Preparation process for improving surface oxidation resistance of carbon-carbon saggar and carbon-carbon saggar

Abstract

The invention relates to the technical field of carbon-carbon sagger surface treatment, and particularly discloses a preparation process for improving the surface oxidation resistance of a carbon-carbon sagger and the carbon-carbon sagger. The preparation technology for improving the surface oxidation resistance of the carbon-carbon sagger comprises the following steps that polyvinyl alcohol, water, carbon-based powder and silicon powder are mixed according to the mass ratio of (0.8-1.2): (3-7): 1: (2.5-3.5), and spraying liquid is obtained; and the spraying liquid is sprayed to the surface of the carbon-carbon sagger twice, and drying is conducted after each time of spraying. And putting the carbon-carbon sagger into a reactor, heating the carbon-carbon sagger in an oxygen-free atmosphere, and reacting the spraying liquid to form the silicon carbide coating. Silicon steam is introduced into the reactor, so that the surface of the carbon-carbon sagger is filled with the silicon steam. And cooling to cure the silicon steam filled on the surface of the carbon-carbon sagger on the surface of the carbon-carbon sagger to form a compact silicon coating. The spraying liquid is converted into a silicon carbide coating, the silicon carbide coating is covered with a compact silicon coating, the silicon coating can react with oxygen molecules at high temperature to generate a silicon dioxide passivation layer, and therefore the carbon-carbon sagger is protected.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of carbon-carbon kiln surface modification, and particularly relates to a preparation process for improving the oxidation resistance of a carbon-carbon kiln surface and the carbon-carbon kiln. BACKGROUND

[0002] The carbon-carbon kiln refers to a kiln made of two kinds of carbon materials, for example, a kiln made of carbon cloth and carbon fibers. The carbon-carbon kiln surface has longitudinal and transverse intersecting fiber lines, which are completely exposed to the gas environment.

[0003] The carbon-carbon kiln can be used as a container for materials that need to be carbonized. When a small amount of oxygen exists in the carbonization environment, the fiber lines on the surface of the carbon-carbon kiln are easily oxidized by oxygen at a carbonization temperature of 600-1100 DEG C, thereby seriously affecting the product quality (including mechanical properties) and appearance of the carbon-carbon kiln, causing the service life of the carbon-carbon kiln to be significantly shortened, and causing economic losses. SUMMARY

[0004] In order to improve the condition that the carbon-carbon kiln is easily oxidized by a small amount of oxygen in the carbonization environment during the process of being used as a carbonization reaction container, the application provides a preparation process for improving the oxidation resistance of a carbon-carbon kiln surface, and the specific scheme is as follows.

[0005] A preparation process for improving the oxidation resistance of a carbon-carbon kiln surface, comprising the following steps.

[0006] S1, polyvinyl alcohol, water, carbon-based powder and silicon powder are mixed according to the mass ratio (0.8-1.2):(3-7):1:(2.5-3.5) to obtain a spraying liquid.

[0007] S2, the spraying liquid is sprayed onto the surface of the carbon-carbon kiln, dried, and then the spraying liquid is sprayed onto the surface of the carbon-carbon kiln again, and dried again, so that the spraying liquid completely covers the surface of the carbon-carbon kiln.

[0008] S3, the carbon-carbon kiln is placed in a reactor, the reactor is filled with an oxygen-free protective gas atmosphere, the carbon-carbon kiln is heated, the polyvinyl alcohol is carbonized, and the silicon powder is liquefied, the liquefied silicon reacts with the carbonization product of the polyvinyl alcohol and the carbon-based powder to form a silicon carbide coating attached to the surface of the carbon-carbon kiln.

[0009] S4, silicon vapor is introduced into the reactor to fill the surface of the carbon-carbon kiln with the silicon vapor.

[0010] S5, the silicon vapor filled on the surface of the carbon-carbon kiln is solidified on the surface of the carbon-carbon kiln by cooling to form a dense silicon coating.

