CN100443223C - Preparation method of in-situ synthesized carbon nanotube/nickel/aluminum reinforced and toughened alumina matrix composite - Google Patents

Abstract

The invention discloses a method for preparing an alumina-based composite material, which belongs to the preparation technology of the alumina-based composite material. The process of the method includes: firstly adding sodium hydroxide or ammonia water dropwise into a solution mixed with nickel nitrate hexahydrate and aluminum powder to react to form Ni(OH) ₂ /Al/Al(OH) ₃ , and then adding the prepared three The metacolloid is dehydrated and calcined to obtain NiO/Al/Al ₂ O ₃ ; then use hydrogen to reduce the obtained NiO/Al/Al ₂ O ₃ to Ni/Al/Al ₂ O ₃ , stop feeding hydrogen, and feed methane and nitrogen to mix CNT/Ni/Al/Al ₂ O ₃ composite powder with controllable carbon nanotube content was obtained by catalytic reaction with gas at a certain temperature for several hours; finally, two methods of powder metallurgy and hot extrusion were used to prepare carbon nanotubes /Ni/Al/Al ₂ O ₃ composites. The advantage of the present invention is that the obtained composite powder can well control the ratio of nickel, aluminum and alumina, and can well solve the dispersion problem of aluminum and carbon nanotubes in the composite material, and the bonding strength of carbon nanotubes and matrix High, forming a network structure, so the comprehensive performance of the composite material has been greatly improved.

Description

Preparation method of in-situ synthesized carbon nanotube/nickel/aluminum reinforced and toughened alumina matrix composite

technical field

The invention relates to a method for preparing an in-situ synthesized carbon nanotube/nickel/aluminum reinforced and toughened alumina-based composite material, which belongs to the preparation technology of the alumina-based composite material.

Background technique

Ceramic materials have the advantages of high strength, high hardness, high temperature resistance, oxidation resistance, good wear resistance at high temperatures, and excellent chemical corrosion resistance. These excellent properties are not available in commonly used metal materials and polymer materials. Therefore, the more are getting more and more attention. However, due to the weakness of the brittleness of the ceramic material itself, it lacks sufficient reliability when used as a structural material. Therefore, improving the brittleness of ceramic materials has become one of the urgent problems to be solved in the field of ceramic materials.

Pure aluminum and nickel metals have good ductility, excellent electrical and thermal conductivity, and other properties, such as magnetism and wave absorption, but their relative hardness is low and their density is relatively high. If we can combine ceramics and metals to play a synergistic effect between the matrix and nanoparticles, we will be able to obtain a very ideal material. Carbon nanotubes (CNTs) have been recognized internationally as a structural material with excellent performance, with high strength and toughness, high elongation, elastic modulus, and excellent wear resistance. Since CNTs is a new type of self-assembled single-molecule material with extremely small scale and excellent mechanical properties, its closed hollow tubular structure has good stability and excellent mechanical properties. It is theoretically estimated that its Young's modulus is as high as 5TPa, which is the same as that of diamond, is about 100 times stronger than steel, but its density is only 1/6 that of steel. It may be the material with the highest specific strength and specific stiffness at present. Carbon nanotubes also have physical properties such as excellent thermal conductivity and electrical properties. Therefore, carbon nanotubes are considered to be the most ideal nanowhisker toughening material and the ultimate form of fiber-like reinforcement phase.

However, the dispersion of carbon nanotubes in composite materials, the infiltration and tight bonding between carbon nanotubes and the matrix, and the maintenance of the intact structure of carbon nanotubes are difficult problems in the development of this type of composite materials. At present, the main methods used in the application of carbon nanotubes in ceramic matrix composites are in-situ generation method, heterocoagulation method and mechanical ball milling method. The in-situ generation method is to directly generate carbon nanotubes in the ceramic matrix to obtain carbon nanotube-ceramic matrix composites. This method can make the carbon nanotubes better dispersed in the matrix, but the combination between the carbon nanotubes and the matrix The strength is not high. The heterocoagulation method disperses the matrix phase and the reinforcing phase in different electrolytes, and properly adjusts the medium of the dispersed phase solution, that is, the pH value of the medium, the electrolyte concentration and the ratio of the number of the two particles, so that the two-phase particles With opposite charges, through electrostatic adsorption, the two phases are well combined, and the electrolyte is electrically neutral, so that the flocculation phenomenon occurs. This method can only improve the dispersion of carbon nanotubes in the matrix to a certain extent, but cannot better solve the problem of carbon nanotubes dispersion. The mechanical ball milling method [3] is to mix ceramic powder and dispersed carbon nanotubes, and ball mill them in a ball milling medium (ethanol). The process of this method is relatively simple, but it is difficult to solve the problem of the dispersion of carbon nanotubes in the alumina matrix composite material and the infiltration between the matrix and the matrix.

