WO2019071839A1 - 氧化石墨烯包覆氮化硅复合粉体、其制备与应用及Al2O3基陶瓷刀具材料 - Google Patents

氧化石墨烯包覆氮化硅复合粉体、其制备与应用及Al2O3基陶瓷刀具材料 Download PDF

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WO2019071839A1
WO2019071839A1 PCT/CN2017/118231 CN2017118231W WO2019071839A1 WO 2019071839 A1 WO2019071839 A1 WO 2019071839A1 CN 2017118231 W CN2017118231 W CN 2017118231W WO 2019071839 A1 WO2019071839 A1 WO 2019071839A1
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graphene oxide
silicon nitride
powder
composite powder
coated silicon
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PCT/CN2017/118231
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English (en)
French (fr)
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许崇海
张文亮
肖光春
陈照强
衣明东
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齐鲁工业大学
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Priority claimed from CN201710953002.6A external-priority patent/CN107619263A/zh
Priority claimed from CN201710952983.2A external-priority patent/CN107573089A/zh
Application filed by 齐鲁工业大学 filed Critical 齐鲁工业大学
Publication of WO2019071839A1 publication Critical patent/WO2019071839A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/10—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/64—Burning or sintering processes
    • C04B35/645—Pressure sintering

Definitions

  • the invention relates to a graphene oxide coated silicon nitride composite powder, a preparation and application thereof and an Al 2 O 3 based ceramic tool material, belonging to the technical field of graphene toughening and reinforcing ceramic composite material and ceramic cutter.
  • graphene toughened and reinforced ceramic nanocomposites have achieved the effects that traditional reinforcing phase materials cannot achieve, see CN106007680A.
  • graphene is a two-dimensional honeycomb carbonaceous material with a unique structure that gives it a strong attraction between the layers. Therefore, the dispersion of graphene in the ceramic matrix is the key to the preparation of high performance ceramic matrix composites.
  • Conventional physical dispersion methods such as mechanical methods, ultrasonic dispersion methods, etc. cannot fundamentally eliminate the attraction between sheets.
  • the chemical dispersion method is complicated and the process introduces some impurities, which is not conducive to the control of experimental conditions.
  • ceramic materials mainly include oxides (Al 2 O 3 , ZrO 2 , etc.) and nitrides (Si 3 N 4 , etc.), among which Al 2 O 3 and Si 3 N 4 are mostly used.
  • the surface energy of Si 3 N 4 particles is large, and it is easy to agglomerate, which affects the mechanical properties and comprehensive properties of ceramic materials.
  • One common method of solving the problem of particle dispersion in the prior art is to surface modify the particles.
  • Alumina-based ceramic tools have high hardness, excellent wear resistance and high temperature mechanical properties, good chemical stability, and are not easy to bond with metals. They are widely used in difficult-to-machine material cutting, ultra-high-speed cutting, and high-speed drying. Cutting and hard cutting.
  • alumina-based ceramic tool materials as one of the ceramic materials, brittleness limits its further development as an excellent ceramic tool material. Therefore, toughening and reinforcing alumina ceramic tool materials is a hot topic in this field.
  • the alumina-based nanocomposite ceramic systems that have been developed include Al 2 O 3 /SiC, Al 2 O 3 /Si 3 N 4 , Al 2 O 3 /TiC, Al 2 O 3 /Ti(C,N), Al 2 O 3 /diamond, Al 2 O 3 /Fe, Al 2 O 3 /W, Al 2 O 3 /Ni, and the like.
  • Studies have shown that adding a proper amount of reinforcing phase to the ceramic matrix can effectively improve the mechanical properties of the tool material.
  • fiber-hardened ceramic matrix composites, carbon nanotube-toughened ceramic materials, and graphene-toughened ceramic tool materials have become the research hotspots, and the material properties have been significantly improved. See CN104909785A, CN103979942A, CN106145957A.
  • the surface of the graphene oxide has a functional group such as a carboxyl group, a hydroxyl group or an epoxy group, and can be used for coating a particulate material.
  • the preparation of the graphene oxide coating material firstly modifies the surface of the particulate material.
  • silane coupling agents have been studied on the surface modification of metal oxides (TiO 2 , SiO 2 , Al 2 O 3 , ZnO, CeO 2 , etc.). Since the metal oxide hydrolysis surface contains a large amount of oxygen-containing groups such as -OH, -COOH, the active groups in the coupling agent molecule (such as -Si-OR) are hydrolyzed and bonded to these oxygen-containing groups to form a strong Chemical bond.
  • Si 3 N 4 and other particles have large surface energy and easy agglomeration, and the surface lacks oxygen-containing groups such as —OH and —COOH, the surface of the particles is first subjected to surface grafting treatment with oxygen-containing groups.
  • the existing methods of surface oxidation are concentrated sulfuric acid, nitric acid, acidic potassium permanganate solution, hypochlorous acid solution as oxidant, although high efficiency, low controllability, environmental pollution is not easy to mass production, and equipment requires high process The process is more complicated.
  • the reported modification method uses toluene as a solvent and nitrogen as a shielding gas to carry out a liquid phase reaction (see CN105884377A); although the effect is improved, there are problems such as cost and environmental protection in industrial production. It has also been reported that the use of ethanol as a solvent and graft modification of nanoparticle powders by a ball milling process using a silane coupling agent is more complicated and less efficient. To date, there have been no reports of graphene oxide coated Si 3 N 4 particles.
  • Each carbon atom of graphene is connected to the other three carbon atoms through a strong ⁇ bond, so that it exhibits excellent physical properties: specific surface area of 2630 m 2 /g, Young's modulus of 1100 GPa, breaking strength of 125 GPa, and the like.
  • specific surface area of 2630 m 2 /g Young's modulus of 1100 GPa
  • breaking strength of 125 GPa breaking strength of 125 GPa
  • the like In view of the outstanding physical properties of graphene, it can become a more efficient toughening and reinforcing body for ceramic tool materials.
  • there is a strong van der Waals force between the graphene sheets and it is difficult to achieve good dispersion between the sheets. For this reason, there is a serious agglomeration phenomenon in the ceramic material as the reinforcing phase, which is not tightly bonded to the matrix and causes structural defects such as pores.
  • the graphene sheets are arranged in a layered manner in the direction of vertical hot pressing in the matrix, and the orientation problem of the sheets seriously affects the toughening and reinforcing properties of the matrix materials.
  • the dispersion of nano-enhanced phase particles in the matrix material is also an urgent problem to be solved in the research of multi-phase ceramic material tool materials.
  • the present invention provides a method for preparing a graphene oxide-coated silicon nitride (Si 3 N 4 @GO) composite powder for a ceramic material.
  • the Si 3 N 4 @GO composite powder has good dispersibility and no agglomeration, and is easy to be added to the ceramic material during application, thereby reinforcing and reinforcing.
  • the invention also provides the application of the graphene oxide coated silicon nitride composite powder for preparing an Al 2 O 3 based ceramic tool material.
  • the invention also provides an Al 2 O 3 -based ceramic tool material which is added with a graphene oxide-coated silicon nitride composite powder and a preparation method thereof. Improve the mechanical properties of Al 2 O 3 based ceramic tool materials.
  • Graphene oxide abbreviated as GO
  • Graphene oxide coated silicon nitride abbreviated as Si 3 N 4 @GO;
  • H 2 O 2 aqueous solution also known as hydrogen peroxide
  • Room temperature has a meaning well known in the art and generally refers to 25 ⁇ 2 °C.
  • a graphene oxide coated silicon nitride (Si 3 N 4 @GO) composite powder is obtained by high temperature oxidation of Si 3 N 4 surface by H 2 O 2 aqueous solution, and then surface graft modification with a silane coupling agent.
  • a positively charged Si 3 N 4 particle whose surface is modified by grafting with a silane coupling agent is encountered, it is self-assembled by electrostatic force.
  • graphene oxide-coated silicon nitride is prepared as follows:
  • the Si 3 N 4 powder is added to the hydrogen peroxide solution, oxidized at 60 to 100 ° C, then dispersed into the hydroalcohol mixed solution, and the coupling agent hydrolysis solution is added, and the amount of the coupling agent is the oxidized Si 3 N 4 powder. 2.5% to 10% of the mass; the temperature is raised to 60 to 90 ° C, the pH is adjusted to 8 to 10, and the reaction is stirred to obtain a Si 3 N 4 suspension modified by the coupling agent; then the Si 3 N 4 suspension is adjusted.
  • the pH value of the turbid liquid is 3 to 5, and it is added to the aqueous dispersion of graphene oxide having a pH of 8 to 10.
  • the mixture is ultrasonically stirred and allowed to stand until the coated particles are completely precipitated, separated and dried to obtain graphene oxide coating. Silicon nitride (Si 3 N 4 @GO) powder.
  • the graphene oxide coating layer has an average thickness of 2 to 8 nm, and the Si 3 N 4 particles have an average particle diameter of 100 to 300 nm. Further preferably, the graphene oxide coating layer has an average thickness of 3 to 5 nm, and the Si 3 N 4 particles have an average particle diameter of 100 to 200 nm.
  • a method for preparing a graphene oxide-coated silicon nitride (Si 3 N 4 @GO) composite powder comprises the steps of:
  • the Si 3 N 4 powder is added to the hydrogen peroxide solution to be sufficiently dispersed, and then oxidized at a temperature of 60 to 100 ° C under magnetic stirring; and the surface oxidized Si 3 N 4 powder is obtained;
  • the surface oxidized Si 3 N 4 powder prepared in step a is dispersed into a hydroalcohol mixed solution, ultrasonically dispersed, and then a coupling agent hydrolysis solution is added, and the amount of the coupling agent is surface oxidized Si 3 N 4 powder.
  • the mass ratio of the surface oxidized Si 3 N 4 powder to graphene oxide is from 15 to 35:1 to 1.5; further preferably from 18 to 30:1; most preferably, the surface oxidized Si 3
  • the mass ratio of N 4 powder to graphene oxide was 20:1.
  • the Si 3 N 4 powder has an average particle diameter of 100 to 200 nm; the particle diameter is important for uniform particles and complete coating. Since the graphene oxide sheets having a structure in the dispersion, Si 3 N 4 particle size is too large it is difficult to achieve completely covered; Si 3 N 4 particle size is too small, a larger surface energy, easily agglomerated particles between It is easy to occur that a plurality of Si 3 N 4 agglomerates are coated with graphene oxide at the same time, resulting in uneven powder particles after coating.
