CN110511001B - Preparation method of graphene conductive alumina ceramic - Google Patents

Abstract

The invention provides a preparation method of graphene conductive alumina ceramic, which improves the strength and toughness of the alumina ceramic by utilizing the physical and chemical stability, unique lamellar structure and excellent conductivity of graphene materials and endows the alumina ceramic with a conductive function; the invention belongs to the field of inorganic functional composite materials, and a preparation method thereof comprises the following steps: (1) dispersing graphene in liquid silicone gel; (2) matching, surface treatment and drying of alumina powder; (3) uniformly mixing the silicon gel dispersed with the graphene and the aluminum oxide powder subjected to matching and surface treatment; (4) molding, hot-molding and vulcanizing the mixed material in the step (3) and finishing the product size; (5) carrying out primary hot-pressing pyrolysis on the formed and vulcanized product in the step (4); (6) sintering the product after the preliminary cracking at high temperature in vacuum to finally obtain the alumina ceramic material product with good compactness, excellent mechanical property and conductive property.

Description

Preparation method of graphene conductive alumina ceramic

Technical Field

The invention provides a preparation method of graphene conductive alumina ceramic, and belongs to the field of composite functional ceramic materials.

Background

Graphene is an excellent new material for gaining the promise in recent years, and is a novel nano material with a hexagonal two-dimensional honeycomb lattice structure formed by single-layer carbon atoms, and the unique microstructure endows the graphene with super-conventional physical and chemical properties, physical characteristics and mechanical properties: the Young modulus reaches 1.0TPa, and the inherent tensile strength is 130 GPa; thermal properties: the thermal conductivity coefficient of the flawless graphene is as high as 5300W/(m.K), and exceeds the high melting point of the existing known material, and researches show that the melting point of the flawless graphene can be as high as 5000K, so that the flawless graphene is not the second choice of the flawless graphene serving as a high-temperature resistant material; electrical properties: ultra-high electron mobility, up to 15000cm, which is hardly affected by temperature²V · s, excellent conductivity and quantum hall effect at room temperature; optical properties: the absorption rate of the single-layer graphene in a wider wavelength range is only 2.3%, the number of layers is increased, the absorption rate of each layer is increased by about 2.3%, and therefore the single-layer or few-layer graphene is in a transparent state; dissolution property: has good solubility in non-polar or weak polar solvent, super hydrophobicity and excellent lipophilicity. Chemical nature, oxidation: can react with active metal; and (3) reducibility: can be oxidized by oxidizing acid at normal temperature and normal pressure to obtain graphene oxide dissolved in water; addition reaction: the graphene may be reacted with H₂Carrying out addition reaction to prepare the graphene with semiconductor property; the other has excellent characteristics such as biocompatibility and high-temperature stability.

The alumina ceramic is made of Al₂O₃Ceramic materials for the main body, commercializedAlumina ceramic YIAl₂O₃The content of the alumina ceramic is usually '99 porcelain', '95 porcelain', '90 porcelain', '85 porcelain' and other varieties, and the alumina ceramic has the greatest advantages that: high hardness (second to diamond), good wear resistance, and small density (3.5-4.0 g/cm)³Compared with most metal materials), excellent insulating property (14-16 MV/m), mature and stable manufacturing process and higher cost performance; the commercial alumina ceramics have wide application and are indispensable.

The conductive ceramic refers to a ceramic material having electron (or hole) conductivity or ion conductivity under certain conditions (temperature, pressure, etc.), and various high-temperature conductive ceramic materials are known: SiC-based, MoSi₂Radicals, ZrO radicals, ThO₂Base, SrCeO₃And the like. One of the complex phase materials is a fluorite fast ion conductor material which is used as a main body, and a certain amount of noble metal such as Ag, Au and the like and electron conductor oxide are added to form a continuous second phase two-phase mixed conductor material in the material. The conductor material is mainly applied to electrode materials, oxygen sensors, oxygen permeable membrane materials and the like of SOFC, the complex phase mixed conductor material requires that the materials have good thermochemistry and mechanical stability under the use condition, and also requires that two phases are chemically inert to each other, but the application development is limited by the difficulty in manufacturing and the high cost of the complex phase mixed conductor material.

Disclosure of Invention

Because of the excellent performance and high cost performance of the traditional alumina ceramic material, in order to widen the application range of the alumina ceramic, the invention aims to solve the problem of endowing the traditional high-insulation alumina ceramic material with conductive performance on the premise of not reducing the performance of the alumina ceramic in other aspects basically, improve the economic value and widen the application range. Therefore, the invention provides a preparation method of graphene conductive alumina ceramic, which relates to a graphene wet dispersion technology, a closest packing and surface treatment technology of spherical inorganic powder materials, a high-temperature sintering technology of ceramic materials and the like, and endows a final product with conductive capability and good mechanical property through the conductivity and physical stability of graphene under a high-temperature condition.

According to the invention, the excellent conductive capability of graphene is utilized, the graphene is dispersed in liquid silicon rubber and then compounded with activated alumina powder, after high-temperature sintering, a small amount of residues of liquid silica gel cracking and graphene are uniformly distributed in the alumina ceramic to become a conductor phase of the ceramic material, and the graphene contains a large amount of freely movable electrons, so that the alumina ceramic has the conductive capability under the conditions of normal pressure and room temperature.

