CN106478125A - A kind of preparation method of B4C modified C/C-SiC brake material - Google Patents

Abstract

The present invention relates to a kind of B₄The preparation method of C modification C/C SiC brake material, is about 0.4～0.6g/cm using vacuum pressure impregnating method in initial density³B is introduced in D refraction statics carbon felt₄C powder, and combine the method that chemical vapor infiltration (CVI) and reactive melt infiltration (RMI) prepare C/C SiC brake material.Using B₄C modification C/C SiC brake material, one side B₄C has protective effect as self-healing constituent element to carbon fiber and carbon base body, can significantly improve the non-oxidizability of material；On the other hand, B₄C has higher specific heat capacity, can improve the overall specific heat of material, effectively reduces brake temperature, improves material friction stability.

Description

A kind of preparation method of B4C modified C/C-SiC brake material

technical field

The invention belongs to the preparation method of C/C-SiC composite material, relates to a preparation method of B ₄ C modified C/C-SiC brake material, which is a method of introducing B ₄ C powder into three-dimensional acupuncture by vacuum pressure impregnation A carbon fiber prefabricated body, and a method for preparing B ₄ C modified C/C-SiC brake material by chemical vapor deposition combined with reactive melt infiltration process.

Background technique

The brake device is the core component for aircraft, high-speed rail, and automobiles to achieve braking and ensure safe operation. It mainly converts kinetic energy into heat energy through the relative motion of the friction surface to achieve the purpose of braking. During the braking process, the brake device converts huge kinetic energy into heat energy in a very short time and dissipates it.

Literature Krenkel W.Cost Effective Processing of Cmc Composites by MeltInfiltration(Lsi‐Process)[M]//25th Annual Conference on Composites,AdvancedCeramics,Materials,and Structures:A:Ceramic Engineering and ScienceProceedings,Volume 22,Issue 3.John Wiley&Sons , Inc., 2008: 443-454. discloses a C/SiC brake material obtained by controlling the cost and obtaining by using the liquid silicon impregnation method in the porous carbon fiber preform, which has been successfully used in Porsche (Porsche9llTurbo), Bentley, On high-end cars such as Bugatti, Lamborghini sports car and Audi. Literature Fan S, Zhang L, Cheng L, et al. Effect of braking pressure and braking speed on the tribological properties of C/SiC aircraft brake materials [J]. Composites Science & Technology, 2010, 70 (6): 959-965. A method for preparing a three-dimensional needle-punched C/SiC brake material. This brake material is prepared by chemical vapor infiltration (CVI process) combined with liquid silicon impregnation (LSI process). At present, this aircraft brake device has been applied in batches in China.

Carbon ceramic brake material has high and stable friction coefficient, small attenuation of friction coefficient under wet conditions, wear resistance, high strength, long service life and other excellent properties. It is a very competitive new generation of brake material. Because the brake material works under the condition of repeated thermal shock, the temperature of the friction interface is high, and hot spots will be formed on the brake interface, which will cause the oxidation of pyrolytic carbon and carbon fibers in the friction interface, resulting in serious wear of the material; more seriously, due to excessive brake temperature High, it will lead to serious oxidation deformation of the brake disc connection, resulting in connection failure and catastrophic accidents. Therefore, it is of great significance to introduce fillers with anti-oxidation, self-healing crack ability, and high specific heat capacity into carbon ceramic brake materials, which can effectively improve the oxidation resistance of carbon fiber and carbon matrix of carbon ceramic brake materials, and reduce the brake temperature.

At present, my country's high-speed trains cover various speed levels from 200 kilometers per hour to 380 kilometers per hour. When emergency braking is performed at a speed of 380 kilometers per hour, the brake temperature has reached 900-1000 ° C, reaching the use limit of powder metallurgy or steel brake materials. However, if the high-speed rail wants to speed up again, the powder metallurgy or steel brake materials currently used can no longer withstand the braking requirements in emergency situations. Carbon ceramic brake material will become the ideal brake material when the speed is higher than 380 kilometers per hour, and B ₄ C modified carbon ceramic brake material will be more suitable for high-speed rail brakes with a speed higher than 380 kilometers per hour.

Contents of the invention

technical problem to be solved

In order to avoid the deficiencies of the prior art, the present invention proposes a preparation method of B ₄ C modified C/C-SiC brake material. Insufficient friction and wear performance, high specific heat components are introduced into the brake material to increase the specific heat capacity of the brake material and reduce the brake temperature; for disc/caliper brake systems, self-healing and anti-oxidation components are introduced into the brake material to Improve the ability of the brake material to resist oxidation and wear, and increase the service life of the brake material.