  • the aqueous hydrogen peroxide solution has a concentration of 15% to 30% by mass.
  • the Si 3 N 4 powder was sufficiently dispersed in hydrogen peroxide by ultrasonic agitation.
  • the Si 3 N 4 powder is added in an amount of 10 to 20 g/L per liter of the aqueous hydrogen peroxide solution. More preferably, the temperature of the surface oxidation treatment of the Si 3 N 4 powder is 70 to 90 °C. The oxidation treatment time is 15 to 30 minutes.
  • step a further comprises, after the end of the oxidation treatment, cooling to room temperature, centrifuging, washing and drying.
  • a surface oxidized Si 3 N 4 powder was obtained.
  • the drying temperature may be a medium temperature of 80 to 120 ° C or a high temperature of 150 to 300 ° C. Further preferably, the drying temperature is 200 to 250 ° C, and the drying time is 6 to 10 hours.
  • the use of high temperature drying is beneficial to the surface oxidation of Si 3 N 4 powder.
  • the drying time is shortened by high temperature drying to further improve the oxidation quality.
  • the washing is to centrifuge the solid matter 2 to 3 times with distilled water; the drying is to dry the cleaned solid in a dry box.
  • the ratio of the surface oxidized Si 3 N 4 powder mass to the hydroalcohol solution volume is 1 to 2 g: 200 to 300 mL.
  • the hydroalcoholic solution is a solution having a volume ratio of water to absolute ethanol of from 1 to 1.5:1 to 1.5.
  • the ultrasonic dispersion time is 30 to 60 min.
  • the coupling agent hydrolysis solution is: the coupling agent is dissolved in the hydroalcoholic solution, and fully hydrolyzed by ultrasonic stirring for 30 to 60 minutes.
  • the present invention first hydrolyzes the coupling agent with a water alcohol mixed solution, so that the coupling agent is more easily dispersed.
  • the ratio of the mass of the coupling agent to the volume of the hydroalcoholic solution is 2.5 to 10 g: 50 to 100 mL, based on 100 g of the surface-oxidized Si 3 N 4 powder.
  • the hydroalcoholic solution is a solution having a volume ratio of water to absolute ethanol of from 1 to 1.5:1 to 1.5.
  • the coupling agent is a silane coupling agent selected from the group consisting of 3-aminopropyltriethoxysilane (KH550), 3-aminopropyltrimethoxysilane (KH540), Coupling agent such as N-2 (aminoethyl) 3-aminopropyltriethoxysilane (KH910) or N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane (KH602) Any one.
  • the amount of the coupling agent is significantly lower than that of the prior art, and the reaction time is shorter.
  • the aqueous graphene oxide dispersion having a pH of 8 to 10 can be prepared as it is in time.
  • the aqueous graphene oxide dispersion is prepared as follows:
  • the concentration of the graphene oxide dispersion is 0.3-0.6 mg/mL, and further, the ultrasonic dispersion is 1 to 2.5 h; adjusting the graphene oxide dispersion by dropping ammonia water
  • the pH value is 8-10.
  • the graphene oxide dispersion is rendered negatively charged.
  • the present inventors have found that adjusting the pH with aqueous ammonia can enhance the surface potential of graphene oxide.
  • the coupling agent has a mass of 4 to 6% of the surface oxidized Si 3 N 4 ; the pH of the suspension is 8.5 to 9.5, and the reaction temperature is 75 to 85 ° C; The coupling agent is graft-modified on the surface of the surface oxidized Si 3 N 4 .
  • the pH adjustment of 3 to 5 is adjusted by adding a dilute hydrochloric acid having a mass fraction of 10 to 15%.
  • the present invention was made acidic by adjusting the coupling agent surface-modified suspension Si 3 N 4, Si 3 N 4 to improve the suspension are positively charged potential energy.
  • the acidic Si 3 N 4 suspension is mixed with the aqueous graphene oxide dispersion having a pH of 8 to 10, and ultrasonically stirred for 30 to 60 minutes.
  • the separating and drying are: removing the supernatant, and placing the obtained precipitate in a vacuum drying oven, and drying at 60 to 80 ° C under vacuum.
  • the drying time is preferably 10 to 12 hours.
  • reaction of the step b is carried out in a three-necked flask under magnetic stirring with a water bath.
  • the present invention directly adds the modified Si 3 N 4 composite powder suspension to the graphene oxide dispersion liquid, and the steps are simple and the coating effect is good. If the amount of coupling agent added is too small, the surface of Si 3 N 4 particles cannot be completely modified by grafting agent, the particle coating is incomplete, and the coating ratio is low; when the coupling agent is added too much, the concentration is high. The condensation occurs after the hydrolysis of the agent, the surface activity of the large coupling agent agglomerates is lowered, and the coupling dose of the grafted particles on the surface of the particles is reduced, resulting in a decrease in the coating ratio. Therefore, a preferred 2.5% to 10% of the present invention is preferred. Most preferably, the coupling agent is added in an amount of from 4 to 6% of the amount of surface oxidized Si 3 N 4 .
  • the Si 3 N 4 @GO composite powder prepared by the invention is used for toughening and strengthening of ceramic materials. Especially for alumina-based composite ceramic tool materials.
  • An alumina-based composite ceramic tool material which is added with a graphene oxide-coated silicon nitride composite powder is formed by hot pressing of the following mass percentage of raw materials:
  • the mass fraction of the raw material component of the composite ceramic cutter material is: graphene oxide coated silicon nitride 10-30%, magnesium oxide 0.25-2%, molybdenum 0.5-3%, nickel 1 ⁇ 3%, the balance is Al 2 O 3 .
  • the mass percentage of the raw material component of the composite ceramic cutter material is: graphene oxide coated silicon nitride 20-21%, magnesium oxide 0.5-0.8%, molybdenum 1 to 1.5%, nickel 1.2-1.5 %, the rest is Al 2 O 3 .
  • the magnesium oxide (sintering aid) has an average particle diameter of 0.5 to 5 ⁇ m, further preferably the magnesium oxide has an average particle diameter of 0.5 to 2 ⁇ m; the average particle diameter of the molybdenum is 10 to 50 ⁇ m, and the average particle of nickel The diameter is 10 to 50 ⁇ m. More preferably, the average particle diameter of nickel and molybdenum is 15 to 45 ⁇ m, respectively.
  • the Al 2 O 3 has an average particle diameter of 100 to 500 nm, and more preferably, the Al 2 O 3 has an average particle diameter of 200 to 300 nm. Further preferably, the Al 2 O 3 is ⁇ -Al 2 O 3 .
  • a method for preparing an alumina-based composite ceramic tool material comprising a graphene oxide-coated silicon nitride composite powder, the raw material component ratio is as described above, and includes the foregoing graphene oxide-coated nitrogen of the present invention.
  • the preparation step of the silicon (Si 3 N 4 @GO) composite powder further includes the steps of:
  • step d Pour the suspension prepared in step c into a ball mill, fill with nitrogen as a shielding gas, and continuously ball mill for 24 to 48 hours.
  • the Si 3 N 4 @GO composite powder prepared in the step b is added to the ball mill tank of the step d together, and the ball milling is continued for 2 to 4 hours to obtain the addition of the graphene oxide-coated silicon nitride composite powder.
  • step e The slurry prepared in step e is dried and sieved to obtain a mixed powder, which is sealed for use.
  • the dried mixed powder obtained in the step f is placed in a mold made of graphite and subjected to hot press sintering to obtain an alumina-based composite ceramic tool material in which a graphene oxide-coated silicon nitride composite powder is added.
  • the polyethylene glycol has a molecular weight of between 2,000 and 10,000, particularly preferably polyethylene glycol 4000; and the polyethylene glycol has a mass of Al 2 O 3 ⁇ 5%.
  • the ultrasonic dispersion and mechanical agitation time is 15 to 30 min; the time of continuing ultrasonic dispersion and mechanical agitation is 15 to 30 min.
  • the ball mill is added with a ball mill ball of a cemented carbide material, and the mass ratio of the ball material is 10 to 20:1. Most preferably, the continuous ball milling time is 30-40 h.
  • the mass ratio of the added Si 3 N 4 @GO composite powder and the ball mill ball is 10 to 20:1; and most preferably, the ball milling time is continued for 2 to 3 hours. Nitrogen is used as a shielding gas.
  • step f the slurry is continuously dried in a vacuum drying oven at 80 to 120 ° C for 12 to 24 hours.
  • the dried powder passed through a 200 mesh sieve.
  • the hot press sintering conditions are: a sintering temperature of 1400 to 1700 ° C, a hot pressing pressure of 20 to 35 MPa, a holding time of 10 to 30 minutes, and a temperature rising rate of 10 to 25 ° C/min.
  • the present invention solves the problems of low controllability and environmental pollution caused by surface modification of Si 3 N 4 particles in the prior art, and imparts excellent surface characteristics to Si 3 N 4 particles by high temperature oxidation on the surface of hydrogen peroxide. Since the Si 3 N 4 particles are mostly lamellar irregular structures, the surface energy is relatively easy to agglomerate and the surface lacks oxygen-containing groups, etc., which increases the technical difficulty for surface coating and modification of the particles. Before the modification, the surface of the Si 3 N 4 powder is first treated with hydrogen peroxide, which overcomes the problems of low controllability, easy operation of impurities, environmental protection and the like in the prior art oxidation method. The invention applies high concentration of hydrogen peroxide to treat Si 3 N 4 particles at a high concentration, has simple operation, low use time, high efficiency and no introduction of impurities.
  • silane coupling agent when used to modify the surface of the particles, toluene is used as a solvent to carry out a liquid phase reaction, so that industrial production has problems such as cost and environmental protection.
  • the invention uses the hydroalcohol mixed solution as a solvent, which is more efficient, economical and practical than the prior art, and is convenient for industrial production.
  • the present invention utilizes a functional group such as a carboxyl group, a hydroxyl group or an epoxy group on the surface of the graphene oxide to ionize a negative charge in water, and encounters a surface band when the surface is grafted with a coupling agent to modify the Si 3 N 4 particle. It has a positive charge and can self-assemble under the force of electrostatic force.
  • the invention directly mixes the dispersed graphene oxide solution and the silicon nitride suspension modified by the coupling agent to form a coating, which is more efficient. Moreover, the powder coating effect is good and the cost is low.