The technical scheme of the invention is as follows: a preparation method of graphene conductive alumina ceramic comprises the following specific steps:

dispersing graphene in liquid silica gel;

step two, carrying out matching treatment, surface treatment and drying treatment on the alumina powder;

step three, uniformly mixing the silica gel dispersed with the graphene in the step one with the alumina powder treated in the step two;

step four, performing molding, hot-pressing vulcanization and product size finishing treatment on the materials mixed in the step three;

step five, preparing the obtained product in the preliminary hot-pressing cracking step four;

and step six, carrying out pressureless high-temperature ceramic sintering on the product subjected to hot-pressing cracking in the step five under a vacuum condition to finally obtain the graphene conductive alumina ceramic material product with excellent mechanical properties and conductive properties.

Further, the graphene in the step one is characterized in that: the powder state is a lamellar structure, the number of layers is less than or equal to 5, and the stacking thickness is less than 10 nm; when the temperature is 25 ℃ and the humidity is 50%, according to the GB/T-245257-^-3Ω·cm。

Further, the liquid silicone gel in the first step is characterized in that: transparent liquid with viscosity of 500-3000 Mpa.s, 1:1 mixing of two components (wherein, the two components refer to the silicon gel which is composed of A and B, the two components are separately placed when not used, when needed, the two components are mixed together according to the proportion of 1:1, and can be vulcanized under certain conditions), the penetration degree is not less than 150mm, and the room temperature operation time is within 10-15 hrs.

Further, the graphene is dispersed in the liquid silica gel in the step one, specifically, graphene powder is added into the liquid silica gel for ultrasonic dispersion for 2-4 hrs at the ultrasonic power of 1KW and the system temperature of less than 30 ℃; wherein: the graphene and the liquid silica gel are prepared from the following components in percentage by mass: graphene: liquid silicone gel 1: 5-12.5.

Further, the alumina powder in the second step is spherical alumina with alpha crystal phase content not less than 99% and grain size distribution range of 0.1-70 um.

Further, the step two of performing the blending treatment, the surface treatment and the drying treatment on the alumina powder body refers to: piling not less than 3 kinds of powder with different grain sizes according to horsfield dense piling theory, mixing with a planetary mixer, spraying silane coupling agent which is dispersed in 98% ethanol solution and does not contain N, P, S element onto the surface of the mixed powder in a spraying mode, and drying at 50-80 ℃.

Preferably, the spherical alumina powders with different types of three particle sizes, four particle sizes and five particle sizes are subjected to stacking and mixing by the horsfield dense stacking theory.

Preferably, two silane coupling agents, namely KH560 and KH570, are used for carrying out surface treatment and drying on the mixed alumina powder.

Further, in the third step, the silica gel dispersed with graphene in the first step and the alumina powder treated in the second step are uniformly mixed according to the proportion of 1: 10-22, wherein the uniform mixing is carried out in a vacuum kneader at the speed of 45-55r/min, the vacuum degree is less than-0.08 MPa, the mixing temperature is less than 50 ℃, and the mixing time is 3-5 hrs.

Preferably, the graphene silica gel and the alumina powder are respectively in the following mass ratio: mixing was carried out at a ratio of 1:10, 1:13, 1:16, 1:19, and 1:22 under the conditions.

Further, the step four of molding and hot-press vulcanizing the mixed materials in the step three refers to: and placing the mixed material in a mold with a certain shape, carrying out mold pressing vulcanization for 2hrs at the temperature of not less than 200 ℃ and under the pressure of not less than 50Mpa, wherein the product size trimming is to remove flash and burr of the vulcanized product or punching with a specific structure shape.

The preferred vulcanization conditions are: 200 deg.C/50 Mpa/2hrs, 225 deg.C/50 MPa/2hrs, 250 deg.C/50 Mpa/2hrs, 200 deg.C/75 MPa/2hrs, 200 deg.C/100 Mpa/2hrs, 225 deg.C/75 Mpa/2hrs, 225 deg.C/100 Mpa/2hrs, 250 deg.C/75 Mpa/2hrs, and 250 deg.C/100 Mpa/2 hrs.

Further, the product prepared in the preliminary hot-pressing cracking step four in the step five is: and (3) placing the product with good size after vulcanization or punching into a hot-pressing sintering furnace, applying pressure of 100-150 Mpa on the surface of the product, keeping the vacuum degree less than-0.08 Mpa, heating to 600 ℃ at the heating rate of 3-5 ℃/min, and carrying out hot-pressing pyrolysis under the condition of keeping the temperature for 3-5 hrs.

Further, the step six of pressureless high-temperature ceramic sintering of the product subjected to the hot-pressing cracking in the step five under the vacuum condition refers to: removing the external pressure of the product cracked in the first step, maintaining the vacuum degree to be less than-0.08 Mpa, selecting the conditions of 1500-1800 ℃ according to different initial formulas to carry out ceramic sintering, and finally obtaining the alumina ceramic materials with different conductive properties.

According to the invention, graphene is well dispersed in liquid silica gel through a high-frequency ultrasonic dispersion process, so that the problems of easy agglomeration and difficult dispersion of graphene are solved, then the liquid silica gel containing graphene and densely-piled activated alumina powder (treated by a silane coupling agent) are uniformly mixed under vacuum strong stirring and mixing to prepare a mixture with plasticity, the graphene is further dispersed in a vulcanized preform through high-temperature mould pressing and vulcanization, and a conductive threshold value is exceeded due to the addition amount of the graphene and the existence of free electrons of the graphene, so that the conductive capability of the vulcanized preform is endowed, and further vacuum high-temperature cracking and vacuum high-temperature sintering are realized, and-H, -CH in the silica gel₃The groups are removed rapidly, and the graphene is hardly involved in the cracking reaction due to the chemical stability, so that the conductivity of the presintered body in the fourth step is maintained, and the high-temperature sintering process in the subsequent fifth step is carried outIn the method, the graphene-silica gel cracking residue-alumina intermolecular recrystallization is carried out, the crystal grains grow, gaps (air holes) and crystal boundaries gradually decrease, the total volume of a blank is shrunk and the density is increased through the transmission of substances, and finally the compact polycrystalline sintered body with a certain microstructure is formed.