Technical solutions

A method for preparing B ₄ C modified C/C-SiC brake material, characterized in that the steps are as follows:

Step 1: Add B ₄ C powder to the aqueous solution of carboxymethyl cellulose sodium CMC with a mass fraction of 0.5% to 1.5%, and prepare the B ₄ C slurry for more than 24 to 48 hours;

Step 2: Under vacuum conditions, immerse the ^three -dimensional needle-punched carbon fiber felt with a density of 0.4-0.6g/cm3 into the B ₄ C slurry, then pass in an inert gas to pressurize to 0.5-3MPa, hold the pressure for 30-60min, and then Take out and dry to obtain a three-dimensional needle-punched carbon fiber preform containing B ₄ C powder;

Step 3: Deposit pyrolytic carbon on the three-dimensional needle-punched carbon fiber preform by chemical vapor infiltration CVI or PIP by carbon-containing polymer impregnation and cracking method to obtain C/C composite material; then conduct vacuum high-temperature heat treatment;

Step 4: Siliconize the C/C composite material in a high-temperature vacuum furnace, the reaction melt is an alloy containing Si, the pressure in the furnace is lower than 50Pa, the reaction temperature is 1300-1900°C, the holding time is 0.5-4h, Cool naturally to room temperature to obtain B ₄ C modified C/C-SiC brake material.

In the step 1, B ₄ C powder with a mass ratio of 5:1-2 (H ₂ O:B ₄ C) is added.

The density of the C/C composite material containing B ₄ C powder prepared in step 3 is 1.3-1.7 g/cm ³ , and the process parameters are: propylene is used as a precursor, and PyC is deposited in the three-dimensional needle-punched C fiber prefabricated body. The temperature is 930°C and the deposition time is 300h.

The treatment temperature of the vacuum high-temperature heat treatment in step 3 is 2500°C, and the holding time is 1h.

The particle size of the B ₄ C powder is less than 5um.

Beneficial effect

The invention proposes a method for preparing a B ₄ C modified C/C-SiC brake material. B ₄ C, as a ceramic phase, has the same hardness as SiC, and is a high-temperature-resistant and wear-resistant ceramic, which can improve the friction and wear performance of the material. The oxidation of B ₄ C at the friction interface to B ₂ O ₃ can heal the defects of the friction interface, prevent the oxidative wear of pyrolytic carbon and carbon fiber, protect the toughening effect of carbon fiber, and reduce the brittle spalling of the friction interface. B ₄ C has higher specific heat, adding a certain amount of B ₄ C can effectively increase the specific heat capacity of the material, reduce the brake temperature, and improve the friction and wear performance.

Therefore, the introduction of high specific heat modified filler B ₄ C into the carbon ceramic brake material can effectively increase the specific heat of the brake material, thereby reducing the brake temperature, and B ₄ C can protect the carbon fiber and carbon matrix during the oxidation process , Reduce material oxidation wear, improve the stability of friction and wear properties of brake materials, and improve the reliability of carbon ceramic brake materials in service. Therefore, B ₄ C modified C/C-SiC brake material will become a new generation of carbon ceramic brake material.

The present invention introduces B ₄ C powder into three-dimensional needle-punched carbon felt with an initial density of about 0.4 to 0.6 g/cm ³ by vacuum pressure impregnation, and combines chemical vapor infiltration (CVI) and reaction melt infiltration (RMI) to prepare C /C-SiC brake material method. Using B ₄ C modified C/C-SiC brake material, on the one hand, B ₄ C as a self-healing component has a protective effect on carbon fiber and carbon matrix, which can significantly improve the oxidation resistance of the material; on the other hand, B ₄ C It has a higher specific heat capacity, which can increase the overall specific heat of the material, effectively reduce the brake temperature, and improve the stability of the friction performance of the material.