  • the obtained Si 3 N 4 @GO composite powder was observed by transmission electron microscopy, and the coating was complete without agglomeration of graphene oxide, and the dispersibility was good. As shown in Figure 2 and Figure 3
  • the present invention successfully Si 3 N 4 @GO prepared composite powder, change the surface properties of particles of Si 3 N 4, Si 3 N impart excellent surface characteristics 4 particles. It provides a new way for the dispersion of graphene in materials, adds a new variety for coating Si 3 N 4 materials, and expands the application space of Si 3 N 4 powder.
  • the Si 3 N 4 @GO composite powder prepared by the invention has good dispersibility and no agglomeration, and is convenient to be added to the ceramic material during application, and does not adversely affect the performance of the ceramic material.
  • the distribution of graphene oxide in the matrix can be more uniformly realized, and the defects caused by the phenomenon of graphene oxide agglomeration on the ceramic material can be avoided.
  • the layered distribution of graphene oxide in a direction parallel to the hot pressing direction of the ceramic substrate can be avoided, and the phenomenon of anisotropy is avoided.
  • the third can be used to toughen and strengthen the effect; the fracture toughness and wear resistance of the ceramic material can be greatly improved.
  • the present invention provides a novel alumina-based ceramic tool material having good mechanical properties.
  • the graphene oxide is surface-coated with a silicon nitride powder surface-modified by a silane coupling agent by an electrostatic self-assembly technique.
  • the coated powder is added to the alumina ceramic matrix, and the graphene-coated Si 3 N 4 toughened Al 2 O 3 -based composite ceramic tool material is obtained by vacuum hot pressing sintering, since the graphene oxide is a graphene Under the condition of vacuum hot pressing sintering, the oxygen-containing group of graphene oxide is decomposed into graphene, which can effectively solve the problem of agglomeration of graphene nano-powder and realize the coordinated toughening of graphene nano-phase.
  • the invention successfully solves the problem that the agglomeration of the graphene as a reinforcing phase in the ceramic material is not tightly combined with the matrix and causes structural defects such as pores, and the controllability and environmental pollution generated in the surface modification of the Si 3 N 4 particles are low. Such problems, while avoiding the problem of orientation of graphene in the ceramic matrix.
  • the present invention adds a graphene oxide-coated silicon nitride composite powder to an alumina ceramic matrix material, and coats silicon nitride with a graphene oxide as a reinforcing phase, and magnesia, molybdenum and nickel are sintering aids.
  • Al 2 O 3 (Si 3 N 4 @GO) composite ceramic tool material was prepared by vacuum hot pressing. This material has good mechanical properties. From the microstructure of the composite ceramic tool material, it is found that the graphene is uniformly dispersed in the alumina matrix and tightly combined with the matrix material. Correspondingly, with the increase of the addition of graphene oxide coated silicon nitride composite powder, the mechanical properties of the ceramic tool material are improved.
  • the alumina-based ceramic tool material with graphene oxide-coated silicon nitride composite powder has the best mechanical properties, hardness 18.4 GPa and fracture toughness 7.6 MPa. ⁇ m 1/2 and bending strength 628 MPa.
  • the process equipment of the invention is simple, easy to operate and high in safety.
  • Figure 1 is an infrared spectrum of KH550-Si 3 N 4 , Si 3 N 4 and KH550.
  • Example 2 is a TEM photograph of a Si 3 N 4 @GO composite powder sample prepared in Example 2.
  • Example 3 is a high-power TEM photograph of a Si 3 N 4 @GO composite powder sample prepared in Example 2.
  • Example 4 is a SEM photograph of the Si 3 N 4 @GO composite powder prepared in Example 2.
  • Example 5 is a SEM topographical view of a fracture surface of a test specimen of an alumina-based ceramic tool material in which a graphene oxide-coated silicon nitride composite powder is added in Example 4.
  • a method for preparing a graphene oxide-coated silicon nitride (Si 3 N 4 @GO) composite powder the steps are as follows:
  • the acidic Si 3 N 4 suspension of the step (3) is mixed with the graphene oxide aqueous dispersion of the step (4) under ultrasonic agitation, ultrasonically stirred for 30 minutes, allowed to stand, precipitated, and the supernatant is removed. It was placed in a vacuum drying oven and vacuum dried at 60 ° C for 12 hours, and dried to obtain a Si 3 N 4 @GO composite powder.
  • the graphene oxide-coated silicon nitride composite powder obtained in this embodiment is dark gray. Observation by transmission electron microscopy showed that Si 3 N 4 @GO was coated with graphene oxide to coat a single Si 3 N 4 particle, and the coating was complete, and there was no agglomeration of graphene oxide, and the dispersibility was good.
  • the average particle diameter of the Si 3 N 4 @GO particles is 106 nm, and the thickness of the graphene oxide coating layer coated on the surface of the Si 3 N 4 particles is about 2 to 4 nm, and the coating effect is good.
  • a method for preparing a graphene oxide-coated silicon nitride (Si 3 N 4 @GO) composite powder the steps are as follows:
  • step (3) mixing the acidic Si 3 N 4 suspension of step (3) with the graphene oxide aqueous dispersion of step (4) under ultrasonic stirring, ultrasonically stirring for 40 min, standing, precipitating, removing the supernatant, and setting
  • the mixture was vacuum dried in a vacuum oven at 70 ° C for 12 hours, and dried to obtain a Si 3 N 4 @GO composite powder.
  • the graphene oxide-coated silicon nitride composite powder obtained in this embodiment is dark gray. Observation by transmission electron microscopy showed that Si 3 N 4 @GO was coated with graphene oxide to coat a single Si 3 N 4 particle, and the coating was complete, and there was no agglomeration of graphene oxide, and the dispersibility was good.
  • the Si 3 N 4 @GO particle has an average particle diameter of 208 nm, and the thickness of the graphene oxide coating layer coated on the surface of the Si 3 N 4 particle is about 3 to 5 nm, and the coating effect is optimal.
  • the transmission electron micrograph of the obtained product is shown in Fig. 2 and Fig. 3.
  • a SEM photograph of the Si 3 N 4 @GO composite powder is shown in Fig. 4 .
  • a method for preparing a graphene oxide-coated silicon nitride (Si 3 N 4 @GO) composite powder the steps are as follows:
  • step (3) mixing the acidic Si 3 N 4 suspension of step (3) with the aqueous graphene oxide dispersion of step (4) under ultrasonic stirring, ultrasonically stirring for 50 min, standing, precipitating, removing the supernatant, and setting
  • the mixture was vacuum dried at 80 ° C for 12 hours in a vacuum drying oven to obtain a Si 3 N 4 @GO composite powder.
  • the color of the graphene oxide-coated silicon nitride composite powder obtained in this embodiment is dark gray. Observation by transmission electron microscopy showed that Si 3 N 4 @GO was coated with graphene oxide to coat a single Si 3 N 4 particle, and the coating was complete, and there was no agglomeration of graphene oxide, and the dispersibility was good.
  • the average particle diameter of the Si 3 N 4 @GO particles is 210 nm, and the thickness of the graphene oxide coating layer coated on the surface of the Si 3 N 4 particles is about 4 to 6 nm, and the coating effect is good.
  • the Si 3 N 4 @GO composite powder prepared in Example 2 was added to an Al 2 O 3 /Ti(C,N) ceramic matrix.
  • Si 3 N 4 @GO toughened Al 2 O 3 /Ti(C,N) nanocomposite ceramic material the mass percentage of raw material components is: Si 3 N 4 @GO 10.5%, Ti(C,N) 15%, MgO 0.5%, Y 2 O 3 0.2%, and the balance is Al 2 O 3 .
  • the average particle diameter of MgO and Y 2 O 3 is 1 to 3 ⁇ m, the average particle diameter of A1 2 O 3 is 300 to 350 nm, the average particle diameter of Ti (C, N) is 100 to 120 nm, and C:N is 7:3. It is prepared by hot pressing sintering according to the prior art (sintering temperature is 1600 ° C, holding time is 25 min, pressure is 25 MP, and heating rate is 20 ° C/min).
  • the prepared Si 3 N 4 @GO toughened Al 2 O 3 /Ti(C,N) nanocomposite ceramic material was subjected to mechanical properties tests after cutting, rough grinding, fine grinding, grinding and polishing, wherein the mechanical properties include dimensions.
  • Hardness, fracture toughness and flexural strength were 21.3 GPa, 7.8 MPa ⁇ m 1/2 and 712 MPa, respectively.
  • Comparative Example 1 GO toughened Al 2 O 3 /Ti(C,N) nanocomposite ceramic material
  • the GO dispersed in the same process in the step (4) of Example 2 was added to the Al 2 O 3 /Ti(C,N) ceramic matrix.
  • GO toughened Al 2 O 3 /Ti(C,N) nanocomposite ceramic materials the mass percentage of raw material components are: GO 0.5%, Ti (C, N) 15%, MgO 0.5%, Y 2 O 3 0.2% The rest is Al 2 O 3 .
  • the average particle diameter of MgO and Y 2 O 3 is 1 to 3 ⁇ m, the average particle diameter of A1 2 O 3 is 300 to 350 nm, the average particle diameter of Ti (C, N) is 100 to 120 nm, and C:N is 7:3. It is prepared by hot pressing sintering according to the prior art (sintering temperature is 1600 ° C, holding time is 25 min, pressure is 25 MP, and heating rate is 20 ° C/min).
  • the prepared GO toughened Al 2 O 3 /Ti(C,N) nanocomposite ceramic material was subjected to mechanical properties tests after cutting, rough grinding, fine grinding, grinding and polishing, wherein the mechanical properties include Vickers hardness and fracture toughness. And bending strength.
  • the hardness, fracture toughness and flexural strength were 19.2 GPa, 6.5 MPa ⁇ m 1/2 and 630 MPa, respectively.
  • Embodiment 4 An alumina-based composite ceramic tool material which is added with a graphene oxide-coated silicon nitride composite powder is formed by hot pressing of the following mass percentage of raw materials:
  • Graphene oxide coated silicon nitride 10.5%, magnesium oxide 0.25%, molybdenum 0.5%, nickel 1%, and the balance is Al 2 O 3 .
  • step 3 pour the suspension prepared in step 2 into a ball mill, fill with nitrogen as a shielding gas, and add a ball mill ball made of cemented carbide.
  • the ball mass ratio is 10:1 and continuous ball milling for 24 hours.