[0011] By adopting the technical scheme, the polyvinyl alcohol is dissolved in water to form a colloid, the carbon-based powder and the silicon powder are dispersed in the colloid to form a spraying liquid, the spraying liquid is sprayed twice and dried twice, so that the spraying liquid completely covers the surface of the carbon-carbon kiln, and if the spraying is only performed once, pores are easily generated after the spraying liquid is dried, and the oxidation resistance of the carbon-carbon kiln is reduced. The carbon-carbon kiln prepared by the preparation process is applied in a carbonization process, if a small amount of oxygen exists in a carbonization environment, the step S3 generates a silicon carbide layer, which can block some oxygen molecules, but some oxygen molecules still penetrate the silicon carbide layer to contact the fiber silk lines of the carbon-carbon kiln to oxidize the fiber silk lines. To this end, the silicon coating layers generated in the steps S4 and S5 can react with the oxygen molecules to generate a silicon dioxide passivation layer in a high carbonization temperature, so as to protect the carbon-carbon kiln, the fiber silk is basically not oxidized, the carbon-carbon kiln maintains good mechanical properties and appearance, the service period is lengthened, and the loss is reduced.

[0012] In an embodiment of the preparation process for improving the oxidation resistance of the surface of the carbon-carbon kiln, in the step S1, the carbon-based powder is carbon powder and / or graphite powder.

[0013] By adopting the technical scheme, the carbon powder and the graphite powder provide a powder carbon source, and the specification can be 100-400 mesh, but is not limited thereto, for example, 200 mesh, and at a high temperature, the carbon powder and / or the graphite powder can fully react with the silicon powder to generate a silicon carbide oxidation resistance layer. The mesh number of the silicon powder can be 200-325 mesh, but is not limited thereto.

[0014] In an embodiment of the preparation process for improving the oxidation resistance of the surface of the carbon-carbon kiln, in the step S2, the thickness of the spraying liquid sprayed on the surface of the carbon-carbon kiln each time is 0.07-0.10 mm.

[0015] By adopting the technical scheme, the surface of the carbon-carbon kiln is completely covered by spraying twice.

[0016] In an embodiment of the preparation process for improving the oxidation resistance of the surface of the carbon-carbon kiln, in the step S3, the carbon-carbon kiln is heated to 1500-1700 ℃ and kept for 1-3 h.

[0017] By adopting the technical scheme, the polyvinyl alcohol is degraded and carbonized at a high temperature of 1500-1700 ℃ to form coke adhered to the surface of the carbon-carbon kiln, and the coke can react with molten silicon to generate silicon carbide at the temperature. In addition, the carbon-based powder can also react with the molten silicon to generate silicon carbide at the temperature.

[0018] In an embodiment of the preparation process for improving the oxidation resistance of the surface of the carbon-carbon kiln, in the step S4, after the silicon vapor is introduced into the reactor, the air pressure in the reactor is 1.1-1.2 atm.

[0019] By adopting the technical scheme, the micro-positive pressure of 1.1-1.2 atm is favorable for the silicon vapor to fill the carbon carbon die surface.

[0020] In step S4, the silicon vapor of 1800-1850 DEG C is introduced into the reactor, and the silicon vapor is kept filling the carbon carbon die surface for 6-8 h.

[0021] By adopting the technical scheme, the silicon vapor completely covers the carbon carbon die surface, and prepares for the solidification of the dense silicon coating.

[0022] In step S5, the cooling includes: cooling from 1800-1850 DEG C to 1100-1200 DEG C at a cooling rate of 5-10 DEG C / min.

[0023] By adopting the technical scheme, in the cooling process, the silicon vapor filling the carbon carbon die surface is solidified on the carbon carbon die surface to form the dense silicon coating, which can prevent the oxygen molecules from penetrating.

[0024] A carbon carbon die is prepared according to the preparation process, the carbon carbon die surface is attached with a silicon carbide coating and a dense silicon coating from inside to outside, the thickness of the silicon carbide coating is 0.14-0.2 mm, and the thickness of the silicon coating is 0.2-0.5 mm; the silicon coating is uniform in color and smooth in appearance.

