A modified electrode paste, its preparation method and application

Abstract

The application belongs to the technical field of electrode paste preparation, and particularly relates to a modified electrode paste and a preparation method and application thereof. The Ni-Co-Fe alloy is coated with silane modified CNTs, the Ni-Co-Fe alloy serves as a catalytic core to improve the graphitization degree and the conductive efficiency of the carbon matrix, and the silane modified CNTs coating layer prevents alloy agglomeration and inhibits excessive carbon penetration, thereby ensuring long-term stability of the catalytic system; the Fe-Mn alloy is coated with carbon, the Fe-Mn alloy serves as a buffer core, a melting point gradient is formed in the Fe-Mn solid solution and the Mn enrichment area, phase change energy is absorbed under thermal stress, and the outer carbon layer forms a strong and tough interface with the carbon matrix under catalysis, thereby strengthening the thermal shock resistance; the TiC@SiC composite particles match the thermal expansion of the carbon matrix through the SiC shell layer to reduce internal stress, and the TiC core provides hard enhancement, thereby achieving a synergistic improvement of the thermal shock resistance and the conductive stability, and being suitable for high-temperature harsh environments such as ore smelting furnaces.

Description

Technical Field

[0001] This invention relates to the field of electrode paste preparation technology, and in particular to a modified electrode paste, its preparation method, and its application. Background Technology

[0002] Electrode paste, as a core conductive consumable in the smelting process of submerged arc furnaces, directly determines the continuity, safety, and economy of smelting production. The interior of a submerged arc furnace is constantly exposed to high temperatures, accompanied by frequent temperature fluctuations, intense oxidation erosion, and slag scouring. This places stringent demands on the thermal shock resistance and conductivity stability of the electrode paste. To improve thermal shock resistance, the industry often introduces ceramic phases such as SiC and TiC as reinforcing components. However, current methods only combine the ceramic phase with carbon-based aggregates / binders through physical mixing or simple coating, resulting in weak interfacial bonding. During the frequent thermal shock cycles of submerged arc furnaces, the significant difference in thermal expansion coefficients between the ceramic phase and carbon-based materials easily generates peeling stress, causing cracks to propagate rapidly along the two-phase interface. Furthermore, the added ceramic particles are prone to agglomeration, significantly weakening the thermal shock resistance enhancement effect. These agglomerates also disrupt the continuous conductive network within the electrode paste, creating an antagonistic problem of enhanced performance inevitably leading to decreased conductivity. This further exacerbates the performance contradiction and fails to meet the demand for synergistic improvement in the thermal shock resistance and conductivity stability of electrode paste under the harsh operating conditions of submerged arc furnaces. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a modified electrode paste, its preparation method, and its applications. By coating a Ni-Co-Fe alloy with silane-modified CNTs (carbon nanotubes), the Ni-Co-Fe alloy acts as a catalytic core, enhancing the graphitization degree and conductivity of the carbon matrix. Simultaneously, the silane-modified CNTs coating prevents alloy agglomeration and inhibits excessive carburization, ensuring long-term stability of the catalytic system. Furthermore, a Fe-Mn alloy is carbon-coated, with the Fe-Mn alloy acting as a buffer core. Internally, a melting point gradient is formed between the Fe-Mn solid solution and the Mn-rich region, allowing for energy absorption through phase transition under thermal stress. The external carbon layer forms a strong and tough interface with the carbon matrix under catalysis, enhancing thermal shock resistance. The TiC@SiC composite particles reduce internal stress by matching the thermal expansion of the carbon matrix through the SiC shell, while the TiC core provides hard reinforcement, achieving a synergistic improvement in thermal shock resistance and electrical conductivity stability, making it suitable for high-temperature and harsh environments such as submerged arc furnaces.

[0004] To achieve the above objectives, the present invention employs the following technical solution:

[0005] In a first aspect, the present invention provides a modified electrode paste, the electrode paste comprising Ni-Co-Fe alloy@silane modified carbon nanotubes, carbon-coated Fe-Mn alloy, composite filler, binder and additives;

[0006] The Ni-Co-Fe alloy@silane-modified carbon nanotubes are obtained by sintering and reducing Ni powder, Co powder, Fe powder and carbon nanotubes after modification with a first silane coupling agent;

[0007] The carbon-coated Fe-Mn alloy is obtained by carbonizing Fe-Mn alloy powder, thermoplastic phenolic resin, and hexamethylenetetramine.

[0008] The composite filler comprises active aggregate, TiC@SiC composite particles, modified carbon fiber-SiC whisker mixture, and Ti powder; the active aggregate is obtained by removing impurities from graphitized petroleum coke and electrically calcined anthracite with hydrochloric acid and activation with CO2; the TiC@SiC composite particles are obtained by coating TiC powder with tetraethyl orthosilicate and thermoplastic phenolic resin and then calcining; the modified carbon fiber-SiC whisker mixture is obtained by mixing short-cut carbon fibers with SiC whiskers after nitric acid oxidation and modification with a second silane coupling agent;

[0009] The binder comprises modified coal tar pitch and polyamic acid; the modified coal tar pitch is obtained by air oxidation, formaldehyde crosslinking and maleic anhydride grafting onto polypropylene of medium-temperature coal tar pitch;

[0010] The additives include butyl stearate and sodium lignosulfonate.

[0011] Further, the mass ratio of the Ni-Co-Fe alloy@silane-modified carbon nanotubes, carbon-coated Fe-Mn alloy, composite filler, binder, and additives is (119-141):(100-110):(138-155):(154-176):(0.4-0.6); the mass ratio of Ni powder, Co powder, Fe powder, and carbon nanotubes is (55-65):(18-22):(18-22):(28-32); the mass ratio of Fe-Mn alloy powder, thermoplastic phenolic resin, and hexamethylenetetramine is (95-105):(9-11):(0.4-0.6); the mass ratio of Fe to Mn in the Fe-Mn alloy powder is 8:2; the TiC The mass ratio of powder, tetraethyl orthosilicate, and thermoplastic phenolic resin is (28-32):(7-9):(2-2.4); the mass ratio of active aggregate, modified carbon fiber-SiC whisker mixture, and Ti powder is (80-90):(28-32):(0.4-0.6); the mass ratio of graphitized petroleum coke and electrically calcined anthracite is (55-65):(35-45); the mass ratio of chopped carbon fiber and SiC whiskers is (14-16):(14-16); the mass ratio of modified coal tar pitch and polyamic acid is (145-165):(9-11); and the mass ratio of butyl stearate and sodium lignosulfonate is (0.25-0.35):(0.15-0.25).

[0012] Furthermore, the particle size of the Ni powder, Co powder, and Fe powder is 50-100 nm; the diameter of the carbon nanotubes is 10-20 nm, and the length is 5-10 μm; the first silane coupling agent is KH-560; the particle size of the Fe-Mn alloy powder is 200 mesh; the softening point of the thermoplastic phenolic resin is 80-100℃; the particle size of the TiC powder is 4-6 μm; and the particle size of the Ti powder is 40-60 nm.

[0013] Furthermore, the graphitized petroleum coke has a particle size of 3-5 mm; the electrically calcined anthracite has a particle size of 1-3 mm and a fixed carbon content of ≥95%; the chopped carbon fibers have a diameter of 5-10 μm and a length of 1-3 mm; the second silane coupling agent is KH-550; the SiC whiskers have a diameter of 0.5-1 μm and a length of 10-20 μm; the intermediate-temperature coal tar pitch has a softening point of 80-90℃ and a fixed carbon content of ≥80%; and the polyamic acid has a glass transition temperature of 120-140℃, a solid content of ≥90%, and an imidization rate of ≤10%.

[0014] Secondly, the present invention provides a method for preparing a modified electrode paste, comprising the following steps:

[0015] S1. Ni powder, Co powder, Fe powder and carbon nanotubes are added to anhydrous ethanol to make a slurry. An ethanol aqueous solution containing the first silane coupling agent is added. The mixture is reduced in an H2 / Ar mixed atmosphere, heated, switched to an Ar atmosphere, cooled, and naturally cooled to room temperature to obtain Ni-Co-Fe alloy@silane modified carbon nanotubes.

[0016] S2. Fe-Mn alloy powder, thermoplastic phenolic resin and hexamethylenetetramine are mixed, anhydrous ethanol is added and the mixture is evaporated and concentrated to obtain moist particles. The particles are dried, nitrogen gas is introduced, the temperature is gradually increased and then decreased to room temperature to obtain carbon-coated Fe-Mn alloy. Tetraethyl orthosilicate, thermoplastic phenolic resin and ethanol are mixed to obtain a coating solution. TiC powder is added to the coating solution, spray dried, argon gas is introduced and calcined to obtain TiC@SiC composite particles.

