CN109665855B

CN109665855B - A kind of preparation method of carbon/carbon-boron nitride friction reducing composite material

Info

Publication number: CN109665855B
Application number: CN201910060868.3A
Authority: CN
Inventors: 刘富海; 易茂中; 冉丽萍
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2019-01-23
Filing date: 2019-01-23
Publication date: 2021-10-08
Anticipated expiration: 2039-01-23
Also published as: CN109665855A

Abstract

本发明公开了一种碳/碳‑氮化硼减摩复合材料的制备方法，将经石墨化处理的C/C坯体酸化处理，洗涤至中性获得预处理C/C坯体，然后浸泡于含改性剂的溶液中，反应获得官能化的C/C坯体，然后再将官能化的C/C坯体浸渍于h‑BN浆料中，烘干即得C/C‑BN预制体，C/C‑BN预制体再经碳源碳化增密、石墨化处理即得C/C‑BN减摩复合材料；所述改性剂选自硅烷偶联剂或聚乙烯醇(PVA)。本发明首创的采用浆料浸渍的方法获得BN基体，通过对C/C坯体进行官能化处理后，在浸渍浆料过程中可以有效的将BN粉体引入C/C坯体。此方法可有效避免碳纤维的损伤，保证C/C‑BN复合材料具有优异的结构强度。所得C/C‑BN复合材料具有优良的摩擦磨损性能。The invention discloses a preparation method of a carbon/carbon-boron nitride friction-reducing composite material. The graphitized C/C body is acidified, washed to neutrality to obtain a pretreated C/C body, and then soaked In the solution containing the modifier, the functionalized C/C green body is obtained by reaction, and then the functionalized C/C green body is immersed in the h-BN slurry, and dried to obtain the C/C-BN prefabricated The C/C-BN preform is then carbonized, densified and graphitized to obtain a C/C-BN friction-reducing composite material; the modifier is selected from silane coupling agent or polyvinyl alcohol (PVA) . The BN matrix is obtained by the method of slurry impregnation initiated by the present invention. After the C/C green body is functionalized, the BN powder can be effectively introduced into the C/C green body during the process of dipping the slurry. This method can effectively avoid the damage of carbon fibers and ensure that the C/C‑BN composites have excellent structural strength. The obtained C/C‑BN composites have excellent friction and wear properties.

Description

Preparation method of carbon/carbon-boron nitride antifriction composite material

Technical Field

The invention relates to a preparation method of a carbon/carbon-boron nitride antifriction composite material, belonging to the technical field of new materials.

Background

The C/C composite material has the advantages of low density, high strength, excellent thermal conductivity, proper friction coefficient, small volume abrasion, good processability and the like, is commonly applied to brake materials, and is also a friction first material in a plurality of autoclaves, chemical equipment and high-speed rotating mechanical structures. The C/C composite material is applied to sealing of aeroengine shafts and the like, and low friction coefficient and small abrasion are also the focus of domestic and foreign research.

However, the C/C friction material starts to oxidize at about 400 ℃ in air, the oxidation significantly reduces the braking performance and the service life of the material, and when the material is used for sealing materials, the friction coefficient and the wear rate are both too large, and the average friction coefficient of the C/C friction material is as high as 0.35, so how to further improve the friction coefficient and the wear rate of the C/C friction material applied to the sealing materials still remains a key point and a difficulty point to be paid attention to in future research.

Boron nitride has three crystal structures, hexagonal boron nitride (h-BN), hexagonal close-packed boron nitride and cubic boron nitride. Among them, hexagonal boron nitride (h-BN) is an excellent high-temperature solid lubricant, which has not only excellent thermophysical properties but also more superior oxidation resistance and frictional wear properties as compared with carbon materials. The oxidation resistance of the hexagonal boron nitride is obviously superior to that of the carbon/carbon composite material, the h-BN obviously starts to oxidize at 850 ℃, and the carbon/carbon composite material starts to oxidize at 450 ℃. And there are many similarities between BN and C, including density, thermal conductivity, heat capacity and crystal structure. The h-BN is adopted to partially replace a carbon matrix in the carbon/carbon composite material, so that carbon fiber reinforced carbon and hexagonal boron nitride (C/C-BN) friction materials with good oxidation resistance and friction performance can be obtained. The friction coefficient and the wear rate of the C/C-BN friction material are insensitive to the change of load, when the C/C-BN friction material is coupled with a ceramic ball, the friction coefficient is low, a B2O3 film formed by BN oxidation can improve the oxidation resistance of the material, and the influence on the friction and wear performance of the material is small.

At present, research on C/C-BN friction materials at home and abroad is relatively less, and processes for preparing a BN matrix mainly comprise a Precursor impregnation cracking method (PIP) and a Chemical Vapor Infiltration method (CVI).

