CN110818400A - Preparation method of high-density mullite ceramic powder - Google Patents

Abstract

The patent of the present invention relates to a preparation method of high-density mullite ceramic powder, which uses sodium silicate nonahydrate, aluminum sulfate octadecahydrate, ammonia water, hydrochloric acid and n-amyl alcohol as the main raw materials, and europium oxide as the sintering agent. The mullite ceramic powder prepared by the method of the present invention promotes the sintering of the mullite powder, so that the powder dispersion degree is improved, the surface activity is enhanced, the powder body is more dense, and the internal crystal state is more complete, and the mulliteization process is promoted.

Description

A kind of preparation method of high-density mullite ceramic powder

technical field

The invention relates to the technical field of inorganic chemical industry, in particular to a preparation method of high-density mullite ceramic powder.

Background technique

As a very important refractory material in industry, mullite ceramics have the characteristics of superior high temperature resistance, high high temperature strength and creep resistance, low thermal expansion coefficient and good chemical stability. Its strength and toughness increase with temperature, so mullite ceramics are ideal high-temperature structural materials. However, the mechanical properties of mullite at room temperature are not good, the strength and toughness of mullite ceramic materials are low, and it is difficult to sinter densely, which limits the wide application of mullite. Therefore, the preparation of mullite composites has become the main way to make up for the defects of mullite.

Rare earth elements have the advantages of promoting sintering and reducing sintering temperature, which can improve the defects of traditional mullite. With the development of the economy, metallurgy, construction, non-ferrous metals, etc. will face new challenges, and the production of these industries is inseparable from refractory materials, so the application of rare earth in the refractory material industry will definitely enter a new era, and it will also bring Great economic and social benefits.

SUMMARY OF THE INVENTION

The invention aims to make up for the deficiencies of the prior art, and the object is to provide a preparation method of high-density mullite ceramic powder. The mullite ceramic powder prepared by the method of the invention promotes sintering due to europium oxide, so that the powder is higher than The surface area is increased, the powder is denser, and the internal crystalline state is more complete, which promotes the mulliteization process.

To achieve the above object, the present invention is achieved through the following technical solutions:

A method for preparing high-density mullite ceramic powder, characterized in that, using sodium silicate nonahydrate, aluminum sulfate octadecahydrate, ammonia water, hydrochloric acid and n-amyl alcohol as main raw materials, using europium oxide as a sintering-promoting agent, and using 100 parts by weight, the formulation dosage and operation steps of each material are as follows:

Sodium silicate nonahydrate (Na ₂ SiO ₃ 9H ₂ O) 4-6 parts

Aluminum sulfate octadecahydrate (Al ₂ (SO ₄ ) ₃ ·18H ₂ O) 12-20 parts

Ammonia, the molar volume concentration is 12-15mol/L 10-15 parts

Hydrochloric acid, molar volume concentration is 5-8mol/L 5-15 parts

Europium oxide 0.5-2 parts

50-60 parts of n-amyl alcohol

Step 1, dissolving sodium silicate nonahydrate and aluminum sulfate octadecahydrate in water respectively, and configuring into a sodium silicate aqueous solution whose molar volume concentration is 3mol/L and an aqueous aluminum sulfate solution whose molar volume concentration is 3mol/L;

Step 2, dissolving europium oxide in the hydrochloric acid of 10% formula amount, and configure into europium chloride salt solution;

Step 3, mix the sodium silicate aqueous solution with 90% of the hydrochloric acid of the formula, continue stirring for 15-20 minutes, and let stand for 20-40 minutes to obtain a silicic acid sol;

Step 4, add the europium oxide salt solution obtained in step 2 to the silicic acid sol, continue stirring for 15-20 minutes, then add ammonia water and an aqueous solution of aluminum sulfate octadecahydrate to it in turn, continue stirring for 15-20 minutes, and let stand for 20- 40 minutes to obtain a sol-gel solution;

Step 5, continuously add water dropwise to the sol-gel solution, and perform suction filtration for 20-30 hours to obtain a gel product;

Step 6: Mix the obtained gel product with n-amyl alcohol, raise the temperature to 99°C at a heating rate of 2-3°C/min, azeotropic distillation for 45-60 minutes, and place the obtained material at 100-120°C to dry for 1 -3 hours to obtain mullite precursor powder;

In the seventh step, the mullite precursor powder is sintered at 900-1200° C. for 1-3 hours to obtain a high-density mullite ceramic powder.

The preferred molar volume concentration of hydrochloric acid in the step 1 is 6-7 mol/L.

The preferred molar volume concentration of ammonia water in the step 1 is 14-15mol/L.

Compared with the prior art, the invention has the beneficial effects that: europium oxide has obvious promoting effect on the sintering degree and crystalline state of mullite ceramic powder; The specific surface area was increased by 52 m ² /g.

