CN112094124A

CN112094124A - Carbon source for refractory material and preparation method thereof

Info

Publication number: CN112094124A
Application number: CN202010027003.XA
Authority: CN
Inventors: 霍开富; 高标; 陈振东; 付继江; 李忠红
Original assignee: Wuhan Bai Smythe New Material Co ltd; Wuhan University of Science and Engineering WUSE
Current assignee: Wuhan Bai Smythe New Material Co ltd; Wuhan University of Science and Engineering WUSE; Wuhan University of Science and Technology WHUST
Priority date: 2020-01-10
Filing date: 2020-01-10
Publication date: 2020-12-18

Abstract

The invention provides a carbon source for preparing refractory materials, which consists of an inner core of a powder raw material and an outer layer of nano carbon, wherein the thickness of a nano carbon layer coated on the surface of the powder raw material is 2-100nm, preferably 5-50nm, and the powder raw material is selected from magnesium oxide, aluminum oxide, mullite or clay. The invention also provides a preparation method for preparing the carbon source of the refractory material, which uses commercially available powder raw material particles as raw materials to prepare the carbon source coated with the carbon layer with the nanometer thickness by using a vapor deposition method, a liquid phase method or a hot melting method. The nano carbon source with the shell-core structure realizes the uniform coating of a carbon layer with a nano thickness on the surface of a refractory material raw material, thereby realizing the high dispersion of carbon, and is suitable for various carbon-containing refractory materials including but not limited to: magnesia carbon brick, alumina carbon brick, calcium carbon brick, magnesia alumina carbon brick, clay carbon brick, kaolin carbon brick and other refractory material products made of one or more than two refractory material raw materials.

Description

Carbon source for refractory material and preparation method thereof

Technical Field

The invention relates to the technical field of refractory materials, in particular to a carbon source for preparing a refractory material and a preparation method thereof.

Background

The refractory material refers to a material with physical and chemical properties allowing the refractory material to be used in a high-temperature environment, is widely applied to the industrial fields of metallurgy, chemical industry, petroleum, mechanical manufacturing, silicate, power and the like, and is used in the largest amount in the metallurgical industry. The carbon-containing refractory material is a high-temperature composite material prepared by using oxides and carbon as main raw materials and using carbon as a high-temperature binding phase. The carbon-containing refractory material has good high temperature resistance, slag resistance and thermal shock resistance, and is widely applied to various parts of the metallurgical kiln. Common carbon-containing refractory materials comprise magnesia carbon, mullite, dolomite, alumina carbon and aluminosilicate, and when the carbon-containing refractory materials are used in the field of steelmaking, high-temperature molten steel is in direct contact with the surface of the carbon-containing refractory materials, and carbon is dissolved and diffused to molten steel at high temperature, so that the carbon content of the steel is increased, and the quality of the steel is reduced. In order to improve the quality of steel, the direct solution is to reduce the carbon content in the carbon-containing refractory material, but the reduction of the carbon content leads to the reduction of the slag resistance and the thermal shock resistance of the material, so that the service life of the material is shortened.

The traditional preparation method of the carbon-containing refractory material is to directly add graphite into an oxide, wherein the carbon content is usually 10-20%. With the development of technologies such as clean steel, external refining, energy conservation and emission reduction in the steel industry and the like, the requirement on refractory materials is continuously increased. Although researchers develop a great deal of research on development and application of low-carbon refractory materials, the popularization and application of the low-carbon refractory materials are limited due to the fact that the service life of the low-carbon refractory materials is shorter than that of the traditional carbon-containing refractory materials, the effect of reducing the recarburization of molten steel is not obvious, and the like. The adverse effects of the reduction in carbon content in the carbonaceous refractory material are: 1. the uniformity of heat conduction of the product is deteriorated, so that the thermal shock resistance of the product is deteriorated; 2. the wettability of the slag and molten steel with the refractory material is enhanced, resulting in deterioration of slag resistance thereof. Therefore, reducing the carbon content to achieve a low carbon refractory material is a great demand in the metallurgical industry on the premise of ensuring thermal shock resistance and slag resistance.