  • the Si 3 N 4 @GO composite powder prepared in Example 2 and the ball mill ball were added to the ball mill tank according to the mass ratio of the third step, wherein the Si 3 N 4 @GO composite powder was added in an amount of 10.5. % (the amount of graphene oxide added was 0.5%) and ball milling was continued for 2 hours to obtain a slurry of an alumina-based composite ceramic tool material to which a graphene oxide-coated silicon nitride composite powder was added.
  • the slurry of the alumina-based composite ceramic cutter material obtained by adding the graphene oxide-coated silicon nitride composite powder is continuously dried in a vacuum drying oven at 80 ° C for 12 hours, and then sieved to obtain a mixed powder, which is sealed and used.
  • the dried mixed powder obtained in the step 5 is charged into a mold made of graphite for hot press sintering, the sintering temperature is 1450 ° C, the hot pressing pressure is 20 MPa, the holding time is 15 min, and the heating rate is 10 ° C / min, that is, added oxidation is obtained.
  • the prepared alumina-based ceramic cutter material with the addition of graphene oxide-coated silicon nitride composite powder is prepared into a ceramic spline of 3 mm ⁇ 4 mm ⁇ 30 mm by steps of cutting, coarse grinding, fine grinding, grinding and polishing.
  • the mechanical properties were measured as follows: hardness 18.2 GPa, fracture toughness 5.2 MPa ⁇ m 1/2 , and flexural strength 502 MPa.
  • the SEM topography of the fracture surface of the test specimen is shown in Fig. 2.
  • Embodiment 5 An alumina-based composite ceramic tool material which is added with a graphene oxide-coated silicon nitride composite powder is formed by hot pressing of the following mass percentage of raw materials:
  • step 3 pour the suspension prepared in step 2 into a ball mill, fill with nitrogen as a shielding gas, and add a ball mill ball made of cemented carbide.
  • the ball mass ratio is 15:1 and continuous ball milling for 36 hours.
  • the Si 3 N 4 @GO composite powder prepared in Example 2 and the ball mill ball were added to the ball mill tank according to the mass ratio of the step 3, wherein the Si 3 N 4 @GO composite powder was added in an amount of 21 % (the amount of graphene oxide added was 1%), and ball milling was again performed for 3 hours to obtain a slurry of an alumina-based composite ceramic tool material to which a graphene oxide-coated silicon nitride composite powder was added.
  • the slurry of the alumina-based composite ceramic cutter material obtained by adding the graphene oxide-coated silicon nitride composite powder is continuously dried in a vacuum drying oven at 90 ° C for 18 hours, and then sieved to obtain a mixed powder, which is sealed and used.
  • the dried mixed powder obtained in the step 5 is loaded into a mold made of graphite for hot press sintering, the sintering temperature is 1600 ° C, the hot pressing pressure is 30 MPa, the holding time is 30 min, and the heating rate is 15 ° C / min, that is, added oxidation is obtained.
  • the alumina-based ceramic tool material with the addition of graphene-coated alumina composite powder was prepared into a ceramic spline of 3 mm ⁇ 4 mm ⁇ 30 mm by cutting, coarse grinding, fine grinding, grinding and polishing. Its mechanical properties are: hardness of 18.4 GPa, fracture toughness of 7.6 MPa ⁇ m 1/2 , and flexural strength of 628 MPa.
  • Embodiment 6 An alumina-based composite ceramic tool material which is added with a graphene oxide-coated silicon nitride composite powder is formed by hot pressing of the following mass percentage of raw materials:
  • step 3 pour the suspension prepared in step 2 into a ball mill, fill with nitrogen as a protective gas, and add a ball mill ball made of cemented carbide.
  • the ball mass ratio is 20:1 and continuous ball milling for 48 hours.
  • Si 3 N 4 @GO composite powder prepared in Example 2 and the ball mill ball were added to the ball mill tank according to the mass ratio of the step 3, wherein the Si 3 N 4 @GO composite powder was added in an amount of 26.25. % (addition amount of graphene oxide was 1.25%), and ball milling again for 3 hours to obtain a slurry of an alumina-based composite ceramic tool material to which a graphene oxide-coated silicon nitride composite powder was added.
  • the slurry of the alumina-based composite ceramic cutter material obtained by adding the graphene oxide-coated silicon nitride composite powder was continuously dried in a vacuum drying oven at 100 ° C for 24 hours, and then sieved to obtain a mixed powder.
  • the dried mixed powder obtained in the step 5 is charged into a mold made of graphite for hot pressing sintering, the sintering temperature is 1700 ° C, the hot pressing pressure is 30 MPa, the holding time is 30 min, and the heating rate is 15 ° C / min, that is, added oxidation is obtained.
