Composite conductive material and preparation method and application thereof

Abstract

The invention provides a composite conductive material and a preparation method and application thereof. The preparation method of the composite conductive material comprises the following steps: 1) carrying out acidification chambering treatment on attapulgite to obtain an attapulgite carrier; and 2) the attapulgite carrier is immersed in a modification solution for a pyrolytic reaction, the composite conductive material is obtained, and the composite conductive material comprises attapulgite and a cobalt-doped carbon nanomaterial loaded on the surface of the attapulgite, wherein the modification solution comprises a Co source, a chelating agent and an organic ligand. According to the method, the electron transmission capacity is enhanced through cobalt doping, meanwhile, agglomeration of the carbon material is inhibited through an attapulgite framework, and the resistivity of the composite conductive material is effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of special materials for electrical equipment, and in particular to a composite conductive material and a preparation method and application thereof. BACKGROUND

[0002] In an ultra / extra-high voltage alternating current transmission system, the operating overvoltage generated at the moment of closing of a circuit breaker can reach 2-3 times the rated voltage, which seriously threatens the safe operation of core equipment such as gas insulated switchgear and transformers. As an important component of a high-voltage circuit breaker, the closing resistor plays an important role in buffering voltage oscillation, weakening overvoltage, and suppressing arc reignition during the breaking process of the circuit breaker, and is one of the core electrical protection elements of ultra / extra-high voltage power transmission and transformation equipment.

[0003] Carbon composite ceramic resistors are widely used as closing resistors because they have inductance-free characteristics, strong anti-pulse ability, good corrosion resistance, and excellent mechanical properties, and can adapt to the operation requirements of power grids in complex environments. However, existing carbon composite ceramic resistors generally have high resistivity and the conductive material is prone to agglomeration, which directly affects the conductive performance of the carbon composite ceramic resistor and the stability and safety of the power grid system.

[0004] Therefore, effectively improving the dispersity of the conductive material and reducing the resistivity of the carbon composite ceramic resistor has become a key to ensuring the stable operation of the power grid system. SUMMARY

[0005] The present application provides a preparation method of a composite conductive material, which achieves the technical effect of improving the dispersity of the composite conductive material.

[0006] The present application also provides a composite conductive material obtained by the above preparation method, which achieves the technical effect of promoting electron transport.

[0007] The present application also provides a carbon composite ceramic resistor material, which includes the above composite conductive material, and achieves the technical effect of reducing the resistivity of the carbon composite ceramic resistor material.

[0008] The present application also provides a preparation method of a carbon composite ceramic resistor material, which is used to prepare the above carbon composite ceramic resistor material.

[0009] The present application also provides a carbon composite ceramic resistor for electrical equipment, which includes the above carbon composite ceramic resistor material or the carbon composite ceramic resistor material obtained by the above preparation method.

[0010] The first aspect of the present application provides a preparation method of a composite conductive material, which includes:

[0011] 1) acidizing and expanding the attapulgite to obtain an attapulgite carrier;

[0012] 2) impregnating the attapulgite carrier in a modified solution to perform a pyrolysis reaction, to obtain the composite conductive material, the composite conductive material comprising attapulgite and cobalt-doped carbon nanomaterials loaded on the surface of the attapulgite; wherein the modified solution comprises a Co source, a chelating agent and an organic ligand.

[0013] The preparation method as described above, wherein the pyrolysis in step 2) is performed under a nitrogen atmosphere, the pyrolysis temperature is 600-800℃, the pyrolysis time is 1-3h, and the flow rate of the nitrogen is 20-80mL / min.

[0014] The preparation method as described above, wherein the acid for acidizing and reaming in step 1) comprises at least one of hydrochloric acid, methanesulfonic acid and fluorosulfonic acid, the concentration of the aqueous solution of the acid is 0.5-1mol / L, and the acidizing time is 1-2h; and / or,

[0015] The Co source in step 2) comprises at least one of cobalt acetate, cobalt nitrate and cobalt chloride, the chelating agent comprises at least one of hydroxyethylidene diphosphonic acid, citric acid and ethylenediaminetetraacetic acid, and the organic ligand comprises at least one of benzimidazole, 2-methylimidazole and 2-ethylimidazole.

[0016] The preparation method as described above, wherein the mass ratio of the attapulgite carrier, the Co source, the chelating agent and the organic ligand is 8-10:2-4:1-2:7-9.

[0017] The second aspect of the present application provides a composite conductive material, which is obtained by the preparation method of the first aspect.

[0018] The material as described above, wherein the composite conductive material comprises a first pore structure, a second pore structure and a third pore structure, the pore size of the first pore structure is 50-80nm, the pore size of the second pore structure is 3-5nm, and the pore size of the third pore structure is 0.6-1nm.

[0019] The third aspect of the present application provides a carbon composite ceramic resistance material, the raw materials of the material comprising a composite conductive material, a ceramic phase raw material, a dispersing agent, a nucleation initiator and a transient liquid phase raw material.