The thermal stability and slag resistance of the carbon-containing refractory material mainly depend on the composition and structure of the material, the contact probability and the binding performance of raw material particles and carbon particles are improved, namely, the size of the carbon particles is reduced, the dispersion uniformity of the carbon particles is ensured, and the carbon-containing refractory material is an important measure for improving the thermal stability and slag resistance of the low-carbon refractory material. The carbon content of the carbon-containing refractory material can be effectively reduced by introducing a nano carbon source (such as nano graphite sheets, carbon nano tubes, nano carbon black and the like) to replace or partially replace graphite, the structure of the material is improved to enable the material to be densified, the contact probability of carbon and raw material particles is increased, and the thermal shock resistance and the slag resistance of the carbon-containing refractory material can be effectively improved. However, the nanocarbon has a large specific surface area and a high surface energy, and is easy to agglomerate in the synthesis and storage processes, and on the other hand, the nanocarbon has a large density difference with the matrix material, so that the nanocarbon is difficult to effectively disperse with the matrix material to form uniform distribution, so that the nanocarbon has uneven heat conductivity, and the nanocarbon has the problems of reduced thermal shock resistance and slag resistance, shortened service life and the like. In addition, the price of nanocarbon also limits its application in practical production.

In order to solve the problems of high carbon content and uneven dispersion of the existing carbon-containing refractory material, a novel nano carbon source needs to be developed urgently.

Disclosure of Invention

The invention aims to solve the problems that: the carbon source is used for preparing the carbon-containing refractory material, and the prepared carbon-containing refractory material has the characteristics of low carbon content and excellent thermal shock resistance and slag resistance.

The technical scheme provided by the invention for solving the problems is as follows: a carbon source for a carbonaceous refractory material and a method for producing the same are provided.

The carbon source has a core-shell structure and is composed of a raw material powder inner core and a nano carbon outer layer, wherein the thickness of the nano carbon layer coated on the surface of the powder raw material is 1-150nm, and the thickness of the nano carbon layer is preferably 2-50 nm.

Further, the powdery raw material of the carbon source may be a refractory raw material selected from mullite, dolomite, flint clay, silicon carbide, spinel, calcium oxide, magnesia, alumina, clay or silica powder, and preferably magnesia, alumina, mullite or clay.

Furthermore, the particle size of the powder raw material can be adjusted according to the use requirement without being influenced by the size. The carbon source of the present invention has no specific requirements on the shape of the powdered raw material.

The carbon source is suitable for preparing aggregate and fine powder of the carbon-containing refractory material, wherein the aggregate generally refers to granular material with the grain diameter (namely the granularity) of more than 0.088 mm; fines generally refer to particulate material having a particle size (i.e., particle size) of less than 0.088 mm.

The carbon source can be directly used as a raw material for preparing a refractory material product, and can also be partially added into the raw material to prepare the refractory material product.

The invention provides a preparation method for carbon sources of carbon-containing refractory materials, which provides a preparation method for uniform distribution and tight combination of carbon sources in the carbon-containing refractory materials, and the preparation method comprises the following steps: a carbon layer with a nanometer thickness is coated on the surface of raw material powder for refractory materials.

The method for preparing the carbon source of the present invention includes, but is not limited to, gas phase, hot melt method, liquid phase method, and the like.

The gas phase method comprises the following steps: placing the powder raw material of the refractory material in a high-temperature furnace body, heating to 300-1700 ℃, introducing a carbon-containing precursor (selected from methane, ethane, acetylene, ethanol and the like) and argon/nitrogen mixed gas (the content of the carbon-containing gas is 0.1-99%) into the furnace body, and preserving heat to prepare a carbon source for the refractory material; the carbon source for the refractory material coated by carbon layers with different thicknesses is prepared by adjusting the concentration, the reaction temperature and the reaction time of the carbon-containing precursor.

The liquid phase method comprises the following steps: soaking a powder raw material of a refractory material in an aqueous solution containing carbon organic matters (selected from glucose, sucrose, fructose and the like) with the concentration of 0.01-5 mol/L, filtering the solution, drying the filtered solution in drying equipment, and then carbonizing the dried solution in a high-temperature furnace body (with the atmosphere of nitrogen/argon) at the temperature of 300-1700 ℃ to prepare a carbon-coated refractory material carbon source; the carbon source of the refractory material coated by carbon layers with different thicknesses is prepared by adjusting the concentration, the reaction temperature and the reaction time of the carbon-containing organic matter aqueous solution.