The invention has the beneficial effects that:

(1) a small amount of graphene-silicon gel compound is mixed with the densely-piled activated alumina powder to prepare a material with plasticity and conductivity, so that the molding of some special-shaped parts and complex parts becomes simple.

(2) The method for preparing the functional ceramic by pyrolyzing the organic precursor at high temperature breaks through the traditional ceramic preparation process; the defects of multiple working procedures, long time consumption, poor strength of the prefabricated blank and the like of the traditional process are also improved well. Through the steps of high-temperature pressure cracking and high-temperature sintering, the defects of bubbling, cracking, rapid expansion of microcracks, stress concentration and the like in the preparation of ceramics by an organic matter cracking method are overcome, and the doping of graphene and the cracking residual phase of silica gel play a role in strengthening and toughening, so that the sintered alumina ceramic product has excellent performances of high hardness, high strength, super wear resistance and the like.

(3) The dispersion problem of the graphene is greatly improved, the sintered alumina ceramic product has better conductivity by adding a small amount of graphene, and the conductivity of the alumina ceramic product is not influenced in a larger temperature range (such as room temperature-1200 ℃), so that the application range of the alumina ceramic material is widened, and the economic and practical values of the alumina ceramic material are improved.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

For better explanation of the present invention, the following specific examples are incorporated to further describe the preparation method of the graphene conductive alumina ceramic. However, this embodiment is not intended to limit the present invention, and all similar methods and similar variations using the present invention are intended to fall within the scope of the present invention.

Example 1

(1) Dispersion of graphene in liquid silicone gel:

the selection characteristics are as follows: the volume resistivity of the graphene powder is less than or equal to 1.0 x 10 under the pressure of 20-30 MPa according to the GB/T-245721-^-35g of omega cm graphene powder; evenly dividing the silicon gel into two parts, adding the two parts into AB bi-component addition type liquid silicone gel meeting the conditions, namely adding 2.5g of graphene powder into the component A, adding 2.5g of graphene powder into the component B (if the two components are mixed in advance, the two parts are easy to be vulcanized due to local overheating in the ultrasonic treatment process, and the two parts cannot be mixed together before the graphene is completely dispersed because of certain room-temperature operable time for preventing the silicon gel from being vulcanized in advance), then carrying out ultrasonic dispersion on the silicon gel added with the A, B components of the graphene for 2hrs respectively with the ultrasonic power of 1KW, and keeping the temperature of the system to be less than 30 ℃; the preferable control of the mass ratio of the graphene to the two-component silica gel is as follows: graphene two-component silicone gel (component a + component B) 1: 12.5.

(2) Matching, surface treatment and drying of alumina powder:

selecting three alumina powders with different particle diameters meeting the characteristic conditions, stacking according to horsfield dense stacking theory, mixing by using a planetary mixer, spraying KH560 silane coupling agent dispersed in 98% ethanol solution onto the surface of the mixed powder in a spraying mode in the mixing process, and then drying at 50 ℃.

(3) Uniformly mixing the silicon gel dispersed with the graphene with the dried alumina powder subjected to matching and surface treatment:

and (2) mixing the silicon gel containing graphene in the step (1) (the silicon gel containing graphene is formed by dispersing two components of graphene together) and the dried alumina powder which is compounded and subjected to surface treatment in the step (2) according to the mass ratio of 1:10 in a vacuum kneader at the speed of 50r/min, the vacuum degree of-0.08 MPa, the mixing temperature of less than 50 ℃ and the mixing time of 3 hrs.

(4) Hot die pressing, molding, vulcanizing and trimming the size of the product of the mixed material in the step (3):

placing the mixed materials in a mold with a certain shape, and carrying out mold pressing vulcanization for 2hrs at a temperature of not less than 200 ℃ and a pressure of not less than 50Mpa, wherein the preferable vulcanization conditions are as follows: 200 ℃/50Mpa/2 hrs. And then the flash and burr of the vulcanized product are manually removed, or the die cutting and punching of the regular piece, the special-shaped piece and the complex piece are carried out.

(5) And (4) performing primary hot-pressing pyrolysis to form a vulcanized product:

and (3) placing the vulcanized product with good size in a hot-pressing sintering furnace, applying pressure of 100Mpa on the surface of the product, wherein the vacuum degree is less than-0.08 Mpa, heating to 600 ℃ at the heating rate of 3 ℃/min, and preserving heat for 5hrs to carry out primary thermal cracking.

(6) And (3) sintering the product after the initial cracking at high temperature in vacuum, removing the external pressure of the product after the cracking in the step (5), maintaining the vacuum degree to be less than-0.08 Mpa, and selecting the 1500 ℃ condition according to different initial formulas to carry out ceramic sintering, thereby finally obtaining the alumina ceramic material product with good compactness, excellent mechanical property and conductive property. And conducting performance and mechanical performance are tested, and the results are shown in the attached table.

Example 2

(1) Dispersion of graphene in liquid silicone gel:

the selection characteristics are as follows: the volume resistivity of the graphene powder is less than or equal to 1.0 x 10 under the pressure of 20-30 MPa according to the GB/T-245721-^-35g of omega cm graphene powder; evenly dividing the silicon gel into two parts, adding the two parts into AB bi-component addition type liquid silicone gel meeting the conditions, namely adding 2.5g of graphene powder into the component A, adding 2.5g of graphene powder into the component B, then carrying out ultrasonic dispersion on the silicone gel of A, B components added with graphene for 2hrs respectively with the ultrasonic power of 1KW, and keeping the temperature of the system to be less than 30 ℃; the preferable control of the mass ratio of the graphene to the two-component silica gel is as follows: graphene: two-component silicone gel (component a + component B) 1: 12.5.

