow, and the impurity content is small; it can meet the requirements of the chromium carbide/vanadium composite powder in metallurgy, electronics, and catalysts. And high temperature coating materials and other fields of application.

Detailed ways

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

Example 1:

Take ammonium dichromate 4.20g, ammonium metavanadate 3.80g and nano carbon black 2.19g by weight, and they are placed in 50ml of deionized water, after stirring, a uniform mixed solution is obtained, and the mixed solution is placed in a dry place. box, heated at 100-200°C for 1-3h, then dried at 50-100°C for 1-5h, and finally obtained precursor powder containing chromium source, vanadium source and carbon source; the obtained precursor The powder is placed in a vacuum carbon tube furnace, and under vacuum conditions, it is carbonized and reduced at 800-1100° C. for 0.5-2 hours to obtain a nano-chromium carbide/vanadium composite powder with an average particle size of <100 nm and uniform particle size distribution (weight ratio 1:1).

Example 2:

Get ammonium dichromate 4.20g, ammonium metavanadate 7.60g and nanometer carbon black 3.51g by weight, place 50ml deionized water, obtain the mixed solution that mixes after stirring, mixed solution is placed in drying box, in Heating at 100-200°C for 1-3 hours, and then drying at 50-100°C for 1-5 hours to obtain a precursor powder containing chromium source, vanadium source and carbon source; place the obtained precursor powder in a tube In a type furnace, under the protective condition of argon or hydrogen atmosphere, carbonization and reduction are carried out at 800-1100°C for 0.5-2 hours to obtain nano-chromium carbide/vanadium composite powder with an average particle size of <100nm and uniform particle size distribution (weight ratio 1:2).

Example 3:

Take 4.20g of ammonium dichromate, 3.80g of ammonium metavanadate and 5.48g of glucose according to the weight ratio, put them in 50ml of deionized water, and stir to obtain a uniform solution. Heating under conditions for 1-3 hours, then drying at 50-100°C for 1-5 hours, and finally obtaining a precursor powder containing chromium source, vanadium source and carbon source; place the obtained precursor powder in a vacuum carbon tube furnace , under vacuum conditions, at 800-1000 ℃, 0.5-2h carbonization reduction, the average particle size <100nm, uniform particle size distribution of nano-chromium carbide / vanadium composite powder (weight ratio 1:1).

Example 4:

Take 4.20g of ammonium dichromate, 7.60g of ammonium metavanadate and 8.34g of starch according to the weight ratio, put them in 50ml of deionized water, and stir to obtain a uniform solution. Heating under conditions for 1-3 hours, then drying at 50-100°C for 1-5 hours, and finally obtaining a precursor powder containing chromium source, vanadium source and carbon source; place the obtained precursor powder in a vacuum carbon tube furnace , under vacuum conditions, at 800-1000 ° C, 0.5-2h carbon reduction, the average particle size < 100nm, uniform particle size distribution of nano-chromium carbide / vanadium composite powder (weight ratio 1:2).

Example 5:

Take 4.20g of ammonium dichromate, 7.60g of ammonium metavanadate and 8.34g of sucrose according to the weight ratio, put them in 50ml of deionized water, and stir to obtain a uniform solution. Heating under conditions for 1-3 hours, then drying at 50-100°C for 1-5 hours, and finally obtaining a precursor powder containing chromium source, vanadium source and carbon source; placing the obtained precursor powder in a tube furnace, Under the protective condition of argon or hydrogen atmosphere, carbonization reduction is carried out at 800-1000°C for 0.5-2 hours to produce nano-chromium carbide/vanadium composite powder with average particle size <100nm and uniform particle size distribution (weight ratio 1:2) .

Embodiment 6:

Get ammonium chromate 6.67g, ammonium metavanadate 3.80g and nanometer carbon black 2.19g by weight, and they are placed in the deionized water of 50ml, obtain the mixed solution that mixes after stirring, mixed solution is placed in drying box , heating at 100-200°C for 1-3h, and then drying at 50-100°C for 1-5h to obtain a precursor powder containing chromium source, vanadium source and carbon source; the obtained precursor powder Put it in a vacuum carbon tube furnace, and under vacuum conditions, carbonize and reduce at 800-1100°C for 0.5-2 hours to obtain nano-chromium carbide/vanadium composite powder with an average particle size of <100nm and uniform particle size distribution (weight ratio 1 : 1).