  • the alumina-based ceramic tool material with the addition of graphene-coated alumina composite powder was prepared into a ceramic spline of 3 mm ⁇ 4 mm ⁇ 30 mm by cutting, coarse grinding, fine grinding, grinding and polishing. Its mechanical properties are: hardness 18.1 GPa, fracture toughness 6.8 MPa ⁇ m 1/2 , and bending strength 526 MPa.
  • step 3 pour the suspension prepared in step 2 into a ball mill, fill with nitrogen as a shielding gas, and add a ball mill ball made of cemented carbide.
  • the ball mass ratio is 15:1 and continuous ball milling for 36 hours.
  • the Si 3 N 4 powder having an average particle diameter of 200 nm and the ball mill ball are added to the ball mill tank according to the mass ratio of the step 3, wherein the Si 3 N 4 powder is added in an amount of 21% and ball milled again for 3 hours.
  • a slurry of an alumina-based composite ceramic tool material to which silicon nitride powder is added is obtained.
  • the slurry of the obtained alumina-based composite ceramic cutter material to which silicon nitride powder was added was continuously dried in a vacuum drying oven at 90 ° C for 18 hours, and then sieved to obtain a mixed powder, which was sealed for use.
  • the dried mixed powder obtained in the step 5 is loaded into a mold made of graphite for hot press sintering, the sintering temperature is 1600 ° C, the hot pressing pressure is 30 MPa, the holding time is 30 min, and the heating rate is 15 ° C / min, that is, nitrogen is added.
  • Alumina-based composite ceramic tool material for silicon powder is added.
  • the prepared alumina-based ceramic tool material was prepared into 3mm ⁇ 4mm ⁇ 30mm ceramic spline by cutting, coarse grinding, fine grinding, grinding and polishing.
  • the mechanical properties were as follows: hardness 17.6GPa, fracture toughness 4.6 MPa ⁇ m 1/2 and bending strength 432 MPa.

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Abstract

一种氧化石墨烯包覆氮化硅复合粉体、其制备与应用及Al2O3基陶瓷刀具材料。将Si3N4粉体在双氧水中进行高温表面氧化，再用偶联剂进行Si3N4表面的接枝改性处理。然后用氧化石墨烯水包覆接枝改性的Si3N4粒子，得到氧化石墨烯包覆氮化硅复合粉体。还提供了添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料，其由以下质量百分比的原料经热压烧结而成：氧化石墨烯包覆氮化硅5～30％，氧化镁0.25～5％，钼0.5～5％，镍0.5～5％，其余为Al2O3。该氧化石墨烯包覆氮化硅复合粉体包覆完整性好，将氧化石墨烯包覆氮化硅复合粉体添加应用到陶瓷材料中，可使陶瓷材料的力学性能明显提升。

Description

氧化石墨烯包覆氮化硅复合粉体、其制备与应用及Al 2O 3基陶瓷刀具材料 技术领域
本发明涉及一种氧化石墨烯包覆氮化硅复合粉体、其制备与应用及Al 2O 3基陶瓷刀具材料，属于石墨烯增韧补强陶瓷复合材料及陶瓷刀具技术领域。
背景技术
目前，石墨烯增韧补强陶瓷纳米复合材料已取得传统增强相材料无法达到的效果，参见CN106007680A。但是，石墨烯是一种二维蜂窝状碳质新材料，其独特的结构，使其片层之间具有强的吸引力。所以石墨烯在陶瓷基体中的分散问题是制备高性能陶瓷基复合材料的关键。传统的物理分散方法如机械法、超声分散法等不能从根本上消除片层之间的吸引力。化学分散法，过程又比较繁杂，同时还会引入一些杂质，不利于实验条件的控制。因此，要很好地发挥石墨烯增韧补强作用需要解决其分散问题。另一方面，对于陶瓷材料主要包括氧化物(Al 2O 3、ZrO 2等)和氮化物(Si 3N 4等)两类，其中应用较多的是Al 2O 3和Si 3N 4。而Si 3N 4颗粒表面能较大，也极易产生团聚，影响陶瓷材料的力学性能及综合性能。现有技术解决颗粒分散性问题的一种常见方法是对颗粒物进行表面改性。
氧化铝基陶瓷刀具具有高的硬度、优良的耐磨性能及高温力学性能、良好的化学稳定性、不易与金属发生粘结等优点，被广泛应用于难加工材料切削、超高速切削、高速干切削和硬切削等。然而，氧化铝基陶瓷刀具材料作为陶瓷材料中的一种，脆性限制了其作为一种优秀陶瓷刀具材料的进一步发展。因此，对氧化铝陶瓷刀具材料进行增韧补强是该领域研究的热点。已研制的氧化铝基纳米复相陶瓷体系有Al 2O 3/SiC，Al 2O 3/Si 3N 4，Al 2O 3/TiC，Al 2O 3/Ti(C，N)，Al 2O 3/diamond，Al 2O 3/Fe，Al 2O 3/W，Al 2O 3/Ni等。研究表明在陶瓷基体中加入适量的增强相，可有效提高刀具材料的力学性能。此外，目前纤维增韧的陶瓷基复合材料、碳纳米管增韧的陶瓷材料、石墨烯增韧的陶瓷刀具材料等成为研究的热点，材料性能得到明显改善。参见CN104909785A、CN103979942A、CN106145957A。
氧化石墨烯表面带有羧基、羟基、环氧基等官能团，可用于包覆颗粒材料。制备氧化石墨烯包覆材料首先要对颗粒材料表面改性。目前，硅烷偶联剂对金属氧化物(TiO 2、SiO 2、Al 2O 3、ZnO、CeO 2等)表面改性研究的较多。由于金属氧化物水解表面含有大量—OH、—COOH等含氧基团，偶联剂分子中的活泼基团(如—Si—OR)水解后与这些含氧基团发生键合，形成强的化学键。关于硅烷偶联剂改性Si 3N 4、SiC、TiC等非氧化物的不规则片状粒子()的研究较少。由于Si 3N 4等颗粒表面能较大、易团聚，且表面缺少—OH、—COOH等含氧基团，所以改性 前需首先对粒子进行含氧基团的表面接枝处理。现有的表面氧化常用的方法是浓硫酸、硝酸、酸性高锰酸钾溶液、次氯酸溶液做氧化剂，虽然高效但可控性低，对环境带来污染不易批量生产，而且设备要求高工艺过程更加复杂。目前，已报道的改性方法采用甲苯作为溶剂，氮气为保护气体，进行液相反应(参见CN105884377A)；这样效果虽然有改进，但是出现工业化生产存在成本、环保等问题。还有报道指出，以乙醇为溶剂，利用球磨工艺使用硅烷偶联剂接枝改性纳米颗粒粉体，这种方法工艺更加复杂且效率低。迄今为止，尚未见有氧化石墨烯包覆Si 3N 4颗粒的报道。
石墨烯每个碳原子是通过很强的σ键与其他3个碳原子相连接，致使其表现出优异的物理性能：比表面积2630m 2/g、杨氏模量1100GPa、断裂强度125GPa等。鉴于石墨烯突出的物理性能，可成为陶瓷刀具材料更高效的增韧补强体。但是石墨烯片层之间存在强的范德华力，片层之间很难实现良好的分散。为此，作为增强相在陶瓷材料中存在严重的团聚现象，与基体结合不紧密且引起气孔等结构缺陷。此外，石墨烯片体在基体中呈垂直热压方向的层状排布，片体的取向问题严重影响其在基体材料中增韧补强性能的发挥。同时，纳米增强相粒子在基体材料中的分散问题，也是复相陶瓷材刀具材料研究亟待解决的问题。
发明内容
针对现有技术的不足，本发明提供一种用于陶瓷材料的氧化石墨烯包覆氮化硅(Si 3N 4@GO)复合粉体的制备方法。该Si 3N 4@GO复合粉体分散性好，无团聚，便于应用时添加到陶瓷材料中，起到增韧补强的作用。
本发明还提供所述氧化石墨烯包覆氮化硅复合粉体的应用，用于制备Al 2O 3基陶瓷刀具材料。
本发明还提供一种添加氧化石墨烯包覆氮化硅复合粉体的Al 2O 3基陶瓷刀具材料及其制备方法。提高Al 2O 3基陶瓷刀具材料的力学性能。
术语说明：
氧化石墨烯：简写为GO；
氧化石墨烯包覆氮化硅：简写为Si 3N 4@GO；
H 2O 2水溶液：又称双氧水；
室温：具有本领域公知的含义，一般是指25±2℃。
本发明的技术方案如下：
一种氧化石墨烯包覆氮化硅(Si 3N 4@GO)复合粉体，是通过H 2O 2水溶液高温氧化Si 3N 4表面，再用硅烷偶联剂进行表面接枝改性，形成带有正电荷的Si 3N 4粒子，然后用氧化石墨烯(GO)包覆Si 3N 4，利用氧化石墨烯表面带有羧基、羟基、环氧基官能团，在水中电离带有负电 荷，遇到表面被硅烷偶联剂接枝改性的带有正电荷的Si 3N 4粒子时，在静电力作用下进行自组装制得。
更进一步的，所述氧化石墨烯包覆氮化硅是按以下方法制备的：
将Si 3N 4粉体加入到双氧水中，在60～100℃氧化处理，然后分散到水醇混合溶液中，添加偶联剂水解溶液，偶联剂用量为氧化处理后Si 3N 4粉体质量的2.5％～10％；升温至60～90℃，调节pH值为8～10，搅拌反应得到偶联剂表面改性的Si 3N 4悬浊液；然后调节所述Si 3N 4悬浊液pH值为3～5，加入到pH值为8～10的氧化石墨烯水分散液中混合，超声搅拌后静置，直至包覆粒子全部沉淀，分离、干燥，得氧化石墨烯包覆氮化硅(Si 3N 4@GO)粉体。
根据本发明，优选的，所述氧化石墨烯包覆氮化硅中，氧化石墨烯包覆层平均厚度在2～8nm，Si 3N 4粒子的平均粒径为100～300nm。进一步优选的氧化石墨烯包覆层平均厚度在3～5nm，Si 3N 4粒子的平均粒径为100～200nm。
根据本发明，一种氧化石墨烯包覆氮化硅(Si 3N 4@GO)复合粉体的制备方法，包括步骤：
a.将Si 3N 4粉体加入到双氧水中，使充分分散，然后于温度60～100℃、磁力搅拌条件下氧化处理；制得表面氧化的Si 3N 4粉体；