[0025] By adopting the technical scheme, the silicon carbide coating can resist the penetration of most oxygen molecules, and the dense silicon coating can prevent the oxygen molecules from penetrating.

[0026] In summary, the preparation process and the carbon carbon die have the following beneficial effects: the preparation process sprays carbon and silicon on the die product surface, and generates the silicon carbide coating through high-temperature treatment, and then fills the silicon vapor and solidifies to generate the dense silicon coating outside the silicon carbide coating, the appearance of the sprayed die is smooth and beautiful, the oxidation resistance is enhanced, the product quality is improved, and the service life of the carbon carbon die is prolonged. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The preparation process for improving the oxidation resistance of the carbon carbon die surface is shown in the flowchart. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the following embodiments, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0029] The square box-shaped carbon-carbon anode was prepared by the following steps: (1) 10 pieces of the same 300 g / m 2 square plain carbon cloth and 10 pieces of the same 75 g / m 2 square carbon fiber web were alternately stacked and needled layer by layer to obtain a square multilayer cloth, and a plurality of the multilayer cloth was prepared. Five multilayer cloths were taken as five surfaces of the square box with the upper opening, and were spliced in the mold to form a square box with the upper opening, that is, an anode preform.

[0030] (2) The epoxy resin was introduced into the mold, and the anode preform was soaked for 3 h, and then heated to 200 DEG C and kept for 2 h to make the anode preform cured and formed, and then demolded to obtain a blank body; (3) The blank body was carbonized in a nitrogen atmosphere at 1000 DEG C for 6 h to obtain a square box-shaped carbon-carbon anode with the upper opening.

[0031] A batch of the same carbon-carbon anode without coating was prepared by the above method.

[0032] Embodiment 1 Reference Figure 1 A preparation process for improving the surface oxidation resistance of the carbon-carbon anode, the carbon-carbon anode was first polished and dusted, and then cleaned with alcohol in all directions, and then dried at 80 DEG C, and then the following steps were performed.

[0033] S1, polyvinyl alcohol, water, carbon-based powder and silicon powder were mixed according to the mass ratio of 1:5:1:3 to obtain a spraying liquid. The carbon-based powder is carbon powder with a specification of 200 mesh. The silicon powder is 200 mesh.

[0034] S2, the spraying liquid was uniformly sprayed onto the surface of the carbon-carbon anode using an air pressure spray gun, the spraying thickness was 0.08 mm, and the spraying liquid was dried at 75 DEG C for 7 min; the spraying liquid was sprayed onto the surface of the carbon-carbon anode again, the spraying thickness was 0.08 mm, and the spraying liquid was dried again at 75 DEG C for 7 min, so that the spraying liquid completely covered the surface of the carbon-carbon anode.

[0035] S3, the carbon-carbon anode was placed in a reaction furnace with a nitrogen atmosphere, and the carbon-carbon anode was heated to 1600 DEG C and kept for 2 h, so that the polyvinyl alcohol was carbonized and the silicon powder was liquefied, and the liquefied silicon reacted with the carbon-based powder and the carbonized product of the polyvinyl alcohol to form a silicon carbide coating attached to the surface of the carbon-carbon anode.

[0036] S4, 1825℃ silicon vapor is introduced into the reaction furnace, the gas pressure in the reaction furnace reaches 1.15 atm of micro-positive pressure state, and is maintained for 7h to fill the silicon vapor on the surface of the carbon carbon die.

[0037] S5, the initial 1825℃ temperature is reduced to 1150℃ at a cooling rate of 7℃ / min, the silicon vapor filled on the surface of the carbon carbon die is solidified on the surface of the carbon carbon die to form a dense silicon coating, the thickness of the silicon coating is 0.35mm; the silicon coating is uniform in color, without obvious color difference, and the outer surface is smooth.

[0038] Example 2 A preparation process for improving the oxidation resistance of the surface of the carbon carbon die, the surface of the carbon carbon die is first polished and treated with dust absorption, and the carbon carbon die is cleaned with alcohol in all directions, and then dried at 80℃. The following steps are then performed.