[0020] The material as described above, wherein the ceramic phase raw material comprises alumina, kaolin and crystalline silicon element, the dispersing agent comprises at least one of aminotri(methylene) phosphonic acid, sodium lignosulfonate and sodium sulfosalicylate, the nucleation initiator comprises at least one of ammonium bismuth citrate, zirconyl nitrate and ammonium fluorotitanate, and the transient liquid phase raw material comprises at least one of monohydrate citric acid, boric acid and acetic acid; and / or,

[0021] The mass ratio of the composite conductive material, the ceramic phase raw material, the dispersant, the nucleation initiator, and the transient liquid phase raw material is 4-10:80-90:1-2:1-2:4-8.

[0022] The material as described above, wherein the mass ratio of the alumina, the kaolin, and the crystalline silicon element is 5-6:3.5-4.5:0.5-1.5.

[0023] The material as described above, wherein the carbon composite ceramic resistance material is prepared by a method comprising the following process:

[0024] After mixing the mixture comprising the composite conductive material, the ceramic phase raw material, and the dispersant and the mixed solution comprising the nucleation initiator and the transient liquid phase raw material, the carbon composite ceramic resistance material is obtained by heating at 1-10℃ / min to 250-350℃ under 200-300Mpa and then maintaining for 0.5-4h.

[0025] The fourth aspect of the present application provides a preparation method of a carbon composite ceramic resistance material, comprising:

[0026] After mixing the mixture comprising the composite conductive material, the ceramic phase raw material, and the dispersant and the mixed solution comprising the nucleation initiator and the transient liquid phase raw material, the carbon composite ceramic resistance material is obtained by heating at 1-10℃ / min to 250-350℃ under 200-300Mpa and then maintaining for 0.5-4h.

[0027] The preparation method as described above, wherein the mixture is prepared by a method comprising the following process:

[0028] After wet ball milling the composite conductive material, the ceramic phase raw material, and the dispersant, the mixture is sieved by a 40-60 mesh sieve and dried at 80-120℃ for 4-10h; wherein the ball milling medium is deionized water, the ball-to-material ratio is 2:1, 3:1, or 4:1, the ball milling time is 3-6h, and the ball milling rotation speed is 280-360r / min.

[0029] The preparation method as described above, wherein the mixed solution further comprises deionized water, the mass ratio of the nucleation initiator, the transient liquid phase raw material, and the deionized water is 0.5-1.5:3.5-5.5:13-16, and the addition amount of the mixed solution is 5-15wt% of the mixture.

[0030] The fifth aspect of the present application provides a carbon composite ceramic resistance for electrical equipment, which comprises the carbon composite ceramic resistance material of the third aspect or the carbon composite ceramic resistance material obtained by the preparation method of the fourth aspect.

[0031] The resistance as described above, wherein the electrical equipment uses a carbon composite ceramic resistance with a bulk density of the carbon composite ceramic resistance being greater than or equal to 2.30 g / cm 3 , a compressive strength being greater than or equal to 130 MPa, a resistivity being 325-360 Ω·cm, a temperature coefficient being -0.10--0.05% / ℃, and a voltage coefficient being -7.5--0.5%·cm / kV.

[0032] The composite conductive material of the present application is prepared by acidizing and expanding the attapulgite to obtain an attapulgite carrier, and then immersing the attapulgite carrier in a modified solution to perform a pyrolysis reaction, thereby obtaining the composite conductive material. The composite conductive material comprises attapulgite and cobalt-doped carbon nanomaterials loaded on the surface of the attapulgite. The modified solution comprises a Co source, a chelating agent and an organic ligand, thereby improving the dispersibility of the composite conductive material and promoting electron transmission. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the present application clearer, the following will describe the technical solutions in the embodiments of the present application in a clear and complete manner with reference to the embodiments of the present application. Obviously, the described embodiments are only some, but not all of the embodiments of the present application. Based on the embodiments in the present application, any other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0034] In an ultra-high voltage and extra-high voltage AC power transmission network, the closing operation of a circuit breaker may cause an operating overvoltage with an amplitude of 2-3 times the rated voltage, which poses a serious safety hazard to key equipment such as gas insulated switchgear and power transformers. As a key component of a high-voltage circuit breaker, a closing resistor can effectively alleviate voltage surges, reduce the amplitude of overvoltage, and suppress arc reignition during the breaking process, and thus has become one of the important protective elements for ensuring the safe and stable operation of a power transmission and transformation system.