b.取步骤a制得的表面氧化的Si 3N 4粉体分散到水醇混合溶液中，超声分散，之后添加偶联剂水解溶液，偶联剂用量为表面氧化的Si 3N 4粉体质量的2.5％～10％；继续超声搅拌使混合均匀；升温至60～90℃，调节pH值为8～10，在磁力搅拌下反应2-4小时；得到偶联剂表面改性的Si 3N 4悬浊液；然后调节所述Si 3N 4悬浊液pH值为3～5，将得到的酸性Si 3N 4悬浊液与pH值为8～10的氧化石墨烯水分散液混合，超声搅拌后静置，直至包覆粒子全部沉淀，分离、干燥，获得氧化石墨烯包覆氮化硅(Si 3N 4@GO)复合粉体。
根据本发明优选的，所述表面氧化的Si 3N 4粉体与氧化石墨烯的质量比为15～35:1～1.5；进一步优选18～30:1；最优选的，表面氧化的Si 3N 4粉体与氧化石墨烯的质量比为20:1。
根据本发明优选的，所述Si 3N 4粉体平均粒径为100～200nm；该粒径对于颗粒均匀及包覆完全较为重要。由于氧化石墨烯在分散液中具有片体结构，Si 3N 4颗粒粒径过大很难实现完全包覆；Si 3N 4颗粒粒径太小，则表面能较大，粒子之间易团聚，容易出现同时有多个Si 3N 4团聚粒子被氧化石墨烯包覆在一起的现象，造成包覆后粉体颗粒不均匀。
根据本发明优选的，步骤a中，双氧水溶液浓度为15％～30％质量百分比。采用超声搅拌使Si 3N 4粉体在双氧水充分分散。
根据本发明优选的，步骤a中，按每升双氧水溶液计，Si 3N 4粉体的加入量为10～20g/L。进一步优选，对所述Si 3N 4粉体表面氧化处理的温度为70～90℃。氧化处理时间为15～30min。
根据本发明优选的，步骤a中还包括，在氧化处理结束后，冷却至室温，离心分离，清 洗、干燥。制得表面氧化的Si 3N 4粉体。干燥温度可以采用80-120℃的中温，也可以采用150～300℃的高温。进一步优选的，所述干燥温度为200～250℃，干燥时间为6～10小时。采用高温干燥，有利于Si 3N 4粉体表面氧化。通过高温干燥缩短干燥时间，进一步提高氧化质量。所述清洗是用蒸馏水离心清洗固体物2～3次；所述干燥是将清洗后的固体物置于干燥箱中干燥。
所述步骤b中，所述表面氧化的Si 3N 4粉体质量与所述水醇溶液体积之比为1～2g:200～300mL。进一步的,所述水醇溶液为水与无水乙醇体积比1～1.5:1～1.5的溶液。所述超声分散的时间为30～60min。
进一步的,所述步骤b中，所述偶联剂水解溶液是：将偶联剂溶于水醇溶液中，超声搅拌30～60min充分水解。本发明首先将偶联剂用水醇混合溶液水解，使得偶联剂更易于分散。进一步的,以表面氧化的Si 3N 4粉体质量为100g计，所述偶联剂的质量与所述水醇溶液的体积之比为2.5～10g:50～100mL。所述水醇溶液是水与无水乙醇体积比1～1.5:1～1.5的溶液。
根据本发明优选的，步骤b中，所述偶联剂是硅烷偶联剂，选自3-氨丙基三乙氧基硅烷(KH550)、3-氨丙基三甲氧基硅烷(KH540)、N-2(氨乙基)3-氨丙基三乙氧基硅烷(KH910)或N-2(氨乙基)3-氨丙基甲基二甲氧基硅烷(KH602)等偶联剂的任意一种。本发明中偶联剂用量较现有技术有明显降低，且反应时间更短。
步骤b中，所述pH值为8～10的氧化石墨烯水分散液可按现有及时制备。本发明优选的，步骤b中，所述氧化石墨烯水分散液按以下方法配制：
将氧化石墨烯(GO)加入蒸馏水中，超声分散，氧化石墨烯分散液浓度为0.3～0.6mg/mL，进一步的,所述超声分散1～2.5h；通过滴加氨水调节氧化石墨烯分散液的pH值＝8～10。使得氧化石墨烯分散液呈负电性。本发明发现，用氨水调节pH能使氧化石墨烯表面电位能增强。
进一步优选的,所述步骤b中，所述偶联剂质量为表面氧化的Si 3N 4用量的4～6％；调节悬浊液pH为8.5～9.5，反应温度为75～85℃；进行偶联剂对表面氧化的Si 3N 4表面接枝改性反应。
进一步优选的,所述步骤b中，所述调节pH值为3～5是滴加质量分数10～15％的稀盐酸调节。本发明通过调节偶联剂表面改性的Si 3N 4悬浊液呈酸性，提高Si 3N 4悬浊液正电位能。
进一步优选的,所述步骤b中，将酸性Si 3N 4悬浊液与pH值为8～10的氧化石墨烯水分散液混合，超声搅拌30～60min。
进一步优选的,所述步骤b中，所述分离、干燥是，去除上清液，将所得沉淀物置于真空干燥箱中，60～80℃真空干燥。优选干燥时间10～12小时。
进一步优选的,所述步骤b的反应在三口烧瓶中水浴磁力搅拌下进行。
由于本发明偶联剂添加量少，改性效果好，本发明直接将改性处理的Si 3N 4复合粉体悬浊液添加到氧化石墨烯分散液中，步骤简便，包覆效果好。如偶联剂添加量过少，Si 3N 4颗粒表面不能完全被偶联剂接枝改性，颗粒包覆不完全，包覆率低；当偶联剂添加量过大，高浓度偶联剂水解后发生缩合，大的偶联剂团聚体的表面活性降低，接枝在颗粒表面的偶联剂量减少，致使包覆率下降。因此本发明优选的2.5％～10％较为适宜。最优选的，偶联剂添加量为表面氧化的Si 3N 4用量的4-6％。
本发明制备的Si 3N 4@GO复合粉体，用于陶瓷材料的增韧补强。特别是用于氧化铝基复合陶瓷刀具材料。
一种添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料，是由以下质量百分比的原料经热压烧结而成：
氧化石墨烯包覆氮化硅5～30％，氧化镁0.25～5％，钼0.5～5％，镍0.5～5％，其余为Al 2O 3；
根据本发明，优选的，所述复合陶瓷刀具材料的原料组分质量百分比为：氧化石墨烯包覆氮化硅10～30％，氧化镁0.25～2％，钼0.5～3％，镍1～3％，其余为Al 2O 3。
更进一步的，最优选所述复合陶瓷刀具材料的原料组分质量百分比为：氧化石墨烯包覆氮化硅20～21％，氧化镁0.5～0.8％，钼1～1.5％，镍1.2～1.5％，其余为Al 2O 3。
根据本发明，优选的，所述氧化镁(烧结助剂)平均粒径为0.5～5μm，进一步优选氧化镁平均粒径为0.5～2μm；钼的平均粒径为10～50μm，镍的平均粒径为10～50μm。进一步优选的，镍和钼平均粒径分别为15～45μm。
根据本发明，优选的，所述Al 2O 3平均粒径为100～500nm，进一步优选，所述Al 2O 3平均粒径为200～300nm。进一步优选，所述Al 2O 3为α-Al 2O 3。
根据本发明，所述添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料的制备方法，原料组分比例如前所述，包括本发明前述的氧化石墨烯包覆氮化硅(Si 3N 4@GO)复合粉体的制备步骤，还包括步骤：
c.将一定量的聚乙二醇添加到无水乙醇中，使其完全溶解；加入Al 2O 3，超声分散并机械搅拌，再加入氧化镁、钼和镍，继续超声分散并机械搅拌，得到混合均匀的悬浮液。
d.将步骤c中制得的悬浮液倒入球磨灌，充入氮气作为保护气体，连续球磨24～48h。
e.将步骤b中制得的Si 3N 4@GO复合粉体和球磨球一起加入到步骤d的球磨罐中，继续球磨2～4h，得添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料的料浆。
f.将步骤e制得的料浆干燥、过筛得到混合粉料，密封备用。
g.将步骤f所得干燥的混合粉料装入到材质为石墨的模具中进行热压烧结，得到添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料。
根据本发明优选的，步骤c中，所述的聚乙二醇分子量在2000～10000之间，特别优选聚乙二醇4000；所述的聚乙二醇的质量为Al 2O 3质量的1～5％。步骤c中，所述的超声分散并机械搅拌的时间是15～30min；所述的继续超声分散并机械搅拌的时间是15～30min。
根据本发明优选的，步骤d中，所述的球磨，加入硬质合金材质的球磨球，球料质量比为10～20：1。最优选的，连续球磨时间30-40h。
根据本发明优选的，步骤e中，所述添加Si 3N 4@GO复合粉体和球磨球的球料质量比为10～20：1；最优选的，继续球磨时间2～3h。氮气作为保护气体。
根据本发明优选的，步骤f中，所述料浆在真空干燥箱80～120℃下连续干燥12～24h。干燥后的粉体过200目筛。
根据本发明优选的，步骤g中，所述热压烧结条件为：烧结温度1400～1700℃，热压压力20～35MPa，保温时间10～30min，升温速度10～25℃/min。
本发明的技术特点及有益效果：
1、本发明解决现有技术对Si 3N 4粒子表面改性中产生的可控性低、环境污染等问题，通过用双氧水表面高温氧化赋予Si 3N 4粒子优异的表面特性。由于Si 3N 4颗粒多是片层状不规则结构，表面能较大易团聚且表面缺少含氧基团等，为颗粒的表面包覆和改性增加了技术难题。改性前首先用双氧水对Si 3N 4粉体进行表面氧化处理，克服了现有技术氧化方法可控性低操作复杂、易引入杂质、环保等问题。本发明应用一定浓度的双氧水高温处理Si 3N 4颗粒，操作简单，用时少，效率高且不会引入杂质。
2、目前硅烷偶联剂改性颗粒表面时，采用甲苯作为溶剂，进行液相反应，这样工业化生产存在成本、环保等问题。本发明应用水醇混合溶液作为溶剂，相比现有技术更加高效，经济实用，便于工业生产。
3、本发明利用氧化石墨烯表面带有羧基、羟基、环氧基等官能团，在水中电离带有负电荷，遇到表面被接枝改性偶联剂的Si 3N 4粒子时因表面带有正电荷，能够在静电力推动下发生自组装行为。本发明直接将分散好的氧化石墨烯溶液和偶联剂改性后的氮化硅悬浊液混合实现包覆制备，更加高效。而且粉体包覆效果好，成本低廉。所得Si 3N 4@GO复合粉体通过透射电镜观察，包覆完整，无氧化石墨烯团聚现象，分散性好。如图2、图3所示
4、本发明成功制备了Si 3N 4@GO复合粉体，改变了Si 3N 4粒子的表面特性，赋予Si 3N 4粒子优异的表面特性。为石墨烯在材料中的分散提供一种新的途径，为包覆Si 3N 4材料增加了一种新的品种，拓展了Si 3N 4粉体的应用空间。本发明制备的Si 3N 4@GO复合粉体分散性好，无团聚，便于应用时向陶瓷材料中添加，不会对其制备陶瓷材料的性能带来不利影响。
5、通过将Si 3N 4@GO复合粉体添加到陶瓷基体中，一是可以更加均匀的实现氧化石墨烯 在基体内的分布，避免氧化石墨烯团聚现象对陶瓷材料带来的缺陷。第二可以避免氧化石墨烯在平行于陶瓷基体热压方向的层状分布，避免了各向异性的现象。第三可以很好的起到增韧补强的效果；可大幅度提高陶瓷材料的断裂韧性，耐磨性能。
6、本发明提供一种新型的力学性能好的氧化铝基陶瓷刀具材料。首先通过静电自组装技术将氧化石墨烯对通过硅烷偶联剂表面改性的氮化硅粉体进行表面包覆。将包覆粉体添加到氧化铝陶瓷基体中，通过真空热压烧结，获得石墨烯包覆Si 3N 4增韧的Al 2O 3基复合陶瓷刀具材料，由于氧化石墨烯是石墨烯的派生物，真空热压烧结下，氧化石墨烯含氧基团分解转变为石墨烯，在有效解决石墨烯纳米粉体团聚问题的同时，实现石墨烯纳米相的协调增韧。本发明成功解决了石墨烯作为增强相在陶瓷材料中存在的团聚与基体结合不紧密且引起气孔等结构缺陷的问题，以及Si 3N 4粒子表面改性中产生的可控性低、环境污染等问题，同时避免了石墨烯在陶瓷基体中的取向性问题。
7、本发明将氧化石墨烯包覆氮化硅复合粉体添加到氧化铝陶瓷基体材料中，以氧化石墨烯包覆氮化硅为增强相，氧化镁、钼和镍为烧结助剂，经真空热压烧结制备Al 2O 3(Si 3N 4@GO)复合陶瓷刀具材料。该材料具有良好的力学性能。从复合陶瓷刀具材料的微观结构中观察发现，石墨烯均匀分散于氧化铝基体中，与基体材料结合紧密。相应的，随着添加氧化石墨烯包覆氮化硅复合粉体的增加，陶瓷刀具材料的力学性能随之改善。当氧化石墨烯包覆氮化硅的质量分数为21％时，添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基陶瓷刀具材料的力学性能最优，硬度18.4GPa、断裂韧性7.6MPa·m 1/2、抗弯强度628MPa。
