阅读说明：本技术 一种以酚醛树脂为碳源的烧结制备多孔碳化硅陶瓷的方法 (Method for preparing porous silicon carbide ceramic by sintering with phenolic resin as carbon source ) 是由 刘建恒 于 2020-06-16 设计创作，主要内容包括：本发明公开了一种以酚醛树脂为碳源的烧结制备多孔碳化硅陶瓷的方法,涉及复合材料陶瓷制备技术领域,包括以下步骤：石墨烯、碳化锆、碳化硼、碳化硅、交联剂或偶联剂、胶体载体混合；研磨得石墨烯/碳化物聚合物初聚物,加入防絮凝剂、防沉淀剂,经高能研磨机研磨获得无溶剂胶体；加入碳化硅晶须和酚醛树脂、无水乙醇,球磨后得到陶瓷浆料；陶瓷浆料经干燥、挤压成型、程序升温/降温烧结后,得到碳化硅陶瓷。本发明采用酚醛树脂作为碳化硅陶瓷的碳源,陶瓷均匀致密且各方面性能均有所提升；将部分浆料制备成胶体,成品均匀；采用特定的程序升温/降温烧结方式,避免了由于烧结不均匀导致的产品缺陷,所得成品更加适用于高精密度工业生产要求。(The invention discloses a method for preparing porous silicon carbide ceramic by sintering by taking phenolic resin as a carbon source, which relates to the technical field of composite material ceramic preparation and comprises the following steps: mixing graphene, zirconium carbide, boron carbide, silicon carbide, a cross-linking agent or a coupling agent and a colloid carrier; grinding to obtain a graphene/carbide polymer primary polymer, adding an anti-flocculant and an anti-precipitant, and grinding by a high-energy grinder to obtain a solvent-free colloid; adding silicon carbide crystal whiskers, phenolic resin and absolute ethyl alcohol, and performing ball milling to obtain ceramic slurry; and drying, extruding and molding the ceramic slurry, and carrying out temperature programmed/reduced sintering to obtain the silicon carbide ceramic. According to the invention, phenolic resin is used as a carbon source of the silicon carbide ceramic, the ceramic is uniform and compact, and the performances of all aspects are improved; preparing part of the slurry into colloid, and obtaining a uniform finished product; and a specific temperature programming/cooling sintering mode is adopted, so that the product defect caused by uneven sintering is avoided, and the obtained finished product is more suitable for the high-precision industrial production requirement.)

1. A method for preparing porous silicon carbide ceramic by sintering with phenolic resin as a carbon source is characterized by comprising the following steps: the method comprises the following steps:

(1) mixing graphene, zirconium carbide, boron carbide, silicon carbide, a cross-linking agent or a coupling agent and a colloid carrier, and uniformly mixing the materials at high stirring;

(2) adding the mixture obtained in the step (1) into a charging bucket, and grinding to obtain a graphene/carbide polymer primary polymer;

(3) adding an anti-flocculant and an anti-precipitant into the obtained graphene/carbide polymer primary polymer, and grinding by a high-energy grinder to obtain a solvent-free colloid;

(4) adding silicon carbide whiskers and phenolic resin into the solvent-free colloid obtained in the step (3), adding absolute ethyl alcohol, and performing ball milling to obtain ceramic slurry;

(5) and drying, extruding and molding the obtained ceramic slurry, and carrying out temperature programmed/reduced sintering to obtain the silicon carbide ceramic.

2. The method for preparing porous silicon carbide ceramic by sintering with phenolic resin as carbon source according to claim 1, wherein: the graphene, the zirconium carbide, the boron carbide, the silicon carbide cross-linking agent or coupling agent and the colloid carrier in the step (1) are calculated according to the mass parts: 1-5 parts of graphene, 1-5 parts of zirconium carbide, 6-10 parts of boron carbide, 15-30 parts of silicon carbide, 0.1-0.5 part of a cross-linking agent or a coupling agent and 100 parts of a colloidal carrier; the high stirring is mechanical stirring at the speed of 350rpm and the high stirring time is 20-60 min.