The document "High density carbon fiber/boron nitride matrix composites: preparation of composites with an explicit fibrous resistance. seghi Steven, Lee, James economi, James carbon,43(2005) 2035-. Compared with the C/C composite material, the wear rate of the C/C-BN friction material is only 50 percent or even lower than that of the C/C composite material. They believe that the introduction of h-BN improves the stability of the tribofilm of the material under different energy loads, reduces the oxidative wear and the generation of particulate abrasive dust, thereby reducing the wear and reducing the influence of energy loads and temperature. However, the BN prepared by a precursor impregnation cracking method has a relatively large layer spacing d (002), and the precursor is easy to generate cracks and holes in the high-temperature cracking process.

Article of literature "Microstructural and cubic bearings of C/C-BN compositions characterized by chemical vapor infiltration, Fan, Xiameng, Yin, Xiaoweii, Cheng, Yu, Zhang, Litong, Cheng, Laifei, ceramics International,38(2012)6137-₃-NH₃-Ar-H₂h-BN is deposited on the surface of the carbon fiber as a gas source, and after the heat treatment at 1600 ℃, the interplanar spacing of BN obtained by vapor deposition is found to be

The smaller interplanar spacing leads to an improved moisture absorption resistance of the BN matrix, but due to the BCl, the BN matrix has a lower interplanar spacing than BN obtained under low-temperature treatment₃Is a toxic gas, so the practical production is limited. In addition, most of BN prepared by the chemical vapor infiltration method has an amorphous structure, the stability is poor, the chemical vapor deposition process has a plurality of and complicated control factors, and the form of the BN component is difficult to accurately control.

Domestic patent (CN101875562B) discloses that powder is scattered by adopting a layer-by-layer method, BN powder is uniformly adhered to two surfaces of a single-layer carbon fiber net blank, the net blank is laminated layer by layer and then the laminated net blank is needled to prepare a carbon fiber preform material containing the BN powder, and then a pyrolytic carbon matrix is obtained by utilizing a CVI method to prepare a carbon fiber reinforced carbon and boron nitride double-matrix (C/C-BN) friction material. However, the method increases the difficulty of needling, and besides, the BN powder easily damages the carbon fibers, so that the mechanical property is reduced.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a preparation method of a carbon/carbon-boron nitride (C/C-BN) antifriction composite material with uniform tissue structure, oxidation resistance and frictional wear performance, and the preparation method is simple and easy to control, low in cost and short in period.

In order to achieve the above purpose, the invention provides the following technical scheme:

the invention relates to a preparation method of a carbon/carbon-boron nitride antifriction composite material, which comprises the following steps: acidifying the graphitized C/C blank, washing to be neutral to obtain a pretreated C/C blank, then soaking in a solution containing a modifier to react to obtain a functionalized C/C blank, soaking the functionalized C/C blank in BN slurry, drying to obtain a C/C-BN preform, and carbonizing, densifying and graphitizing the C/C-BN preform by a carbon source to obtain a C/C-BN composite friction material; the modifier is selected from silane coupling agent or polyvinyl alcohol (PVA).

The BN matrix is obtained by adopting the slurry dipping method for the first time, after the C/C blank is functionalized, BN powder can be effectively introduced into the C/C blank in the slurry dipping process, meanwhile, vacuum conditions and pressurization conditions are not needed in the process, the BN slurry (slurry containing the BN powder) can be introduced into the interior of the preform only through the capillary force of the BN slurry, and meanwhile, the introduced BN powder can be uniformly dispersed among the inner layers of the preform without agglomeration. The method can effectively avoid the damage of the carbon fiber and ensure that the C/C-BN composite friction material has excellent mechanical property.

In a preferred embodiment, the preparation method of the graphitized C/C body comprises the following steps: the carbon fiber preform is degummed at 2100-graded temperature of 2300 ℃, then the propylene is used as an air source, a pyrolytic carbon layer is obtained by a chemical vapor infiltration method (CVI method), and then the graphitization treatment at 2100-graded temperature of 2300 ℃ is carried out.

As a further preference, the carbon fiber preform is selected from 2.5D needled bulk felts, the 2.5D needled bulk felt having a density of 0.55-0.65g/cm³。

Further preferably, the density of the C/C body is 0.7-0.8g/cm³。

Preferably, the graphitized C/C green body is soaked in a nitric acid solution for acidification treatment for 1-2h at 50-60 ℃, and the mass fraction of nitric acid in the nitric acid solution is 50-65%.

Preferably, when the modifier is a silane coupling agent, the solvent of the solution containing the modifier is a mixed solvent of ethanol and water, and the mass ratio of the ethanol to the water is 9-12: 1.

Preferably, when the modifier is a silane coupling agent, the mass fraction of the modifier in the solution containing the modifier is 4-10%.

Further preferably, when the modifier is a silane coupling agent, the mass fraction of the modifier in the modifier-containing solution is 4 to 6%.