[0035] The existing closing resistors used in ultra- / extra-high voltage circuit breakers are mostly carbon composite ceramic resistors. Such a resistor is composed of a ceramic matrix and carbon uniformly dispersed in the matrix, has the characteristics of substantially no inductance and strong anti-pulse capability, can effectively absorb and dissipate high pulse energy, and has the advantages of corrosion resistance and good mechanical properties. However, the resistor has problems in practical application, such as agglomeration of conductive materials, high sintering temperature, and high resistivity. Based on this, the inventors believe that activated attapulgite with a hierarchical pore structure loaded with MOF-derived cobalt-doped carbon nanomaterials can be introduced as a composite conductive material. The electronic transmission capability is enhanced by cobalt doping, and the uniform distribution of the conductive network is ensured by using the attapulgite framework to inhibit the agglomeration of carbon materials. In addition, combined with the cold sintering technology, the forming and sintering densification are completed synchronously through the synergistic effect of uniaxial pressure and transient liquid phase, thereby avoiding problems such as carbon oxidation, uncontrolled grain growth, and high energy consumption.

[0036] Based on this, the first aspect of the application provides a preparation method of a composite conductive material, comprising:

[0037] 1) performing acidizing and hole-expanding treatment on the attapulgite to obtain an attapulgite carrier;

[0038] 2) immersing the attapulgite carrier in a modified solution to perform a pyrolysis reaction, to obtain a composite conductive material, the composite conductive material comprising the attapulgite and a cobalt-doped carbon nanomaterial loaded on the surface of the attapulgite; wherein the modified solution comprises a Co source, a chelating agent and an organic ligand.

[0039] The application performs acidizing and hole-expanding treatment on the attapulgite to obtain an attapulgite carrier. The acidizing treatment can destroy the crystal lattice structure of the attapulgite, forming a multi-level pore system, to provide active sites for the subsequent loading of MOF-derived cobalt-doped carbon nanomaterials. The attapulgite carrier is immersed in a modified solution to perform a pyrolysis reaction, to obtain a composite conductive material, the composite conductive material comprising the attapulgite and a cobalt-doped carbon nanomaterial loaded on the surface of the attapulgite, and the modified solution comprising a Co source, a chelating agent and an organic ligand. The MOF precursor is carbonized at high temperature, and the cobalt element is uniformly doped into the carbon skeleton through the coordination of the chelating agent, to form a composite conductive phase with a multi-level pore structure. The skeleton structure of the attapulgite inhibits the agglomeration of the carbon material through physical confinement effect, and the Co-N-C active sites doped with cobalt significantly improve the electronic transmission efficiency, and the synergistic effect of the two reduces the resistivity of the composite conductive material.

[0040] In a specific embodiment, the pyrolysis is performed under a nitrogen atmosphere, the pyrolysis temperature is 600-800℃, the pyrolysis time is 1-3h, and the flow rate of nitrogen is 20-80mL / min. The nitrogen atmosphere prevents oxidation of the carbon material by isolating the oxygen environment, and the flow rate controlled within the range of 20-80mL / min ensures that the volatile substances generated during the pyrolysis process are promptly discharged, avoiding the collapse of the pore structure. The pyrolysis temperature is selected based on thermogravimetric analysis (TGA) data, and this temperature range corresponds to the peak value of the complete decomposition and carbonization reaction of the MOF structure. The pyrolysis time is controlled to ensure that the cobalt element can diffuse into the carbon skeleton to form a uniform doping distribution.

[0041] Further, the acid for acidizing and hole-expanding includes at least one of hydrochloric acid, methanesulfonic acid and fluorosulfonic acid, the concentration of the aqueous solution of the acid is 0.5-1mol / L, and the acidizing time is 1-2h. Hydrochloric acid is a strong inorganic acid that can effectively dissolve impurities such as carbonates in attapulgite and partially erode the silicate skeleton, playing a role in initial hole-expanding and increasing the specific surface area. Exemplarily, when the concentration of the aqueous solution of the acid is 1mol / L and the acidizing time is 2h, the acidizing reaction can proceed sufficiently, thereby exhibiting excellent hole-expanding effect.

[0042] Further, the Co source includes at least one of cobalt acetate, cobalt nitrate, and cobalt chloride, the chelating agent includes at least one of hydroxyethylidene diphosphonic acid, citric acid, and ethylenediaminetetraacetic acid, and the organic ligand includes at least one of benzimidazole, 2-methylimidazole, and 2-ethylimidazole. Exemplarily, cobalt acetate is selected as the Co source, hydroxyethylidene diphosphonic acid is selected as the chelating agent, and benzimidazole is selected as the ligand. Cobalt acetate has good solubility in an alcohol solution, and the chelate formed by cobalt acetate and hydroxyethylidene diphosphonic acid can effectively control the release rate of cobalt ions, avoiding agglomeration of carbon materials caused by excessively high local concentration. Benzimidazole forms a stable MOF structure through coordination with cobalt ions, and the molecular size of benzimidazole is moderate, so that the multi-level pore structure can be reserved after pyrolysis.