[0039] S1, polyvinyl alcohol, water, carbon-based powder and silicon powder are mixed according to a mass ratio of 0.8:3:1:2.5 to obtain a spraying liquid. The carbon-based powder is graphite powder with a specification of 100 mesh. The silicon powder is 300 mesh.

[0040] S2, the spraying liquid is uniformly sprayed onto the surface of the carbon carbon die using an air pressure spray gun, the spraying thickness is 0.07mm, and drying is performed at 70℃ for 5min; the spraying liquid is sprayed onto the surface of the carbon carbon die again, the spraying thickness is 0.07mm, and drying is performed again at 70℃ for 5min to completely cover the surface of the carbon carbon die with the spraying liquid.

[0041] S3, the carbon carbon die is placed in a reaction furnace, the reaction furnace is filled with nitrogen atmosphere, and the carbon carbon die is heated to 1500℃ and maintained for 3h to carbonize the polyvinyl alcohol and liquefy the silicon powder, the liquefied silicon reacts with the carbon-based powder and the carbonized product of the polyvinyl alcohol to form a silicon carbide coating attached to the surface of the carbon carbon die.

[0042] S4, 1800℃ silicon vapor is introduced into the reaction furnace, the gas pressure in the reaction furnace reaches 1.1 atm of micro-positive pressure state, and is maintained for 6h to fill the silicon vapor on the surface of the carbon carbon die.

[0043] S5, the initial 1800℃ temperature is reduced to 1100℃ at a cooling rate of 10℃ / min, the silicon vapor filled on the surface of the carbon carbon die is solidified on the surface of the carbon carbon die to form a dense silicon coating, the thickness of the silicon coating is 0.2mm; the silicon coating is uniform in color, and the outer surface is smooth.

[0044] Example 3 The preparation process for improving the oxidation resistance of the surface of the carbon carbon die is as follows: first, the carbon carbon die is subjected to surface grinding and dust absorption treatment, and then is cleaned with alcohol in all directions, and is dried at 80 DEG C; and then the following steps are performed.

[0045] S1, polyvinyl alcohol, water, carbon-based powder, and silicon powder are mixed according to a mass ratio of 1.2:7:1:3.5 to obtain a spraying liquid. The carbon-based powder is carbon powder with a specification of 400 mesh. The silicon powder is 325 mesh.

[0046] S2, the spraying liquid is uniformly sprayed onto the surface of the carbon carbon die using an air pressure spray gun, with a spraying thickness of 0.10 mm, and is dried at a temperature of 80 DEG C for 10 min; the spraying liquid is sprayed onto the surface of the carbon carbon die again, with a spraying thickness of 0.10 mm, and is dried at a temperature of 80 DEG C for 10 min again, so that the spraying liquid completely covers the surface of the carbon carbon die.

[0047] S3, the carbon carbon die is placed in a reaction furnace, which is in a nitrogen atmosphere, and the carbon carbon die is heated to 1700 DEG C and is kept for 1 h, so that the polyvinyl alcohol is carbonized and the silicon powder is liquefied, and the liquefied silicon reacts with the carbon-based powder and the carbonized product of the polyvinyl alcohol to form a silicon carbide coating attached to the surface of the carbon carbon die.

[0048] S4, silicon vapor at 1850 DEG C is introduced into the reaction furnace, the gas pressure in the reaction furnace reaches a micro-positive pressure state of 1.2 atm, and is kept for 8 h, so that the silicon vapor fills the surface of the carbon carbon die.

[0049] S5, the temperature of 1850 DEG C is reduced to 1200 DEG C at a cooling rate of 5 DEG C / min, so that the silicon vapor filled on the surface of the carbon carbon die is solidified on the surface of the carbon carbon die to form a dense silicon coating with a thickness of 0.5 mm; the silicon coating is uniform in color and smooth in appearance.

[0050] Comparative Example 1 A preparation process for improving the oxidation resistance of the surface of the carbon carbon die, and the difference from Example 1 is that steps S4 and S5 are cancelled, i.e. there is no silicon coating, and the thickness of the silicon carbide coating is increased to the sum of the thicknesses of the silicon carbide coating and the silicon coating in Example 1, and the specific steps are as follows.