Preferably, when the modifier is polyvinyl alcohol, the solvent in the modifier-containing solution is water, and the mass fraction of the modifier is 25-35%.

Preferably, the pretreated C/C body is soaked in a solution containing a modifier, the pH value is adjusted to 4-5, ultrasonic hydrolysis reaction is carried out for 2-3h, and then drying is carried out for 2-2.5h at 70-85 ℃ to obtain the functionalized C/C body.

Preferably, the silane coupling agent is at least one selected from the group consisting of gamma-aminopropyltriethoxysilane (KH-550), gamma-glycidoxypropyltrimethoxysilane (KH-560), and gamma-methacryloxypropyltrimethoxysilane (KH-570).

In a preferred embodiment, the solid content (volume fraction) of the BN powder in the BN slurry is 10 to 33 vol%.

In a preferred embodiment, the pH value of the BN slurry is 6-8. In the present invention, the pH of the BN slurry has some effect on the flow properties of the slurry.

In the present invention, a density of 0.9g/cm can be obtained depending on the solid content of the BN slurry³-1.2g/cm³The C/C-BN preform of (1).

In a preferable scheme, the BN powder in the BN slurry is subjected to surface pretreatment firstly, and the surface pretreatment adopts the following two schemes,

the first scheme is as follows: placing the BN powder in an air atmosphere to carry out heat treatment at 850-870 ℃ for 55-65 min;

or

Scheme II: mixing BN powder, deionized water and a tetramethylammonium hydroxide solution according to a mass ratio of 8-10:3-6:1, then ball-milling for 10-15h, drying, and then carrying out heat treatment for 5-7h at the temperature of 550-650 ℃ in an air atmosphere; in the tetramethylammonium hydroxide solution, the mass fraction of the tetramethylammonium hydroxide is 5-10%;

the drying temperature is 120-150 ℃.

The inventor finds that by performing surface pretreatment on BN powder to enable the BN powder to have hydrophilic groups, the BN powder can be uniformly dispersed in slurry, so that the slurry has good fluidity, and in addition, in the surface pretreatment process, the treatment conditions also need to be effectively controlled, for example, when the scheme is adopted, a micro-oxidized BN powder surface is formed, and the time and the temperature are controlled to enable the oxidation weight to be increased to be below 0.3g, the BN slurry with the best fluidity can be obtained, and meanwhile, excessive loss of BN can not be brought. And the second scheme is not so harsh on the oxidation condition of BN, but has longer time, and is suitable for a large-scale preparation process.

For further optimization, the BN powder is hexagonal BN powder, the particle size is 0.8-1 mu m, and the purity is more than or equal to 98%.

In a preferred scheme, the preparation process of the BN slurry comprises the following steps: dispersing the surface-pretreated BN powder into an aqueous solution containing a dispersing agent, and then carrying out ball milling to obtain BN slurry, wherein the dispersing agent is polyethyleneimine and/or ammonium polyacrylate; the pH value of the aqueous solution containing the dispersing agent is 6-8.

The BN slurry prepared by the invention has low viscosity and good flow property.

Preferably, the rotation speed of the ball mill is 160-190r/min, the time is 1-1.5h, and the ball-to-material ratio is 5:1-7: 1.

More preferably, the addition amount of the dispersant is 3.8 to 4.5% by mass of the BN powder.

Preferably, the dipping time is 5-15 min.

In the invention, when the pretreatment is carried out on the C/C green body and the slurry is reasonably prepared, the impregnation can be finished only by soaking the pretreated C/C green body in the slurry and standing for 5-15min, and the method is equivalent to the impregnation in the prior art, so that the method is simple and quick, but can bring the effect of uniform impregnation without damaging fibers.

Preferably, the drying temperature is 80-85 ℃, and the drying time is 1.5-2 h.

In the invention, the drying step can be performed by freeze drying or drying in a conventional oven or other equipment, so that the conventional oven can be used for drying in order to save cost, and at the moment, the drying is effectively controlled according to the temperature and time, otherwise, the drying time is too long, so that the powder is easily aggregated on the surface to form a glaze-shaped shell. And if freeze drying is adopted, the phenomenon of surface incrustation can not occur.

In a preferred scheme, the mode of carbonizing and densifying the C/C-BN preform by a carbon source is liquid-phase carbon source resin impregnation carbonization and densification or gas-phase carbon source CVI densification, and the preferred mode is gas-phase carbon source CVI densification.

More preferably, in the case of impregnating, carbonizing and densifying with a liquid-phase carbon source resin, a furan resin is used as the liquid-phase carbon source.

In the invention, when the liquid-phase carbon source is adopted for impregnation, carbonization and densification, the conventional technology can be adopted.