8、本发明工艺设备简单，操作简便，安全性高。
附图说明
图1为KH550-Si 3N 4，Si 3N 4和KH550的红外光谱图。
图2为实施例2制备的Si 3N 4@GO复合粉体样品的TEM照片。
图3为实施例2制备的Si 3N 4@GO复合粉体样品的高倍TEM照片。
图4为实施例2制备的Si 3N 4@GO复合粉体的SEM照片。
图5为实施例4添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基陶瓷刀具材料的测试试样断裂面SEM形貌图。
具体实施方式
下面结合附图和实施例对本发明技术方案做进一步说明。但不限于此。
实施例1：
氧化石墨烯包覆氮化硅(Si 3N 4@GO)复合粉体的制备方法，步骤如下：
(1)称取平均粒径为100nm的原料Si 3N 4粉体2g，加入200mL浓度为15％的双氧水溶 液，磁力搅拌，升温至70℃，反应15min。冷却至室温，离心分离，并用蒸馏水清洗2～3次，置于干燥箱中200℃高温干燥6个小时，获得表面氧化的Si 3N 4粉体。
(2)配制3-氨丙基三甲氧基硅烷(KH540)硅烷偶联剂溶液：硅烷偶联剂用量为0.05g，滴加到50mL无水乙醇:蒸馏水＝1:1体积比的溶液中，超声水解30min备用。
(3)取步骤(1)制备的表面氧化的Si 3N 4粉体2g，置于200mL无水乙醇:蒸馏水＝1:1体积比的溶液中超声搅拌1h，将(2)中配制的3-氨丙基三甲氧基硅烷(KH540)硅烷偶联剂溶液添加到氮化硅悬浊液中，然后用质量分数为10％的氨水溶液调节pH值为8，置于带回流装置的三口烧瓶中，磁力搅拌，加热温度到70℃，反应2h，滴加质量分数10％的稀盐酸溶液，调节体系pH至3，得酸性Si 3N 4悬浊液。
(4)称取80mg氧化石墨烯(GO)置于200mL蒸馏水中(浓度为0.4mg/mL)超声2h，用质量分数为10％的氨水调节pH值为8。得氧化石墨烯水分散液。
(5)将步骤(3)的酸性Si 3N 4悬浊液在超声搅拌条件下与步骤(4)的氧化石墨烯水分散液混合，超声搅拌30min，静置、沉淀，去除上清液，置于真空干燥箱中，60℃真空干燥12小时，干燥后得到Si 3N 4@GO复合粉体。
本实施例获得的氧化石墨烯包覆氮化硅复合粉体为深灰色。通过透射电镜观察，Si 3N 4@GO为氧化石墨烯包覆单个Si 3N 4颗粒，且包覆完整，无氧化石墨烯团聚现象，分散性好。Si 3N 4@GO颗粒平均粒径为106nm，包覆在Si 3N 4颗粒表面的氧化石墨烯包覆层厚度在2～4nm左右，包覆效果良好。
实施例2：
氧化石墨烯包覆氮化硅(Si 3N 4@GO)复合粉体的制备方法，步骤如下：
(1)称取平均粒径为200nm的原料Si 3N 4粉体2g，加入200mL浓度为20％的双氧水溶液，磁力搅拌，升温至80℃，反应20min。冷却至室温，离心分离，并用蒸馏水清洗2～3次，置于干燥箱中220℃高温干燥8个小时，获得表面氧化的Si 3N 4粉体。
(2)配制3-氨丙基三乙氧基硅烷(KH-550)硅烷偶联剂溶液，硅烷偶联剂用量为0.1g，滴加到80mL无水乙醇:蒸馏水＝1:1体积比的溶液中，超声水解40min备用。
(3)取步骤(1)制备的表面氧化的Si 3N 4粉体2g，置于200mL无水乙醇:蒸馏水＝1:1体积比的溶液中超声搅拌0.5h，将(2)中配制的3-氨丙基三乙氧基硅烷(KH-550)硅烷偶联剂溶液添加到氮化硅悬浊液中，然后用质量分数为10％的氨水溶液调节pH值为9，置于带回流装置的三口烧瓶中，磁力搅拌，加热温度到80℃，反应3h，滴加质量分数10％的稀盐酸溶液，调节体系pH至4。得酸性Si 3N 4悬浊液。
(4)称取100mg氧化石墨烯(GO)置于200mL蒸馏水中(浓度为0.5mg/mL)超声1.5h，用质量分数为10％的氨水调节pH值到9。得氧化石墨烯水分散液。
(5)将步骤(3)的酸性Si 3N 4悬浊液超声搅拌条件下与步骤(4)的氧化石墨烯水分散液混合，超声搅拌40min，静置、沉淀，去除上清液，置于真空干燥箱中，70℃真空干燥12小时，干燥后得到Si 3N 4@GO复合粉体。
本实施例获得的氧化石墨烯包覆氮化硅复合粉体为深灰色。通过透射电镜观察，Si 3N 4@GO为氧化石墨烯包覆单个Si 3N 4颗粒，且包覆完整，无氧化石墨烯团聚现象，分散性好。Si 3N 4@GO颗粒平均粒径为208nm，包覆在Si 3N 4颗粒表面的氧化石墨烯包覆层厚度在3～5nm左右，包覆效果最佳。所得产品透射电镜图如图2和图3所示。Si 3N 4@GO复合粉体的SEM照片如图4所示。
实施例3：
氧化石墨烯包覆氮化硅(Si 3N 4@GO)复合粉体的制备方法，步骤如下：
(1)称取平均粒径为200nm的原料Si 3N 4粉体2g，加入200mL浓度为30％的双氧水溶液，磁力搅拌，升温至90℃，反应30min。冷却至室温，离心分离，并用蒸馏水清洗2～3次，置于干燥箱中250℃高温干燥10个小时获得表面氧化的Si 3N 4粉体。
(2)配制N-2(氨乙基)3-氨丙基三乙氧基硅烷(KH910)硅烷偶联剂溶液，硅烷偶联剂用量为0.2g，滴加到100mL无水乙醇:蒸馏水＝1:1体积比的溶液中，超声水解50min备用。
(3)取步骤(1)制备的表面氧化的Si 3N 4粉体2g，置于300mL无水乙醇:蒸馏水＝1:1体积比的溶液中超声搅拌1h，将(2)中配制的N-2(氨乙基)3-氨丙基三乙氧基硅烷(KH910)硅烷偶联剂溶液添加到氮化硅悬浊液中，然后用质量分数为10％的氨水溶液调节PH值为10，置于带回流装置的三口烧瓶中，磁力搅拌，加热温度到90℃，反应4h，滴加质量分数10％的稀盐酸溶液，调节体系pH至5。获得酸性Si 3N 4悬浊液。
(4)称取110mg氧化石墨烯(GO)置于200mL蒸馏水中(浓度为0.55mg/mL)超声1h，用质量分数为10％的氨水调节pH值到10。获得氧化石墨烯水分散液。
(5)将步骤(3)的酸性Si 3N 4悬浊液超声搅拌条件下与步骤(4)的氧化石墨烯水分散液混合，超声搅拌50min，静置、沉淀，去除上清液，置于真空干燥箱中，80℃真空干燥12小时，干燥后得到Si 3N 4@GO复合粉体。
本实施例获得的氧化石墨烯包覆氮化硅复合粉体颜色为深灰色。通过透射电镜观察，Si 3N 4@GO为氧化石墨烯包覆单个Si 3N 4颗粒，且包覆完整，无氧化石墨烯团聚现象，分散性好。Si 3N 4@GO颗粒平均粒径为210nm，包覆在Si 3N 4颗粒表面的氧化石墨烯包覆层厚度在4～6nm左右，包覆效果良好。
应用例：Si 3N 4@GO增韧Al 2O 3/Ti(C,N)纳米复合陶瓷材料(该应用例)
将本实施例2制备的Si 3N 4@GO复合粉体添加到Al 2O 3/Ti(C,N)陶瓷基体中。
Si 3N 4@GO增韧Al 2O 3/Ti(C,N)纳米复合陶瓷材料，原料组分的质量百分比为：Si 3N 4@GO 10.5％，Ti(C,N)15％，MgO 0.5％，Y 2O 3 0.2％，其余为Al 2O 3。
MgO和Y 2O 3平均粒径为1～3μm，A1 2O 3平均粒径为300～350nm；Ti(C,N)平均粒径为100～120nm，其C:N为7:3。按现有技术经热压烧结制备(烧结温度为1600℃,保温时间为25min,压力为25MP,升温速率为20℃/min)。
所制得的Si 3N 4@GO增韧Al 2O 3/Ti(C,N)纳米复合陶瓷材料经过切割、粗磨、精磨、研磨和抛光后进行力学性能测试，其中力学性能包括维氏硬度、断裂韧性和抗弯强度。其硬度、断裂韧性和抗弯强度分别为21.3GPa、7.8MPa·m 1/2和712MPa。
对比例1:GO增韧Al 2O 3/Ti(C,N)纳米复合陶瓷材料
将实施例2步骤(4)同等工艺分散的GO添加到Al 2O 3/Ti(C,N)陶瓷基体中。
GO增韧Al 2O 3/Ti(C,N)纳米复合陶瓷材料，原料组分的质量百分比为：GO 0.5％，Ti(C,N)15％，MgO 0.5％，Y 2O 3 0.2％，其余为Al 2O 3。
MgO和Y 2O 3平均粒径为1～3μm，A1 2O 3平均粒径为300～350nm；Ti(C,N)平均粒径为100～120nm，其C:N为7:3。按现有技术经热压烧结制备(烧结温度为1600℃,保温时间为25min,压力为25MP,升温速率为20℃/min)。
所制得的GO增韧Al 2O 3/Ti(C,N)纳米复合陶瓷材料经过切割、粗磨、精磨、研磨和抛光后进行力学性能测试，其中力学性能包括维氏硬度、断裂韧性和抗弯强度。其硬度、断裂韧性和抗弯强度分别为19.2GPa、6.5MPa·m 1/2和630MPa。
实施例4、一种添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料，是由以下质量百分比的原料经热压烧结而成：
氧化石墨烯包覆氮化硅10.5％，氧化镁0.25％，钼0.5％，镍1％，其余为Al 2O 3。
制备步骤如下：
1.将质量为Al 2O 3质量的1％的聚乙二醇添加到无水乙醇中，使其完全溶解，超声分散并机械搅拌15min；加入平均半径为200nm的Al 2O 3粉体，继续超声分散并机械搅拌15min，获得Al 2O 3分散液。
2.添加烧结助剂MgO平均粒径为0.5μm和金属Ni、Mo平均粒径为15μm到步骤1所述的Al 2O 3分散液中，然后超声分散并机械搅拌15min，得到混合均匀的悬浮液。
3.将步骤2中制得的悬浮液倒入球磨灌，充入氮气作为保护气体，加入硬质合金材质的球磨球，球料质量比为10:1，连续球磨24h。
4.将实施例2制得的Si 3N 4@GO复合粉体和球磨球按步骤3球料质量比加入到球磨罐中，其中，Si 3N 4@GO复合粉体的添加量为10.5％(氧化石墨烯的添加量为0.5％)继续球磨2h，获得添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料的料浆。
5.将所得添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料的料浆在真空干燥箱80℃下连续干燥12h，然后过筛得到混合粉料，密封备用。
6.将步骤5所得干燥的混合粉料装入到材质为石墨的模具中进行热压烧结，烧结温度1450℃，热压压力20MPa，保温时间15min，升温速度10℃/min，即得到添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料。
将制得的添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基陶瓷刀具材料经切割加工、粗磨、精磨、研磨和抛光等步骤制备成3mm×4mm×30mm的陶瓷样条，测得其力学性能为：硬度18.2GPa、断裂韧性5.2MPa·m 1/2、抗弯强度502MPa。测试试样断裂面SEM形貌图如图2所示。
实施例5、一种添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料，是由以下质量百分比的原料经热压烧结而成：
石墨烯包覆氮化硅21％，氧化镁0.5％，钼1％，镍1.25％，其余为Al 2O 3。
1.将质量为Al 2O 3质量的2％的聚乙二醇添加到无水乙醇中，使其完全溶解，超声分散并机械搅拌25min；加入平均半径为200nm的Al 2O 3，继续超声分散并机械搅拌30min，获得Al 2O 3分散液。