(2) Matching, surface treatment and drying of alumina powder:

selecting four kinds of alumina powder with different grain diameters meeting the characteristic conditions, stacking according to horsfield dense stacking theory, mixing by using a planetary mixer, spraying KH570 silane coupling agent dispersed in 98% ethanol solution onto the surface of the mixed powder in a spraying mode in the mixing process, and then drying at 80 ℃.

(3) Uniformly mixing the silicon gel dispersed with the graphene with the dried alumina powder subjected to matching and surface treatment:

and (3) mixing the silicon gel containing graphene in the step (1) and the dried alumina powder matched and surface-treated in the step (2) according to the mass ratio of 1:13 in a vacuum kneader at the speed of 50r/min, the vacuum degree of less than-0.08 MPa, the mixing temperature of less than 50 ℃ and the mixing time of 4 hrs.

(4) Hot die pressing, molding, vulcanizing and trimming the size of the product of the mixed material in the step (3):

placing the mixed materials in a mold with a certain shape, and carrying out mold pressing vulcanization for 2hrs at a temperature of not less than 200 ℃ and a pressure of not less than 50Mpa, wherein the preferable vulcanization conditions are as follows: 225 ℃/50MPa/2 hrs. And then the flash and burr of the vulcanized product are manually removed, or the die cutting and punching of the regular piece, the special-shaped piece and the complex piece are carried out.

(5) And (4) performing primary hot-pressing pyrolysis to form a vulcanized product:

and (3) placing the vulcanized product with good size in a hot-pressing sintering furnace, applying pressure of 120Mpa on the surface of the product, raising the temperature to 600 ℃ at the temperature rise rate of 3 ℃/min, and preserving the temperature for 5hrs to carry out primary thermal cracking, wherein the vacuum degree is less than-0.08 Mpa.

(6) And (3) sintering the product after the initial cracking at high temperature in vacuum, removing the external pressure of the product after the cracking in the step (5), maintaining the vacuum degree to be less than-0.08 Mpa, and selecting the 1500 ℃ condition according to different initial formulas to carry out ceramic sintering, thereby finally obtaining the alumina ceramic material product with good compactness, excellent mechanical property and conductive property. And conducting performance and mechanical property test are carried out.

Example 3

(1) Dispersion of graphene in liquid silicone gel:

the selection characteristics are as follows: the volume resistivity of the graphene powder is less than or equal to 1.0 x 10 under the pressure of 20-30 MPa according to the GB/T-245721-^-35g of omega cm graphene powder; evenly dividing the silicon gel into two parts, adding the two parts into AB bi-component addition type liquid silicone gel meeting the conditions, namely adding 2.5g of graphene powder into the component A, adding 2.5g of graphene powder into the component B, then carrying out ultrasonic dispersion on the silicone gel of A, B components added with graphene for 2hrs respectively with the ultrasonic power of 1KW, and keeping the temperature of the system to be less than 30 ℃; the preferable control of the mass ratio of the graphene to the two-component silica gel is as follows: graphene: two-component silicone gel (component a + component B) 1: 12.5.

(2) Matching, surface treatment and drying of alumina powder:

selecting five kinds of alumina powder with different particle diameters meeting the characteristic conditions, stacking according to horsfield dense stacking theory, mixing by using a planetary mixer, spraying KH560 silane coupling agent dispersed in 98% ethanol solution onto the surface of the mixed powder in a spraying mode in the mixing process, and then drying at 50 ℃.

(3) Uniformly mixing the silicon gel dispersed with the graphene with the dried alumina powder subjected to matching and surface treatment:

and (3) mixing the silicon gel containing graphene in the step (1) and the dried alumina powder matched and surface-treated in the step (2) according to the mass ratio of 1:16 in a vacuum kneader at the speed of 50r/min, the vacuum degree of less than-0.08 MPa, the mixing temperature of less than 50 ℃ and the mixing time of 5 hrs.

(4) Hot die pressing, molding, vulcanizing and trimming the size of the product of the mixed material in the step (3):

placing the mixed materials in a mold with a certain shape, and carrying out mold pressing vulcanization for 2hrs at a temperature of not less than 200 ℃ and a pressure of not less than 50Mpa, wherein the preferable vulcanization conditions are as follows: 250 deg.C/50 MPa/2 hrs. And then the flash and burr of the vulcanized product are manually removed, or the die cutting and punching of the regular piece, the special-shaped piece and the complex piece are carried out.

(5) And (4) performing primary hot-pressing pyrolysis to form a vulcanized product:

and (3) placing the vulcanized product with good size in a hot-pressing sintering furnace, applying 150Mpa pressure on the surface of the product, wherein the vacuum degree is less than-0.08 Mpa, heating to 600 ℃ at the heating rate of 4 ℃/min, and preserving heat for 5hrs to carry out primary thermal cracking.

(6) And (3) sintering the product after the initial cracking at high temperature in vacuum, removing the external pressure of the product after the cracking in the step (5), maintaining the vacuum degree to be less than-0.08 Mpa, and performing ceramic sintering at 1600 ℃ according to different initial formulas to finally obtain the alumina ceramic material product with good compactness, excellent mechanical properties and conductive performance. And conducting performance and mechanical property test are carried out.