[0051] The carbon carbon die is subjected to surface grinding and dust absorption treatment, and then is cleaned with alcohol in all directions, and is dried at 80 DEG C, and then the following steps are performed.

[0052] S1, polyvinyl alcohol, water, carbon-based powder, and silicon powder are mixed according to a mass ratio of 1.2:7:1:3.5 to obtain a spraying liquid. The carbon-based powder is carbon powder with a specification of 400 mesh. The silicon powder is 325 mesh.

[0053] S2, the spraying liquid is uniformly sprayed on the surface of the carbon carbon die by using the air pressure spray gun, the spraying thickness is 0.25mm, and the spraying liquid is dried at 75℃ for 7min; the spraying liquid is sprayed on the surface of the carbon carbon die again, the spraying thickness is 0.26mm, and the spraying liquid is dried at 75℃ for 7min again, so that the spraying liquid completely covers the surface of the carbon carbon die.

[0054] S3, the carbon carbon die is placed in a reaction furnace, the reaction furnace is in a nitrogen atmosphere, the carbon carbon die is heated to 1600℃ and kept for 2h, so that the polyvinyl alcohol is carbonized and the silicon powder is liquefied, the liquefied silicon and the carbon-based powder and the carbonized product of the polyvinyl alcohol react to form a silicon carbide coating attached to the surface of the carbon carbon die.

[0055] Comparative Example 2 A preparation process for improving the oxidation resistance of the surface of the carbon carbon die, which is different from Example 1 in that steps S1, S2 and S3 are cancelled, that is, there is no silicon carbide coating, and the parameters of steps S4 and S5 are adjusted, and the thickness of the silicon coating is increased to the sum of the thicknesses of the silicon carbide coating and the silicon coating in Example 1, as follows.

[0056] A preparation process for improving the oxidation resistance of the surface of the carbon carbon die, the surface of the carbon carbon die is first polished and dusted, and the carbon carbon die is cleaned with alcohol in all directions, and then dried at 80℃, and then the following steps are performed.

[0057] S4, the carbon carbon die is placed in a reaction furnace, the air in the reaction furnace is replaced with nitrogen, heated to 1825℃, and 1825℃ silicon vapor is introduced into the reaction furnace, the gas pressure in the reaction furnace reaches a micro-positive pressure state of 1.15atm, and kept for 8h, so that the silicon vapor fills the surface of the carbon carbon die.

[0058] S5, the temperature of 1825℃ is reduced to 1150℃ at a cooling rate of 5℃ / min, so that the silicon vapor filled in the surface of the carbon carbon die is solidified on the surface of the carbon carbon die to form a dense silicon coating, and the thickness of the silicon coating is 0.51mm; the silicon coating is uniform in color, without obvious color difference, and the outer surface is smooth.

[0059] Comparative Example 3 A preparation process for improving the oxidation resistance of the surface of the carbon carbon die, which is different from Example 1 in that step S2 only sprays the spraying liquid once, and the thickness of the single spraying liquid is increased to the same thickness as the two spraying liquids in Example 1, as follows.

[0060] A preparation process for improving the oxidation resistance of the surface of the carbon carbon die, the surface of the carbon carbon die is first polished and dusted, and the carbon carbon die is cleaned with alcohol in all directions, and then dried at 80℃, and then the following steps are performed.

[0061] S1, polyvinyl alcohol, water, carbon-based powder, silicon powder were mixed according to the mass ratio of 1:5:1:3 to obtain a spraying liquid. The carbon-based powder was carbon powder with a specification of 200 mesh. The silicon powder was 200 mesh.

[0062] S2, the spraying liquid was uniformly sprayed onto the entire surface of the carbon-carbon die by using an air pressure spray gun, the spraying thickness was 0.16 mm, and the die was dried at a temperature of 75°C for 7 min.