Embodiment 7:

Get ammonium chromate 6.67g, ammonium dichromate 4.20g, ammonium metavanadate 7.60g and nano activated carbon 4.38g by weight ratio, and they are placed in 50ml deionized water, after stirring, obtain the mixed solution that mixes, mix The solution is placed in a drying oven, heated at 100-200°C for 1-3 hours, then dried at 50-100°C for 1-5 hours, and finally the precursor powder containing chromium source, vanadium source and carbon source is obtained; the precursor The body powder is placed in a tube furnace, and under the protection of argon or hydrogen atmosphere, it is carbonized and reduced at 800-1100°C for 0.5-2 hours to obtain nano-chromium carbide/vanadium with an average particle size of <100nm and uniform particle size distribution. Composite powder (weight ratio 1:1).

Embodiment 8:

Get ammonium dichromate 4.20g, ammonium polyvanadate 6.48g and nanometer carbon black 3.50g by weight ratio, and they are placed in the deionized water of 50ml, after stirring, obtain the mixed solution that mixes evenly, mixed solution is placed In a drying oven, heat at 100-200°C for 1-3 hours, then dry at 50-100°C for 1-5 hours, and finally obtain a precursor powder containing chromium source, vanadium source and carbon source; The body powder is placed in a vacuum carbon tube furnace, and under vacuum conditions, it is carbonized and reduced at 800-1100 ° C for 0.5-2 hours to obtain a nano-chromium carbide/vanadium composite powder with an average particle size of <100 nm and uniform particle size distribution (weight ratio 1:2).

Embodiment 9:

Take ammonium dichromate 4.20g, ammonium metavanadate 3.80g, polyammonium vanadate 3.24g and nano carbon black 3.51g by weight, and they are placed in 50ml of deionized water, and after stirring, a uniform mixture is obtained. solution, put the mixed solution in a drying oven, heat at 100-200°C for 1-3h, then dry at 50-100°C for 1-5h, and finally obtain a precursor containing chromium source, vanadium source and carbon source powder; the obtained precursor powder is placed in a tube furnace, and under the protection of argon or hydrogen atmosphere, it is carbonized and reduced at 800-1100°C for 0.5-2 hours to obtain an average particle size of <100nm and a particle size distribution of Uniform nano-chromium carbide/vanadium composite powder (weight ratio 1:2).

Claims (5)

1. a preparation method of nanometer chromium carbide/vanadium composite powder, is characterized in that: described preparation method comprises the following steps: a. Take 4.20-10.90g of powdered chromium salt, 3.70g-7.70g of ammonium vanadate, and 2.20g-8.40g of carbonaceous reducing agent by weight, put them in deionized water or distilled water, and stir evenly to prepare to obtain a solution or mixture; b. Put the solution or mixed solution obtained in step a in a drying oven, heat at 100-200°C for 1-3 hours, and dry at 50-100°C for 1-5 hours, and finally obtain the chromium source, vanadium source and carbon Source precursor powder; c. Place the precursor powder obtained in step b in a high-temperature reaction furnace, and carry out carbonization and reduction at 800-1100°C for 0.5-2 hours under the protection conditions of vacuum, argon or hydrogen atmosphere, and obtain an average particle size of < 100nm nano-chromium carbide/vanadium composite powder with uniform particle size distribution. 2. The preparation method according to claim 1, characterized in that: the powdery chromium salt is any one of ammonium chromate or ammonium dichromate or its mixture. 3. The preparation method according to claim 1, characterized in that: said powdered ammonium vanadate is any one of ammonium metavanadate or ammonium polyvanadate or its mixture. 4. The preparation method according to claim 1, characterized in that: the carbonaceous reducing agent is any one of nano-carbon black, nano-activated carbon, glucose, starch or sucrose. 5. The preparation method according to claim 1, characterized in that: the high-temperature reaction furnace is any one of carbon tube furnace, tube furnace, induction furnace, microwave sintering furnace, rotary kiln, pusher kiln or tunnel kiln kind.