[0043] It should be noted that the mass ratio of the attapulgite carrier, the Co source, the chelating agent, and the organic ligand is 8-10:2-4:1-2:7-9. Exemplarily, when the mass ratio of the attapulgite carrier, the Co source, the chelating agent, and the organic ligand is 10:2:1:7, the attapulgite carrier can ensure the stability of the skeleton structure, the Co source and the chelating agent can achieve uniform doping of cobalt elements, and the organic ligand is helpful to form a three-dimensionally cross-linked MOF structure, and the multi-level pore system reserved after pyrolysis increases the specific surface area of the composite conductive material.

[0044] In a specific embodiment, after the acidizing and hole-expanding treatment of step 1), the attapulgite is further washed to neutral and dried, the drying temperature is 60-100°C, and the drying time is 2-8h.

[0045] Further, before the pyrolysis of step 2), the attapulgite carrier impregnated with the modified solution is further dried, the drying temperature is 60-100°C, and the drying time is 2-8h.

[0046] The second aspect of the present application provides a composite conductive material, which is obtained by the preparation method of the first aspect.

[0047] In a specific embodiment, the composite conductive material includes a first pore structure, a second pore structure, and a third pore structure, the pore size of the first pore structure is 50-80nm, the pore size of the second pore structure is 3-5nm, and the pore size of the third pore structure is 0.6-1nm. The formation mechanism of the multi-level pore structure is that the primary pore (50-80nm) generated by the acidizing and hole-expanding treatment serves as a macroscopic conductive channel, the secondary pore (3-5nm) is formed by the pyrolysis of the organic ligand during the MOF-derived carbonization process, and the tertiary pore (0.6-1nm) is generated by the cobalt-doping-induced crystalline growth. The multi-level pore system promotes liquid phase penetration through capillary action, and the Co-N-C active sites form an electron transport network on the pore surface, so that the resistivity of the material is effectively reduced, and the temperature coefficient is controlled within a suitable range.

[0048] The third aspect of the present application provides a carbon composite ceramic resistance material, the raw materials of the material including composite conductive material, ceramic phase raw material, dispersant, nucleation initiator and transient liquid phase raw material. Among them, the dispersant can effectively prevent the agglomeration of conductive nanoparticles in the ceramic slurry, and ensure its high uniform distribution. The transient liquid phase raw material will be temporarily melted to form a liquid phase during sintering, further promoting the rearrangement and densification of conductive particles through capillary force, forming a uniform, complete and stable three-dimensional conductive network. The nucleation initiator can induce the uniform precipitation and growth of the ceramic phase during sintering, refine the grain, and control the final microstructure.

[0049] In a specific embodiment, the ceramic phase raw material includes alumina, kaolin and crystalline silicon element, the dispersant includes at least one of aminotri-methylene phosphonic acid, sodium lignosulfonate and sodium sulfosalicylate, the nucleation initiator includes at least one of ammonium bismuth citrate, zirconyl nitrate and ammonium fluorotitanate, and the transient liquid phase raw material includes at least one of citric acid monohydrate, boric acid and acetic acid. Illustratively, when ammonium bismuth citrate is used as the nucleation initiator and citric acid monohydrate is used as the transient liquid phase raw material, the BiO + The nanoparticles act as seeds, and cooperate with the citric acid monohydrate to induce the nucleation of the ceramic phase at a low temperature of 250-350°C, avoiding the abnormal growth of grains caused by traditional high-temperature sintering.

[0050] Specifically, the mass ratio of the composite conductive material, the ceramic phase raw material, the dispersant, the nucleation initiator and the transient liquid phase raw material is 4-10:80-90:1-2:1-2:4-8. The amount range of the composite conductive material ensures that the conductive phase (cobalt-doped carbon nanomaterial) can form a conductive path that penetrates the ceramic matrix without excessive aggregation. The high proportion of the ceramic phase raw material ensures that the material is essentially ceramic, thereby having the high-temperature stability, arc resistance and mechanical hardness required by resistance materials.

[0051] Further, the mass ratio of the alumina, kaolin and crystalline silicon element is 5-6:3.5-4.5:0.5-1.5. Among them, when the mass ratio of the alumina, kaolin and crystalline silicon element is 5:4:1, the XRD analysis shows that the mullite phase can be formed, which improves the thermal shock stability of the material.

[0052] Based on the further research of the inventor, it is found that the carbon composite ceramic resistance material is prepared by a method including the following process: mixing a mixture including a composite conductive material, a ceramic phase raw material and a dispersant with a mixed solution including a nucleation initiator and a transient liquid phase raw material, and then heating to 250-350°C at 1-10°C / min under a uniaxial pressure of 200-300MPa and keeping for 0.5-4h to obtain the carbon composite ceramic resistance material. The cold sintering process realizes the densification of the material through the uniaxial pressure (200-300MPa) and the dissolution-precipitation mechanism of the transient liquid phase.