Example 4

(1) Dispersion of graphene in liquid silicone gel:

the selection characteristics are as follows: the volume resistivity of the graphene powder is less than or equal to 1.0 x 10 under the pressure of 20-30 MPa according to the GB/T-245721-^-35g of omega cm graphene powder; evenly dividing the silicon gel into two parts, adding the two parts into AB bi-component addition type liquid silicone gel meeting the conditions, namely adding 2.5g of graphene powder into the component A, adding 2.5g of graphene powder into the component B, then carrying out ultrasonic dispersion on the silicone gel of A, B components added with graphene for 3hrs respectively with the ultrasonic power of 1KW, and keeping the temperature of the system to be less than 30 ℃; the preferable control of the mass ratio of the graphene to the two-component silica gel is as follows: graphene: two-component silicone gel (component a + component B) 1: 9.

(2) Matching, surface treatment and drying of alumina powder:

selecting three alumina powders with different particle diameters meeting the characteristic conditions, stacking according to horsfield dense stacking theory, mixing by using a planetary mixer, spraying KH560 silane coupling agent dispersed in 98% ethanol solution onto the surface of the mixed powder in a spraying mode in the mixing process, and then drying at 50 ℃.

(3) Uniformly mixing the silicon gel dispersed with the graphene with the dried alumina powder subjected to matching and surface treatment:

and (3) mixing the silicon gel containing graphene in the step (1) and the dried alumina powder matched and surface-treated in the step (2) according to the mass ratio of 1:22 in a vacuum kneader at the speed of 50r/min, the vacuum degree of less than-0.08 MPa, the mixing temperature of less than 50 ℃ and the mixing time of 5 hrs.

(4) Hot die pressing, molding, vulcanizing and trimming the size of the product of the mixed material in the step (3):

placing the mixed materials in a mold with a certain shape, and carrying out mold pressing vulcanization for 2hrs at a temperature of not less than 200 ℃ and a pressure of not less than 50Mpa, wherein the preferable vulcanization conditions are as follows: 200 ℃/75MPa/2 hrs. And then the flash and burr of the vulcanized product are manually removed, or the die cutting and punching of the regular piece, the special-shaped piece and the complex piece are carried out.

(5) And (4) performing primary hot-pressing pyrolysis to form a vulcanized product:

and (3) placing the vulcanized product with good size in a hot-pressing sintering furnace, applying 150Mpa pressure on the surface of the product, wherein the vacuum degree is less than-0.08 Mpa, heating to 600 ℃ at the heating rate of 5 ℃/min, and preserving heat for 3hrs for primary thermal cracking.

(6) And (3) sintering the product after the initial cracking at high temperature in vacuum, removing the external pressure of the product after the cracking in the step (5), maintaining the vacuum degree to be less than-0.08 Mpa, and selecting the condition of 1800 ℃ according to different initial formulas to carry out ceramic sintering, thereby finally obtaining the alumina ceramic material product with good compactness, excellent mechanical property and conductive property. And conducting performance and mechanical property test are carried out.

Example 5

(1) Dispersion of graphene in liquid silicone gel:

the selection characteristics are as follows: the volume resistivity of the graphene powder is less than or equal to 1.0 x 10 under the pressure of 20-30 MPa according to the GB/T-245721-^-35g of omega cm graphene powder; evenly divided into two parts, and added into AB bi-component addition type liquid silicone gel meeting the conditions, namely 2.5g of graphene powder is added into the component A, and the component B is added into the component BAdding 2.5g of graphene powder into the silicon gel, then carrying out ultrasonic dispersion on A, B components of silicon gel added with graphene for 3hrs respectively with 1KW of ultrasonic power, and keeping the temperature of the system less than 30 ℃; the preferable control of the mass ratio of the graphene to the two-component silica gel is as follows: graphene: two-component silicone gel (component a + component B) 1: 9.

(2) Matching, surface treatment and drying of alumina powder:

selecting four kinds of alumina powder with different grain diameters meeting the characteristic conditions, stacking according to horsfield dense stacking theory, mixing by using a planetary mixer, spraying KH570 silane coupling agent dispersed in 98% ethanol solution onto the surface of the mixed powder in a spraying mode in the mixing process, and then drying at 80 ℃.

(3) Uniformly mixing the silicon gel dispersed with the graphene with the dried alumina powder subjected to matching and surface treatment:

and (3) mixing the silicon gel containing graphene in the step (1) and the dried alumina powder matched and surface-treated in the step (2) according to the mass ratio of 1:19 in a vacuum kneader at the speed of 50r/min, the vacuum degree of less than-0.08 MPa, the mixing temperature of less than 50 ℃ and the mixing time of 5 hrs.

(4) Hot die pressing, molding, vulcanizing and trimming the size of the product of the mixed material in the step (3):

placing the mixed materials in a mold with a certain shape, and carrying out mold pressing vulcanization for 2hrs at a temperature of not less than 200 ℃ and a pressure of not less than 50Mpa, wherein the preferable vulcanization conditions are as follows: 200 ℃/100Mpa/2 hrs. And then the flash and burr of the vulcanized product are manually removed, or the die cutting and punching of the regular piece, the special-shaped piece and the complex piece are carried out.

(5) And (4) performing primary hot-pressing pyrolysis to form a vulcanized product:

and (3) placing the vulcanized product with good size in a hot-pressing sintering furnace, applying 150Mpa pressure on the surface of the product, wherein the vacuum degree is less than-0.08 Mpa, heating to 600 ℃ at the heating rate of 5 ℃/min, and preserving heat for 3hrs for primary thermal cracking.

(6) And (3) sintering the product after the initial cracking at high temperature in vacuum, removing the external pressure of the product after the cracking in the step (5), maintaining the vacuum degree to be less than-0.08 Mpa, and selecting 1700 ℃ according to different initial formulas to perform ceramic sintering to finally obtain the alumina ceramic material product with good compactness, excellent mechanical properties and conductive performance. And conducting performance and mechanical property test are carried out.