[0017] S3. Graphitized petroleum coke and electrically calcined anthracite are mixed, purified with hydrochloric acid, washed with water to pH=7, dried for the first time, and activated with CO2 to obtain active aggregate; short-cut carbon fibers are oxidized with nitric acid, washed with water to pH=7, dried for the second time, and an ethanol solution containing a second silane coupling agent is added. The mixture is ultrasonicated, and SiC whiskers are added to obtain modified carbon fiber-SiC whisker mixture. Active aggregate, TiC@SiC composite particles and Ti powder are added and mixed to obtain composite filler;

[0018] S4. Medium-temperature coal tar pitch is oxidized by passing air through it, cross-linked by adding formaldehyde, and then composite modified by adding maleic anhydride-grafted polypropylene. It is then naturally cooled to room temperature to obtain modified coal tar pitch. After preheating the modified coal tar pitch, butyl stearate is added to obtain modified coal tar pitch containing butyl stearate.

[0019] S5. Mix Ni-Co-Fe alloy@silane-modified CNTs, carbon-coated Fe-Mn alloy and composite filler, add modified coal tar pitch containing butyl stearate, knead, add polyamic acid, heat and knead, add sodium lignosulfonate aqueous solution, cool and knead to obtain electrode paste; fill the electrode paste into a preheated mold coated with zinc stearate, and then perform gradient pressure, gradient drying under nitrogen atmosphere and natural cooling to room temperature to obtain modified electrode paste.

[0020] Further, in S1, the mass-to-volume ratio of Ni powder, anhydrous ethanol, and an aqueous ethanol solution containing the first silane coupling agent is (55-65) g : (90-110) mL : (28-32) mL; the volume ratio of ethanol to deionized water in the aqueous ethanol solution containing the first silane coupling agent is 9:1, and the mass fraction of the first silane coupling agent is 0.8wt%-1.2wt%; the flow rate of the H2 / Ar mixed atmosphere is 45-55 mL / min, and the volume ratio of H2 to Ar in the H2 / Ar mixed atmosphere is 5:95; the heating step is: heating to 680-720℃ at 4-6℃ / min and holding for 2.5-3.5h; the flow rate of the Ar atmosphere is 45-55 mL / min; the cooling step is: cooling to 430-470℃ at 1.5-2.5℃ / min and holding for 0.8-1.2h.

[0021] Ni-Co-Fe alloy with silane-modified CNTs is the core catalytic and dispersion stabilizing component of the electrode paste. Ni and Co, as transition metals, possess excellent catalytic activity. Under high-temperature conditions, they can adsorb loosely structured disordered carbon in the carbon matrix, migrating within the alloy particles and epitaxially growing along the ordered lattice, thus transforming disordered carbon into regular graphite crystals and significantly improving the graphitization degree of the carbon matrix. Fe, as a heterogeneous nucleation core for graphite, refines graphite microcrystals, ensuring the uniformity of the graphitization process and optimizing the continuity and conductivity of the conductive network. The silane-modified CNTs form a coating layer. On one hand, the steric hindrance effect of CNTs effectively prevents the agglomeration of alloy particles during preparation and service, ensuring sufficient exposure of catalytic active sites. On the other hand, the porous hybrid silane layer formed by the hydrolysis of the silane coupling agent reduces the carbon migration rate, inhibits excessive carburization, and blocks the erosion of alloy particles by the oxidizing medium, ensuring the long-term stability of the catalytic system and providing core support for the conductivity stability of the electrode paste.

[0022] Further, in step S2, the mass-to-volume ratio of the Fe-Mn alloy powder to anhydrous ethanol is (95-105) g : (45-55) mL; the evaporation and concentration temperature is 55-65℃, and the evaporation and concentration time is 15-25 min; the drying temperature is 75-85℃, and the drying time is 1.5-2.5 h; the nitrogen flow rate is 35-45 mL / min; the gradient heating program is as follows: heating at 1.5-2.5℃ / min to 380-420℃ and holding for 0.8-1.2 h, then at 2.5-3... The temperature is increased to 780-820℃ at a rate of 5℃ / min and held for 1.5-2.5h; the cooling rate is 2.5-3.5℃ / min; the mass-to-volume ratio of tetraethyl orthosilicate to ethanol is (7-9) g: (35-45) mL; the spray drying conditions are: inlet air temperature 160-180℃, outlet air temperature 85-95℃, and feed rate 10-14 mL / min; the argon gas flow rate is 45-55 mL / min; the calcination step is: increasing the temperature to 1400-1440℃ at a rate of 7-9℃ / min and holding for 3-4h.

[0023] Carbon-coated Fe-Mn alloy and TiC@SiC composite particles synergistically construct a dual system for stress buffering and wear resistance enhancement in electrode paste. In the carbon-coated Fe-Mn alloy, the internal high-melting-point Fe-Mn solid solution and low-melting-point Mn-rich region form a natural melting point gradient. When the Mn-rich region undergoes a melting phase transformation at high temperatures, it can absorb a large amount of stress generated by thermal shock, while the Fe-Mn solid solution remains solid to maintain the structural framework, achieving a balance between stress absorption and structural support. The external carbon coating is formed by the carbonization reaction of thermoplastic phenolic resin. The phenolic resin undergoes cross-linking and dehydrogenation reactions at high temperatures, transforming into an amorphous carbon layer with a high degree of graphitization. This carbon layer can be further graphitized under the catalysis of Ni-Co-Fe alloy, forming a continuous transition interface with the carbon matrix of the electrode paste, avoiding interfacial delamination between heterogeneous materials, and significantly improving stress transfer efficiency and thermal shock resistance.

[0024] The core-shell structure of TiC@SiC composite particles synergistically provides wear resistance and thermal shock resistance: the thermal expansion coefficients of the SiC shell and the carbon matrix are highly matched, which can effectively reduce interfacial thermal stress at high temperatures and reduce microcracks caused by thermal expansion mismatch during thermal shock; at the same time, SiC has excellent chemical stability and corrosion resistance, which can block the erosion of TiC core by molten slag and corrosive gases in electric arc furnaces; the TiC core has extremely high wear resistance and impact resistance, which can resist mechanical wear and impact during the installation and service of electrode paste, and extend the service life of electrode paste; a strong Ti-Si-C transition layer is formed between the core and shell through interfacial reaction at high temperature, which prevents the shell from falling off during service and ensures the long-term stability of the synergistic effect of the core-shell structure.

[0025] Further, in step S3, the mass-to-volume ratio of the graphitized petroleum coke to hydrochloric acid is (55-65) g:(180-220) mL; the mass fraction of the hydrochloric acid is 9wt%-11wt%; the temperature of the first drying step is 95-105℃, and the drying time is 1.5-2.5 h; the CO2 activation step is as follows: CO2 with a flow rate of 55-65 mL / min is introduced and activated at 880-920℃ for 2-3 h; the short-cut carbon fibers, nitric acid, and the solution containing the second silane... The mass-to-volume ratio of the coupling agent in the ethanol solution is (14-16) g : (90-110) mL : (28-32) mL; the mass fraction of the nitric acid is 4 wt%-6 wt%; the oxidation temperature is 75-85℃, and the oxidation time is 25-35 min; the second drying temperature is 55-65℃, and the second drying time is 1-2 h; the mass fraction of the second silane coupling agent in the ethanol solution containing the second silane coupling agent is 0.8 wt%-1.2 wt%.

[0026] Composite fillers form the core of the electrode paste's structural framework, constructing a robust and dense support system through the synergistic action of multiple components. Graphitized petroleum coke and electrically calcined anthracite are acid-washed to remove impurities affecting performance. A heterogeneous reaction at high temperature, activated by CO2 (C + CO2 → 2CO), forms numerous micropores and mesopores within the aggregate. Simultaneously, this reaction selectively etches disordered carbon and defects on the aggregate surface, promoting the rearrangement of graphite crystals along the stress direction, optimizing the regularity of the crystal structure, and reducing the resistance to lattice distortion during thermal expansion. Thus, the activated aggregate exhibits low expansion characteristics, achieving a good match with the thermal expansion characteristics of other functional components, further optimizing the thermal shock resistance of the electrode paste.