[0053] The fourth aspect of the present application provides a preparation method of the carbon composite ceramic resistor material, comprising the following steps:

[0054] After mixing the mixture comprising the composite conductive material, the ceramic phase raw material and the dispersant, and the mixed solution comprising the nucleation initiator and the transient liquid phase raw material, the mixture is heated to 250-350°C at 1-10°C / min under 200-300 MPa, and then is kept for 0.5-4 h, to obtain the carbon composite ceramic resistor material. At the low temperature of 250-350°C, the BiO + The nanocrystalline seeds react with Al 3+ , Si 4+ in the liquid phase to form mullite crystal nuclei, and the grain size of the crystal nuclei in the growth process is significantly lower than that of the grains formed by traditional high-temperature sintering, thereby improving the compressive strength of the material.

[0055] In a specific embodiment, the mixture is prepared by a method comprising the following process: after the composite conductive material, the ceramic phase raw material and the dispersant are mixed by wet ball milling, the mixture is sieved by a 40-60 mesh sieve, and then is dried at 80-120°C for 4-10 h; wherein the ball milling medium is deionized water, the ball-to-material ratio is 2:1, 3:1 or 4:1, the ball milling time is 3-6 h, and the ball milling rotation speed is 280-360 r / min. For example, when the ball milling time is 5 h and the ball milling rotation speed is 300 r / min, the composite conductive material (cobalt-doped carbon nanomaterial) can be effectively dispersed and uniformly embedded between the particles of the ceramic phase raw material by the impact, shearing and grinding effects of the grinding balls.

[0056] In addition, the mixed solution further comprises deionized water, and the mass ratio of the nucleation initiator, the transient liquid phase raw material and the deionized water is 0.5-1.5:3.5-5.5:13-16, and the addition amount of the mixed solution is 5-15 wt% of the mixture. The addition amount of the mixed solution is controlled to be 5-15 wt% of the mixture, which can ensure that the liquid phase penetrates into the interstitial gaps of the particles under the action of pressure, and the particles are rearranged and a dense structure is formed by capillary force.

[0057] The fifth aspect of the present application provides a carbon composite ceramic resistor for electrical equipment, which comprises the carbon composite ceramic resistor material of the third aspect, or the carbon composite ceramic resistor material obtained by the preparation method of the fourth aspect.

[0058] It should be noted that the volume density of the carbon composite ceramic resistor for electrical equipment is ≥2.30 g / cm 3, the compressive strength is greater than or equal to 130 MPa, the resistivity is 325-360 Ω·cm, the temperature coefficient is -0.10 to -0.05% / ℃, and the voltage coefficient is -7.5 to -0.5%·cm / kV. The carbon composite ceramic resistor material is sequentially subjected to mechanical grinding treatment, aluminum electrode spraying, and insulating paint. The mechanical grinding treatment removes surface defects generated during sintering by using a diamond grinding wheel. The aluminum electrode spraying uses a magnetron sputtering process to ensure the interface bonding between the electrode and the material. The thickness of the insulating paint is controlled to be 50-100 μm. The experimental results show that the resistance value fluctuation rate of the resistor is very small after 1000 times of continuous operation under a ±10 kV pulse voltage, which meets the stability requirements of the closing resistor of the ultra / extra-high voltage circuit breaker under the impact load.

[0059] In the following, the present application is further described through specific examples.

[0060] Example 1

[0061] The present embodiment provides a preparation method of a carbon composite ceramic resistor for electrical equipment, comprising the following steps:

[0062] 1) Dip the attapulgite in a 1 mol / L methanesulfonic acid solution for 2 h for acid washing, activation and hole expansion. After the acid washing, the attapulgite is washed with deionized water until the pH value is 7, and then is placed in a vacuum drying oven for drying at 80℃ for 6 h to obtain an activated attapulgite carrier.

[0063] 2) Dip the activated attapulgite carrier in a modified solution comprising cobalt acetate, hydroxyethylidene diphosphonic acid and benzimidazole for stirring and reaction for 2 h (the mass ratio of the attapulgite carrier, cobalt acetate, hydroxyethylidene diphosphonic acid and benzimidazole is 10:2:1:7), filter and then place in a vacuum drying oven for drying at 80℃ for 2 h, and then perform pyrolysis reaction, with nitrogen gas being introduced for atmosphere protection, the nitrogen gas flow rate being 30 mL / min, the pyrolysis temperature being 600℃, and the pyrolysis time being 2 h to obtain a composite conductive material.

[0064] 3) Wet ball mill the composite conductive material, ceramic phase raw material and aminotri (methylenephosphonic acid) for 4 h, with deionized water as the ball milling medium, the ball-to-material ratio being 2:1, and the ball milling speed being 300 r / min. The ceramic phase raw material comprises alumina, kaolin and crystalline silicon element, with the mass ratio being 5:4:1. Then sieve with a 40-mesh sieve and dry at 100℃ for 6 h to granulate and obtain a mixture. Then dissolve bismuth ammonium citrate and citric acid monohydrate in deionized water to obtain a mixed solution. The mass ratio of bismuth ammonium citrate, citric acid monohydrate and deionized water is 1:4:15. The mass ratio of the composite conductive material, ceramic phase raw material, aminotri (methylenephosphonic acid), bismuth ammonium citrate and citric acid monohydrate is 8:86:1:1:4.