3. The method for preparing porous silicon carbide ceramic by sintering with phenolic resin as carbon source according to claim 1, wherein: the graphene/carbide polymer primary polymer, the anti-flocculant and the anti-precipitant in the step (3) comprise the following components in parts by mass: 120 portions of graphene/carbide polymer primary polymer, 0.03 to 0.10 portion of graphene/carbide polymer primary polymer and 0.1 to 0.8 portion of anti-precipitation agent; the grinding time is 2-5 h.

4. The method for preparing porous silicon carbide ceramic by sintering with phenolic resin as carbon source according to claim 1, wherein: the graphene in the step (1) is graphene oxide or physical graphene; the cross-linking agent or the coupling agent is 2, 5-dimethyl-2, 5-di-tert-butyl hexane peroxide (bis 25), titanate or DCP; the colloid carrier is epoxy resin, a plasticizer or an epoxy resin reactive diluent, and comprises epoxy resin F51, E51, dibutyl phthalate, dioctyl phthalate, phosphate, epoxy resin reactive diluents 501, 600, 692 and the like; the deflocculant in the step (3) is polyacrylamide, Efka LP-9009 (an additive of Efka chemical company, model number Efka LP-9009), BEVLOID6721 (Ronghong defoamer, model number BEVLOID6721) and the like; the anti-precipitation agent is polyethylene wax, polyamide wax and the like, and comprises easily dispersible polyethylene wax, a humble 202P, polyamide wax 6900-20X, polyamide wax 4400-20X and the like.

5. The method for preparing porous silicon carbide ceramic by sintering with phenolic resin as carbon source according to claim 1, wherein: the solvent-free colloid, the silicon carbide whisker, the phenolic resin and the absolute ethyl alcohol in the step (4) are calculated according to the mass parts: 120-260 parts of solvent-free colloid, 10-25 parts of silicon carbide whisker, 30-90 parts of phenolic resin and 10-30 parts of absolute ethyl alcohol; the ball milling time is 1-3 h.

6. The method for preparing porous silicon carbide ceramic by sintering with phenolic resin as carbon source according to claim 1, wherein: drying in the step (5), wherein the drying temperature is 60-90 ℃, and the drying time is 2-48 h; and (3) performing extrusion forming, wherein the pressure is 50-250 MPa.

7. The method for preparing porous silicon carbide ceramic by sintering with phenolic resin as carbon source according to claim 1, wherein: and (5) performing temperature programming/temperature reduction sintering, specifically: and (3) preserving heat for a period of time after the first temperature rise, cooling, preserving heat after the second temperature rise, and naturally cooling to room temperature.

8. The method for preparing porous silicon carbide ceramic by sintering with phenolic resin as carbon source according to claim 7, wherein: the first temperature rise is carried out, the temperature rise rate is 50-200 ℃/min, the temperature rise is carried out to 2400 ℃, and the heat preservation time is 20-50min after the first temperature rise; the temperature is reduced, wherein the temperature reduction rate is 30-100 ℃/min, the temperature is reduced to 1300 ℃ and 1500 ℃, and the heat preservation time is 10-20 min; and finally, heating for the second time, wherein the heating rate is 50-200 ℃/min, the heating is carried out to 1800-2000 ℃ and the heat preservation time after the second heating is 10-20 min.

9. The method for preparing porous silicon carbide ceramic by sintering with phenolic resin as carbon source according to claim 7, wherein: the first temperature rise is carried out, the temperature rise rate is 50-200 ℃/min, the temperature rise is carried out to 2400 ℃, and the heat preservation time is 20-50min after the first temperature rise; the temperature is reduced, wherein the temperature reduction rate is 30-100 ℃/min, the temperature is reduced to 1300 ℃ and 1500 ℃, and the temperature is preserved for a period of time; finally, the temperature is raised for the second time, wherein the heating rate is 50-200 ℃/min, the temperature is raised to 1800-2000 ℃ and the heat preservation time is 10-20min after the second temperature rise;

in temperature programming/cooling, the relationship between the holding time is as follows:

wherein, t_mFor the holding time after cooling, t_pM is the holding time after the first temperature rise_fM is the mass of the phenolic resin_jIs the total mass of the ceramic slurry.