[0027] After being modified by nitric acid oxidation, short-cut carbon fibers have a large number of active functional groups such as carboxyl and hydroxyl groups introduced on their surface. These functional groups react with the amino groups of KH-550 silane coupling agent. The other end of the silane coupling agent can form chemical bonds with the surface of SiC whiskers and aggregates, so that the carbon fibers and SiC whiskers are firmly bonded together to form an interwoven reinforcing network. With its excellent tensile strength and fracture toughness, the carbon fiber can effectively bridge the micro-cracks in the matrix and prevent the cracks from propagating and penetrating. The SiC whiskers are dispersed in the matrix in a one-dimensional structure and form a spatial interwoven network with the carbon fibers, which significantly improves the mechanical strength and deformation resistance of the electrode paste. Ti powder, as a nanoscale auxiliary component, has a high specific surface area, which enables it to fill the tiny pores between aggregates, carbon fibers, and SiC whiskers. At high temperatures, Ti can undergo interfacial reactions with carbon matrix, SiC, etc., to form transition phases such as TiC and TiSi2. These transition phases can strengthen the interfacial bonding force between components, reduce interfacial porosity and defects, and further improve the structural compactness and overall synergistic effect of the composite filler, providing structural support for the mechanical strength and thermal shock resistance of the electrode paste.

[0028] Further, in step S4, the mass ratio of the medium-temperature coal tar pitch, formaldehyde, and maleic anhydride-grafted polypropylene is (140-160):(2.8-3.2):(4-5); the air flow rate is 15-25 mL / min; the oxidation modification temperature is 220-240℃, and the oxidation modification time is 2.5-3.5 h; the crosslinking modification step is: maintaining a stirring rate of 280-320 r / min, raising the temperature to 120-140℃ and holding the reaction for 1-2 h; the composite modification step is: raising the temperature to 140-160℃, maintaining a stirring rate of 280-320 r / min and stirring for 25-35 min; the preheating temperature is 75-85℃.

[0029] Modified coal tar pitch, as the core binder of electrode paste, achieves synergistic optimization of interfacial bonding strength and high-temperature stability through multi-step modification. First, air oxidation modification is performed: under high-temperature and aerobic conditions, the coal tar pitch molecular chains partially break, generating a large number of small molecular fragments containing polar functional groups such as carboxyl, hydroxyl, and carbonyl groups. These polar functional groups not only enhance the reactivity of the coal tar pitch but also strengthen its interaction with the surface of inorganic fillers. Simultaneously, some molecular chains undergo cross-linking during oxidation, forming a suitable network structure, avoiding the defects of insufficient bonding strength and easy flow at high temperatures inherent in pure coal tar pitch. Formaldehyde, as a cross-linking agent, undergoes a hydroxymethylation reaction with the aldehyde groups on the coal tar pitch molecular chains, generating hydroxymethyl derivatives. Subsequently, hydroxymethyl groups interact with each other or with each other. It undergoes a condensation reaction with the active hydrogen on the coal tar pitch molecular chain to form a stable cross-linked network, which significantly improves the bonding strength, thermal stability, and anti-flow properties of the coal tar pitch, making the binder less prone to softening and deformation during high-temperature service. Maleic anhydride-grafted polypropylene serves as a compatibilizer. The polar groups of maleic anhydride in its molecular structure react with the polar functional groups of coal tar pitch, while the non-polar segments of polypropylene can form a compatible interface with organic components such as polyamic acid. This effectively improves the compatibility between organic binders and inorganic fillers, reduces stress concentration and porosity defects at the interface, and enhances the uniformity and stability of the bonding system.

[0030] Butyl stearate, as a lubricant, allows its long-chain alkyl groups to insert between the coal tar pitch molecular chains, reducing intermolecular forces and significantly improving the processing fluidity of the modified coal tar pitch. This reduces uneven component dispersion caused by excessive viscosity during mixing, and facilitates the binder's full coating and firm bonding of each functional component. Simultaneously, butyl stearate slowly volatilizes during subsequent drying, leaving no residue that could affect the electrode paste's performance. The overall modified coal tar pitch not only achieves tight bonding of components during molding, ensuring the structural integrity and density of the green body, but also gradually graphitizes at high temperatures, forming a stable carbon matrix that synergistically works with other functional components to maintain the structural stability and conductivity of the electrode paste.

[0031] Further, in step S5, the kneading speed is 75-85 r / min, and the kneading time is 25-35 min; the heating and kneading step is: heating to 170-190℃ and kneading at 90-110 r / min for 18-22 min; the mass-to-volume ratio of sodium lignosulfonate to deionized water in the sodium lignosulfonate aqueous solution is (0.15-0.25) g : (4-6) mL; the cooling and kneading step is: cooling to 120-140℃ and kneading at 55-65 r / min for 12-18 min; the coating stearin The preheating temperature of the zinc acid mold is 65-75℃; the gradient pressurization procedure is as follows: maintain pressure at 2.5-3.5MPa for 4-6 minutes, then increase the pressure to 18-22MPa and maintain for 12-18 minutes, and finally increase the pressure to 26-30MPa and maintain for 8-12 minutes; the nitrogen flow rate is 8-12mL / min; the gradient drying procedure is as follows: first maintain at 75-85℃ for 1.5-2.5 hours, then maintain at 95-105℃ for 8-12 hours, then maintain at 120-140℃ for 10-14 hours, and finally maintain at 140-160℃ for 20-28 hours.

[0032] Sodium lignosulfonate, as a dispersant and wetting agent, has hydrophilic and hydrophobic groups in its molecular structure that can interact with the aqueous phase, binder phase, and inorganic filler surface, respectively. On the one hand, it reduces the interfacial tension between components, further improves the wettability of the binder phase to the filler, and avoids local agglomeration. On the other hand, it hinders particle re-aggregation through steric hindrance, improves the dispersion uniformity of the system, and a small amount of water can adjust the viscosity of the kneading system, making it easier to form a uniform and dense paste during subsequent cooling and kneading. Moreover, the water will be completely removed during the subsequent drying process without affecting the performance of the green body.

[0033] Gradient pressure molding is based on the laws of particle rearrangement and densification: the initial low-pressure stage mainly promotes the preliminary rearrangement of particles inside the green body and reduces large pores; the intermediate medium-pressure stage makes the particles closer together and realizes point-to-surface contact between particles; the final high-pressure stage causes the particles to undergo elastic deformation and plastic flow, filling the remaining micropores, while strengthening the interfacial bonding between components, eliminating internal stress concentration, and forming a green body with a dense structure and uniform stress.

[0034] The gradient drying process serves a dual purpose: dehydration and performance curing. The low-temperature stage primarily removes free water and residual solvents from the preform, while slow heating prevents cracking caused by rapid water evaporation. The medium-to-high-temperature stage removes bound water and triggers the thermal imidization reaction of polyamic acid. The carboxyl and imine groups on the polyamic acid molecular chain undergo dehydration and cyclization, gradually transforming into polyimide with an imide ring structure. The resulting cross-linked network exhibits excellent high-temperature resistance, forming the high-temperature framework of the electrode paste. Simultaneously, the modified coal tar pitch undergoes further cross-linking and graphitization during drying, forming a synergistic and stable bonding system with the polyimide. Ultimately, the catalytic, reinforcing, and buffering effects of each functional component are solidified within the dense preform structure, ensuring the electrode paste exhibits excellent thermal shock resistance, electrical conductivity stability, and mechanical strength during high-temperature service.

[0035] Thirdly, this invention discloses the application of a modified electrode paste in the preparation of electrodes for smelting in electric arc furnaces or submerged arc furnaces.

[0036] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0037] This scheme involves coating Ni-Co-Fe alloys with silane-modified CNTs and Fe-Mn alloys with carbon, and preparing TiC@SiC composite particles to obtain a modified electrode paste, achieving a synergistic improvement in thermal shock resistance and electrical conductivity. Using the Ni-Co-Fe alloy as the catalytic core, Ni and Co, with their transition metal catalytic activity at high temperatures, can adsorb loosely structured disordered carbon in the carbon matrix, which then migrates within the alloy particles and epitaxially grows into graphite crystals along the ordered lattice of the alloy. Simultaneously, Fe acts as a heterogeneous nucleation core for graphite, refining the graphite microcrystals and ensuring the uniformity of the graphitization process, thereby improving the graphitization degree and electrical conductivity of the carbon matrix. The silane-modified CNT coating layer, on the one hand, utilizes the steric hindrance effect of CNTs to prevent alloy particle agglomeration; on the other hand, the porous hybrid silane layer formed by the hydrolysis of the silane coupling agent reduces the carbon migration rate, inhibits excessive carburization, and blocks oxidative corrosion, ensuring the long-term stability of the catalytic system. Using an Fe-Mn alloy as a buffer core, coated with a carbon layer formed by the carbonization of phenolic resin, a melting point gradient is formed between the high-melting-point Fe-Mn solid solution and the low-melting-point Mn-rich region. After the Mn-rich region melts, it can absorb a large amount of stress through phase transformation, while the Fe-Mn solid solution remains solid to maintain the structural framework, achieving a balance between energy absorption and support. Furthermore, the outer carbon layer can undergo graphitization under the catalysis of Ni-Co-Fe alloy, forming a strong and tough interface with the carbon matrix through a continuous transition, further enhancing thermal shock resistance. In addition, the SiC shell of the TiC@SiC composite particles can match the thermal expansion of the carbon matrix to reduce interfacial stress and block corrosive media, while the TiC core enhances wear resistance and impact resistance with its high hardness, providing a reliable guarantee for the stable operation of electrode paste under the harsh conditions of submerged arc furnaces. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the preparation method of a modified electrode paste according to the present invention. Detailed Implementation

[0039] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the application will be further described in detail below with reference to embodiments. However, this should not be construed as limiting the scope of this application to the following examples. All other embodiments obtained by those skilled in the art without creative effort without departing from the above-described methodological spirit of this application are within the scope of protection of this application.