[0065] 4) After the mixture is mixed with the mixed solution uniformly, the mixture is filled in a cold sintering mold, the mixed solution is added in an amount of 10wt% of the mixture, a uniaxial pressure of 200MPa is applied, heating is performed to 300℃ at a temperature increasing rate of 5℃ / min and holding is performed for 2h, to obtain a carbon composite ceramic resistance material.

[0066] 5) The carbon composite ceramic resistance material is subjected to mechanical grinding treatment, spraying of an aluminum electrode and insulating paint, to obtain a carbon composite ceramic resistance for electrical equipment.

[0067] Example 2

[0068] 1) Attapulgite is placed in a methanesulfonic acid solution with a concentration of 1mol / L, and is immersed for 2h for acid washing activation and hole expansion. After the acid washed attapulgite is washed with deionized water to a pH value of 7, it is placed in a vacuum drying oven and dried at 80℃ for 6h, to obtain an activated attapulgite carrier.

[0069] 2) The activated attapulgite carrier is immersed in a modified solution including cobalt acetate, hydroxyethylidene diphosphonic acid and benzimidazole, and is stirred for reaction for 2h (the mass ratio of the attapulgite carrier, cobalt acetate, hydroxyethylidene diphosphonic acid and benzimidazole is 10:2:1:7), is filtered and is placed in a vacuum drying oven and dried at 80℃ for 2h, and then is subjected to a pyrolysis reaction, nitrogen is introduced for atmosphere protection, the nitrogen flow rate is 30mL / min, the pyrolysis temperature is 600℃, and the pyrolysis time is 2h, to obtain a composite conductive material.

[0070] 3) The composite conductive material, ceramic phase raw material, and aminotri (methylenephosphonic acid) are subjected to wet ball milling for 4h, the ball milling medium is deionized water, the ball-to-material ratio is 2:1, and the ball milling rotation speed is 300r / min. The ceramic phase raw material includes alumina, kaolin and crystalline silicon element, and the mass ratio is 5:4:1. Then, after being sieved by a 40-mesh sieve, it is dried at 100℃ for 6h, to obtain a mixture. Then, bismuth ammonium citrate and citric acid monohydrate are dissolved in deionized water to obtain a mixed solution. The mass ratio of bismuth ammonium citrate, citric acid monohydrate and deionized water is 1:4:15. The mass ratio of the composite conductive material, ceramic phase raw material, aminotri (methylenephosphonic acid), bismuth ammonium citrate and citric acid monohydrate is 9:86:1:1:4.

[0071] 4) After the mixture is mixed with the mixed solution uniformly, the mixture is filled in a cold sintering mold, the mixed solution is added in an amount of 10wt% of the mixture, a uniaxial pressure of 200MPa is applied, heating is performed to 300℃ at a temperature increasing rate of 5℃ / min and holding is performed for 2h, to obtain a carbon composite ceramic resistance material.

[0072] 5) The carbon composite ceramic resistance material is subjected to mechanical grinding treatment, spraying of an aluminum electrode and insulating paint, to obtain a carbon composite ceramic resistance for electrical equipment.

[0073] Example 3

[0074] 1) Place the attapulgite in a 1 mol / L methanesulfonic acid solution and soak for 2 hours for acid washing, activation and pore expansion. After acid washing, the attapulgite is washed with deionized water until the pH value is 7, and then placed in a vacuum drying oven at 80℃ for 6 hours to obtain an activated attapulgite carrier.

[0075] 2) The activated attapulgite carrier was impregnated in a modified solution containing cobalt acetate, hydroxyethylidene diphosphonic acid and benzimidazole and stirred for 2 hours (the mass ratio of attapulgite carrier, cobalt acetate, hydroxyethylidene diphosphonic acid and benzimidazole was 10:2:1:7). After filtration, it was placed in a vacuum drying oven at 80℃ for 2 hours and then subjected to pyrolysis. Nitrogen gas was introduced for atmosphere protection at a flow rate of 30 mL / min, a pyrolysis temperature of 600℃ and a pyrolysis time of 2 hours to obtain a composite conductive material.

[0076] 3) The composite conductive material, ceramic phase raw material, and aminotrimethylenephosphonic acid were wet-milled for 4 hours using deionized water as the milling medium, with a ball-to-material ratio of 2:1 and a milling speed of 300 r / min. The ceramic phase raw material consisted of alumina, kaolin, and crystalline silicon in a mass ratio of 5:4:1. The mixture was then sieved through a 40-mesh sieve and dried at 100℃ for 6 hours, followed by granulation to obtain a mixture. Bismuth ammonium citrate and citric acid monohydrate were then dissolved in deionized water to obtain a mixed solution. The mass ratio of bismuth ammonium citrate, citric acid monohydrate, and deionized water was 1:4:15. The mass ratio of the composite conductive material, ceramic phase raw material, aminotrimethylenephosphonic acid, bismuth ammonium citrate, and citric acid monohydrate was 8:86:1:1:4.