Wherein the hot melting method is as follows: uniformly mixing a powder raw material for a refractory material and an organic precursor (selected from asphalt, resin, glucose and the like) according to a certain proportion, putting the mixture into thermal coating equipment, heating to 150-350 ℃ in a protective atmosphere environment (nitrogen or argon and the like), preserving the temperature, then heating to 300-1700 ℃ for carbonization, and preparing a carbon source for the carbon-coated refractory material; the carbon source of the refractory material coated by carbon layers with different thicknesses is prepared by adjusting the concentration, the reaction temperature and the reaction time of the organic precursor.

The carbon source with the shell-core structure realizes the uniform coating of a carbon layer with a nanometer thickness on the surface of refractory material raw material powder, thereby further realizing the high dispersion and tight combination of carbon, and is suitable for various carbon-containing refractory materials, including but not limited to: magnesia carbon brick, alumina carbon brick, calcium carbon brick, magnesia alumina carbon brick, clay carbon brick, kaolin carbon brick and other refractory material products made of one or more than two refractory material raw materials.

Compared with the prior art, the technical scheme of the invention has the following advantages:

1. the refractory material product prepared from the nanometer-thickness carbon-coated refractory material raw material powder can realize carbon uniformity

The carbon content in the carbon-containing refractory material can be effectively reduced by uniform distribution;

2. the carbon is uniformly distributed in the method, so that stress concentration caused by nonuniform carbon distribution is avoided, and the mechanical property of a refractory material product is improved;

3. the uniform distribution of carbon in the method can improve the heat conduction uniformity of the carbon-containing refractory material, avoid the thermal stress concentration caused by the non-uniform distribution of carbon and improve the thermal shock resistance of the refractory material product;

4. according to the method, the carbon layer uniformly coats the surface of the raw material powder, and a carbon protective layer is formed on the surface of each particle, so that the molten steel resistance and slag corrosion resistance of the refractory material product can be improved.

5. The method reduces the carbon content to reduce the heat conductivity coefficient on the premise of ensuring the performance of the refractory material product, improves the heat insulation and heat preservation performance of the product, and is beneficial to reducing energy consumption.

Drawings

FIG. 1 is a scanning electron micrograph of (a. raw material of magnesium oxide; b. carbon-coated carbon source of magnesium oxide; c. carbon shell: residue after hydrochloric acid treatment of carbon-coated magnesium oxide) in example 1 of the present invention;

FIG. 2 is a transmission electron micrograph of (a. carbon-coated magnesium oxide carbon source; b. carbon shell) in example 1 of the present invention;

FIG. 3 is an XRD pattern of the carbon shell in example 1 of the present invention;

FIG. 4 is a Raman diagram of a carbon shell in example 1 of the present invention;

FIG. 5 is a thermogravimetric plot of carbon coated magnesium oxide in example 1 of the present invention;

FIG. 6 is a digital photograph of a normal temperature fracture-resistant surface of comparative example 1(a. magnesia carbon brick produced in this example; b. magnesia carbon brick for ladle slag line produced by a certain domestic company) in accordance with the present invention;

FIG. 7 is a photograph showing the results of the comparative example 1 of the present invention (a. magnesia carbon brick produced in this example; b. magnesia carbon brick for ladle slag line produced by the above domestic company) after resisting slag corrosion;

FIG. 8 is a scanning electron micrograph of example 2(a. corundum particles; b. carbon-coated corundum carbon source) according to the present invention;

FIG. 9 is a transmission electron micrograph of a carbon-coated corundum carbon source in example 2 of the present invention;

FIG. 10 is a Raman spectrum of a carbon-coated corundum carbon source in example 2 of the present invention;

FIG. 11 is a thermogram of a carbon-coated corundum carbon source in example 2 of this invention;

FIG. 12 is a scanning electron micrograph of example 3(a. mullite grains; b. carbon-coated mullite carbon source) of the present invention;

FIG. 13 is a transmission electron micrograph of a carbon-coated mullite carbon source in example 3 of the present invention;

FIG. 14 is a Raman spectrum of a carbon-coated mullite carbon source in example 3 of the present invention;

FIG. 15 is a thermogram of a carbon-coated mullite carbon source in example 4 of the present invention.

Detailed Description

The present invention is further illustrated by the following specific examples, which are not intended to limit the scope of the invention.