[0063] S3, the carbon-carbon die was placed in a reaction furnace, the reaction furnace was in a nitrogen atmosphere, the carbon-carbon die was heated to 1600°C and maintained for 2 h, so that the polyvinyl alcohol was carbonized and the silicon powder was liquefied, and the liquefied silicon reacted with the carbon-based powder and the carbonized product of the polyvinyl alcohol to form a silicon carbide coating attached to the surface of the carbon-carbon die.

[0064] S4, silicon vapor at 1825°C was introduced into the reaction furnace, the gas pressure in the reaction furnace reached a micro-positive pressure state of 1.15 atm, and was maintained for 7 h, so that the silicon vapor filled the surface of the carbon-carbon die.

[0065] S5, the initial temperature of 1825°C was reduced to 1150°C at a cooling rate of 7°C / min, so that the silicon vapor filled on the surface of the carbon-carbon die was solidified on the surface of the carbon-carbon die to form a dense silicon coating, the thickness of the silicon coating was 0.35 mm; the silicon coating was uniform in color, no obvious color difference, and the outer surface was smooth.

[0066] It should be noted that the initial carbon-carbon die put into each of the above examples and each of the comparative examples was the same carbon-carbon die without coating.

[0067] Test Example 1 The carbon-carbon die with coating prepared in Examples 1-3 and Comparative Examples 1-3, and the carbon-carbon die without coating were subjected to ablation test, the carbon-carbon die was placed in air for ablation, the ablation temperature was 1100°C, the ablation time was 48 h, and the weight loss after ablation was detected.

[0068] Table 1 Ablation test of double-coated die Table 2 Ablation test of single-coated die Table 3 Ablation test of uncoated die In Tables 1-3, the weight loss ratio = weight loss / original weight*100%.

[0069] From table 1-3, it can be seen that under the condition of the same total thickness of the coating, the silicon carbide coating plus silicon coating double coating of the carbon carbon hearth of examples 1-3 is more resistant to oxidation, and the weight loss is small, while the carbon carbon hearth of comparative examples 1-2 only has silicon carbide coating or only has silicon coating is relatively easy to be oxidized and lose weight. The weight loss ratio of the uncoated hearth reaches 36.90%, which is significantly higher than that of the carbon carbon hearth prepared in examples 1-3, indicating that the double coating of the silicon carbide coating plus silicon coating covering the surface of the carbon carbon hearth of examples 1-3 significantly improves the oxidation resistance of the carbon carbon hearth.

[0070] Comparative example 3 is also a double coating scheme, but when spraying the spraying liquid layer of comparative example 3, it is sprayed once, while the spraying of the spraying liquid layer of examples 1-3 is divided into two times, and the two times are dried, which causes the weight loss ratio of comparative example 3 to be higher than that of examples 1-3, because the two times of spraying, the latter one can cover the pores of the former one, improve the coverage of the hearth surface after the spraying liquid layer is converted into silicon carbide coating, and improve the oxidation resistance of the hearth.

[0071] The carbon carbon hearth prepared according to the method of examples 1-3 is applied to carbonization reaction as a container for materials that need to be carbonized. If there is a small amount of oxygen in the carbonization environment, for carbonization temperature of 600-1100℃, the silicon coating on the surface of the carbon carbon hearth is oxidized to form a silicon dioxide passivation layer, which prevents further oxidation and blocks the penetration of oxygen molecules. The inner layer of silicon carbide coating further blocks oxygen molecules, which together protect the fiber filaments on the surface of the carbon carbon hearth. The relatively dense silicon coating wraps the silicon carbide coating, making it not easy to fall off. The silicon carbide coating improves the adhesion of the silicon coating to the carbon carbon hearth, which also makes the silicon coating not easy to fall off. The inner layer of silicon carbide coating and the outer layer of silicon coating together improve the oxidation resistance of the carbon carbon hearth.

[0072] If there is only silicon coating, the adhesion of the silicon coating to the carbon carbon hearth is slightly worse than that of the silicon carbide coating to the carbon carbon hearth, which causes the density of the single silicon coating to decrease compared to the silicon coating of the double coating scheme, so that a small amount of oxygen molecules can penetrate through the silicon coating, and the weight loss ratio increases compared to the double coating scheme.