Preferably, the liquid-phase carbon source resin impregnation, carbonization and densification process comprises the following steps: soaking the C/C-BN preform in furan resin at 60-65 ℃ for more than or equal to 1 hour in vacuum, then adding phosphoric acid into the furan resin, continuing vacuum impregnation for 30-50min, then carrying out pressurized impregnation for 1.5-2.5 hours, curing after the impregnation is finished, and then carbonizing;

the pressure during the pressure impregnation is 1.4-1.6MPa,

the temperature rise procedure of the solidification is to raise the temperature to 60-120 ℃, keep the temperature for 4-5h, then continue to raise the temperature to 120-180 ℃, keep the temperature for 5-7h, finally raise the temperature to 190-200 ℃ and keep the temperature for 1.5-3 h.

The carbonization temperature is increased to 900-.

More preferably, when the vapor phase carbon source CVI is used for densification, one of methane, propylene or natural gas is used as a carbon source gas, hydrogen is used as a diluent gas, the volume ratio of the carbon source gas to the diluent gas is 1:1-3, the vapor deposition time is 80-150 hours, and the deposition temperature is 800-.

In the preferable scheme, the temperature of the graphitization treatment is 1800-2100 ℃, and the time of the graphitization treatment is 8-15 h.

In a preferred embodiment, the density of the C/C-BN composite friction material is 1.5-1.75g/cm³。

The BN matrix is obtained by adopting the slurry dipping method for the first time, after the C/C blank is functionalized, BN powder can be effectively introduced into the C/C blank in the slurry dipping process, meanwhile, vacuum conditions and pressurization conditions are not needed in the process, the BN slurry (slurry containing the BN powder) can be introduced into the interior of the prefabricated body only through the capillary force of the BN slurry, and meanwhile, the introduced BN powder can be uniformly dispersed in the interior of the prefabricated body without agglomeration. The preparation method can effectively avoid the damage of the carbon fiber and ensure that the C/C-BN composite friction material has excellent mechanical property and frictional wear property.

Particularly, the BN matrix introduced by the invention does not damage fibers, is uniformly distributed, is quickly formed in the friction process, has wide coverage, is smoothly covered in the fiber and matrix areas, does not have a wavy step structure and the friction membrane is broken, and has less carbon fiber abraded, so that the carbon fiber can well support the friction membrane on the surface, and the friction coefficient and the wear rate are effectively reduced under the synergistic action.

Compared with the prior art, the advantages and positive effects are as follows:

(1) the C/C-BN friction material is prepared by the original process of combining the slurry impregnation method and the chemical vapor infiltration, the material tissue is uniform, the production process is simple and easy to control, and the preparation cost is low.

(2) By controlling the solid content of the BN slurry and the deposition time of chemical vapor infiltration, the contents of a BN matrix and pyrolytic carbon in the material can be controlled, thereby realizing the control of the microstructure and the performance of the material.

(3) Compared with the method of spraying powder by a layer-laying method, laminating and needling the powder by a layer-laying method and performing chemical vapor infiltration, the performance of the carbon fiber in the composite material prepared by the invention is kept, and compared with the method of injecting h-BN slurry by a needle, the method of the invention does not damage the carbon fiber, the effect of reinforcing the carbon fiber is preserved, and the preparation period is short. The reason is that the h-BN is introduced into the blank body through the capillary force, so that the carbon fiber is not damaged, the weftless fabric layer can well play a reinforcing role, and external auxiliary vacuum equipment is not needed.

(4) The C/C-BN friction material prepared by the invention has excellent friction and wear properties, low and stable friction coefficient, wear resistance, high strength, high temperature resistance, corrosion resistance and a series of advantages.

In conclusion, the production process is simple and easy to control, the preparation cost is low, and the method is suitable for industrial production. The C/C-BN composite friction material prepared by the invention has controllable microstructure and performance, uniform structure, high strength, high temperature resistance, corrosion resistance, excellent friction and wear performance and wide application prospect.

Drawings

FIG. 1 TEM image of the oxidized h-BN powder in example 1.

FIG. 2 TEM image of the lamellar structure of the h-BN powder from example 1.

FIG. 3 TEM image of h-BN powder after hydrolysis + oxidation in example 2.

FIG. 4 TEM image of h-BN powder after hydrolysis + oxidation in example 2.

FIG. 5 SEM image of the distribution area of particles after impregnating the C/C porous body with BN slurry in example 3.

FIG. 6 SEM image of the distribution area of particles after impregnating the C/C porous body with BN slurry in example 3.

FIG. 7 SEM image of the grinding crack morphology of the C/C-BN composite material obtained in example 1.

FIG. 8 SEM image of the grinding crack morphology of the C/C-BN composite material obtained in example 1.

Detailed Description

The present invention is further illustrated by the following examples.