Example 1

The carbon-coated magnesium oxide particles prepared by a gas phase method are used as raw materials, the preparation method comprises the steps of placing the magnesium oxide particles in a high-temperature furnace body, heating to 900 ℃, introducing a mixed gas of acetylene and nitrogen (the acetylene content is 20%) into a cavity, and reacting for 4 hours to prepare a carbon-coated magnesium oxide carbon source (the carbon content is about 1%, and the carbon layer thickness is about 15 nm).

As can be seen from the scanning electron microscope image of FIG. 1(a. raw material of magnesium oxide; b. magnesium oxide coated with carbon; c. carbon shell: residue after hydrochloric acid treatment of carbon-coated magnesium oxide), the carbon-coated magnesium oxide carbon source prepared in this example maintains the basic morphology of the raw material, and the residue after hydrochloric acid treatment is a hollow carbon shell and maintains the same morphology as the raw material magnesium oxide carbon source, thus proving the uniformity of carbon coating.

As can be seen from the transmission electron micrograph of FIG. 2(a. carbon-coated magnesium oxide; b. carbon shell), the thickness of the carbon shell uniformly coated on the surface layer of the magnesium oxide carbon source was about 15nm, and the carbon shell had good crystallinity.

The XRD diffraction pattern of the carbon shell in FIG. 3 shows that the peak appearing at 26 ℃ corresponds to graphite, which indicates that the carbon shell on the surface of the magnesium oxide has good crystallinity.

As can be seen from the raman spectrum of the carbon shell of fig. 4, the carbon layer exhibits a strong G peak with graphitic properties, demonstrating good crystallinity.

From the thermogravimetric plot of the carbon-coated magnesium oxide in fig. 5, the carbon content of the carbon-coated magnesium oxide prepared in this example was about 1%.

Comparative example 1

The carbon-coated magnesia carbon source prepared in the example 1, an antioxidant and a bonding agent are prepared into a low-carbon magnesia carbon brick according to a certain proportion and a certain process, and the low-carbon magnesia carbon brick is compared with a magnesia carbon brick for a ladle slag line produced by a certain company in China.

Through detection, the parameters of the low-carbon magnesia carbon brick prepared in example 1 are as follows: the carbon content was 3%, the apparent porosity was 4.8%, and the bulk density was 3.08g/cm³(ii) a The normal temperature compressive strength is 108 MPa; the normal temperature rupture strength is 39 MPa; the sample can bear air quenching and 0.3MPa after heat treatment at 950 DEG CThe number of alternations between the three-point bending stresses indicates the thermal shock resistance, and the sample was destroyed after 12 tests.

The magnesia carbon brick for the ladle slag line produced by the domestic company has the following parameters: the carbon content was 14%, the apparent porosity was 2.8%, and the bulk density was 3.02g/cm³(ii) a The normal-temperature compressive strength is 36 MPa; the normal temperature rupture strength is 17 MPa; the thermal shock resistance of the sample is represented by the alternating times between air quenching and three-point bending stress of 0.3MPa after the sample can bear heat treatment at 950 ℃, and the comparative sample is damaged after 6 tests.

As can be seen from the appearance of the normal-temperature fracture-resistant section of FIG. 6(a, the magnesia carbon brick prepared in example 1; b, the magnesia carbon brick produced by the above-mentioned domestic company), the fracture surface of the magnesia carbon brick prepared in this example is relatively flat, the fracture mode is transgranular fracture, and the fracture mode of the magnesia carbon brick produced by the above-mentioned domestic company is mainly intergranular fracture, which indicates that the magnesia carbon brick prepared in this example exhibits excellent fracture resistance.

The low-carbon magnesia carbon brick prepared in the example 1 and the magnesia carbon brick produced by the domestic company are respectively placed in a corundum crucible by taking a square sample of 25mm by 25mm, and then are corroded for 2 hours at 1550 ℃ by converter steel slag of a certain domestic steel mill, as shown in a picture after the slag corrosion resistance of a steel slag (a. the magnesia carbon brick prepared in the example; b. the magnesia carbon brick for a ladle slag line produced by the domestic company) in FIG. 7, after the steel slag corrosion, the magnesia carbon brick prepared in the example has shallow corrosion depth and flat and uniform corrosion surface, and a sample keeps relatively complete; and the corrosion of the contrast sample is deeper, more corrosion pits appear, and the sample is seriously damaged. The low-carbon magnesia carbon brick prepared by the embodiment has good slag corrosion resistance.

