Research on the application of nano-carbon materials such as graphene in refractories--PUDA graphite packing machine

2 The influence of nano-carbon materials on multi-carbon refractories

The carbon source cited in traditional carbon-containing refractories is mostly graphite. According to the amount of graphite, it is divided into multi-carbon refractories and low-carbon refractories. It is generally believed that carbon-containing refractories with graphite content not higher than 8% become low-carbon Refractories, and carbon-containing refractories with graphite content higher than 8% become multi-carbon refractories.

Studies have shown that the introduction of graphite can increase the thermal shock resistance and corrosion resistance of refractory products. However, if the graphite content is too high, the oxidation resistance of refractory products will become worse. Graphite will interact with air during high-temperature use. The oxygen reacts to generate CO and CO2 gases, which cause the porosity of refractory products to increase, reduce the corrosion resistance of refractory materials, and thereby reduce the service life of refractory materials; excessive carbon in the steelmaking process, It will increase the carbon content in the molten steel, which is an influential factor that is not conducive to the production of low-carbon steel and clean steel; the carbon loss process is accompanied by a large amount of heat loss, which is not conducive to energy saving and emission reduction in the steelmaking process, and increases the production cost of steelmaking. . However, if the graphite content is reduced alone, the thermal shock resistance and corrosion resistance of refractory products will be greatly reduced. It is not conducive to the preservation of refractory properties.

Carbon nanotubes and graphene in carbon nanomaterials were first discovered in 1991 and 2004, respectively. Because of their unique properties, they have attracted the attention of many scholars. At the same time, they are expected to improve the mechanical properties of low-carbon refractories. Carbon source. Many scholars have studied the influence of nano-carbon materials on the properties of refractory materials in the context of multi-carbon, and have obtained many results. For example, Zhu et al. used carbon nanotubes to partially or completely replace flake graphite and used the same preparation process to prepare magnesium-carbon refractories. , And studied the differences in the microstructure, mechanical properties, and thermal shock resistance of magnesia-carbon refractories with carbon nanotubes as the carbon source and flake graphite as the carbon source. Experiments show that when carbon nanotubes are used as a carbon source and sintered at 1000°C and 1400°C, they exhibit higher mechanical properties than graphite carbon sources. This result shows that carbon nanotubes are used as a carbon source to be added to magnesia-carbon refractory products. The magnesia-carbon refractory products can be strengthened and toughened. For the comparison of the thermal shock resistance of magnesia-carbon refractories, it also shows better performance than flake graphite. The thermal shock resistance of magnesia-carbon refractories with 5% carbon nanotubes is equivalent to that of magnesia-carbon refractories with 10% flake graphite.

QinghuWang et al. prepared Al2O3-C refractories containing graphene oxide nanosheets (GONs) with aluminum, silicon and SiO2 as additives. The results showed that compared with Al2O3-C refractories without GONs, Al2O3-C refractories doped with GONs The material's normal temperature modulus of rupture (CMOR), flexural modulus (E), force and displacement curves and other mechanical properties have been improved. This improvement is attributed to the strengthening effect of GONs at 800℃ and the synergistic strengthening effect with graphite flakes and in-situ whisker formation at 1000~1400℃. Table 1 shows the specific data of the experiment.

Table 1 Room temperature rupture modulus and flexural modulus of different amounts of graphene oxide nanosheet samples fired at different temperatures

Tianbin Zhu et al. studied the effects of graphite oxide nanosheets (GONS), carbon nanotubes (CNT) and carbon black (CB) on the microstructure evolution, mechanical properties and thermomechanical properties of magnesia-carbon refractories. It is compared with the traditional magnesia-carbon refractories containing 10% flake graphite prepared under the same conditions. Because of the existence of nano-carbon and the in-situ formation of ceramic phase in MA. The carbon nanotube-containing component has a higher cold rupture modulus after coking at 1000°C and 1400°C, and the addition of nanocarbon improves the thermal shock resistance of the material.

AtulVMaldhure et al. used nickel nitrate as a catalyst and phenolic resin as a binder to study the effect of in-situ synthesis of carbon nanotubes on the properties of magnesium-aluminum-carbon refractories. Experiments show that 3% nickel nitrate can catalyze the modification and structural rearrangement of phenolic resin in the heat treatment process to form carbon nanotubes, and the in-situ synthesis of carbon nanotubes enhances the mechanical properties of magnesium-aluminum-carbon refractory products. The compressive strengths at room temperature at 800℃, 1000℃, 1200℃ and 1400℃ are increased by 10.15%, 30.75%, 41.09%, 25.62% respectively. At the same time, the volume density of the product increases and the porosity decreases, resulting in further improvement of the oxidation resistance of the magnesium-aluminum-carbon refractory products.

Guo Wei et al. used ferrocene as a catalyst and phenolic resin as a binder to study the effect of ferrocene addition on the performance of aluminum-carbon refractories. The experiment showed that the addition of ferrocene should be in the range of 0-2%, especially After heat treatment at 1000°C, it is beneficial to improve the mechanical properties of the product, and because the addition of ferrocene catalyzes the phenolic resin in the heat treatment process, the inside of the product forms carbon nanomaterials in situ, and the carbon nanomaterials formed in situ help It reacts with the additive Si to form β-SiC whiskers, which further improves the strength of the aluminum-carbon refractory. However, the addition of catalyst can not change the oxidation resistance of aluminum-carbon refractories.

In the context of multi-carbon, the mechanical properties of refractory materials can be improved no matter whether the carbon nanomaterials are directly added or the carbon nanomaterials are synthesized in situ. After heat treatment, graphite and nano-carbon materials jointly improve the mechanical properties of refractory materials. When a certain antioxidant is added to refractory products, nano-carbon materials are more likely to interact with ceramic whiskers with certain antioxidant properties, and further improve the refractory properties. toughness. Due to the existence of certain defects in nano-carbon materials, oxidation and structural alteration are prone to occur, resulting in nano-carbon materials that cannot completely replace graphite as a carbon source under a multi-carbon background, and the effect of partially replacing graphite as a carbon source is relatively good.

However, under the background of multi-carbon, when the carbon nanomaterials are directly added, the research on the structure change mechanism of the carbon nanomaterials with the increase of temperature is still obscure, especially at temperatures above 1400 ℃, the research has not been involved too much. In different atmospheres, such as the influence of oxidizing atmosphere and reducing atmosphere on nano-carbon materials, the above-mentioned research has not done targeted research. The process of introducing nano-carbon materials by in-situ growth method can catalyze the concrete reflection mechanism of ceramic phase whiskers to a certain extent, and it needs further discussion.

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