[0073] If there is only silicon carbide coating, because the density of the silicon carbide coating is not as good as that of the silicon coating, the single silicon carbide coating is more likely to allow oxygen molecules to penetrate compared to the double coating scheme, so its weight loss ratio increases compared to the double coating scheme.

[0074] The scheme of covering the surface of the carbon carbon hearth with silicon carbide coating and silicon coating in sequence in the present application improves the oxidation resistance of the carbon carbon hearth, improves the product quality and appearance of the carbon carbon hearth, extends the service life of the carbon carbon hearth, and reduces the loss of the hearth.

[0075] Although the present application has been described in detail with reference to the foregoing embodiments, the technical solutions recorded in the foregoing embodiments can be modified by those skilled in the art, or some technical features thereof can be replaced by equivalents, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A preparation process for improving the anti-oxidation ability of the surface of carbon-carbon sagger, characterized in that: The following steps are involved: S1, polyvinyl alcohol, water, carbon-based powder, and silicon powder are mixed in a mass ratio of (0.8-1.2):(3-7):1:(2.5-3.5) to obtain a spraying liquid; S2, spraying the spraying liquid onto the surface of the carbon-carbon sagger, and after drying, spraying the spraying liquid onto the surface of the carbon-carbon sagger again, and drying again, so that the spraying liquid completely covers the surface of the carbon-carbon sagger; S3, placing the carbon-carbon sagger in a reactor, wherein the reactor is provided with an oxygen-free protective gas atmosphere, heating the carbon-carbon sagger to carbonize the polyvinyl alcohol and liquefy the silicon powder, and reacting the liquefied silicon with the carbon-based powder and the carbonized product of the polyvinyl alcohol to form a silicon carbide coating attached to the surface of the carbon-carbon sagger; S4, introducing silicon vapor into the reactor so that the silicon vapor fills the surface of the carbon-carbon sagger; S5, cooling to allow the silicon vapor filling the surface of the carbon-carbon sagger to solidify on the surface of the carbon-carbon sagger to form a dense silicon coating.

2. The preparation process for improving the surface oxidation resistance of carbon-carbon sagger according to claim 1, characterized in that: In step S1, the carbon-based powder is carbon powder and / or graphite powder.

3. The preparation process for improving the surface oxidation resistance of carbon-carbon sagger according to claim 1, characterized in that: In step S2, the thickness of the spraying liquid sprayed onto the surface of the carbon-carbon sagger each time is 0.07-0.10 mm.

4. The preparation process for improving the oxidation resistance of the carbon-carbon sagger surface according to claim 1, characterized in that: In step S3, the carbon-carbon sagger is heated to 1500-1700° C. and maintained for 1-3 hours.

5. The preparation process for improving the surface oxidation resistance of carbon-carbon sagger according to claim 1, characterized in that: In step S4, after silicon vapor is introduced into the reactor, the gas pressure in the reactor is 1.1-1.2 atm.

6. The preparation process for improving the surface oxidation resistance of carbon-carbon sagger according to claim 1 or 5, characterized in that: In step S4, silicon vapor at 1800-1850° C. is introduced into the reactor and maintained for 6-8 hours, so that the silicon vapor fills the surface of the carbon-carbon sagger.

7. The preparation process for improving the anti-oxidation ability of the carbon-carbon sagger surface according to claim 6, characterized in that: The cooling in step S5 includes cooling from 1800-1850° C. to 1100-1200° C. at a cooling rate of 5-10° C. / min.

8. A carbon-carbon sagger, characterized in that: According to the preparation process according to any one of claims 1 to 7, a silicon carbide coating and a dense silicon coating are attached to the surface of the carbon-carbon sagger from the inside to the outside, the thickness of the silicon carbide coating is 0.14 to 0.2 mm, and the thickness of the silicon coating is 0.2 to 0.5 mm; the silicon coating has a uniform color and a smooth surface.

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