[0040] The singular forms “for,” “or,” “a,” “any,” and “described” used in this application are intended to include the plural forms unless the context clearly indicates otherwise. Furthermore, the terms “first” and “second” are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0041] Example 1

[0042] like Figure 1 As shown, a method for preparing a modified electrode paste includes the following steps:

[0043] S1. Weigh 60g of Ni powder with a particle size of 80nm, 20g of Co powder with a particle size of 80nm, 20g of Fe powder with a particle size of 80nm, and 30g of CNTs with a tube diameter of 15nm and a length of 7μm. Add 100mL of anhydrous ethanol and ultrasonically disperse at 40kHz for 15min to prepare a slurry. Add 30 mL of KH-560 silane coupling agent ethanol-water solution to the slurry, wherein the mass fraction of KH-560 silane coupling agent is 1 wt%, and the volume ratio of ethanol to deionized water is 9:1. Continue sonication for 20 min, then transfer to a double planetary ball mill, using agate balls as the grinding medium, with a ball-to-material ratio of 8:1. First, ball mill at 200 r / min for 30 min, then adjust to 280 r / min for 30 min to obtain a mixed slurry. Transfer the mixed slurry directly to a tube furnace, and introduce a H2 / Ar mixed atmosphere at a flow rate of 50 mL / min, wherein the volume ratio of H2 to Ar is 5:95. Gentle reduction is performed by heating to 700℃ at 5℃ / min and holding for 3 h. After reduction, switch to Ar at a flow rate of 50 mL / min, cool to 450℃ at 2℃ / min and hold for 1 h, and allow to cool naturally to room temperature to obtain Ni-Co-Fe alloy@silane modified CNTs.

[0044] S2. Mix 100g of 200-mesh Fe-Mn alloy powder (Fe to Mn mass ratio of 8:2), 10g of thermoplastic phenolic resin powder with a softening point of 90℃, and 0.5g of hexamethylenetetramine at 1000r / min for 10 minutes. Add 50mL of anhydrous ethanol and use a rotary evaporator to mix and concentrate the mixture for 20 minutes in a 60℃ water bath at 60r / min to obtain moist particles. Preliminarily cure the particles in an 80℃ oven for 2 hours. The solidified particles were transferred to a fluidized bed reactor and carbonized under a nitrogen atmosphere with a gradient temperature increase at a flow rate of 40 mL / min: first, the temperature was increased to 400℃ at a rate of 2℃ / min and held for 1 h, then increased to 800℃ at a rate of 3℃ / min and held for 2 h. After carbonization, the temperature was further reduced to room temperature at a rate of 3℃ / min under a nitrogen atmosphere to obtain a carbon-coated Fe-Mn alloy. 30 g of TiC powder with a particle size of 5 μm was weighed and mixed with 8 g of tetraethyl orthosilicate and 2.2 g of thermoplastic phenolic resin. A coating solution consisting of resin and 40 mL of ethanol, wherein the softening point of the thermoplastic phenolic resin is 90 °C, was ultrasonically dispersed for 20 min and spray-dried under the conditions of inlet air temperature of 170 °C, outlet air temperature of 90 °C, and feed rate of 12 mL / min to prepare precursor microspheres. The precursor microspheres were placed in a graphite crucible, placed in a tube furnace, and argon gas with a flow rate of 50 mL / min was introduced. The temperature was increased to 1420 °C at 8 °C / min and calcined for 3.5 h to obtain TiC@SiC composite particles.

[0045] S3. Mix 60g of graphitized petroleum coke with a particle size of 4mm and 40g of electrically calcined anthracite with a particle size of 2mm and a fixed carbon content of ≥95%. Add 200mL of 10wt% hydrochloric acid solution and soak for 3h to remove impurities, stirring once every 30min during the process. Then wash repeatedly with deionized water until pH=7, and dry in an oven at 100℃ for 2h to obtain dried mixed aggregate. Transfer the dried mixed aggregate to a tube furnace and activate it at 900℃ for 2.5h by introducing CO2 at a flow rate of 60mL / min to obtain activated aggregate. Take 15g of short-cut carbon fibers with a diameter of 7μm and a length of 2mm and add 100mL of 5wt% nitric acid solution. Ultrasonically oxidize at 80℃ for 30min, wash with water until pH=7, and dry at 60℃ for 1.5h to obtain dried carbon fibers. Add 30mL of... A KH-550 silane coupling agent ethanol solution, wherein the mass fraction of KH-550 is 1 wt%, was modified by ultrasonication for 20 min. Subsequently, it was mixed with 15 g of SiC whiskers with a diameter of 0.7 μm and a length of 15 μm and stirred for 15 min to obtain a modified carbon fiber-SiC whisker mixture. 84 g of active aggregate, 31 g of TiC@SiC composite particles, 30 g of carbon fiber-SiC whisker mixture, and 0.5 g of Ti powder with a particle size of 50 nm were mixed to obtain a composite filler.

[0046] S4. Place 150g of medium-temperature coal tar pitch with a softening point of 85℃ and a fixed carbon content of ≥80% in a closed reactor. Introduce air at a rate of 20mL / min for oxidation modification. The reaction temperature is 230℃, and the reaction is maintained for 3 hours. After the oxidation reaction is completed, add 3g of formaldehyde as a crosslinking agent. Maintain the stirring rate at 300r / min, raise the temperature to 130℃, and maintain the reaction for 1.5 hours to complete the crosslinking modification. Continue to add 4.5g of maleic anhydride-grafted polypropylene as a compatibilizer to the system. Raise the temperature to 150℃, maintain the stirring rate at 300r / min, and stir for 30 minutes. Allow it to cool naturally to room temperature to obtain modified coal tar pitch. Preheat the modified coal tar pitch to 80℃ and add 0.3g of butyl stearate to it and stir to dissolve it to obtain modified coal tar pitch containing butyl stearate.

[0047] S5. Premix 130g Ni-Co-Fe alloy@silane-modified CNTs, 104g carbon-coated Fe-Mn alloy, and 145g composite filler at 100℃ for 15min. Increase the temperature to 150℃, add 155g modified coal tar pitch containing dissolved butyl stearate, and knead at 80r / min for 30min. Then, directly add 10g polyamic acid powder with a glass transition temperature of 130℃, a solid content ≥90%, and an imidization rate ≤10%. Increase the temperature to 180℃ and knead at 100r / min for 20min. During this period, activate the vacuum system of the kneader twice, each time evacuating to -0.05MPa and maintaining it for 2min to remove low-boiling-point substances and air. Finally, an aqueous solution of sodium lignosulfonate was added, wherein the mass-to-volume ratio of sodium lignosulfonate to deionized water was 0.2 g: 5 mL. The mixture was cooled to 130 °C and kneaded for 15 min at 60 r / min to obtain an electrode paste. The mold was preheated to 70 °C and the inner wall was uniformly coated with zinc stearate release agent. The electrode paste was then uniformly filled into the mold and molded using a gradient pressure process: first, the pressure was maintained at 3 MPa for 5 min, then increased to 20 MPa and maintained for 15 min, and finally increased to 28 MPa and maintained for 10 min to solidify the shape and obtain a green body. Nitrogen gas with a flow rate of 10 mL / min was introduced for gradient drying: first, the body was kept at 80 °C for 2 h, then at 100 °C for 10 h, then at 130 °C for 12 h, and finally at 150 °C for 24 h. The body was then naturally cooled to room temperature to obtain the modified electrode paste.