The magnesia carbon brick prepared in this example had a thermal conductivity of 6.8W/(m.K) at 300 ℃ and the magnesia carbon brick produced by the above domestic company had a thermal conductivity of 24.7W/(m.K) at 300 ℃.

Example 2

The preparation method comprises the steps of placing the corundum particles in a high-temperature furnace body, heating to 950 ℃, introducing mixed gas of acetylene and nitrogen (the acetylene content is 30%) into the cavity, and reacting for 6 hours to prepare the carbon-coated corundum carbon source. Wherein the carbon content is about 4.9% and the carbon layer thickness is about 40 nm.

Through detection, as can be seen from a scanning electron microscope image of fig. 8(a. corundum particles; b. corundum carbon source after carbon coating), the carbon-coated corundum carbon source prepared in the embodiment maintains the basic morphology of the raw material, and shows the uniformity of carbon coating.

As can be seen from the transmission electron micrograph of FIG. 9 (the carbon-coated corundum carbon source), the thickness of the carbon shell uniformly coated on the surface of the corundum particles was about 40nm, and the corundum particles had good crystallinity.

As can be seen from the raman spectrum of fig. 10 (the corundum carbon source after carbon coating), the carbon layer exhibited a strong G peak with graphitic properties, indicating that its crystallinity is good.

As can be seen from the thermogravimetric plot of the carbon-coated corundum carbon source in FIG. 11, the carbon content of the carbon-coated magnesium oxide prepared in this example was about 4.9%.

Example 3

The carbon-coated mullite particles are prepared by a gas phase method, the preparation method comprises the steps of placing the mullite particles in a high-temperature furnace body, heating to 850 ℃, introducing mixed gas of acetylene and nitrogen (the content of acetylene is 25%) into a cavity, and reacting for 8 hours to prepare the carbon-coated mullite carbon source. Wherein the carbon content is about 5.1% and the carbon layer thickness is about 25 nm.

Through detection, as can be seen from a scanning electron microscope image of fig. 12(a. mullite grains; b. mullite carbon source after carbon coating), the carbon-coated mullite carbon source prepared in the embodiment maintains the basic morphology of the raw material, and shows the uniformity of carbon coating.

As can be seen from the transmission electron micrograph of fig. 13 (carbon-coated mullite carbon source), the carbon shell uniformly coated on the surface layer of the mullite grains had a thickness of about 25nm and good crystallinity.

As can be seen from the raman spectrum of fig. 14 (carbon-coated mullite carbon source), the carbon layer exhibits a strong G peak with graphitic properties, indicating good crystallinity.

As can be seen from the thermogravimetric plot of the carbon source of carbon-coated mullite in fig. 15, the carbon content in the carbon-coated mullite grains prepared in this example was about 5.1%.

Example 4

The carbon-coated bauxite particles are prepared by a liquid phase method, the preparation method comprises the steps of soaking bauxite powder particles in an aqueous solution with the concentration of 1mol/L glucose, filtering the solution, drying the solution in drying equipment at 100 ℃, then placing the drying equipment in a high-temperature furnace body (the atmosphere is nitrogen/argon), heating to 950 ℃, and reacting for 3 hours to prepare the carbon-coated bauxite carbon source. Wherein the carbon content is about 3.2% and the carbon layer thickness is about 15 nm.

Example 5

Preparing the carbon-coated corundum particles by adopting a hot melting method: the preparation method comprises the following steps of mixing corundum particle raw materials and glucose according to the proportion of 1: uniformly mixing the components in a mass ratio of 0.2, putting the mixture into hot coating equipment, heating to 280 ℃ in a protective atmosphere environment (nitrogen/argon) at a heating rate of 3 ℃/min, preserving heat for 0.5h, heating to 900 ℃ at a heating rate of 5 ℃/min, and preserving heat for 2h to prepare the carbon-coated corundum carbon source. Wherein the carbon content is about 6.2% and the carbon layer thickness is about 35 nm.

Example 6

The carbon-coated refractory clay particles prepared by a gas phase method are used as raw materials, and the preparation method comprises the steps of placing the refractory clay particles in a high-temperature furnace body, heating to 800 ℃, introducing a mixed gas of methane and nitrogen (the methane content is 15%) into a cavity, and reacting for 2 hours to prepare the carbon-coated refractory clay carbon source (the carbon content is about 0.5%, and the thickness of a carbon layer is about 7 nm).