Description of drawings

Figure 1 is a scanning electron microscope (SEM) image of the sample prepared by the comparative example, which is a comparative example without adding europium oxide;

Fig. 2 is the scanning electron microscope (SEM) of the sample prepared in Example 1;

Fig. 3 is the scanning electron microscope (SEM) of the sample prepared in Example 2;

4 is a scanning electron microscope (SEM) image of the sample prepared in Example 3.

Detailed ways

Below in conjunction with embodiment, the preparation method of the present invention is further described:

Comparative ratio:

4kg of sodium silicate nonahydrate and 18kg of aluminum sulfate octahydrate are dissolved in water respectively, and configured into a sodium silicate aqueous solution that molar volume concentration is 3mol/L and an aqueous aluminum sulfate solution that molar volume concentration is 3mol/L; The aqueous solution and the 15kg concentration were mixed with 6mol/L hydrochloric acid, and after 15 minutes of continuous stirring, let stand for 30 minutes to obtain a silicic acid sol; adding 13kg of concentration successively to the silicic acid sol was 15mol/L ammonia water and an aqueous solution of aluminum sulfate octadecahydrate, After continuing to stir for 15 minutes, let stand for 30 minutes to obtain a sol-gel solution; continue to add water dropwise to the sol-gel solution, and filter for 24 hours to obtain a gel product; mix the obtained gel product with 50kg of n-pentane Mix alcohol and heat up to 99°C at a heating rate of 2°C/min. After azeotropic distillation for 60 minutes, the resulting material is dried at 110°C for 2 hours to obtain mullite precursor powder; The mullite ceramic powder was obtained by sintering the body at 1500°C for 2 hours.

As shown in Figure 1, the specific surface area of the mullite ceramic powder prepared in this comparative example is 162.3 m ² /g and the relative density is 83%.

Example 1:

A method for preparing high-density mullite ceramic powder, characterized in that, using sodium silicate nonahydrate, aluminum sulfate octadecahydrate, ammonia water, hydrochloric acid and n-amyl alcohol as main raw materials, and using europium oxide as sintering-promoting agent, specifically The operation steps are as follows:

4kg of sodium silicate nonahydrate and 18kg of aluminum sulfate octahydrate are respectively dissolved in water, and configured to be the sodium silicate aqueous solution that molar volume concentration is 3mol/L and the molar volume concentration of aluminum sulfate aqueous solution that is 3mol/L; 0.2kg is oxidized Dissolve europium in 1kg of 6mol/L hydrochloric acid, and configure it into a europium chloride salt solution; mix the sodium silicate aqueous solution with 12kg of 6mol/L hydrochloric acid, continue stirring for 15 minutes, and let stand for 30 minutes to obtain silicic acid Sol; add above-mentioned europium oxide salt solution in silicic acid sol, continue to stir for 15 minutes, then add 13kg concentration to it successively and be 15mol/L ammoniacal liquor and 18-hydrate aluminum sulfate aqueous solution, continue stirring after 15 minutes, leave standstill for 30 minutes, That is, a sol-gel solution is obtained; water is continuously added dropwise to the sol-gel solution, and suction filtration is performed for 24 hours to obtain a gel product; The heating rate was raised to 99°C, and after azeotropic distillation for 60 minutes, the obtained material was dried at 110°C for 2 hours to obtain mullite precursor powder; the mullite precursor powder was sintered at 1000°C for 2 hours, That is, high-density mullite ceramic powder is obtained.

As shown in FIG. 2 , the agglomeration phenomenon of the mullite ceramic powder prepared in this example is weakened, and there are larger pores. The specific surface area of the powder reached 187.2 m ² /g, the relative density was 92%, and the internal crystalline state was more complete.

Example 2:

A method for preparing high-density mullite ceramic powder, characterized in that, using sodium silicate nonahydrate, aluminum sulfate octadecahydrate, ammonia water, hydrochloric acid and n-amyl alcohol as main raw materials, and using europium oxide as sintering-promoting agent, specifically The operation steps are as follows:

5kg of sodium silicate nonahydrate and 19kg of aluminum sulfate octahydrate are dissolved in water respectively, and configured to be the sodium silicate aqueous solution that molar volume concentration is 3mol/L and the molar volume concentration of aluminum sulfate aqueous solution that is 3mol/L; 0.5kg is oxidized Dissolve europium in 1kg of 6mol/L hydrochloric acid, and configure it into a europium chloride salt solution; mix the sodium silicate aqueous solution with 12kg of 6mol/L hydrochloric acid, continue stirring for 15 minutes, and let stand for 30 minutes to obtain silicic acid Sol; add above-mentioned europium oxide salt solution in silicic acid sol, continue stirring for 15 minutes, then add 11kg concentration to wherein successively and be 15mol/L ammoniacal liquor and octadecahydrate aluminum sulfate aqueous solution, continue stirring after 15 minutes, leave standstill for 30 minutes, That is, a sol-gel solution is obtained; water is continuously added dropwise to the sol-gel solution, and the gel product is obtained by suction filtration for 24 hours; the obtained gel product is mixed with 51.5 kg of n-amyl alcohol, and the temperature is increased at a temperature of 2 °C/min. The temperature was raised to 99°C, and after azeotropic distillation for 60 minutes, the resulting material was dried at 110°C for 2 hours to obtain mullite precursor powder; the mullite precursor powder was sintered at 1000°C for 2 hours, namely High-density mullite ceramic powder was obtained.