Example 6

(1) Dispersion of graphene in liquid silicone gel:

the selection characteristics are as follows: the volume resistivity of the graphene powder is less than or equal to 1.0 x 10 under the pressure of 20-30 MPa according to the GB/T-245721-^-35g of omega cm graphene powder; evenly dividing the silicon gel into two parts, adding the two parts into AB bi-component addition type liquid silicone gel meeting the conditions, namely adding 2.5g of graphene powder into the component A, adding 2.5g of graphene powder into the component B, then carrying out ultrasonic dispersion on the silicone gel of A, B components added with graphene for 3hrs respectively with the ultrasonic power of 1KW, and keeping the temperature of the system to be less than 30 ℃; the preferable control of the mass ratio of the graphene to the two-component silica gel is as follows: graphene: two-component silicone gel (component a + component B) 1: 9.

(2) Matching, surface treatment and drying of alumina powder:

selecting five kinds of alumina powder with different particle diameters meeting the characteristic conditions, stacking according to horsfield dense stacking theory, mixing by using a planetary mixer, spraying KH560 silane coupling agent dispersed in 98% ethanol solution onto the surface of the mixed powder in a spraying mode in the mixing process, and then drying at 50 ℃.

(3) Uniformly mixing the silicon gel dispersed with the graphene with the dried alumina powder subjected to matching and surface treatment:

and (3) mixing the silicon gel containing graphene in the step (1) and the dried alumina powder matched and surface-treated in the step (2) according to the mass ratio of 1:10 in a vacuum kneader at the speed of 50r/min, the vacuum degree of less than-0.08 MPa, the mixing temperature of less than 50 ℃ and the mixing time of 4 hrs.

(4) Hot die pressing, molding, vulcanizing and trimming the size of the product of the mixed material in the step (3):

placing the mixed materials in a mold with a certain shape, and carrying out mold pressing vulcanization for 2hrs at a temperature of not less than 200 ℃ and a pressure of not less than 50Mpa, wherein the preferable vulcanization conditions are as follows: 225 deg.C/75 Mpa/2 hrs. And then the flash and burr of the vulcanized product are manually removed, or the die cutting and punching of the regular piece, the special-shaped piece and the complex piece are carried out.

(5) And (4) performing primary hot-pressing pyrolysis to form a vulcanized product:

and (3) placing the vulcanized product with good size in a hot-pressing sintering furnace, applying pressure of 100Mpa on the surface of the product, wherein the vacuum degree is less than-0.08 Mpa, heating to 600 ℃ at the heating rate of 3 ℃/min, and preserving heat for 5hrs to carry out primary thermal cracking.

(6) And (3) sintering the product after the initial cracking at high temperature in vacuum, removing the external pressure of the product after the cracking in the step (5), maintaining the vacuum degree to be less than-0.08 Mpa, and performing ceramic sintering at 1600 ℃ according to different initial formulas to finally obtain the alumina ceramic material product with good compactness, excellent mechanical properties and conductive performance. And conducting performance and mechanical property test are carried out.

Example 7

(1) Dispersion of graphene in liquid silicone gel:

the selection characteristics are as follows: the volume resistivity of the graphene powder is less than or equal to 1.0 x 10 under the pressure of 20-30 MPa according to the GB/T-245721-^-35g of omega cm graphene powder; evenly dividing the silicon gel into two parts, adding the two parts into AB bi-component addition type liquid silicone gel meeting the conditions, namely adding 2.5g of graphene powder into the component A, adding 2.5g of graphene powder into the component B, then carrying out ultrasonic dispersion on the silicone gel of A, B components added with graphene for 4hrs respectively with the ultrasonic power of 1KW, and keeping the temperature of the system to be less than 30 ℃; the preferable control of the mass ratio of the graphene to the two-component silica gel is as follows: graphene: two-component silicone gel (component a + component B) ═ 1: 5.

(2) Matching, surface treatment and drying of alumina powder:

selecting three alumina powders with different particle diameters meeting the characteristic conditions, stacking according to horsfield dense stacking theory, mixing by using a planetary mixer, spraying a KH570 silane coupling agent dispersed in 98% ethanol solution onto the surface of the mixed powder in a spraying mode in the mixing process, and then drying at the temperature of 80 ℃.

(3) Uniformly mixing the silicon gel dispersed with the graphene with the dried alumina powder subjected to matching and surface treatment:

and (3) mixing the silicon gel containing graphene in the step (1) and the dried alumina powder matched and surface-treated in the step (2) according to the mass ratio of 1:10 in a vacuum kneader at the speed of 50r/min, the vacuum degree of less than-0.08 MPa, the mixing temperature of less than 50 ℃ and the mixing time of 3 hrs.

(4) Hot die pressing, molding, vulcanizing and trimming the size of the product of the mixed material in the step (3):

placing the mixed materials in a mold with a certain shape, and carrying out mold pressing vulcanization for 2hrs at a temperature of not less than 200 ℃ and a pressure of not less than 50Mpa, wherein the preferable vulcanization conditions are as follows: 225 deg.C/100 Mpa/2 hrs. And then the flash and burr of the vulcanized product are manually removed, or the die cutting and punching of the regular piece, the special-shaped piece and the complex piece are carried out.

(5) And (4) performing primary hot-pressing pyrolysis to form a vulcanized product:

and (3) placing the vulcanized product with good size in a hot-pressing sintering furnace, applying pressure of 100Mpa on the surface of the product, wherein the vacuum degree is less than-0.08 Mpa, heating to 600 ℃ at the heating rate of 3 ℃/min, and preserving heat for 5hrs to carry out primary thermal cracking.

