Preparation method of carbon-containing refractory material

Abstract

A preparation method of a carbon-containing refractory material belongs to the technical field of refractory materials, and comprises the following steps: acidizing a carbon nanotube to obtain a carboxyl carbon nanotube, adding polysilazane and a catalyst into a carboxyl carbon nanotube dispersion liquid, and carrying out an amidation reaction in an inert atmosphere to obtain a modified carbon nanotube; mixing the refractory material powder, the modified carbon nanotubes and an adhesive in proportion, performing compression molding, and curing at 100-120 DEG C to obtain a molded sample; and placing the molded sample in an inert atmosphere, heating to 1200-1400 DEG C, and keeping the temperature for 2-4 hours to obtain the carbon-containing refractory material. The carboxyl carbon nanotube and polysilazane are subjected to amidation reaction, polysilazane can be grafted on the surface of the carbon nanotube, the dispersity of the carbon nanotube is improved, meanwhile, polysilazane can be pyrolyzed and converted into a ceramic coating in the firing process of the refractory material, and the ceramic coating can protect the structure of the carbon nanotube and prevent the carbon nanotube from being oxidized; therefore, the performance of the refractory material is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of refractory materials, and particularly relates to a preparation method of carbon-containing refractory materials. Background Art

[0002] Carbon-containing refractory materials play an important role in the metallurgical industry and are very important in steelmaking production. They are particularly widely used in key parts such as ladle linings and three major continuous casting pieces. Most of the carbon sources used in traditional carbon-containing refractory materials are graphite. According to the amount of graphite, they are divided into multi-carbon refractory materials and low-carbon refractory materials. Generally, carbon-containing refractory materials with a graphite content not higher than 8% are called low-carbon refractory materials, while carbon-containing refractory materials with a graphite content higher than 8% are called multi-carbon refractory materials.

[0003] The introduction of graphite can increase the thermal shock stability and erosion resistance of refractory products. However, due to the disadvantages of graphite itself, at high temperatures, graphite will react with oxygen in the air to generate COx gas, resulting in an increase in the porosity of refractory products, reducing the erosion resistance of refractory materials, and thus reducing the service life of refractory materials. If only starting from reducing the graphite content, the thermal shock stability and erosion resistance of refractory products will be greatly reduced. Carbon nanotubes have better mechanical and thermal properties compared with graphite, and can improve the thermal shock stability and erosion resistance of low-carbon refractory materials while reducing the overall carbon content of the material. However, the addition of a large amount of carbon nanotubes will cause agglomeration, and directly adding carbon nanotubes will lead to a reduction in the mechanical properties of refractory materials. Moreover, some carbon nanotubes will be consumed due to oxidation or structural transformation during the firing process. Therefore, improvement is needed. Summary of the Invention

[0004] In view of the above situation, in order to overcome at least part of the defects of the above prior art, the present invention provides a preparation method of carbon-containing refractory materials.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: The present invention provides a preparation method of carbon-containing refractory materials, which is characterized by comprising: Taking carbon nanotubes for acidification treatment to obtain carboxylated carbon nanotubes, adding polysilazane and a catalyst to the carboxylated carbon nanotube dispersion, and carrying out amidation reaction under an inert atmosphere to obtain modified carbon nanotubes; Mixing refractory powder, the modified carbon nanotubes and a binder in proportion, pressing and molding, and curing at 100°C - 120°C to obtain a molded sample; Placing the molded sample under an inert atmosphere, heating to 1200°C - 1400°C, and holding for 2h - 4h to obtain carbon-containing refractory materials.

[0006] In some embodiments, the conditions for the amidation reaction include: a temperature of 130°C - 140°C and a time of 20 h - 30 h; and / or, the inert atmosphere used in the amidation reaction is at least one of a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere.

[0007] In some embodiments, the mass ratio of the carboxyl carbon nanotubes to the polysilazane is 1:2 - 3.

[0008] In some embodiments, the mass ratio of the carboxyl carbon nanotubes to the catalyst is 1:1 - 1.5; and / or, the catalyst includes one or a mixture of more than one of metal-based chlorides, metal-based nitrates, and metal oxides.