At present, the preparation techniques of metal and ceramic matrix composites mainly include mechanical mixing and dispersion method, sol-gel method, microemulsion and reverse micelle method. The mechanical mixing and dispersing method is to mix nano-powder into matrix powder for mixing, ball milling, forming, and sintering to obtain nano-composite ceramics. The preparation process of this method is simple, but the disadvantage is that the ball milling itself cannot completely destroy the agglomeration between nanoparticles, and cannot achieve uniform dispersion of the two-phase composition. The sol-gel method is to hydrolyze the metal organic alkoxide or inorganic salt solution, polymerize the solute into a sol and then solidify the gel, dry at low temperature, and then calcined to obtain nanoparticles. This process has unique advantages in the preparation of ceramic matrix composites, especially metal-ceramics: Compared with traditional powder mixing methods, the dispersion between metal and ceramic phases is higher, which is more conducive to enhancing toughness and ductility. The microemulsion and reverse micelle method use two mutually incompatible solvents (organic solvent and aqueous solution). By selecting surfactants and controlling the relative content, the size of the water phase droplets can be controlled at the nanometer level. Emulsion droplets collide with each other to exchange substances, and chemical reactions occur in water. Each water-phase micro-region is equivalent to a "micro-reactor" to limit the size of product particles to obtain nanoparticles. Appropriate surfactants can be adsorbed on the surface of nanoparticles to stabilize and protect the generated particles, prevent further growth of the particles, and modify the surface of the particles. The shape of the water-phase domain can also be controlled by selecting the surfactant, so that nanoparticles of different shapes can be obtained.

Contents of the invention

The invention aims to provide a method for preparing an in-situ synthesized carbon nanotube/nickel/aluminum reinforced and toughened alumina-based composite material. The method can make the content of aluminum and carbon nanotubes in the composite material controllable and uniformly dispersed, and meanwhile, the carbon tubes and the matrix have good infiltration and high bonding strength.

The present invention is achieved through the following technical scheme, a method for preparing in-situ synthesized carbon nanotube/nickel/aluminum reinforced and toughened alumina-based composite material, which is characterized in that it includes the following process:

1, Ni/Al/Al ₂ O The preparation of catalyzer: nickel nitrate hexahydrate (commercially available product, purity > 96%) and _aluminum powder (commercially available product, 400 orders) are 0.127: 1-1.24 with mass ratio: 1 Add to 1L deionized water, then add 0.01-1mol/L sodium hydroxide or ammonia water with a mass concentration of 36% to the above solution dropwise under the condition of stirring with a magnetic stirrer until the pH value of the solution is 7-12 , the reaction produces Ni(OH) 2 /Al/Al(OH) ₃ with a mass ratio of Ni element to Al element of 0.025:1-0.25:1, and a mass ratio of Al to Al(OH) ₃ of 0.01:1-0.654 _:1 Ternary colloid, then dehydrate the ternary colloid at 150-300°C and 150-350mL/min nitrogen atmosphere for 2-4 hours, then calcined at 350-500°C for 2-4 hours, the furnace heating rate is 8°C/ min to obtain NiO/Al/Al ₂ O ₃ catalyst precursor powder.

2. Preparation of carbon nanotube/Ni/Al/Al ₂ O ₃ composite powder by chemical vapor deposition (Chemical Vapor Deposition, CVD): Take the NiO/Al/Al ₂ O ₃ catalyst precursor powder obtained in step 1 and spread it in a quartz boat , and place the quartz boat in the constant temperature zone in the middle of the quartz reaction tube. First, nitrogen is introduced into the reaction tube to remove the air. ₂ gas for 1.5-4 hours, reduce the precursor NiO/Al/Al ₂ O ₃ to the catalyst Ni/Al/Al ₂ O ₃ , stop feeding hydrogen, and then feed 420-780mL/min methane and nitrogen mixed gas (V _N2 :V _CH4 =6:1-12:1), react at 500-650°C for 0.1-4 hours, stop feeding the mixed gas, and lower the furnace temperature to room temperature 20-25°C under a nitrogen atmosphere of 5-75mL/min °C to obtain a carbon nanotube/Ni/Al/Al ₂ O ₃ composite powder with a carbon nanotube content of 0.1-50%.