In the following examples, the density and the open porosity of the prepared C/C-BN friction material and the C/C composite material as a control were measured by the Archimedes drainage method, and the frictional wear performance was measured on a HT-1000 ball-pan frictional wear tester with a sample size of

The mating part adopts a diameter of

The experimental conditions of the silicon nitride ball are as follows: speed: pressure 0.5 m/s: 5N at 25 deg.C and 450 deg.C

Example 1

(1) The density was 0.55g/cm³The three-dimensional needled carbon felt is prepared by laminating T-700 laid carbon cloth and a net tire, wherein the fiber direction of the adjacent laid carbon cloth is vertical, and a relay piercing process is adopted.

(2) Vacuum heat treatment: taking the three-dimensional needled carbon felt as a prefabricated part, heating to 2100 ℃ at a proper heating rate (10 ℃/min) in a vacuum atmosphere, and carrying out vacuum heat treatment for 1 h.

(3) Chemical vapor infiltration: depositing the needled whole felt preform by using propylene as a carbon source gas for 30-40h to obtain a density of about 0.7g/cm³The C/C preform of (1). And graphitizing the C/C preform at 2100 ℃ for 1 h.

(4) Functional group grafting of low-density blank

Soaking the low-density green body obtained in the step (1) in dilute nitric acid (concentration) for acidification treatment for 2h, filtering and washing to be neutral, and soaking the green body in a silane coupling agent KH-550, wherein the silane coupling agent: ethanol: adjusting the pH value to 4-5 with acetic acid in a mixed solution of water 1:17.1:1.9, carrying out ultrasonic hydrolysis reaction for 2h, and drying at 85 ℃ for 2h to obtain a C/C blank functionalized by grafting a functional group.

(5) Preparing low-viscosity BN slurry with different solid phase contents

Using Polyethyleneimine (PEI) as a dispersing agent, adding the PEI into water to obtain an aqueous solution containing the dispersing agent, adjusting the pH value of the aqueous solution containing the dispersing agent to be 7, carrying out high-temperature micro-oxidation treatment on BN powder at 870 ℃ for 55min, wherein the obtained micro-oxidation BN powder is shown in a figure 1-2, and after the h-BN powder is oxidized, the original lamellar structure of the h-BN powder is not damaged, only an oxide layer with the thickness of 4-7nm is arranged at the edge of a crystal grain, so that the h-BN particle can be seen to have complete crystal form, and interlamination is realizedA distance of

And then adding BN powder into an aqueous solution containing a dispersing agent, and carrying out ball milling for 1h in a planetary ball mill to prepare the BN water-based ceramic slurry with the solid content of 30 v%, wherein the adding amount of the dispersing agent is 4.2% of the mass of the BN powder, the BN powder is hexagonal BN powder, and the average particle size of the BN powder is 800 nm.

(6) And (3) dipping the C/C green body functionalized in the step (5) in the BN water-based ceramic slurry in the step (4) for 10min to obtain a C/C-BN prefabricated body.

(7) Drying: and (4) removing the water in the three-dimensional needled whole felt soaked in the step (6), wherein the drying temperature is 80 ℃, and the time is 1.5 h.

(8) Chemical vapor infiltration: and (3) placing the needled whole felt containing the BN powder obtained in the step (7) into a chemical vapor deposition furnace, and depositing a pyrolytic carbon matrix wrapping the hexagonal BN powder on the surface of the needled whole felt containing the hexagonal boron nitride powder by adopting a chemical vapor infiltration method to prepare the carbon fiber reinforced carbon and boron nitride dual-matrix (C/C-BN) composite material, wherein when CVI is densified, propylene is used as a carbon source gas, hydrogen is used as a diluent gas, the volume ratio of the carbon source gas to the diluent gas is 1:1, the vapor deposition time is 150 hours, and the deposition temperature is 950 ℃. And graphitizing the C/C-BN composite material at 2100 ℃ for 10h to obtain the C/C-BN composite friction material. The density of the obtained C/C-BN composite material is 1.58g/cm³。

Tests prove that the C/C-BN composite material obtained in the embodiment has the bending strength of 180.76MPa, the compression strength of 147.9MPa, the friction coefficient of 0.09 and the wear rate of 5.4 multiplied by 10^-5mm³N^-1m^-1。

In the friction process of the C/C-BN composite material obtained in the embodiment, the friction coefficient is always kept below 0.15 (average is 0.09), the friction mutation phenomenon is not obvious, through the observation of figures 7 and 8, the friction film is fast to form and wide in coverage, the friction film is flat in the areas of fibers and a base body, a wavy step structure and the breakage of the friction film are avoided, and the carbon fibers are less abraded, so that the carbon fibers can well support the friction film on the surface, and the friction coefficient and the abrasion rate are reduced.

Example 2

(3) Chemical vapor infiltration: propylene is used as carbon source gas to deposit the needled whole felt preform for 30-40h to obtain the density of about 0.7g/cm³The C/C preform of (1). And graphitizing the C/C preform at 2100 ℃ for 1 h.