[0077] 4) After the mixture and the liquid are mixed evenly, the mixture is filled into a cold sintering mold. The amount of liquid added is 10 wt% of the mixture. A uniaxial pressure of 250 MPa is applied, and the mixture is heated to 350 °C at a heating rate of 5 °C / min and held for 2 h to obtain carbon composite ceramic resistance material.

[0078] 5) The carbon composite ceramic resistor material is mechanically ground, coated with aluminum electrodes and insulating varnish to obtain a carbon composite ceramic resistor for electrical equipment.

[0079] Comparative Example 1

[0080] 1) The spherical graphite, ceramic phase raw material, aminotri-methylene phosphonic acid are wet ball milled for 4h, the ball milling medium is deionized water, the ball to material ratio is 2:1, and the ball milling speed is 300r / min. The ceramic phase raw material includes alumina, kaolin and crystalline silicon element, and the mass ratio is 5:4:1. Then, after sieving with a 40-mesh sieve, drying at 100℃ for 6h, and granulation, a mixture is obtained. Then, the bismuth ammonium citrate and citric acid monohydrate are dissolved in deionized water to obtain a mixed solution. The mass ratio of bismuth ammonium citrate, citric acid monohydrate and deionized water is 1:4:15. The mass ratio of spherical graphite, ceramic phase raw material, aminotri-methylene phosphonic acid, bismuth ammonium citrate and citric acid monohydrate is 8:86:1:1:4.

[0081] 2) After the mixture is uniformly mixed with the mixed solution, it is filled in a cold sintering mold, the mixed solution is added in an amount of 10wt% of the mixture, a uniaxial pressure of 200MPa is applied, heated to 300℃ at a heating rate of 5℃ / min and kept for 2h, to obtain a carbon composite ceramic resistance material.

[0082] 3) The carbon composite ceramic resistance material is subjected to mechanical grinding treatment, aluminum electrode spraying and insulating paint to obtain a carbon composite ceramic resistance for electrical equipment.

[0083] Comparative Example 2

[0084] 1) The alumina, kaolin, cristobalite, conductive carbon black, polyvinylpyrrolidone and polyvinyl alcohol are wet ball milled for 4h, the ball milling medium is deionized water, the ball to material ratio is 2:1, and the ball milling speed is 300r / min. The mass ratio of alumina, kaolin, cristobalite, conductive carbon black, polyvinylpyrrolidone and polyvinyl alcohol is 50:35:10:5:1.2:1. Then, after sieving with a 40-mesh sieve, drying at 100℃ for 6h, and granulation, a spherical powder is obtained.

[0085] 2) After the spherical powder is pressed into a shape, high-temperature sintering at 1300℃ for 2h is performed to obtain a carbon composite ceramic resistance material.

[0086] 3) The carbon composite ceramic resistance material is subjected to mechanical grinding treatment, aluminum electrode spraying and insulating paint to obtain a carbon composite ceramic resistance for electrical equipment.

[0087] Test Example 1

[0088] The carbon composite ceramic resistance of the examples and comparative examples is tested, the bulk density is tested according to GB / T25995-2010, the compressive strength is tested according to GB / T8489-2006, the resistivity is calculated by LCR bridge measurement, the temperature coefficient is calculated by LCR bridge combined with electric heating constant temperature blast drying oven measurement, and the voltage coefficient is measured by loading voltage in a lightning reaction reactor, and the results are shown in Table 1.

[0089] Table 1

[0090]

[0091] As can be seen from Table 1, the carbon composite ceramic resistor in Comparative Example 1 uses direct addition of carbon material as the conductive phase, and the bulk density and compressive strength are lower than those of Example 1, and the resistivity is larger, which is because the dispersibility of spherical graphite is poor, and agglomeration is easy to occur, thereby destroying the uniformity of the ceramic structure and the continuity of the conductive network. The carbon composite ceramic resistor in Comparative Example 2 has a preparation process of traditional high-temperature sintering, and the sintering temperature is as high as 1300℃, which is 1000℃ higher than that of Example 1, and the ceramic structure is also prone to agglomeration or segregation, thereby resulting in that the mechanical properties and electrical properties are lower than those of the carbon composite ceramic resistor in Example 1. The carbon composite ceramic resistor obtained by the present application has excellent mechanical properties, the bulk density is ≥2.30 g / cm 3 , the compressive strength is ≥130 MPa, and the electrical properties are also more stable.

[0092] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a composite conductive material, characterized in that, Includes the following steps: 1) Acidification and pore-expanding treatment is performed on attapulgite to obtain an attapulgite carrier; 2) The attapulgite carrier is impregnated in a modified solution and subjected to a pyrolysis reaction to obtain the composite conductive material, wherein the composite conductive material comprises attapulgite and cobalt-doped carbon nanomaterials loaded on the surface of the attapulgite; wherein the modified solution comprises a Co source, a chelating agent and an organic ligand.