[0009] In some embodiments, the method for preparing the carboxyl carbon nanotube dispersion includes: dispersing carboxyl carbon nanotubes in N,N-dimethylformamide, performing ultrasonic treatment, where the time for ultrasonic treatment is 1 h - 2 h and the power is 200 W - 300 W.

[0010] In some embodiments, the ratio of the refractory powder, the modified carbon nanotubes, and the binder is 80:(1 - 8):(3 - 5).

[0011] In some embodiments, the binder includes one or a mixture of more than one of an epoxy resin binder, a polyurethane binder, and a phenolic resin binder.

[0012] In some embodiments, the acidification treatment includes: Adding carbon nanotubes to concentrated nitric acid, ultrasonically dispersing, heating to 100°C - 110°C, washing, and drying to obtain carboxyl carbon nanotubes.

[0013] In some embodiments, the concentration of the concentrated nitric acid is 65% - 70%, and the addition amount of the carbon nanotubes in the concentrated nitric acid is 15 g / L - 20 g / L.

[0014] In some embodiments, the refractory powder includes one or a mixture of more than one of fused white corundum, alumina, silica, aluminum powder, and silicon powder.

[0015] The beneficial effects achieved by the present invention are as follows: Through acidification treatment, carboxyl groups can be introduced onto the surface of carbon nanotubes to improve the reaction activity of carbon nanotubes. By performing an amidation reaction on the carboxyl carbon nanotubes and polysilazane, polysilazane can be grafted onto the surface of carbon nanotubes to improve the dispersibility of carbon nanotubes. At the same time, polysilazane can be pyrolytically converted into a ceramic coating during the firing process of the refractory material. The ceramic coating can protect the structure of carbon nanotubes and prevent carbon nanotubes from being oxidized, thereby improving the performance of the refractory material. Specific embodiments

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0017] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to the described content can be applied to the present invention. The preferred implementation methods and materials described herein are for illustrative purposes only and do not limit the content of this application.

[0018] In view of the deficiencies in the prior art mentioned in the background art, an embodiment of the present invention provides a method for preparing a carbon-containing refractory material, including: Taking carbon nanotubes and performing acidification treatment to obtain carboxylated carbon nanotubes. Adding polysilazane and a catalyst to the carboxylated carbon nanotube dispersion, and performing an amidation reaction under an inert atmosphere to obtain modified carbon nanotubes; After mixing refractory material powder, modified carbon nanotubes, and a binder in proportion, pressing them into a shape, and curing at 100°C - 120°C to obtain a shaped sample; Placing the shaped sample under an inert atmosphere, heating it to 1200°C - 1400°C, and holding for 2h - 4h to obtain a carbon-containing refractory material.

[0019] Due to its unique structure, carbon nanotubes have excellent mechanical and thermal properties. As a filler added to refractory materials, they can improve the thermal shock stability and erosion resistance of low-carbon refractory materials while reducing the overall carbon content of the materials. However, the addition of a large amount of carbon nanotubes will cause agglomeration, and carbon nanotubes will be consumed during the firing process of refractory materials due to oxidation or structural transformation.

[0020] Through acidification treatment, carboxyl groups can be introduced onto the surface of carbon nanotubes to improve the reaction activity of carbon nanotubes. Performing an amidation reaction between carboxylated carbon nanotubes and polysilazane can graft polysilazane onto the surface of carbon nanotubes to improve the dispersion of carbon nanotubes. At the same time, polysilazane can be pyrolytically converted into a ceramic coating during the firing process of refractory materials, and the ceramic coating can protect the structure of carbon nanotubes and prevent carbon nanotubes from being oxidized, thereby improving the performance of refractory materials.

[0021] In some embodiments, the conditions for the amidation reaction include: the temperature is 130°C - 140°C, and the time is 20h - 30h. Controlling the temperature of the amidation reaction at 130°C - 140°C can increase the reaction rate and facilitate the progress of the amidation reaction. Controlling the time at 20h - 30h can enable the amidation reaction to proceed fully and increase the yield of modified carbon nanotubes.

[0022] In some embodiments, the inert atmosphere used in the amidation reaction is at least one of a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere. Using an inert atmosphere can prevent impurities (such as oxygen, moisture, etc.) in the reaction system from having a negative impact on the reaction and ensure the smooth progress of the reaction.