2.添加烧结助剂MgO平均粒径为1μm和金属Ni、Mo平均粒径为20μm到步骤1所述的Al 2O 3分散液中，然后超声分散并机械搅拌20min，得到混合均匀的悬浮液。
3.将步骤2中制得的悬浮液倒入球磨灌，充入氮气作为保护气体，加入硬质合金材质的球磨球，球料质量比为15:1，连续球磨36h。
4.将实施例2制得的Si 3N 4@GO复合粉体和球磨球按步骤3球料质量比加入到球磨罐中，其中，Si 3N 4@GO复合粉体的添加量为21％(氧化石墨烯的添加量为1％)，再次球磨3h，获得添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料的料浆。
5.将所得添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料的料浆在真空干燥箱90℃下连续干燥18h，然后过筛得到混合粉料，密封备用。
6.将步骤5所得干燥的混合粉料装入到材质为石墨的模具中进行热压烧结，烧结温度1600℃，热压压力30MPa，保温时间30min，升温速度15℃/min，即得到添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料。
将制得的添加石墨烯包覆氧化铝复合粉体的氧化铝基陶瓷刀具材料经切割加工、粗磨、精磨、研磨和抛光等步骤制备成3mm×4mm×30mm的陶瓷样条，测得其力学性能为：硬度18.4GPa、断裂韧性7.6MPa·m 1/2、抗弯强度628MPa。
实施例6、一种添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料，是由以下质量百分比的原料经热压烧结而成：
石墨烯包覆氮化硅26.25％，氧化镁0.75％，钼2％，镍2.5％，其余为Al 2O 3。
1.将质量为Al 2O 3质量的5％的聚乙二醇添加到无水乙醇中，使其完全溶解，超声分散并机械搅拌30min；加入平均半径为200nm的Al 2O 3，继续超声分散并机械搅拌30min，获得Al 2O 3分散液。
2.添加烧结助剂MgO平均粒径为2μm和金属Ni、Mo平均粒径为30μm到步骤1所述的Al 2O 3分散液中，然后超声分散并机械搅拌30min，得到混合均匀的悬浮液。
3.将步骤2中制得的悬浮液倒入球磨灌，充入氮气作为保护气体，加入硬质合金材质的球磨球，球料质量比为20:1，连续球磨48h。
4.将实施例2制得的Si 3N 4@GO复合粉体和球磨球按步骤3球料质量比加入到球磨罐中，其中，Si 3N 4@GO复合粉体的添加量为26.25％(氧化石墨烯的添加量为1.25％)，再次球磨3h，获得添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料的料浆。
5.将所得添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料的料浆在真空干燥箱100℃下连续干燥24h，然后过筛得到混合粉料。
6.将步骤5所得干燥的混合粉料装入到材质为石墨的模具中进行热压烧结，烧结温度1700℃，热压压力30MPa，保温时间30min，升温速度15℃/min，即得到添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料。
将制得的添加石墨烯包覆氧化铝复合粉体的氧化铝基陶瓷刀具材料经切割加工、粗磨、精磨、研磨和抛光等步骤制备成3mm×4mm×30mm的陶瓷样条，测得其力学性能为：硬度18.1GPa、断裂韧性6.8MPa·m 1/2、抗弯强度526MPa。
对比例2.使用未包覆的Si 3N 4粉体制备氧化铝基复合陶瓷刀具材料
1.将质量为Al 2O 3质量的2％的聚乙二醇添加到无水乙醇中，使其完全溶解，超声分散并机械搅拌25min；加入平均半径为200nm的Al 2O 3，继续超声分散并机械搅拌30min，获得Al 2O 3分散液。
2.添加烧结助剂MgO平均粒径为1μm和金属Ni、Mo平均粒径为20μm到步骤1所述的Al 2O 3分散液中，然后超声分散并机械搅拌20min，得到混合均匀的悬浮液。
3.将步骤2中制得的悬浮液倒入球磨灌，充入氮气作为保护气体，加入硬质合金材质的球磨球，球料质量比为15:1，连续球磨36h。
4.将平均粒径为200nm的Si 3N 4粉体和球磨球按步骤3球料质量比加入到球磨罐中，其 中，Si 3N 4粉体的添加量为21％，再次球磨3h，获得添加氮化硅粉体的氧化铝基复合陶瓷刀具材料的料浆。
5.将所得添加氮化硅粉体的氧化铝基复合陶瓷刀具材料的料浆在真空干燥箱90℃下连续干燥18h，然后过筛得到混合粉料，密封备用。
6.将步骤5所得干燥的混合粉料装入到材质为石墨的模具中进行热压烧结，烧结温度1600℃，热压压力30MPa，保温时间30min，升温速度15℃/min，即得到添加氮化硅粉体的氧化铝基复合陶瓷刀具材料。
将制得的氧化铝基陶瓷刀具材料经切割加工、粗磨、精磨、研磨和抛光等步骤制备成3mm×4mm×30mm的陶瓷样条，测得其力学性能为：硬度17.6GPa、断裂韧性4.6MPa·m 1/2、抗弯强度432MPa。

Claims (10)

  1. 一种氧化石墨烯包覆氮化硅复合粉体，是通过H 2O 2水溶液高温氧化Si 3N 4表面，再用硅烷偶联剂进行表面接枝改性，形成带有正电荷的Si 3N 4粒子，然后用氧化石墨烯(GO)包覆Si 3N 4，利用氧化石墨烯表面带有羧基、羟基、环氧基官能团，在水中电离带有负电荷，遇到表面被硅烷偶联剂接枝改性的带有正电荷的Si 3N 4粒子时，在静电力作用下进行自组装制得；优选的，所述氧化石墨烯包覆Si 3N 4复合粉体，氧化石墨烯包覆层平均厚度在2～8nm，Si 3N 4粒子的平均粒径为100～300nm。
  2. 一种权利要求1所述的氧化石墨烯包覆氮化硅复合粉体的制备方法,包括步骤:
    a.将Si 3N 4粉体加入到双氧水中，使充分分散，然后于温度60～100℃、磁力搅拌条件下氧化处理；制得表面氧化的Si 3N 4粉体；
    b.取步骤a制得的表面氧化的Si 3N 4粉体分散到水醇混合溶液中，超声分散，之后添加偶联剂水解溶液，偶联剂用量为表面氧化的Si 3N 4粉体质量的2.5％～10％；继续超声搅拌使混合均匀；升温至60～90℃，调节pH值为8～10，在磁力搅拌下反应2-4小时；得到偶联剂表面改性的Si 3N 4悬浊液；然后调节所述Si 3N 4悬浊液pH值为3～5，将得到的酸性Si 3N 4悬浊液与pH值为8～10的氧化石墨烯水分散液混合，超声搅拌后静置，直至包覆粒子全部沉淀，分离、干燥，获得氧化石墨烯包覆氮化硅(Si 3N 4@GO)复合粉体。
  3. 如权利要求1所述的氧化石墨烯包覆氮化硅复合粉体的制备方法，其特征在于步骤a中的反应条件包括下列之一个或多个：
    A.所述Si 3N 4粉体平均粒径为100～200nm；
    B.按每升双氧水计，Si 3N 4粉体的加入量为10～20g/L；
    C.对所述Si 3N 4粉体表面氧化处理的温度为70～90℃。
  4. 根据权利要求1所述的氧化石墨烯包覆氮化硅复合粉体的制备方法，其特征在于步骤a中还包括，在氧化处理结束后，冷却至室温，离心分离，清洗，干燥；优选的，Si 3N 4粉体干燥时的温度为200～250℃。
  5. 根据权利要求1所述的氧化石墨烯包覆氮化硅复合粉体的制备方法，其特征在于步骤b中的反应条件包括下列之一个或多个：
    A.所述表面氧化的Si 3N 4粉体质量与所述水醇溶液体积之比为1～2g:200～300mL；优选的,所述水醇溶液是水与无水乙醇体积比1～1.5:1～1.5的溶液；
    B.所述偶联剂质量为表面氧化的Si 3N 4用量的4～6％；优选的，调节悬浊液pH为8.5～9.5，反应温度为75～85℃；
    C.所述表面氧化的Si 3N 4粉体与氧化石墨烯的质量比为15～35:1～1.5；
    D.所述表面氧化的Si 3N 4粉体与氧化石墨烯的质量比为20:1；
    E.所述偶联剂水解溶液是：将偶联剂溶于水醇溶液中，超声搅拌30～60min充分水解；优选的,以表面氧化的Si 3N 4粉体质量为100g计，所述偶联剂的质量与所述水醇溶液的体积之比为2.5～10g:50～100mL；
    F.所述氧化石墨烯水分散液按以下方法配制：将氧化石墨烯(GO)加入蒸馏水中，超声分散，氧化石墨烯分散液浓度为0.3～0.6mg/mL；滴加氨水调节氧化石墨烯分散液的pH值＝8～10。
  6. 一种根据权利要求1～5任一项所述的制备方法制备的氧化石墨烯包覆Si 3N 4复合粉体的应用，用于陶瓷材料增韧补强。
  7. 一种添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料，包括权利要求1～5任一项所述的制备方法制备的氧化石墨烯包覆Si 3N 4复合粉体，其特征在于是由以下质量百分比的原料经热压烧结而成：
    氧化石墨烯包覆氮化硅5～30％，氧化镁0.25～5％，钼0.5～5％，镍0.5～5％，其余为Al 2O 3。
  8. 如权利要求7所述的添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料，其特征在于所述复合陶瓷刀具材料的原料组分质量百分比为：氧化石墨烯包覆氮化硅10～30％，氧化镁0.25～2％，钼0.5～3％，镍1～3％，其余为Al 2O 3；优选的，所述复合陶瓷刀具材料的原料组分质量百分比为：氧化石墨烯包覆氮化硅20～21％，氧化镁0.5～0.8％，钼1～1.5％，镍1.2～1.5％，其余为Al 2O 3。
  9. 权利要求7或8所述添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料的制备方法，包括权利要求2-5任一项所述的步骤a或步骤b，还包括步骤：
    c.将一定量的聚乙二醇添加到无水乙醇中，使其完全溶解；加入Al 2O 3，超声分散并机械搅拌，再加入氧化镁、钼和镍，继续超声分散并机械搅拌，得到混合均匀的悬浮液；
    d.将步骤c中制得的悬浮液倒入球磨灌，充入氮气作为保护气体，连续球磨24～48h；
    e.将步骤b中制得的Si 3N 4@GO复合粉体和球磨球一起加入到步骤d的球磨罐中，继续球磨2～4h，得添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料的料浆；
    f.将步骤e制得的料浆干燥、过筛得到混合粉料，密封备用；
    g.将步骤f所得干燥的混合粉料装入到材质为石墨的模具中进行热压烧结，得到添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料。
  10. 如权利要求9所述添加氧化石墨烯包覆氮化硅复合粉体的氧化铝基复合陶瓷刀具材料的制备方法，其特征在于：步骤d中连续球磨时间30-40h，步骤e中继续球磨时间2～3h；步骤f中，所述料浆在真空干燥箱80～120℃下连续干燥12～24h；步骤g中，所述热压烧结条 件为：烧结温度1400～1700℃，热压压力20～35MPa，保温时间10～30min，升温速度10～25℃/min。
PCT/CN2017/118231 2017-10-13 2017-12-25 氧化石墨烯包覆氮化硅复合粉体、其制备与应用及Al2O3基陶瓷刀具材料 WO2019071839A1 (zh)

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