[0048] Example 2

[0049] like Figure 1 As shown, a method for preparing a modified electrode paste includes the following steps:

[0050] S1. Weigh 55g of Ni powder with a particle size of 50nm, 18g of Co powder with a particle size of 50nm, 18g of Fe powder with a particle size of 50nm, and 28g of CNTs with a tube diameter of 10nm and a length of 5μm. Add 90mL of anhydrous ethanol and ultrasonically disperse at 40kHz for 15min to prepare a slurry. Add 28 mL of KH-560 silane coupling agent ethanol-water solution to the slurry, wherein the mass fraction of KH-560 silane coupling agent is 0.8 wt%, and the volume ratio of ethanol to deionized water is 9:1. Continue sonication for 20 min, then transfer to a double planetary ball mill, using agate balls as the grinding medium, with a ball-to-material ratio of 8:1. First, ball mill at 200 r / min for 30 min, then adjust to 280 r / min for 30 min to obtain a mixed slurry. Transfer the mixed slurry directly to a tube furnace, and introduce a H2 / Ar mixed atmosphere at a flow rate of 45 mL / min, wherein the volume ratio of H2 to Ar is 5:95. Gentle reduction is performed by heating to 680℃ at 4℃ / min and holding at that temperature for 2.5 h. After reduction, switch to Ar at a flow rate of 45 mL / min, cool to 430℃ at 1.5℃ / min and hold at that temperature for 0.8 h, and allow to cool naturally to room temperature to obtain Ni-Co-Fe alloy@silane modified CNTs.

[0051] S2. 95g of 200-mesh Fe-Mn alloy powder (Fe to Mn mass ratio of 8:2), 9g of thermoplastic phenolic resin powder with a softening point of 80℃, and 0.4g of hexamethylenetetramine were dry-mixed at 1000r / min for 10 minutes. 45mL of anhydrous ethanol was added, and the mixture was concentrated while mixing at 55℃ water bath and 60r / min using a rotary evaporator for 15 minutes to obtain moist particles. The particles were then preliminarily cured in an oven at 75℃ for 1.5h. The solidified particles were transferred to a fluidized bed reactor and carbonized under a nitrogen atmosphere with a gradient temperature increase at a flow rate of 35 mL / min: first, the temperature was increased to 380℃ at a rate of 1.5℃ / min and held for 0.8 h, then increased to 780℃ at a rate of 2.5℃ / min and held for 1.5 h. After carbonization, the temperature was further reduced to room temperature at a rate of 2.5℃ / min under a nitrogen atmosphere to obtain a carbon-coated Fe-Mn alloy. 28 g of TiC powder with a particle size of 4 μm was weighed and added to a mixture of 7 g of tetraethyl orthosilicate and 2 g of... A coating solution consisting of thermoplastic phenolic resin and 35 mL of ethanol, wherein the softening point of the thermoplastic phenolic resin is 80℃, was ultrasonically dispersed for 20 min and spray-dried under the conditions of inlet air temperature of 160℃, outlet air temperature of 85℃, and feed rate of 10 mL / min to prepare precursor microspheres. The precursor microspheres were placed in a graphite crucible, placed in a tube furnace, and argon gas with a flow rate of 45 mL / min was introduced. The temperature was increased to 1400℃ at 7℃ / min and calcined for 3 h to obtain TiC@SiC composite particles.

[0052] S3. Mix 55g of graphitized petroleum coke with a particle size of 3mm and 35g of electrically calcined anthracite with a particle size of 1mm and a fixed carbon content of ≥95%. Add 180mL of 9wt% hydrochloric acid solution and soak for 3h to remove impurities, stirring once every 30min during the process. Then wash repeatedly with deionized water until pH=7, and dry in a 95℃ oven for 1.5h to obtain dried mixed aggregate. Transfer the dried mixed aggregate to a tube furnace and activate it at 880℃ for 2h by introducing CO2 at a flow rate of 55mL / min to obtain activated aggregate. Take 14g of aggregate with a diameter of 5μm and a length of 1... Short-cut carbon fibers (mm in diameter) were added to 90 mL of a 4 wt% nitric acid solution and ultrasonically oxidized at 75 °C for 35 min. After washing with water until pH=7, the fibers were dried at 55 °C for 1 h to obtain dried carbon fibers. 28 mL of a KH-550 silane coupling agent ethanol solution (KH-550 mass fraction in the ethanol solution was 0.8 wt%) was added, and the mixture was ultrasonically modified for 20 min. Subsequently, it was mixed with 14 g of SiC whiskers with a diameter of 0.5 μm and a length of 10 μm and stirred for 15 min to obtain a modified carbon fiber-SiC whisker mixture. 80 g of active aggregate, 30 g of TiC@SiC composite particles, 28 g of the carbon fiber-SiC whisker mixture, and 0.4 g of Ti powder with a particle size of 40 nm were mixed to obtain a composite filler.

[0053] S4. Place 140g of medium-temperature coal tar pitch with a softening point of 80℃ and a fixed carbon content of ≥80% in a closed reactor. Introduce air at a rate of 15mL / min for oxidation modification. The reaction temperature is 220℃, and the reaction is maintained at this temperature for 2.5h. After the oxidation reaction is completed, add 2.8g of formaldehyde as a crosslinking agent. Maintain the stirring rate at 280r / min, raise the temperature to 120℃, and maintain the reaction at this temperature for 1h to complete the crosslinking modification. Continue to add 4g of maleic anhydride-grafted polypropylene as a compatibilizer to the system. Raise the temperature to 140℃, maintain the stirring rate at 280r / min, and stir for 25min. Allow it to cool naturally to room temperature to obtain modified coal tar pitch. Preheat the modified coal tar pitch to 75℃ and add 0.25g of butyl stearate to it and stir to dissolve it to obtain modified coal tar pitch containing butyl stearate.

[0054] S5. Premix 119g of Ni-Co-Fe alloy@silane-modified CNTs, 100g of carbon-coated Fe-Mn alloy, and 138g of composite filler at 100℃ for 15min. Increase the temperature to 150℃, add 145g of modified coal tar pitch containing dissolved butyl stearate, and knead at 75r / min for 25min. Then, directly add 9g of polyamic acid powder with a glass transition temperature of 120℃, a solid content ≥90%, and an imidization rate ≤10%. Increase the temperature to 170℃ and knead at 90r / min for 18min. During this process, activate the vacuum system of the kneader twice, each time evacuating to -0.05MPa and maintaining it for 2min to remove low-boiling-point substances and air. Finally, an aqueous solution of sodium lignosulfonate was added, wherein the mass-to-volume ratio of sodium lignosulfonate to deionized water was 0.15 g: 4 mL. The mixture was cooled to 120 °C and kneaded for 12 min at 55 r / min to obtain the electrode paste. The mold was preheated to 65 °C and the inner wall was uniformly coated with zinc stearate release agent. The electrode paste was then uniformly filled into the mold and shaped using a gradient pressure process: first, the pressure was maintained at 2.5 MPa for 6 min, then increased to 18 MPa and maintained for 18 min, and finally increased to 26 MPa and maintained for 12 min to solidify the shape and obtain the green body. Nitrogen gas with a flow rate of 8 mL / min was introduced for gradient drying: first, the temperature was maintained at 75 °C for 2.5 h, then at 95 °C for 12 h, then at 120 °C for 14 h, and finally at 140 °C for 28 h. The mixture was then naturally cooled to room temperature to obtain the modified electrode paste.

[0055] Example 3

[0056] like Figure 1 As shown, a method for preparing a modified electrode paste includes the following steps:

[0057] S1. Weigh 65g of Ni powder with a particle size of 100nm, 22g of Co powder with a particle size of 100nm, 22g of Fe powder with a particle size of 100nm, and 32g of CNTs with a tube diameter of 20nm and a length of 10μm. Add 110mL of anhydrous ethanol and ultrasonically disperse at 40kHz for 15min to prepare a slurry. Add 32 mL of KH-560 silane coupling agent ethanol-water solution to the slurry, wherein the mass fraction of KH-560 silane coupling agent is 1.2 wt%, and the volume ratio of ethanol to deionized water is 9:1. Continue sonication for 20 min, then transfer to a double planetary ball mill, using agate balls as the grinding medium, with a ball-to-material ratio of 8:1. First, ball mill at 200 r / min for 30 min, then adjust to 280 r / min for 30 min to obtain a mixed slurry. Transfer the mixed slurry directly to a tube furnace, and introduce a H2 / Ar mixed atmosphere at a flow rate of 55 mL / min, wherein the volume ratio of H2 to Ar is 5:95. Gentle reduction is performed by heating to 720℃ at 6℃ / min and holding at that temperature for 3.5 h. After reduction, switch to Ar at a flow rate of 55 mL / min, cool to 470℃ at 2.5℃ / min and hold at that temperature for 1.2 h, and allow to cool naturally to room temperature to obtain Ni-Co-Fe alloy@silane modified CNTs.