[0023] In some embodiments, the mass ratio of carboxyl carbon nanotubes to polysilazane is 1:2 - 3. By setting the mass ratio of carboxyl carbon nanotubes to polysilazane to 1:2 - 3, the surface of the carbon nanotubes can be fully grafted with polysilazane, increasing the grafting amount of polysilazane, and thus fully protecting the carbon nanotubes during the firing process.

[0024] In some embodiments, the mass ratio of carboxyl carbon nanotubes to the catalyst is 1:1 - 1.5. The catalyst can lower the activation energy of the reaction, accelerate the reaction process, and improve the reaction efficiency. By setting the mass ratio of carboxyl carbon nanotubes to the catalyst to 1:1 - 1.5, the reaction efficiency of the amidation reaction can be improved, while avoiding the influence of excessive catalyst accumulation on the catalytic efficiency.

[0025] In some embodiments, the catalyst includes one or a mixture of metal chlorides, metal nitrates, and metal oxides. Metal chlorides, metal nitrates, and metal oxides have good catalytic effects on the amidation reaction between carboxyl carbon nanotubes and polysilazane, and zinc chloride is preferred.

[0026] In some embodiments, the method for preparing the carboxyl carbon nanotube dispersion includes: dispersing carboxyl carbon nanotubes in N,N - dimethylformamide and performing ultrasonic treatment. The time of ultrasonic treatment is 1h - 2h, and the power is 200W - 300W. Ultrasonic treatment can break the interaction force between carboxyl carbon nanotubes, promote the dispersion of carboxyl carbon nanotubes, and is beneficial to the preparation of the carboxyl carbon nanotube dispersion.

[0027] In some embodiments, the ratio of refractory powder, modified carbon nanotubes, and binder is 80:(1 - 8):(3 - 5). Among them, the refractory powder, as the main component, accounts for a relatively high proportion. The ratio of modified carbon nanotubes can be adjusted according to requirements, but if it is too low, its strengthening effect cannot be fully exerted, and if it is too high, the forming difficulty increases. The binder can tightly combine the refractory powder and modified carbon nanotubes together.

[0028] In some embodiments, the binder includes one or a mixture of epoxy resin binders, polyurethane binders, and phenolic resin binders. Epoxy resin binders, polyurethane binders, and phenolic resin binders all have good adhesion, can provide good interfacial bonding force, and improve the performance of refractory materials.

[0029] In some embodiments, the acidification treatment includes: adding carbon nanotubes into concentrated nitric acid, ultrasonically dispersing, heating to 100°C - 110°C, washing, and drying to obtain carboxylated carbon nanotubes. Concentrated nitric acid can acidify and oxidize carbon nanotubes, thereby introducing hydroxyl groups on the surface of carbon nanotubes. It should be noted that the reaction temperature is 100°C - 110°C. If the temperature is too low, the reaction efficiency is too low, and if the temperature is too high, the structure of carbon nanotubes will be damaged.

[0030] In some embodiments, the concentration of concentrated nitric acid is 65% - 70%, and the addition amount of carbon nanotubes in concentrated nitric acid is 15 g / L - 20 g / L. The concentration of concentrated nitric acid has a direct impact on its oxidation ability. If the concentration is too high, the reaction will be too violent and the structure of carbon nanotubes will be damaged. If the concentration is too low, the oxidation effect is poor. Therefore, the concentration of concentrated nitric acid needs to be set at 65% - 70%.

[0031] In some embodiments, the refractory powder includes one or more mixtures of fused white corundum, alumina, silica, aluminum powder, and silicon powder. Fused white corundum has high melting point, high hardness, high wear resistance, and good chemical stability, which can improve the thermal shock resistance and erosion resistance of refractory materials. Alumina and silica have high melting points and good chemical stability, and are mainly used as refractory fillers. Aluminum powder is mainly used as an additive to promote sintering, and the addition of silicon powder can increase the density and strength of refractory materials.

[0032] The present invention will be further described below by way of specific embodiments.

[0033] The experimental methods in the following embodiments are all conventional methods unless otherwise specified; the test materials used in the following embodiments are all obtained from commercial channels unless otherwise specified.

[0034] The refractory powder used in the following embodiments includes the following components in parts by weight: 60 parts of fused white corundum, 10 parts of alumina, 10 parts of silica, 2 parts of aluminum powder, and 3 parts of silicon powder.