Example 7

Preparing carbon-coated refractory clay particles by a hot-melt method: the preparation method comprises the following steps of mixing the raw materials of the refractory clay particles and fructose according to the proportion of 1: uniformly mixing the components in a mass ratio of 0.35, putting the mixture into thermal coating equipment, heating to 300 ℃ at a heating rate of 3 ℃/min in a protective atmosphere environment (nitrogen/argon), preserving heat for 1h, heating to 800 ℃ at a heating rate of 4 ℃/min, and preserving heat for 3h to prepare the carbon-coated refractory clay carbon source. Wherein the carbon content is about 6.7% and the carbon layer thickness is about 64 nm.

Example 8

The preparation method comprises the steps of soaking spinel powder particles in a 1.5mol/L sucrose aqueous solution, filtering the solution, drying the solution in drying equipment at 90 ℃, heating the solution to 900 ℃ in a high-temperature furnace body (the atmosphere is nitrogen/argon), and reacting for 4 hours to prepare the carbon-coated spinel carbon source. Wherein the carbon content is about 4.8% and the carbon layer thickness is about 32 nm.

It should be noted that the above detailed description is only for exemplary purposes, and the present invention is not limited to the above described embodiments. Any equivalent modifications and substitutions to those skilled in the art are also within the scope of the present invention. Accordingly, equivalent changes and modifications made without departing from the spirit and scope of the present invention should be covered by the present invention.

Claims

1. A carbon source for refractory materials, characterized by: the carbon source has a core-shell structure and is composed of a raw material powder inner core and a nano carbon outer layer.

2. The carbon source according to claim 1, wherein the nano carbon layer coated on the surface of the raw material powder has a thickness of 1 to 150nm, preferably 2 to 50 nm.

3. The carbon source according to claim 1, wherein the raw material powder is selected from the group consisting of magnesia, alumina, calcia, zirconia, mullite, dolomite and clay.

4. The method for producing a carbon source according to claim 1, wherein a carbon source is prepared by coating a nano-thickness carbon layer on the surface of the raw material powder particles by a vapor phase method, a liquid phase method or a hot-melt method.

5. The vapor phase method as claimed in claim 4, wherein the raw material powder particles are placed in a high temperature furnace body and heated to 1700 ℃, the mixed gas of the carbon-containing precursor and argon or nitrogen is introduced into the furnace body for heat preservation, and the carbon source coated by the carbon layer with different thicknesses is prepared by adjusting the concentration of the precursor, the reaction temperature and the reaction time.

6. The liquid phase method as claimed in claim 4, wherein the raw material powder particles are soaked in a carbon-containing precursor solution, the solution is filtered out and dried in a drying device, and then the carbon-containing precursor solution is placed in a high temperature furnace (the protective gas is nitrogen/argon) to be carbonized at the temperature of 300-1700 ℃, and carbon sources coated by carbon layers with different thicknesses are prepared by adjusting the solution concentration, the reaction temperature and the reaction time of the carbon-containing precursor.

7. A hot melting method as claimed in claim 4, wherein the raw material powder particles and the carbon-containing powder are mixed uniformly according to a certain ratio and then placed into a hot coating device, the temperature is raised to 350 ℃ in a protective atmosphere (nitrogen/argon), the temperature is maintained, then the temperature is raised to 1700 ℃ for carbonization, and the carbon source coated by the carbon layer with different thickness is prepared by adjusting the ratio of the raw material powder to the carbon-containing powder, the reaction temperature and the reaction time.

8. The gas phase process of claim 5, wherein the carbon-containing precursor is selected from the group consisting of methane, ethane, acetylene, ethanol, benzene, toluene, acetone, carbon monoxide, and mixtures thereof.

9. The liquid phase process of claim 6, wherein the carbon-containing precursor is selected from the group consisting of glucose, sucrose, dopamine, aniline, oleic acid, benzene, toluene, and mixtures thereof.

10. A hot melt process according to claim 7, wherein said carbonaceous powder is selected from the group consisting of glucose, pitch, sucrose, and mixtures thereof.

11. Use of a carbon source according to any one of claims 1 to 3 in the preparation of a carbonaceous refractory material.