Technical Field

The invention relates to the technical field of composite ceramic preparation, in particular to a method for preparing porous silicon carbide ceramic by sintering by taking phenolic resin as a carbon source.

Background

Silicon carbide ceramic is a novel ceramic material with excellent mechanical property, good oxidation resistance, corrosion resistance and high temperature performance, and has attracted extensive attention and application in industrial production due to its excellent mechanical, chemical and even electrical conductivity.

At present, carbon microspheres (graphite or carbon black) are generally used as a carbon source in the preparation process of silicon carbide ceramics in the field, but the carbon source has the problems of easy agglomeration, uneven dispersion of the carbon source, overlarge carbon particle size, limited ceramic density and the like before or during sintering due to the inherent form of the carbon source; in addition, in the preparation of silicon carbide ceramics at present, slurry is usually simply mixed before sintering, and since ceramic slurry formed by silicon carbide, a carbon source and other materials cannot be kept in a uniform and stable state in the sintering process (even before sintering), silicon carbide is not uniformly distributed, and the sintering temperature is improperly controlled, the temperature of each part in the sintering process is not uniform, the hardness and toughness of each part of the final ceramic product are not uniform, and the product quality is affected.

Disclosure of Invention

Aiming at the defects of the silicon carbide ceramic caused by the carbon source problem and the unstable slurry, the invention provides a novel method for preparing porous silicon carbide ceramic by sintering by taking phenolic resin as a carbon source, which comprises the following steps:

(1) mixing graphene, zirconium carbide, boron carbide, silicon carbide, a cross-linking agent or a coupling agent and a colloid carrier, and uniformly mixing the materials at high stirring;

(2) adding the mixture obtained in the step (1) into a charging bucket, and grinding to obtain a graphene/carbide polymer primary polymer;

(3) adding an anti-flocculant and an anti-precipitant into the obtained graphene/carbide polymer primary polymer, and grinding by a high-energy grinder to obtain a solvent-free colloid;

(4) adding silicon carbide whiskers and phenolic resin into the solvent-free colloid obtained in the step (3), adding absolute ethyl alcohol, and performing ball milling to obtain ceramic slurry;

(5) and drying, extruding and molding the obtained ceramic slurry, and carrying out temperature programmed/reduced sintering to obtain the silicon carbide ceramic.

The graphene, the zirconium carbide, the boron carbide, the silicon carbide cross-linking agent or coupling agent and the colloid carrier in the step (1) are calculated according to the mass parts: 1-5 parts of graphene, 1-5 parts of zirconium carbide, 6-10 parts of boron carbide, 15-30 parts of silicon carbide, 0.1-0.5 part of a cross-linking agent or a coupling agent and 100 parts of a colloidal carrier; the high stirring is mechanical stirring at the speed of 350rpm and the high stirring time is 20-60 min.

And (3) grinding for 1-3 h.

The graphene/carbide polymer primary polymer, the anti-flocculant and the anti-precipitant in the step (3) comprise the following components in parts by mass: 120 portions of graphene/carbide polymer primary polymer, 0.03 to 0.10 portion of graphene/carbide polymer primary polymer and 0.1 to 0.8 portion of anti-precipitation agent; the grinding time is 2-5 h.

The graphene in the step (1) is graphene oxide or physical graphene; the cross-linking agent or the coupling agent is 2, 5-dimethyl-2, 5-di-tert-butyl hexane peroxide (bis 25), titanate or DCP; the colloid carrier is epoxy resin, a plasticizer or an epoxy resin reactive diluent, and comprises epoxy resin F51, E51, dibutyl phthalate, dioctyl phthalate, phosphate, epoxy resin reactive diluents 501, 600, 692 and the like; the deflocculant in the step (3) is polyacrylamide, EfkaLP-9009 (an additive of EfkaKa chemical company, model number EfkaLP-9009), BEVLOID6721 (Ronghong defoamer, model number BEVLOID6721) and the like; the anti-precipitation agent is polyethylene wax, polyamide wax and the like, and comprises easily dispersible polyethylene wax, a humble 202P, polyamide wax 6900-20X, polyamide wax 4400-20X and the like.