2. The preparation method according to claim 1, characterized in that, The pyrolysis described in step 2) is carried out under a nitrogen atmosphere, at a temperature of 600~800℃, for a time of 1~3h, and at a flow rate of 20~80mL / min.

3. The preparation method according to claim 1 or 2, characterized in that, The acid used for acidification and pore expansion in step 1) includes at least one of hydrochloric acid, methanesulfonic acid, and fluorosulfonic acid, wherein the aqueous solution concentration of the acid is 0.5~1 mol / L, and the acidification time is 1~2 h; and / or, The Co source in step 2) includes at least one of cobalt acetate, cobalt nitrate, and cobalt chloride; the chelating agent includes at least one of hydroxyethylidene diphosphonic acid, citric acid, and ethylenediaminetetraacetic acid; and the organic ligand includes at least one of benzimidazole, 2-methylimidazole, and 2-ethylimidazole.

4. The preparation method according to any one of claims 1-3, characterized in that, The mass ratio of the attapulgite carrier, Co source, chelating agent and organic ligand is 8~10:2~4:1~2:7~9.

5. A composite conductive material, characterized in that, It is obtained by the preparation method according to any one of claims 1-4.

6. The material according to claim 5, characterized in that, The composite conductive material includes a first pore structure, a second pore structure, and a third pore structure. The pore size of the first pore structure is 50~80nm, the pore size of the second pore structure is 3~5nm, and the pore size of the third pore structure is 0.6~1nm.

7. A carbon composite ceramic resistive material, characterized in that, The raw materials include composite conductive materials, ceramic phase raw materials, dispersants, nucleation initiators, and transient liquid phase raw materials.

8. The material according to claim 7, characterized in that, The ceramic phase raw material includes alumina, kaolin, and crystalline silicon; the dispersant includes at least one of aminotrimethylenephosphonic acid, sodium lignosulfonate, and sodium sulfosalicylate; the nucleating initiator includes at least one of bismuth ammonium citrate, zirconium oxynitrate, and ammonium fluorotitanate; and the transient liquid phase raw material includes at least one of citric acid monohydrate, boric acid, and acetic acid; and / or, The mass ratio of the composite conductive material, ceramic phase raw material, dispersant, nucleating initiator and transient liquid phase raw material is 4~10:80~90:1~2:1~2:4~8.

9. The material according to claim 8, characterized in that, The mass ratio of alumina, kaolin, and crystalline silicon is 5~6:3.5~4.5:0.5~1.

5.

10. The material according to any one of claims 7-9, characterized in that, The carbon composite ceramic resistive material is prepared by a method including the following process: The mixture comprising the composite conductive material, ceramic phase raw material, and dispersant, and the mixture comprising the nucleating initiator and transient liquid phase raw material are mixed, and then heated to 250-350°C at 1-10°C / min under 200-300 MPa and held at that temperature for 0.5-4 hours to obtain the carbon composite ceramic resistive material.

11. A method for preparing the carbon composite ceramic resistive material according to any one of claims 7-10, characterized in that, Includes the following steps: The carbon composite ceramic resistive material is obtained by mixing a mixture of composite conductive material, ceramic phase raw material, and dispersant with a mixture of nucleating initiator and transient liquid phase raw material, heating the mixture to 250-350°C at 1-10°C / min under 200-300 MPa and holding it at that temperature for 0.5-4 hours.

12. The preparation method according to claim 11, characterized in that, The mixture is prepared by a method comprising the following process: The composite conductive material, ceramic phase raw material, and dispersant are mixed by wet ball milling, sieved through a 40-60 mesh sieve, and dried at 80-120℃ for 4-10 hours. The ball milling medium is deionized water, the ball-to-material ratio is 2:1, 3:1, or 4:1, the ball milling time is 3-6 hours, and the ball milling speed is 280-360 r / min.

13. The preparation method according to claim 11 or 12, characterized in that, The mixture also includes deionized water, and the mass ratio of the nucleating initiator, transient liquid phase raw material and deionized water is 0.5~1.5:3.5~5.5:13~16. The amount of the mixture added is 5~15 wt% of the mixture.

14. A carbon composite ceramic resistor for electrical equipment, characterized in that, This includes the carbon composite ceramic resistive material according to any one of claims 7-10, or the carbon composite ceramic resistive material obtained by the preparation method according to any one of claims 11-13.

15. The resistor according to claim 14, characterized in that, The volume density of the carbon composite ceramic resistor used in the electrical equipment is ≥2.30 g / cm³. 3 The compressive strength is ≥130MPa, the resistivity is 325~360Ω·cm, the temperature coefficient is -0.10~-0.05% / ℃, and the voltage coefficient is -7.5~-0.5%·cm / kV.

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