As shown in FIG. 3 , the agglomeration phenomenon of the mullite ceramic powder prepared in this example is weakened, and there are larger pores. The specific surface area of the powder reached 210.8 m ² /g, the relative density was 95%, and the internal crystalline state was more complete.

Example 3:

A method for preparing high-density mullite ceramic powder, characterized in that, using sodium silicate nonahydrate, aluminum sulfate octadecahydrate, ammonia water, hydrochloric acid and n-amyl alcohol as main raw materials, and using europium oxide as sintering-promoting agent, specifically The operation steps are as follows:

6kg of sodium silicate nonahydrate and 20kg of aluminum sulfate octahydrate are dissolved in water respectively, and configured to be the sodium silicate aqueous solution that molar volume concentration is 3mol/L and the molar volume concentration of aluminum sulfate aqueous solution that is 3mol/L; 0.8kg is oxidized Dissolve europium in 1kg of 6mol/L hydrochloric acid, and configure it into a europium chloride salt solution; mix the sodium silicate aqueous solution with 12kg of 6mol/L hydrochloric acid, continue stirring for 15 minutes, and let stand for 30 minutes to obtain silicic acid Sol; add above-mentioned europium oxide salt solution in silicic acid sol, continue stirring for 15 minutes, then add 10kg concentration to wherein successively and be 15mol/L ammoniacal liquor and 18-hydrate aluminum sulfate aqueous solution, continue stirring after 15 minutes, leave standstill for 30 minutes, That is, a sol-gel solution is obtained; water is continuously added dropwise to the sol-gel solution, and the gel product is obtained by suction filtration for 24 hours; the obtained gel product is mixed with 50.2 kg of n-amyl alcohol, and the temperature is 2°C/min. The heating rate was raised to 99°C, and after azeotropic distillation for 60 minutes, the obtained material was dried at 110°C for 2 hours to obtain mullite precursor powder; the mullite precursor powder was sintered at 1000°C for 2 hours, That is, high-density mullite ceramic powder is obtained.

As shown in Figure 4, the mullite ceramic powder particles prepared in this example are difficult to observe the particle boundaries. The powder has a specific surface area of 214.3 m ² /g, a relative density of 96%, and a more complete internal crystalline state.

Claims (3)

1. The preparation method of the high-density mullite ceramic powder is characterized in that sodium silicate nonahydrate, aluminum sulfate octadecahydrate, ammonia water, hydrochloric acid and n-amyl alcohol are used as main raw materials, europium oxide is used as a sintering promoting agent, and the formula dosage and the operation steps of each material are as follows based on 100 parts by weight:

sodium silicate nonahydrate (Na)₂SiO₃·9H₂O), 4-6 parts

Aluminum sulfate octadecahydrate (Al)₂（SO₄）₃·18H₂O), 12-20 parts

10-15 parts of ammonia water with the molar volume concentration of 12-15mol/L

5-15 parts of hydrochloric acid with the molar volume concentration of 5-8mol/L

0.5-2 parts of europium oxide

N-amyl alcohol, 50-60 portions

Step one, respectively dissolving sodium silicate nonahydrate and aluminum sulfate octadecahydrate into water to prepare a sodium silicate aqueous solution with a molar volume concentration of 3mol/L and an aluminum sulfate aqueous solution with a molar volume concentration of 3 mol/L;

dissolving europium oxide in 10% hydrochloric acid to prepare a europium chloride solution;

mixing the sodium silicate aqueous solution with 90% hydrochloric acid according to the formula amount, continuously stirring for 15-20 minutes, and standing for 20-40 minutes to obtain silicic acid sol;

step four, adding the europium oxide salt solution obtained in the step two into the silicic acid sol, continuously stirring for 15-20 minutes, sequentially adding ammonia water and aluminum sulfate octadecahydrate aqueous solution into the silicic acid sol, continuously stirring for 15-20 minutes, and standing for 20-40 minutes to obtain a sol-gel solution;

continuously dripping water into the sol-gel solution, and performing suction filtration for 20-30 hours to obtain a gel product;

step six, mixing the obtained gel product with n-amyl alcohol, heating to 99 ℃ at the heating rate of 2-3 ℃/min, carrying out azeotropic distillation for 45-60 minutes, and drying the obtained material at the temperature of 100-120 ℃ for 1-3 hours to obtain mullite precursor powder;

and seventhly, sintering the mullite precursor powder at the temperature of 900-.

2. The method for preparing the highly dense mullite ceramic powder of claim 1 wherein in step one, the preferred molar volume concentration of hydrochloric acid is 6-7 mol/L.

3. The preparation method of the highly dense mullite ceramic powder of claim 1 wherein in step one, the preferred molar volume concentration of ammonia is 14-15 mol/L.

Images