3. Prepare carbon nanotube/Ni/Al/Al ₂ O ₃ composite materials by powder metallurgy and hot extrusion respectively:

(1) Powder metallurgy method: first press the composite powder obtained in step 2 into a block at room temperature 20-25°C at 350-1200MPa, the holding time is 30 seconds-2 minutes, and then place the block in a vacuum (0.001-10KPa ) sintering at 1000-1350°C for 0.5-6 hours in a sintering furnace, and then repress the block, the repressing pressure is 1250-2000MPa, and the holding time is 0.25-2 minutes, that is, carbon nanotube/aluminum/nickel raw Reinforced and toughened alumina matrix composites.

(2) Hot extrusion method: first put the composite powder obtained in step 2 into a mold, then press the composite powder into a block at 500-1000°C at 100-1000MPa, and hold the pressure for 2-12 hours to obtain carbon Nanotube/Al/Ni in situ reinforced and toughened alumina matrix composites.

The invention has the advantages that the obtained composite powder can well control the ratio of nickel, aluminum and alumina, and can well solve the dispersion problem of aluminum and carbon nanotubes in the composite material, and the carbon nanotubes in the composite powder are not Agglomeration and dispersion can have a nano-size effect, and the carbon nanotubes and the matrix have a high bonding strength to form a network structure. Therefore, carbon nanotubes and aluminum can effectively strengthen and toughen the alumina-based composite material, making the hardness of the composite material, The comprehensive properties such as strength, toughness and electrical properties have been greatly improved.

Description of drawings

Figure 1: Transmission electron micrograph of carbon nanotube/Ni/Al/Al ₂ O ₃ composite powder prepared by the method of Example 1 of the present invention.

Detailed ways

Example 1:

Add 2.49 grams of nickel nitrate hexahydrate and 19.6 grams of aluminum powder into deionized water, then add 0.1 mol/L sodium hydroxide solution dropwise to the above solution until the pH value of the solution is is 7, the reaction generates Ni(OH) ₂ /Al/Al(OH) ₃ ternary colloid with a mass ratio of Ni element to Al element of 0.025:1, and a mass ratio of Al to Al(OH) ₃ of 0.01:1, and then The prepared ternary colloid was dehydrated at 240°C and 350mL/min nitrogen atmosphere for 2 hours, calcined at 350°C for 2 hours, and the heating rate of the furnace was 8°C/min, so as to obtain the NiO/Al/Al ₂ O ₃ catalyst precursor; The obtained NiO/Al/Al ₂ O ₃ was spread in a quartz boat, and the quartz boat was placed in the constant temperature zone in the middle of the quartz reaction tube. First, nitrogen was introduced into the reaction tube to remove the air, and the temperature was raised to After 600°C, feed H ₂ gas at 10 mL/min for 2 hours to reduce NiO/Al/Al ₂ O ₃ to Ni/Al/Al ₂ O ₃ , stop feeding hydrogen, and then feed methane and Nitrogen mixed gas (V _N2 : V _CH4 = 9: 1), reacted at 600 ° C for 0.5 hours, stopped feeding the mixed gas, and then lowered the furnace temperature to room temperature 20 ° C under a nitrogen atmosphere of 75 mL/min to obtain carbon nano The carbon nanotube/Ni/Al/Al ₂ O ₃ composite powder with a tube mass content of 2%; then press the obtained composite powder into a block at room temperature 20°C at 600 MPa, the holding time is 1 minute, and then the block Sinter at 1150°C for 2 hours in a sintering furnace with a vacuum degree of 10KPa, and then repress the block. Tough alumina matrix composites.

Example 2:

The specific method and steps are the same as in Example 1, except that the different conditions are: the time for vapor phase deposition of carbon nanotubes is 1 hour, and finally a carbon nanotube/Ni/Al/Al ₂ O ₃ composite powder with a mass content of carbon nanotubes of 5% is obtained.