(4) Functional group grafting of low-density blank

Soaking the low-density blank obtained in the step (1) in dilute nitric acid (concentration) for acidification treatment for 2h, filtering and washing to be neutral, and soaking the blank in a silane coupling agent KH-560, wherein the silane coupling agent: ethanol: adjusting the pH value to 4-5 with acetic acid in a mixed solution of water 1:17.1:1.9, carrying out ultrasonic hydrolysis reaction for 2h, and drying at 85 ℃ for 2h to obtain a C/C blank functionalized by grafting a functional group.

(5) Preparing low-viscosity BN slurry with different solid phase contents

And (2) adding Polyethyleneimine (PEI) serving as a dispersing agent into water to obtain an aqueous solution containing the dispersing agent, adjusting the pH value of the aqueous solution containing the dispersing agent to be 7, mixing the h-BN powder, deionized water and 10% tetramethylammonium hydroxide solution according to the proportion of 100g to 60ml to 10ml, and carrying out ball milling for 48h, wherein the surfaces of h-BN particles are subjected to hydrolysis reaction under a strong alkaline condition in the ball milling process. Drying the powder with hydrolyzed surface at 150 deg.c for further use. The powder is subjected to thermal oxidation treatment at 600 ℃ for 6h in the air atmosphere, the obtained pre-treated BN powder has the same effect as that of pre-oxidation at 850 ℃ as shown in figures 3 and 4, and only an oxide layer with the thickness of 4-8nm is generated at the edge of a lamella of h-BN, so that the complete lamella structure of the BN is maintained. And then adding BN powder into an aqueous solution containing a dispersing agent, and carrying out ball milling for 1h in a planetary ball mill to prepare the BN water-based ceramic slurry with the solid content of 20 v%, wherein the adding amount of the dispersing agent is 4.2% of the mass of the BN powder, the BN powder is hexagonal BN powder, and the average particle size of the BN powder is 800 nm.

(7) Drying: and (4) removing the water in the three-dimensional needled whole felt soaked in the step (6), wherein the drying temperature is 85 ℃, and the time is 1.5 h.

(8) Chemical vapor infiltration: and (3) placing the needled whole felt containing the BN powder obtained in the step (7) into a chemical vapor deposition furnace, and depositing a pyrolytic carbon matrix wrapping the hexagonal BN powder on the surface of the needled whole felt containing the hexagonal boron nitride powder by adopting a chemical vapor infiltration method to prepare the carbon fiber reinforced carbon and boron nitride dual-matrix (C/C-BN) composite material, wherein when CVI is densified, natural gas is used as a carbon source gas, hydrogen is used as a diluent gas, the volume ratio of the carbon source gas to the diluent gas is 1:3, the vapor deposition time is 150 hours, and the deposition temperature is 950 ℃. And graphitizing the C/C-BN composite material at 2100 ℃ for 10h to obtain the C/C-BN composite friction material. The density of the obtained C/C-BN composite material is 1.68g/cm³。

Tests prove that the C/C-BN composite material obtained in the embodiment has the bending strength of 138.59MPa, the compression strength of 147.9MPa and the friction coefficient of 0.15 and the wear rate of 3.9 multiplied by 10^-5mm³N^-1m^-1。

Example 3:

(3) Chemical vapor infiltration: propylene is used as carbon source gas to deposit the needled whole felt preform for 30-40h to obtain the density of about 0.7g/cm³The C/C preform of (1).And graphitizing the C/C preform at 2100 ℃ for 1 h.

(4) Functional group grafting of low-density blank

And (2) soaking the low-density blank obtained in the step (1) in dilute nitric acid (concentration) for acidification treatment for 2h, filtering and washing to be neutral, soaking the blank in a polyvinyl alcohol solution with the mass fraction of 30%, ultrasonically soaking for 2h, and drying at 85 ℃ for 2h to obtain the C/C blank functionalized by grafting functional groups.

(5) Preparing low-viscosity BN slurry with different solid phase contents

Adding Polyethyleneimine (PEI) serving as a dispersing agent into water to obtain a dispersing agent-containing aqueous solution, adjusting the pH value of the dispersing agent-containing aqueous solution to 7, subjecting BN powder to high-temperature micro-oxidation treatment at 860 ℃ for 55min, adding the BN powder into the dispersing agent-containing aqueous solution, and performing ball milling for 1h in a planetary ball mill to prepare BN water-based ceramic slurry with the solid content of 10 v%, wherein the adding amount of the dispersing agent is 4.2% of the mass of the BN powder, the BN powder is hexagonal BN powder, and the average particle size of the BN powder is 800 nm.