[0058] S2. Mix 105g of 200-mesh Fe-Mn alloy powder (Fe to Mn mass ratio of 8:2), 11g of thermoplastic phenolic resin powder with a softening point of 100℃, and 0.6g of hexamethylenetetramine at 1000r / min for 10 minutes. Add 55mL of anhydrous ethanol and use a rotary evaporator to mix and concentrate the mixture for 25 minutes in a 65℃ water bath at 60r / min to obtain moist particles. Preliminarily cure the particles in an 85℃ oven for 2.5h. The solidified particles were transferred to a fluidized bed reactor and carbonized under a nitrogen atmosphere with a gradient temperature increase: first, the temperature was increased to 420℃ at a rate of 2.5℃ / min and held for 1.2h, then increased to 820℃ at a rate of 3.5℃ / min and held for 2.5h. After carbonization, the temperature was further reduced to room temperature at a rate of 3.5℃ / min under a nitrogen atmosphere to obtain a carbon-coated Fe-Mn alloy. 32g of TiC powder with a particle size of 6μm was weighed and added to a mixture of 9g of tetraethyl orthosilicate and 2.4... A coating solution consisting of g of thermoplastic phenolic resin and 45 mL of ethanol, wherein the softening point of the thermoplastic phenolic resin is 100℃, was ultrasonically dispersed for 20 min and spray-dried under the conditions of inlet air temperature of 180℃, outlet air temperature of 95℃, and feed rate of 14 mL / min to prepare precursor microspheres. The precursor microspheres were placed in a graphite crucible, placed in a tube furnace, and argon gas with a flow rate of 55 mL / min was introduced. The temperature was increased to 1440℃ at 9℃ / min and calcined for 4 h to obtain TiC@SiC composite particles.

[0059] S3. Mix 65g of graphitized petroleum coke with a particle size of 5mm and 45g of electrically calcined anthracite with a particle size of 3mm and a fixed carbon content of ≥95%. Add 220mL of 11wt% hydrochloric acid solution and soak for 3h to remove impurities, stirring once every 30min during the process. Then wash repeatedly with deionized water until pH=7, and dry in an oven at 105℃ for 2.5h to obtain dried mixed aggregate. Transfer the dried mixed aggregate to a tube furnace and activate it at 920℃ for 3h by introducing CO2 at a flow rate of 65mL / min to obtain activated aggregate. Take 16g of aggregate with a diameter of 10μm and a length of... 3mm short-cut carbon fibers were added to 110mL of a 6wt% nitric acid solution, ultrasonically oxidized at 85℃ for 25min, washed with water until pH=7, and dried at 65℃ for 2h to obtain dried carbon fibers. Then, 32mL of a KH-550 silane coupling agent ethanol solution (KH-550 mass fraction in the ethanol solution was 1.2wt%) was added, and the mixture was ultrasonically modified for 20min. Subsequently, it was mixed with 16g of SiC whiskers with a diameter of 1μm and a length of 20μm and stirred for 15min to obtain a modified carbon fiber-SiC whisker mixture. 90g of active aggregate, 33g of TiC@SiC composite particles, 32g of the carbon fiber-SiC whisker mixture, and 0.6g of Ti powder with a particle size of 60nm were mixed to obtain a composite filler.

[0060] S4. Place 160g of medium-temperature coal tar pitch with a softening point of 90℃ and a fixed carbon content of ≥80% in a sealed reactor. Introduce air at a rate of 25mL / min for oxidation modification. The reaction temperature is 240℃, and the reaction is maintained at this temperature for 3.5h. After the oxidation reaction is completed, add 3.2g of formaldehyde as a crosslinking agent. Maintain the stirring rate at 320r / min, raise the temperature to 140℃, and maintain the reaction at this temperature for 2h to complete the crosslinking modification. Continue to add 5g of maleic anhydride-grafted polypropylene as a compatibilizer to the system. Raise the temperature to 160℃, maintain the stirring rate at 320r / min, and stir for 35min. Allow it to cool naturally to room temperature to obtain modified coal tar pitch. Preheat the modified coal tar pitch to 85℃ and add 0.35g of butyl stearate to it and stir to dissolve it to obtain modified coal tar pitch containing butyl stearate.

[0061] S5. Premix 141g of Ni-Co-Fe alloy@silane-modified CNTs, 110g of carbon-coated Fe-Mn alloy, and 155g of composite filler at 100℃ for 15min. Increase the temperature to 150℃, add 165g of modified coal tar pitch containing dissolved butyl stearate, and knead at 85r / min for 35min. Then, directly add 11g of polyamic acid powder with a glass transition temperature of 140℃, a solid content ≥90%, and an imidization rate ≤10%. Increase the temperature to 190℃ and knead at 110r / min for 22min. During this process, activate the vacuum system of the kneader twice, each time evacuating to -0.05MPa and maintaining it for 2min to remove low-boiling-point substances and air. Finally, an aqueous solution of sodium lignosulfonate was added, wherein the mass-to-volume ratio of sodium lignosulfonate to deionized water was 0.25 g: 6 mL. The mixture was cooled to 140 °C and kneaded for 18 min at 65 r / min to obtain an electrode paste. The mold was preheated to 75 °C and the inner wall was uniformly coated with zinc stearate release agent. The electrode paste was then uniformly filled into the mold and shaped using a gradient pressure process: first, the pressure was maintained at 3.5 MPa for 4 min, then increased to 22 MPa for 12 min, and finally increased to 30 MPa for 8 min to solidify the shape and obtain a green body. Nitrogen gas with a flow rate of 12 mL / min was introduced for gradient drying: first, the temperature was maintained at 85 °C for 1.5 h, then at 105 °C for 8 h, then at 140 °C for 10 h, and finally at 160 °C for 20 h. The mixture was then naturally cooled to room temperature to obtain the modified electrode paste.

[0062] Comparative Example 1

[0063] A modified electrode paste and its preparation method are disclosed. The implementation steps and parameters differ from those in Example 1 except that Ni-Co-Fe alloy@silane modified CNTs are not prepared. The remaining steps and parameters are the same.

[0064] Comparative Example 2

[0065] A modified electrode paste and its preparation method differ from Example 1 in that the medium-temperature coal tar pitch is not modified, but is used directly; the remaining steps and parameters are the same.

[0066] Comparative Example 3

[0067] A modified electrode paste and its preparation method are disclosed. The implementation steps and parameters differ from those in Example 1 except that polyimide is used instead of polyamic acid in the binder system, while the remaining steps and parameters are the same.

[0068] Comparative Example 4

[0069] A modified electrode paste and its preparation method are disclosed. The implementation steps and parameters differ from those in Example 1 except that carbon-coated Fe-Mn alloy and TiC@SiC composite particles are not prepared. The remaining steps and parameters are the same.

[0070] Performance testing:

[0071] Thermal shock resistance: The modified electrode pastes prepared in Examples 1-3 and Comparative Examples 1-4 were processed into cubic samples of 50mm×50mm×50mm, placed in a muffle furnace, heated to 1000℃ at 5℃ / min, held for 30min, and then quickly removed and quenched in 25℃ deionized water to complete one thermal shock cycle. The above cycle was repeated until visible cracks (length ≥5mm) appeared on the sample surface. The number of cycles at this time was recorded, and the results are shown in Table 1.

[0072] Conductivity: First, the modified electrode pastes prepared in Examples 1-3 and Comparative Examples 1-4 were processed into cuboids of 100mm × 20mm × 20mm and tested using the potentiometric probe method. Before testing, the samples were dried in an oven at 110℃ for 2 hours to remove surface moisture. During testing, a constant current I was applied to both ends of the sample, and the voltage drop U was measured between two potentiometric probes with a spacing of L = 50mm in the middle of the sample. The volume resistivity ρ was calculated according to the formula ρ = US / IL (where S is the cross-sectional area of ​​the sample). Each sample was tested 3 times, and the average value was taken. The results are shown in Table 1.

[0073] Bending strength test: The modified electrode pastes prepared in Examples 1-3 and Comparative Examples 1-4 were processed into cuboids of 120mm × 15mm × 15mm and subjected to three-point bending tests using a universal testing machine. The span was set to 100mm and the loading rate to 2mm / min until the specimen broke. The maximum breaking load F was recorded. The bending strength σ was calculated according to the formula σ=3FL / (2bh²) (where L is the span, b is the specimen width, and h is the specimen height). Five specimens were tested in each group, and the average value was taken. The results are shown in Table 1.