Preferably, the amount of the crosslinking agent or the coupling agent in the step (3) can also be adjusted by:

the cross-linking agent or the coupling agent is increased or decreased according to the reaction rate in the experiment, and the experiment reaction rate is obtained according to the following formula:

wherein S is the experimental reaction rate, c is the amount of reaction product, volume of Vt reaction vessel, and R is the reactantThe size, T, is the temperature during the reaction,for integrating a function f (theta) with theta, and theta is 0 toPi is the circumference ratio, lg is the logarithm with the base of 10, and t is the reaction time;

on the basis of the formula, judging the speed of the reaction according to the reaction rate, setting an initial reaction rate in the early stage, reducing the dosage of the cross-linking agent or the coupling agent on the basis when the reaction rate in the experiment is greater than the initial reaction rate, and increasing the dosage of the cross-linking agent or the coupling agent on the basis when the reaction rate in the experiment is less than the initial reaction rate.

The solvent-free colloid, the silicon carbide whisker, the phenolic resin and the absolute ethyl alcohol in the step (4) are calculated according to the mass parts: 120-260 parts of solvent-free colloid, 10-25 parts of silicon carbide whisker, 30-90 parts of phenolic resin and 10-30 parts of absolute ethyl alcohol; the ball milling time is 1-3 h.

And (5) drying at the drying temperature of 60-90 ℃ for 2-48 h.

And (3) performing extrusion forming, wherein the pressure is 50-250 MPa.

And (5) performing temperature programming/temperature reduction sintering, specifically: and (3) preserving heat for a period of time after the first temperature rise, cooling, preserving heat after the second temperature rise, and naturally cooling to room temperature.

The first temperature rise is carried out, the temperature rise rate is 50-200 ℃/min, the temperature rise is carried out to 2400 ℃, and the heat preservation time is 20-50min after the first temperature rise; the temperature is reduced, wherein the temperature reduction rate is 30-100 ℃/min, the temperature is reduced to 1300 ℃ and 1500 ℃, and the temperature is preserved for a period of time; and finally, heating for the second time, wherein the heating rate is 50-200 ℃/min, the heating is carried out to 1800-2000 ℃ and the heat preservation time after the second heating is 10-20 min.

Preferably, in the temperature programming/cooling, the relationship between the holding time is:

wherein, t_mFor the holding time after cooling, t_pM is the holding time after the first temperature rise_fM is the mass of the phenolic resin_jIs the total mass of the ceramic slurry.

Advantageous effects

The invention has the beneficial effects that:

firstly, phenolic resin is used as a carbon source of silicon carbide ceramic, carbide and graphene are uniformly distributed in a slurry system, the particle size of decomposed carbon particles is small, and the ceramic is compact; the mechanical property, the thermodynamic property and the electrical property of the ceramic are enhanced by adding the graphene, the zirconium carbide and the boron carbide; preparing part of the slurry into colloid in the steps (1) - (3), wherein the final slurry can be kept stable and uniform; when the cross-linking agent or the coupling agent is added, whether the amount of the cross-linking agent to be added is appropriate is judged through an experiment, and then the amount of the cross-linking agent in the subsequent operation is increased or decreased according to the reaction rate of the experiment, so that the phenomenon that the reaction rate is too slow, time and labor are consumed can be avoided, and the waste of resources due to too fast reaction can be effectively avoided; a specific temperature programming/cooling sintering mode is adopted and combined with slurry composition, so that the product defect caused by nonuniform sintering is avoided; the obtained finished product has good and uniform mechanical, thermodynamic and electrical properties, and is more suitable for the requirements of high-precision industrial production.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

The following examples and comparative examples are parallel runs, with the same processing steps and parameters, unless otherwise indicated.