[0035] Example 1 Add carbon nanotubes into concentrated nitric acid. The concentration of concentrated nitric acid is 65%, and the addition amount of carbon nanotubes in concentrated nitric acid is 15 g / L. Ultrasonically disperse, heat to 100°C, wash, and dry to obtain carboxylated carbon nanotubes. Disperse the carboxylated carbon nanotubes in N,N-dimethylformamide, and perform ultrasonic treatment. The ultrasonic treatment time is 1 h and the power is 200 W to obtain a carboxylated carbon nanotube dispersion. Add polysilazane and zinc chloride to the carboxylated carbon nanotube dispersion. The mass ratio of carboxylated carbon nanotubes to polysilazane is 1:2, and the mass ratio of carboxylated carbon nanotubes to zinc chloride is 1:1. Perform amidation reaction under a nitrogen atmosphere. The reaction temperature is 130°C and the time is 20 h to obtain modified carbon nanotubes. After mixing refractory powder, modified carbon nanotubes and phenolic resin binder in proportion, with the proportion of refractory powder, modified carbon nanotubes and phenolic resin binder being 80:1:3, it is pressed into shape and cured at 100 °C to obtain a shaped sample; The shaped sample is placed in a nitrogen atmosphere, heated to 1200 °C and kept warm for 2 h to obtain a carbon-containing refractory.

[0036] Example 2 Carbon nanotubes are added to concentrated nitric acid with a concentration of 70%. The addition amount of carbon nanotubes in concentrated nitric acid is 20 g / L. It is ultrasonically dispersed, heated to 110 °C, washed and dried to obtain carboxylated carbon nanotubes. The carboxylated carbon nanotubes are dispersed in N,N-dimethylformamide and ultrasonically treated for 2 h with a power of 300 W to obtain a carboxylated carbon nanotube dispersion; Polysilazane and zinc chloride are added to the carboxylated carbon nanotube dispersion. The mass ratio of carboxylated carbon nanotubes to polysilazane is 1:3, and the mass ratio of carboxylated carbon nanotubes to zinc chloride is 1:1.5. An amidation reaction is carried out in a nitrogen atmosphere at a reaction temperature of 140 °C for 30 h to obtain modified carbon nanotubes; After mixing refractory powder, modified carbon nanotubes and epoxy resin binder in proportion, with the proportion of refractory powder, modified carbon nanotubes and epoxy resin binder being 80:8:5, it is pressed into shape and cured at 120 °C to obtain a shaped sample; The shaped sample is placed in a nitrogen atmosphere, heated to 1400 °C and kept warm for 4 h to obtain a carbon-containing refractory.

[0037] Example 3 Consistent with Example 1, the difference is that the mass ratio of carboxylated carbon nanotubes to polysilazane is 1:2.5.

[0038] Example 4 Consistent with Example 1, the difference is that the mass ratio of carboxylated carbon nanotubes to polysilazane is 1:3.

[0039] Example 5 Consistent with Example 1, the difference is that the proportion of refractory powder, modified carbon nanotubes and binder is 80:3:3.

[0040] Example 6 Consistent with Example 1, the difference is that the proportion of refractory powder, modified carbon nanotubes and binder is 80:5:3.

[0041] Example 7 Consistent with Example 1, the difference is that the proportion of refractory powder, modified carbon nanotubes and binder is 80:6:3.

[0042] Example 8 Consistent with Example 1, the difference is that the ratio of refractory powder, modified carbon nanotubes and binder is 80:7:3.

[0043] Comparative Example 1 Consistent with Example 1, the difference is that carbon nanotubes are used instead of modified carbon nanotubes in the refractory.

[0044] Perform performance tests on the refractories prepared in Examples 1-8 and Comparative Example 1. The specific test contents are as follows: Flexural strength test: Use a WDW-50 universal testing machine and adopt the three-point bending method to measure the maximum load that the specimen can withstand at the time of fracture. The size of the specimen is 10mm×10mm×40mm. During the experiment, the span is set to 32mm and the loading rate is 1mm / min.