[0074] Table 1. Performance test results of the modified electrode pastes prepared in Examples 1-3 and Comparative Examples 1-4

[0075]

[0076] As shown in Table 1, the modified electrode pastes of Examples 1-3 have higher thermal shock resistance cycles and flexural strength than Comparative Examples 1-4, and the volume resistivity of the modified electrode pastes of Examples 1-3 is lower than that of Comparative Examples 1-4. This indicates that the modified electrode pastes of Examples 1-3 have better thermal shock resistance and conductivity stability than Comparative Examples 1-4.

[0077] Comparative Example 1, lacking Ni-Co-Fe alloy@silane-modified CNTs, cannot enhance the graphitization degree of the carbon matrix through the catalytic effect of Ni and Co, resulting in a discontinuous conductive network, which in turn increases resistivity and decreases conductivity. Simultaneously, the loss of the steric hindrance effect of Ni-Co-Fe alloy@silane-modified CNTs makes the remaining components prone to agglomeration, forming structural defects. Bending strength decreases due to impeded stress transmission. More importantly, without uniformly dispersed alloy particles as thermal stress dispersion points, thermal stress cannot be effectively released during thermal shock, and can only be alleviated through crack propagation. Ultimately, thermal shock resistance is significantly weakened, and this structural defect further exacerbates the deterioration of conductivity and strength, creating a vicious cycle.

[0078] Comparative Example 2, where unmodified medium-temperature coal tar pitch was substituted for modified coal tar pitch, showed performance degradation due to insufficient interfacial bonding in the binder system. Modified coal tar pitch, after air oxidation, formaldehyde crosslinking, and maleic anhydride-grafted polypropylene modification, forms a crosslinked network. The maleic anhydride-grafted polypropylene enhances its compatibility with inorganic fillers, enabling it to tightly encapsulate the fillers and form a continuous structure. In contrast, unmodified medium-temperature coal tar pitch lacks a crosslinked network, resulting in weak interfacial bonding with the fillers and a tendency to form interfacial pores. This not only leads to breaks in the conductive network but also reduces flexural strength due to interfacial slippage. Furthermore, the loose interfacial bonding cannot effectively transfer and disperse thermal stress, making the interface prone to peeling and cracking during thermal shock, thus reducing thermal shock resistance.

[0079] In Comparative Example 3, the thermal shock resistance, electrical conductivity, and mechanical strength all significantly deteriorated after polyimide was used instead of polyamic acid. This was due to the failure of the compatibility between the raw material properties and the kneading process. Polyamic acid's glass transition temperature is compatible with the kneading temperature, allowing it to soften and flow during kneading. It fully integrates with modified coal tar pitch to form a continuous and dense binder phase, laying the foundation for a uniform microstructure in the electrode paste. During subsequent gradient drying, polyamic acid gradually undergoes thermal imidization to transform into polyimide, which, with its excellent high-temperature resistance, forms a stable high-temperature skeleton, ensuring the long-term stability of the electrode paste under service conditions. Directly replacing polyamic acid with polyimide violates this design logic because polyimide's glass transition temperature is much higher than the kneading temperature. Under the kneading conditions set in the process, it cannot soften and flow, remaining only as a solid powder. The presence of undispersed particles not only prevents the formation of a continuous binder phase with modified coal tar pitch, but also results in a large number of unevenly dispersed particles and pore defects within the system. These defects not only disrupt the continuity of the conductive network, hindering current transmission, but also make the structure loose and unable to uniformly transmit stress. Under external forces, stress concentration is easily generated. At the same time, pores and undispersed particles themselves are also stress concentration sites during thermal shock. Even small thermal stresses can trigger crack initiation and propagation, ultimately manifesting as increased volume resistivity, decreased flexural strength, and weakened thermal shock resistance. This further confirms that polyamic acid is the key to ensuring the compactness of the electrode paste microstructure and the synergistic stability of its core performance.

[0080] Comparative Example 4, lacking both carbon-coated Fe-Mn alloy and TiC@SiC composite particles, lost the synergistic effect of stress buffering and structural support. The carbon-coated Fe-Mn alloy alleviates thermal stress through the synergistic effect of phase transformation energy absorption in the Mn-rich region and the structural support of the Fe-Mn solid solution, and the carbon coating layer can form a strong and tough interface with the matrix. TiC@SiC, on the other hand, matches thermal expansion through the SiC shell and enhances structural strength through the TiC core; together, they ensure thermal shock resistance and mechanical properties. Without these components, the large amount of thermal stress generated during thermal shock cannot be buffered through phase transformation and acts directly on the carbon matrix, leading to rapid crack propagation and a minimum reduction in thermal shock resistance. Simultaneously, without the reinforcing support, the conductive network becomes discontinuous due to porosity and structural defects, resulting in increased resistivity, and the bending strength also decreases significantly due to the loss of structural integrity. This result confirms the indispensability of the carbon-coated Fe-Mn alloy and TiC@SiC composite particles in the synergistic improvement of thermal shock resistance, conductivity, and strength.

[0081] Comparative Examples 1-4 lacked core functional components such as Ni-Co-Fe alloy@silane-modified CNTs, carbon-coated Fe-Mn alloy, TiC@SiC composite particles, modified coal tar pitch, and polyamic acid. This resulted in the failure of the synergistic effect of "catalytic graphitization-stress buffering-structural reinforcement-bonding molding" among the components. Defects such as porosity, agglomeration, and weak interfacial bonding appeared in the microstructure. Ultimately, this led to a significant reduction in the number of thermal shock cycles, a substantial increase in volume resistivity, and a significant decrease in flexural strength. These combined characteristics resulted in a synergistic deterioration of thermal shock resistance, electrical conductivity, and mechanical strength, which could not meet the stable service requirements of electrode paste under the harsh operating conditions of submerged arc furnaces.

[0082] The above results demonstrate and describe the basic principles and main features of this application, as well as its advantages.

[0083] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A modified electrode paste, characterized in that, The electrode paste comprises Ni-Co-Fe alloy@silane modified carbon nanotubes, carbon-coated Fe-Mn alloy, composite filler, binder, and additives; The Ni-Co-Fe alloy@silane-modified carbon nanotubes are obtained by sintering and reducing Ni powder, Co powder, Fe powder and carbon nanotubes after modification with a first silane coupling agent; The carbon-coated Fe-Mn alloy is obtained by carbonizing Fe-Mn alloy powder, thermoplastic phenolic resin, and hexamethylenetetramine. The composite filler includes active aggregate, TiC@SiC composite particles, modified carbon fiber-SiC whisker mixture, and Ti powder; the active aggregate is obtained by removing impurities from graphitized petroleum coke and electrically calcined anthracite with hydrochloric acid and activating with CO2; the TiC@SiC composite particles are obtained by coating TiC powder with tetraethyl orthosilicate and thermoplastic phenolic resin and then calcining. The modified carbon fiber-SiC whisker mixture is obtained by mixing short-cut carbon fibers with SiC whiskers after nitric acid oxidation and modification with a second silane coupling agent. The binder comprises modified coal tar pitch and polyamic acid; the modified coal tar pitch is obtained by air oxidation, formaldehyde crosslinking and maleic anhydride grafting onto polypropylene of medium-temperature coal tar pitch; The additives include butyl stearate and sodium lignosulfonate.

2. The modified electrode paste according to claim 1, characterized in that, The mass ratio of the Ni-Co-Fe alloy@silane-modified carbon nanotubes, carbon-coated Fe-Mn alloy, composite filler, binder, and additives is (119-141):(100-110):(138-155):(154-176):(0.4-0.6); the mass ratio of Ni powder, Co powder, Fe powder, and carbon nanotubes is (55-65):(18-22):(18-22):(28-32); the mass ratio of Fe-Mn alloy powder, thermoplastic phenolic resin, and hexamethylenetetramine is (95-105):(9-11):(0.4-0.6); the mass ratio of Fe to Mn in the Fe-Mn alloy powder is 8:2; the TiC powder... The mass ratio of tetraethyl orthosilicate to thermoplastic phenolic resin is (28-32):(7-9):(2-2.4); the mass ratio of active aggregate, modified carbon fiber-SiC whisker mixture and Ti powder is (80-90):(28-32):(0.4-0.6); the mass ratio of graphitized petroleum coke and electrically calcined anthracite is (55-65):(35-45); the mass ratio of chopped carbon fiber and SiC whiskers is (14-16):(14-16); the mass ratio of modified coal tar pitch and polyamic acid is (145-165):(9-11); the mass ratio of butyl stearate and sodium lignosulfonate is (0.25-0.35):(0.15-0.25).