As can be seen from fig. 5 and 6, the BN slurry is mainly filled in the chopped fiber layer of the mesh layer, BN particles are tightly adsorbed on the surface of the pyrolytic carbon protective layer of the carbon fiber outer layer due to the function of functional groups, the lamellar structure of the particles is obvious, the shell-like morphology formed by the particles can be seen at the ends of the fibers, the particles form a coating on the surface of the fibers in a manner of tiling and gravel stacking, pores exist among the particles due to the evaporation of moisture during the drying process and the bridging effect of the BN lamellar structure, and when the particles are subsequently densified, the resin is filled among the particles to form a cobblestone floor-like mosaic structure, so that the particles are fixed by the resin carbon. So that the particles can both encapsulate the fibers and be uniformly distributed in the carbon matrix.

(8) Resin impregnation and carbonization: and (4) putting the C/C-BN prefabricated body obtained in the step (7) into an impregnation tank, vacuumizing and heating the impregnation tank to 60-65 ℃, and preserving heat for not less than 1 hour. Adding phosphoric acid with the mass of 6-8% of the resin into the resin storage tank, and preserving the heat for 30-50 min. The vacuum was stopped and nitrogen was charged to 1.4 to 1.6MPa, keeping the temperature of the dipping tank constant at 60 to 65 ℃ and keeping the pressure constant at 1.4 to 1.6MPa, and dipping for 2 hours. Curing temperature: 60-120 ℃, 4-5h 120-190 ℃, 5-7h, 190 ℃ 2 h. The carbonization heating rate is 1 ℃/min, the temperature is increased to 900 ℃, and the temperature is kept for 1 h. Finally, graphitizing the C/C-BN composite material at 2100 ℃ for 10h to obtain the C/C-BN composite material. The density of the obtained C/C-BN composite material is 1.75g/cm³。

Tests prove that the C/C-BN composite material obtained in the embodiment has the bending strength of 153.60MPa, the compression strength of 137.33MPa and the friction coefficient of 0.15 and the wear rate of 4.5 multiplied by 10^-5mm³N^-1m^-1。

Comparative example 1

(4) Functional group grafting of low-density blank

And (2) soaking the low-density blank obtained in the step (1) in dilute nitric acid (concentration) for acidification treatment for 2h, filtering and washing to be neutral, soaking the blank in polyethylene glycol solution, performing ultrasonic treatment for 2h at the temperature of 60 ℃ with water, and drying for 2h at the temperature of 85 ℃ to obtain a pretreated C/C blank.

(5) Preparing low-viscosity BN slurry with different solid phase contents

Adding Polyethyleneimine (PEI) serving as a dispersing agent into water to obtain a dispersing agent-containing aqueous solution, adjusting the pH value of the dispersing agent-containing aqueous solution to be 7, subjecting BN powder to high-temperature micro-oxidation treatment at 870 ℃ for 55min, adding the BN powder into the dispersing agent-containing aqueous solution, and performing ball milling for 1h in a planetary ball mill to prepare a BN water-based ceramic slurry with the solid content of 30 v%, wherein the adding amount of the dispersing agent is 4.2% of the mass of the BN powder, the BN powder is hexagonal BN powder, and the average particle size of the BN powder is 800 nm.

The slurry prepared in comparative example 1 cannot well penetrate the C/C green body, so that the powder is crusted on the surface, and the large concentration gradient of the inner and outer surfaces is caused, so that the powder is not uniformly impregnated.

Comparative example 2

(4) Functional group grafting of low-density blank

(5) Preparing low-viscosity BN slurry with different solid phase contents

Adding Polyethyleneimine (PEI) serving as a dispersing agent into water to obtain a dispersing agent-containing aqueous solution, adjusting the pH value of the dispersing agent-containing aqueous solution to be 7, directly adding BN powder into the dispersing agent-containing aqueous solution without high-temperature micro-oxidation treatment or the operation step of hydrolysis and thermal oxidation treatment of 10% tetramethylammonium hydroxide solution, and performing ball milling for 1h in a planetary ball mill to prepare slurry with good flowability, so that the powder is agglomerated or sticky, wherein the BN powder is hexagonal BN powder, and the average particle size of the BN powder is 800 nm.

Comparative example 3

(4) Functional group grafting of low-density blank

Soaking the low-density green body obtained in the step (1) in dilute nitric acid (concentration) for acidification treatment for 2h, filtering and washing to be neutral, and soaking the green body in a silane coupling agent KH-550, wherein the silane coupling agent: ethanol: adjusting the pH value to 4-5 with acetic acid in a mixed solution of water-4: 17.1:1.9, carrying out ultrasonic hydrolysis reaction at room temperature or below 30 ℃ for 2h, and drying at 85 ℃ for 2h to obtain a C/C blank functionalized by grafting functional groups. It can be seen that there is a white precipitate on the surface of the green body, resulting in no grafting of functional groups inside the green body, so that the BN slurry does not well penetrate into the green body.