[0045] Thermal shock stability test: The test method refers to GB / T30873-2014 "Test Method for Thermal Shock Resistance", which is as follows: After preheating the heating furnace to 1100°C and keeping it warm for 15 minutes, quickly move the specimen to be tested into the furnace chamber. After the furnace temperature rises to 1100°C, keep it warm for 30 minutes, cool the heated specimen for 5 minutes through compressed air, then put it into the furnace chamber at 1100°C and repeat 3 times. After the specimen is completely cooled, measure its flexural strength and calculate the strength retention rate. Strength retention rate = strength after thermal shock / strength before thermal shock × 100%.

[0046] Oxidation resistance test: The test method refers to GB / T13244-1991 "Test Method for Oxidation Resistance of Carbon-Containing Refractories", which is as follows: Place the specimen in the furnace and heat it to 1400°C at the specified heating rate, keep it warm for 2 hours, cut it in half after cooling to room temperature, and measure the decarburized layer thickness. Among them, the shape of the specimen is a cube with a side length of 50mm.

[0047] The test results are shown in Table 1.

[0048] Table 1 Test Results

[0049] As can be seen from Table 1, compared with Comparative Example 1 using carbon nanotubes, Examples 1-8 using modified carbon nanotubes have varying degrees of improvement in flexural strength, thermal shock stability, and oxidation resistance. Thus, it can be seen that the addition of modified carbon nanotubes can improve the properties of refractory materials. And initially, as the addition amount of modified carbon nanotubes increases, the flexural strength, thermal shock stability, and oxidation resistance of the refractory materials all increase to a certain extent, and the improvement amplitude is less with the subsequent increase in the addition amount. Therefore, considering both performance and cost, the mass ratio of refractory powder to modified carbon nanotubes of 80:6-8 is more appropriate.

[0050] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered by the protection scope of the present invention.

Claims

1. A preparation method of a carbon-containing refractory material, characterized in that, Including: Taking carbon nanotubes for acidification treatment to obtain carboxylated carbon nanotubes, adding polysilazane and a catalyst to the carboxylated carbon nanotube dispersion liquid, and carrying out an amidation reaction under an inert atmosphere to obtain modified carbon nanotubes; After mixing refractory powder materials, the modified carbon nanotubes and an adhesive in proportion, press-forming and curing at 100°C - 120°C to obtain a formed sample; Placing the formed sample under an inert atmosphere, heating to 1200°C - 1400°C, and holding for 2h - 4h to obtain a carbon-containing refractory; 2. The preparation method according to claim 1, characterized in that, The conditions of the amidation reaction include: the temperature is 130°C - 140°C, and the time is 20h - 30h; and / or, the inert atmosphere used in the amidation reaction is at least one of a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere; 3. The preparation method according to claim 1, wherein The mass ratio of the carboxylated carbon nanotubes to polysilazane is 1:2 - 3; 4. The preparation method according to claim 1, characterized in that, The mass ratio of the carboxylated carbon nanotubes to the catalyst is 1:1 - 1.5; and / or, the catalyst includes one or a mixture of more of metal-based chlorides, metal-based nitrates, and metal oxides; 5. The preparation method according to claim 1, characterized in that, The preparation method of the carboxylated carbon nanotube dispersion liquid includes: dispersing carboxylated carbon nanotubes in N,N-dimethylformamide, performing ultrasonic treatment, the ultrasonic treatment time is 1h - 2h, and the power is 200W - 300W; 6. The preparation method according to claim 1, wherein The ratio of the refractory powder materials, modified carbon nanotubes, and adhesive is 80:(1 - 8):(3 - 5); 7. The preparation method according to claim 1, characterized in that, The adhesive includes one or a mixture of more of an epoxy resin adhesive, a polyurethane adhesive, and a phenolic resin adhesive; 8. The preparation method according to claim 1, characterized in that, The acidification treatment includes: Adding carbon nanotubes to concentrated nitric acid, ultrasonically dispersing, heating to 100°C - 110°C, washing, and drying to obtain carboxylated carbon nanotubes; 9. The preparation method according to claim 8, characterized in that, The concentration of the concentrated nitric acid is 65% - 70%, and the addition amount of carbon nanotubes in the concentrated nitric acid is 15g / L - 20g / L; 10. The preparation method according to claim 1, characterized in that, The refractory powder materials include one or a mixture of more of fused white corundum, alumina, silica, aluminum powder, and silicon powder.

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