3. The modified electrode paste according to claim 1, characterized in that, The particle size of the Ni powder, Co powder, and Fe powder is 50-100 nm; the diameter of the carbon nanotubes is 10-20 nm, and the length is 5-10 μm; the first silane coupling agent is KH-560; the particle size of the Fe-Mn alloy powder is 200 mesh; the softening point of the thermoplastic phenolic resin is 80-100℃; the particle size of the TiC powder is 4-6 μm; the particle size of the Ti powder is 40-60 nm; and the particle size of the graphitized petroleum coke is 3-5 mm. The electrocalcined anthracite has a particle size of 1-3 mm and a fixed carbon content of ≥95%; the chopped carbon fibers have a diameter of 5-10 μm and a length of 1-3 mm; the second silane coupling agent is KH-550; the SiC whiskers have a diameter of 0.5-1 μm and a length of 10-20 μm; the medium-temperature coal tar pitch has a softening point of 80-90℃ and a fixed carbon content of ≥80%; the polyamic acid has a glass transition temperature of 120-140℃, a solid content of ≥90%, and an imidization rate of ≤10%.

4. A method for preparing a modified electrode paste according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Ni powder, Co powder, Fe powder and carbon nanotubes are added to anhydrous ethanol to make a slurry. An ethanol aqueous solution containing the first silane coupling agent is added. The mixture is reduced in an H2 / Ar mixed atmosphere, heated, switched to an Ar atmosphere, cooled, and naturally cooled to room temperature to obtain Ni-Co-Fe alloy@silane modified carbon nanotubes. S2. Fe-Mn alloy powder, thermoplastic phenolic resin and hexamethylenetetramine are mixed, anhydrous ethanol is added and the mixture is evaporated and concentrated to obtain moist particles. The particles are dried, nitrogen gas is introduced, the temperature is gradually increased and then decreased to room temperature to obtain carbon-coated Fe-Mn alloy. Tetraethyl orthosilicate, thermoplastic phenolic resin and ethanol are mixed to obtain a coating solution. TiC powder is added to the coating solution, spray dried, argon gas is introduced and calcined to obtain TiC@SiC composite particles. S3. Graphitized petroleum coke and electrically calcined anthracite are mixed, purified by hydrochloric acid, washed with water, dried for the first time, and activated with CO2 to obtain active aggregate; short-cut carbon fibers are oxidized with nitric acid, washed with water, dried for the second time, and then an ethanol solution containing a second silane coupling agent is added. The mixture is ultrasonicated and SiC whiskers are added to obtain modified carbon fiber-SiC whisker mixture. Active aggregate, TiC@SiC composite particles and Ti powder are added and mixed to obtain composite filler; S4. Medium-temperature coal tar pitch is oxidized by passing air through it, cross-linked by adding formaldehyde, and then composite modified by adding maleic anhydride-grafted polypropylene. It is then naturally cooled to room temperature to obtain modified coal tar pitch. After preheating the modified coal tar pitch, butyl stearate is added to obtain modified coal tar pitch containing butyl stearate. S5. Mix Ni-Co-Fe alloy@silane-modified CNTs, carbon-coated Fe-Mn alloy and composite filler, add modified coal tar pitch containing butyl stearate, knead, add polyamic acid, heat and knead, add sodium lignosulfonate aqueous solution, cool and knead to obtain electrode paste; fill the electrode paste into a preheated mold coated with zinc stearate, and then perform gradient pressure, gradient drying under nitrogen atmosphere and natural cooling to room temperature to obtain modified electrode paste.

5. The method for preparing a modified electrode paste according to claim 4, characterized in that, In step S1, the mass-to-volume ratio of Ni powder, anhydrous ethanol, and an aqueous ethanol solution containing the first silane coupling agent is (55-65) g : (90-110) mL : (28-32) mL; the volume ratio of ethanol to deionized water in the aqueous ethanol solution containing the first silane coupling agent is 9:1, and the mass fraction of the first silane coupling agent is 0.8wt%-1.2wt%; the flow rate of the H2 / Ar mixed atmosphere is 45-55 mL / min, and the volume ratio of H2 to Ar in the H2 / Ar mixed atmosphere is 5:95; the heating step is: heating to 680-720℃ at 4-6℃ / min and holding for 2.5-3.5h; the flow rate of the Ar atmosphere is 45-55 mL / min; the cooling step is: cooling to 430-470℃ at 1.5-2.5℃ / min and holding for 0.8-1.2h.

6. The method for preparing a modified electrode paste according to claim 4, characterized in that, In step S2, the mass-to-volume ratio of the Fe-Mn alloy powder to anhydrous ethanol is (95-105) g : (45-55) mL; the evaporation and concentration temperature is 55-65℃, and the evaporation and concentration time is 15-25 min; the drying temperature is 75-85℃, and the drying time is 1.5-2.5 h; the nitrogen flow rate is 35-45 mL / min; the gradient heating program is as follows: heating at 1.5-2.5℃ / min to 380-420℃ and holding for 0.8-1.2 h, then at 2.5-3.5℃... The temperature is increased to 780-820℃ at a rate of 7-9℃ / min and held for 1.5-2.5h; the cooling rate is 2.5-3.5℃ / min; the mass-to-volume ratio of tetraethyl orthosilicate to ethanol is (7-9) g: (35-45) mL; the spray drying conditions are: inlet air temperature 160-180℃, outlet air temperature 85-95℃, and feed rate 10-14 mL / min; the argon gas flow rate is 45-55 mL / min; the calcination step is: increasing the temperature to 1400-1440℃ at a rate of 7-9℃ / min and holding for 3-4h.

7. The method for preparing a modified electrode paste according to claim 4, characterized in that, In step S3, the mass-to-volume ratio of the graphitized petroleum coke to hydrochloric acid is (55-65) g:(180-220) mL; the mass fraction of the hydrochloric acid is 9wt%-11wt%; the temperature of the first drying step is 95-105℃, and the drying time is 1.5-2.5 h; the CO2 activation step is as follows: CO2 is introduced at a flow rate of 55-65 mL / min and activated at 880-920℃ for 2-3 h; the short-cut carbon fibers, nitric acid, and the second silane are coupled together. The mass-to-volume ratio of the ethanol solution containing the agent is (14-16) g : (90-110) mL : (28-32) mL; the mass fraction of the nitric acid is 4 wt%-6 wt%; the oxidation temperature is 75-85℃, and the oxidation time is 25-35 min; the temperature of the second drying is 55-65℃, and the second drying time is 1-2 h; the mass fraction of the second silane coupling agent in the ethanol solution containing the second silane coupling agent is 0.8 wt%-1.2 wt%.

8. The method for preparing a modified electrode paste according to claim 4, characterized in that, In step S4, the mass ratio of the medium-temperature coal tar pitch, formaldehyde, and maleic anhydride-grafted polypropylene is (140-160):(2.8-3.2):(4-5); the air flow rate is 15-25 mL / min; the oxidation modification temperature is 220-240℃, and the oxidation modification time is 2.5-3.5 h; the crosslinking modification step is: maintaining a stirring rate of 280-320 r / min, raising the temperature to 120-140℃, and holding the reaction for 1-2 h; the composite modification step is: raising the temperature to 140-160℃, maintaining a stirring rate of 280-320 r / min, and stirring for 25-35 min; the preheating temperature is 75-85℃.

9. The method for preparing a modified electrode paste according to claim 4, characterized in that, In step S5, the kneading speed is 75-85 r / min, and the kneading time is 25-35 min; the heating and kneading step is: heating to 170-190℃ and kneading at 90-110 r / min for 18-22 min; the mass-to-volume ratio of sodium lignosulfonate to deionized water in the sodium lignosulfonate aqueous solution is (0.15-0.25) g : (4-6) mL; the cooling and kneading step is: cooling to 120-140℃ and kneading at 55-65 r / min for 12-18 min; the coating of zinc stearate... The mold preheating temperature is 65-75℃; the gradient pressurization procedure is as follows: maintain pressure at 2.5-3.5MPa for 4-6 minutes, then increase the pressure to 18-22MPa and maintain for 12-18 minutes, and finally increase the pressure to 26-30MPa and maintain for 8-12 minutes; the nitrogen flow rate is 8-12mL / min; the gradient drying procedure is as follows: first maintain temperature at 75-85℃ for 1.5-2.5 hours, then maintain temperature at 95-105℃ for 8-12 hours, then maintain temperature at 120-140℃ for 10-14 hours, and finally maintain temperature at 140-160℃ for 20-28 hours.

10. The application of the modified electrode paste according to any one of claims 1-3 in the preparation of electrodes for smelting in electric arc furnaces or submerged arc furnaces.

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