Claims

1. a preparation method of carbon/carbon-boron nitride friction reducing composite material, it is characterized in that: the C/C green body through graphitization treatment is soaked in nitric acid solution at 50-60 ℃ of acidification treatment 1-2h, so The mass fraction of nitric acid in the nitric acid solution is 50-65%, washed to neutrality to obtain a pretreated C/C body, then soaked in a solution containing a modifier, reacted to obtain a functionalized C/C body, and then The functionalized C/C green body is immersed in the BN slurry and dried to obtain a C/C-BN preform. BN antifriction composite material; the modifier is selected from silane coupling agent or PVA.

2. the preparation method of a kind of carbon/carbon-boron nitride friction reducing composite material according to claim 1, is characterized in that, the described preparation method of the C/C blank through graphitization treatment: the carbon fiber preform Degumming and activation treatment at 2100-2300 ℃, and then using propylene as carbon source to obtain a pyrolytic carbon layer by chemical vapor infiltration method, and then undergoing graphitization treatment at 2100-2300 ℃; the carbon fiber preform is selected from 2.5D acupuncture integral Felt, the density of the 2.5D needle-punched integral felt is 0.55-0.65 g/cm ³ ; the density of the C/C blank is 0.7-0.85 g/cm ³ .

3. the preparation method of a kind of carbon/carbon-boron nitride friction-reducing composite material according to claim 1, is characterized in that: pretreatment C/C body is soaked in the solution containing modifier, adjust pH to 4-5, ultrasonic hydrolysis reaction for 2-3h, drying to obtain functionalized C/C green body;

When the modifier is a silane coupling agent, the solution containing the modifier, the solvent is a mixed solvent of ethanol and water, and the mass ratio of the ethanol to water is 9-12:1; the mass fraction of the modifier 4-10%;

When the modifier is polyvinyl alcohol, in the solution containing the modifier, the solvent is water, and the mass fraction of the modifier is 25-35%.

4. the preparation method of a kind of carbon/carbon-boron nitride friction reducing composite material according to claim 1 or 3, is characterized in that: described silane coupling agent is selected from KH-550, KH-560, KH- At least one of 570.

5. the preparation method of a kind of carbon/carbon-boron nitride friction reducing composite material according to claim 1, is characterized in that:

In the BN slurry, the solid content of the BN powder is 10-33 vol%;

The pH value of the BN slurry is 6-8;

The BN powder is hexagonal BN powder with a particle size of 0.8-1 μm and a purity of ≥98%.

6. the preparation method of a kind of carbon/carbon-boron nitride friction reducing composite material according to claim 1 or 5, is characterized in that:

The BN powder in the BN slurry is first subjected to surface pretreatment, and the method of the surface pretreatment is to adopt the following two schemes:

Option 1: Place the BN powder in an air atmosphere and heat treatment at 850-870°C for 55-65min;

or

Option 2: Mix BN powder, deionized water, and tetramethylammonium hydroxide solution according to the mass ratio of 8-10:3-6:1, then ball mill for 10-15h, dry, and then in an air atmosphere at 550- Heat treatment at 650°C for 5-7 h;

In the tetramethylammonium hydroxide solution, the mass fraction of tetramethylammonium hydroxide is 5-10%.

7. the preparation method of a kind of carbon/carbon-boron nitride friction reducing composite material according to claim 6, is characterized in that:

The preparation process of the BN slurry is as follows: dispersing the surface pretreated BN powder in an aqueous solution containing a dispersant, and then ball milling to obtain the BN slurry, and the dispersant is polyethyleneimine and/or polyacrylic acid Ammonium; the pH of the dispersant-containing aqueous solution is 6-8.

8. the preparation method of a kind of carbon/carbon-boron nitride friction reducing composite material according to claim 7, is characterized in that:

The rotating speed of the ball mill is 160-190r/min, the time is 1-1.5h, and the ball-to-material ratio is 5:1-7:1; the added amount of the dispersant is 3.8-4.5% of the mass of the BN powder.

9. the preparation method of a kind of carbon/carbon-boron nitride friction reducing composite material according to claim 1, is characterized in that:

The carbon source carbonization and densification of the C/C-BN preform is liquid carbon source resin impregnation carbonization densification or gas phase carbon source CVI densification;

When adopting gas-phase carbon source CVI for densification, use any one of methane, propylene, and natural gas as the carbon source gas, and use hydrogen as the diluent gas. The volume ratio of the carbon source gas to the diluent gas is 1:1-3, and the gas The deposition time is 80-150 hours, the deposition temperature is 800-1100℃,

The temperature of the graphitization treatment is 1800-2100°C, and the temperature and time of the graphitization treatment is 8-15h;

The density of the C/C-BN friction reducing composite material is 1.5-1.75 g/cm ³ .