(6) And (3) sintering the product after the initial cracking at high temperature in vacuum, removing the external pressure of the product after the cracking in the step (5), maintaining the vacuum degree to be less than-0.08 Mpa, and selecting 1700 ℃ according to different initial formulas to perform ceramic sintering to finally obtain the alumina ceramic material product with good compactness, excellent mechanical properties and conductive performance. And conducting performance and mechanical property test are carried out.

Example 8

(1) Dispersion of graphene in liquid silicone gel:

the selection characteristics are as follows: the volume resistivity of the graphene powder is less than or equal to 1.0 x 10 under the pressure of 20-30 MPa according to the GB/T-245721-^-35g of omega cm graphene powder; evenly dividing the silicon gel into two parts, adding the two parts into AB bi-component addition type liquid silicone gel meeting the conditions, namely adding 2.5g of graphene powder into the component A, adding 2.5g of graphene powder into the component B, then carrying out ultrasonic dispersion on the silicone gel of A, B components added with graphene for 4hrs respectively with the ultrasonic power of 1KW, and keeping the temperature of the system to be less than 30 ℃; the preferable control of the mass ratio of the graphene to the two-component silica gel is as follows: graphene: two-component silicone gel (component a + component B) ═ 1: 5.

(2) Matching, surface treatment and drying of alumina powder:

selecting four kinds of alumina powder with different particle diameters meeting the characteristic conditions, stacking according to horsfield dense stacking theory, mixing by using a planetary mixer, spraying KH560 silane coupling agent dispersed in 98% ethanol solution onto the surface of the mixed powder in a spraying mode in the mixing process, and then drying at 50 ℃.

(3) Uniformly mixing the silicon gel dispersed with the graphene with the dried alumina powder subjected to matching and surface treatment:

and (3) mixing the silicon gel containing graphene in the step (1) and the dried alumina powder matched and surface-treated in the step (2) according to the mass ratio of 1:16 in a vacuum kneader at the speed of 50r/min, the vacuum degree of less than-0.08 MPa, the mixing temperature of less than 50 ℃ and the mixing time of 4 hrs.

(4) Hot die pressing, molding, vulcanizing and trimming the size of the product of the mixed material in the step (3):

placing the mixed materials in a mold with a certain shape, and carrying out mold pressing vulcanization for 2hrs at a temperature of not less than 200 ℃ and a pressure of not less than 50Mpa, wherein the preferable vulcanization conditions are as follows: 250 deg.C/75 MPa/2 hrs. And then the flash and burr of the vulcanized product are manually removed, or the die cutting and punching of the regular piece, the special-shaped piece and the complex piece are carried out.

(5) And (4) performing primary hot-pressing pyrolysis to form a vulcanized product:

and (3) placing the product with the intact size after vulcanization in a hot-pressing sintering furnace, applying pressure of 120Mpa on the surface of the product, raising the temperature to 600 ℃ at the temperature rise rate of 4 ℃/min, and preserving the temperature for 4hrs to carry out primary thermal cracking, wherein the vacuum degree is less than-0.08 Mpa.

(6) And (3) sintering the product after the initial cracking at high temperature in vacuum, removing the external pressure of the product after the cracking in the step (5), maintaining the vacuum degree to be less than-0.08 Mpa, and performing ceramic sintering at 1600 ℃ according to different initial formulas to finally obtain the alumina ceramic material product with good compactness, excellent mechanical properties and conductive performance. And conducting performance and mechanical property test are carried out.

Example 9

(1) Dispersion of graphene in liquid silicone gel:

the selection characteristics are as follows: the volume resistivity of the graphene powder is less than or equal to 1.0 x 10 under the pressure of 20-30 MPa according to the GB/T-245721-^-35g of omega cm graphene powder; evenly dividing the silicon gel into two parts, adding the two parts into AB bi-component addition type liquid silicone gel meeting the conditions, namely adding 2.5g of graphene powder into the component A, adding 2.5g of graphene powder into the component B, then carrying out ultrasonic dispersion on the silicone gel of A, B components added with graphene for 4hrs respectively with the ultrasonic power of 1KW, and keeping the temperature of the system to be less than 30 ℃; the preferable control of the mass ratio of the graphene to the two-component silica gel is as follows: graphene: two-component silicone gel (component a + component B) ═ 1: 5.

(2) Matching, surface treatment and drying of alumina powder:

selecting five kinds of alumina powder with different particle diameters meeting the characteristic conditions, stacking according to horsfield dense stacking theory, mixing by using a planetary mixer, spraying KH560 silane coupling agent dispersed in 98% ethanol solution onto the surface of the mixed powder in a spraying mode in the mixing process, and then drying at 50 ℃.

(3) Uniformly mixing the silicon gel dispersed with the graphene with the dried alumina powder subjected to matching and surface treatment:

and (3) mixing the silicon gel containing graphene in the step (1) and the dried alumina powder matched and surface-treated in the step (2) according to the mass ratio of 1:22 in a vacuum kneader at the speed of 50r/min, the vacuum degree of less than-0.08 MPa, the mixing temperature of less than 50 ℃ and the mixing time of 5 hrs.

(4) Hot die pressing, molding, vulcanizing and trimming the size of the product of the mixed material in the step (3):

placing the mixed materials in a mold with a certain shape, and carrying out mold pressing vulcanization for 2hrs at a temperature of not less than 200 ℃ and a pressure of not less than 50Mpa, wherein the preferable vulcanization conditions are as follows: 250 deg.C/100 MPa/2 hrs. And then the flash and burr of the vulcanized product are manually removed, or the die cutting and punching of the regular piece, the special-shaped piece and the complex piece are carried out.