Example 3:

The specific method and steps are the same as in Example 1, but the different conditions are: 1.25 grams of nickel nitrate hexahydrate and 19.8 aluminum powder are added to deionized water to obtain Ni: Al: Al ₂ O ₃ =1: 9: 90, and finally carbon nanotubes are obtained A carbon nanotube/Ni/Al/Al ₂ O ₃ composite powder with a mass content of 1.%.

Example 4:

The specific method and steps are the same as in Example 1, but the different conditions are: 1.25 grams of nickel nitrate hexahydrate and 19.8 aluminum powder are added to deionized water to obtain Ni: Al: Al ₂ O ₃ = 1:9:90, and in-situ synthesis of carbon nano The tube time is 1 hour, and finally a carbon nanotube/Ni/Al/Al ₂ O ₃ composite powder with a carbon nanotube mass content of 2.5% is obtained.

Example 5:

The specific method and steps are the same as in Example 1, but the different conditions are: 5 grams of nickel nitrate hexahydrate and 19.0 aluminum powder are added to deionized water to obtain Ni: Al: Al ₂ O ₃ =1: 1: 18, and finally carbon nanotubes are obtained Carbon nanotube/Ni/Al/Al ₂ O ₃ composite powder with a mass content of 3.5%.

Claims (1)

1. A preparation method for in-situ synthesis of carbon nanotubes/nickel/aluminum reinforced and toughened alumina-based composite materials, characterized in that it comprises the following processes: 1) Preparation of Ni/Al/Al ₂ O ₃ catalyst: Add nickel nitrate hexahydrate and aluminum powder with a mass ratio of >96% to 1L deionized water in a mass ratio of 0.127:1-1.24:1, and then add 0.01-1mol/ L sodium hydroxide or ammonia water with a mass concentration of 36% is added dropwise to the above solution under the stirring condition of a magnetic stirrer until the pH value of the solution is 7-12, and the mass ratio of the Ni element to the Al element produced by the reaction is 0.025: 1 -0.25:1, the ternary colloid Ni(OH) ₂ /Al/Al(OH) ₃ with a mass ratio of Al to Al(OH) ₃ of 0.01:1-0.654:1, and the prepared ternary colloid in Dehydration at 150-300°C and 150-350mL/min nitrogen atmosphere for 2-4 hours, followed by calcination at 350-500°C for 2-4 hours, the heating rate of the furnace is 8°C/min, so as to obtain NiO/Al/Al ₂ O ₃ catalyst precursor powder; 2) Preparation of carbon nanotube/Ni/Al/Al ₂ O ₃ composite powder by chemical vapor deposition: Take the NiO/Al/Al ₂ O ₃ catalyst precursor powder obtained in step 1) and spread it in a quartz boat, and place the quartz boat In the constant temperature zone in the middle of the quartz reaction tube, first pass nitrogen gas into the reaction tube to remove the air, and after the temperature rises to 500-650 °C at a rate of 8°C/min, pass _H2 gas at 25-250mL/min for 1.5-4 hours , reduce the precursor NiO/Al/Al ₂ O ₃ to the catalyst Ni/Al/Al ₂ O ₃ , stop feeding hydrogen, then feed 420-780mL/min V _N2 : V _CH4 =6:1-12:1 Mixed gas of methane and nitrogen, reacted at 500-650°C for 0.1-4 hours, stopped feeding the mixed gas, and lowered the furnace temperature to room temperature 20-25°C under a nitrogen atmosphere of 5-75mL/min, to obtain carbon nanotube quality Carbon nanotube/Ni/Al/Al ₂ O ₃ composite powder with a content of 0.1-50%; 3) The carbon nanotube/Ni/Al/Al ₂ O ₃ composite materials were prepared by powder metallurgy and hot extrusion respectively: Press the composite powder obtained in step 2) into a block at a room temperature of 20-25°C at 350-1200 MPa for a holding time of 30 seconds to 2 minutes, and then place the block in a 10 ^-11 -10 ^-7 Torr vacuum sintering furnace Sinter at 1000-1350°C for 0.5-6 hours, and then repress the block. The recompression pressure is 1250-2000MPa, and the holding time is 30 seconds to 2 minutes. Tough alumina matrix composites; Or put the composite powder obtained in step 2) into a mould, and then press the composite powder into a block at 500-1000° C. at 100-1000 MPa for a holding time of 2-12 hours to obtain carbon nanotube/aluminum/nickel raw Reinforced and toughened alumina matrix composites.

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