(5) And (4) performing primary hot-pressing pyrolysis to form a vulcanized product:

and (3) placing the vulcanized product with good size in a hot-pressing sintering furnace, applying 150Mpa pressure on the surface of the product, wherein the vacuum degree is less than-0.08 Mpa, heating to 600 ℃ at the heating rate of 5 ℃/min, and preserving heat for 3hrs for primary thermal cracking.

(6) And (3) sintering the product after the initial cracking at high temperature in vacuum, removing the external pressure of the product after the cracking in the step (5), maintaining the vacuum degree to be less than-0.08 Mpa, and selecting the 1500 ℃ condition according to different initial formulas to carry out ceramic sintering, thereby finally obtaining the alumina ceramic material product with good compactness, excellent mechanical property and conductive property. And conducting performance and mechanical property test are carried out.

In the embodiment, the conductivity of the graphene conductive alumina ceramic is measured by surface resistance and volume resistivity, and test data of the surface resistance and the volume resistivity are shown in an attached table; the mechanical properties are tested for flexural strength and fracture toughness, and the test data are shown in the attached table.

The electrical and mechanical properties are shown in the attached table:

in conclusion, the graphene is dispersed in the liquid silicone rubber by utilizing the excellent conductive capability of the graphene, and then is compounded with the activated alumina powder, after high-temperature sintering, a small amount of residues of liquid silicone gel cracking and the graphene are uniformly distributed in the alumina ceramic to become a conductor phase of the ceramic material, and the graphene contains a large amount of freely movable electrons, so that the alumina ceramic has the conductive capability under the conditions of normal pressure and room temperature.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (6)

1. A preparation method of graphene conductive alumina ceramic is characterized by comprising the following steps: the method comprises the following specific steps:

dispersing graphene in liquid silica gel;

step two, carrying out matching treatment, surface treatment and drying treatment on the alumina powder;

step three, uniformly mixing the silica gel dispersed with the graphene in the step one with the alumina powder treated in the step two;

step four, performing molding, hot-pressing vulcanization and product size finishing treatment on the materials mixed in the step three;

the step three of molding and hot-pressing vulcanization of the mixed materials refers to: placing the mixed material in a mold with a certain shape, carrying out mold pressing vulcanization for 2hrs at the temperature of not less than 200 ℃ and under the pressure of not less than 50Mpa, wherein the product size trimming is to remove flash and burr of the vulcanized product or punch the product with a specific structural shape;

step five, preparing the obtained product in the preliminary hot-pressing cracking step four;

the product prepared in the fourth preliminary hot-pressing cracking step is as follows: placing the product with good size after vulcanization or punching in a hot-pressing sintering furnace, applying pressure of 100-150 Mpa on the surface of the product, wherein the vacuum degree is less than-0.08 Mpa, heating to 600 ℃ at the heating rate of 3-5 ℃/min, and carrying out hot-pressing cracking under the condition of heat preservation for 3-5 hrs;

step six, performing pressureless high-temperature ceramic sintering on the product subjected to hot-pressing cracking in the step five under a vacuum condition to finally obtain a graphene conductive alumina ceramic material product;

the non-pressure high-temperature ceramic sintering of the product subjected to the hot-pressing cracking in the fifth step under the vacuum condition is as follows: removing the external pressure of the product cracked in the first step, maintaining the vacuum degree to be less than 0.08Mpa, and selecting the condition of 1500-1800 ℃ to carry out ceramic sintering, and finally obtaining the alumina ceramic material with different conductive properties.

2. The preparation method of the graphene conductive alumina ceramic according to claim 1, wherein the preparation method comprises the following steps: the graphene in the step one requires: the number of layers is less than or equal to 5, and the stacking thickness is less than 10 nm; when the temperature is 25 ℃ and the humidity is 50%, according to the GB/T-245257-^-3Ω·cm。

3. The preparation method of the graphene conductive alumina ceramic according to claim 1, wherein the preparation method comprises the following steps: dispersing the graphene in the liquid silica gel in the first step, specifically adding graphene powder into the liquid silica gel for ultrasonic dispersion for 2-4 hrs at an ultrasonic power of 1KW and a system temperature of less than 30 ℃; wherein: the graphene and the liquid silica gel are prepared from the following components in percentage by mass: graphene: liquid silicone gel = 1: 5-12.5.

4. The preparation method of the graphene conductive alumina ceramic according to claim 1, wherein the preparation method comprises the following steps: the alumina powder in the second step is spherical alumina with alpha crystal phase content not less than 99% and grain size distribution range of 0.1-70 microns.

5. The preparation method of the graphene conductive alumina ceramic according to claim 1, wherein the preparation method comprises the following steps: the step two of performing matching treatment, surface treatment and drying treatment on the alumina powder body refers to: piling not less than 3 kinds of powder with different grain sizes according to horsfield dense piling theory, mixing with a planetary mixer, spraying silane coupling agent which is dispersed in 98% ethanol solution and does not contain N, P, S element onto the surface of the mixed powder in a spraying mode, and drying at 50-80 ℃.

6. The preparation method of the graphene conductive alumina ceramic according to claim 1, wherein the preparation method comprises the following steps: and in the third step, uniformly mixing the silicon gel dispersed with the graphene in the first step with the alumina powder treated in the second step according to the ratio of 1: 10-22, wherein the uniform mixing is carried out in a vacuum kneader at the speed of 45-55r/min under the conditions that the vacuum degree is less than-0.08 MPa, the mixing temperature is less than 50 ℃ and the mixing time is 3-5 hrs.