Description of drawings

Figure 1 is a flow chart of the preparation process of B ₄ C modified C/C-SiC brake material

Fig. 2 is the XRD spectrum of the C/CB ₄ C-SiC brake material in Example 1 of the present invention

Fig. 3 is the SEM photo of the surface of C/CB ₄ C-SiC brake material in Example 1 of the present invention

detailed description

Now in conjunction with embodiment, accompanying drawing, the present invention will be further described:

Example 1:

Step 1, preparation of C fiber preform:

Firstly, PAN-based T-300 (6～50K) carbon fiber is made into short-fiber tire mesh and non-weft fabric, and then the single-layer 0° non-weft fabric, tire mesh, 90° non-weft fabric, and tire mesh are stacked in sequence , and then use acupuncture technology to make the non-woven fabric and tire net into one. According to the required thickness, after repeated lamination, acupuncture, lamination, acupuncture..., a three-dimensional acupuncture carbon fiber prefabricated body is obtained. The density of the prefabricated body is about 0.55g/cm ³ , the density of the tire mesh layer is about 0.2g/cm ³ , the density of the non-weft cloth layer is about 0.6g/cm ³ , the volume content of carbon fiber is about 40%, and the layer density is about 14 layer/10mm.

Step 2, preparation of B ₄ C slurry:

Add 0.5wt% CMC (sodium carboxymethylcellulose) in distilled water, mix well and adjust the pH value to 11-12 with ammonia water and hydrochloric acid, then add the mass ratio of 5:1 (H ₂ O:B ₄ C) The B ₄ C powder was ball milled for 24 hours to obtain a uniformly mixed B ₄ C slurry.

Step 3, vacuum pressure slurry impregnation:

Put the three-dimensional needle-punched carbon fiber preform obtained in step 1 into the impregnation tank, and after evacuating for 30 minutes, inject B ₄ C slurry, pressurize to 0.9MPa with an inert gas, take it out after impregnation for about 30 minutes, and place it at 150°C Dry for 4 hours to obtain a three-dimensional needle-punched carbon fiber preform containing B ₄ C powder.

Step 4, preparation of C/C composite material containing B ₄ C:

Using propylene as the precursor, PyC was deposited in the three-dimensional needled C fiber preform at a deposition temperature of 930°C and a deposition time of 300 h to prepare a C/C composite with a density of 1.5 g/cm ³ containing B ₄ C powder. The deposited C/C composite material containing B ₄ C is subjected to vacuum high-temperature heat treatment, the treatment temperature is 2500° C., and the holding time is 1 h.

Step 5, reactive melt impregnation:

The C/C composite material containing B ₄ C powder obtained in step 4 is prepared by reactive melt infiltration process under vacuum condition to prepare B ₄ C modified C/C-SiC brake material. The reaction melt is Si, the pressure in the furnace is lower than 50Pa, the reaction temperature is 1580°C, and the holding time is 1h.

The XRD results of B ₄ C modified C/C-SiC brake material are shown in Figure 2, which shows that the material is composed of four phases: C, SiC, B ₄ C and Si. The SEM photo of the material is shown in Figure 3, which shows that B ₄ C mainly exists in the large pores inside the tire mesh layer. The comparison of mass loss between the modified C/C-SiC material and the unmodified material after oxidation at 700 °C for 10 h is shown in Table 1:

Table 1

Table 1 Mass loss rate of materials after oxidation at 700℃ for 10h

It can be seen from the table that the introduction of B ₄ C powder greatly improves the oxidation resistance of the C/C-SiC material itself, and plays an effective role in protecting the material.

The changes in the mass heat capacity J/(g K) of the modified C/C-SiC material and the unmodified material are shown in Table 2:

Table 2

Table 2 Mass heat capacity of materials

It can be seen from the table that the introduction of B ₄ C powder can effectively increase the specific heat of the material, which is beneficial to reduce the brake temperature.

Example 2:

Step 1, preparation of C fiber preform:

Firstly, PAN-based T-300 (6～50K) carbon fiber is made into short-fiber tire mesh and non-weft fabric, and then the single-layer 0° non-weft fabric, tire mesh, 90° non-weft fabric, and tire mesh are stacked in sequence , and then use acupuncture technology to make the non-woven fabric and tire net into one. According to the required thickness, after repeated lamination, acupuncture, lamination, acupuncture..., a three-dimensional acupuncture carbon fiber prefabricated body is obtained. The density of the prefabricated body is about 0.55g/cm ³ , the density of the tire mesh layer is about 0.2g/cm ³ , the density of the non-weft cloth layer is about 0.6g/cm ³ , the volume content of carbon fiber is about 40%, and the layer density is about 14 layer/10mm.

Step 2, preparation of B ₄ C slurry:

Add 1.0wt% CMC (sodium carboxymethylcellulose) in distilled water, mix well and adjust the pH value to 11-12 with ammonia water and hydrochloric acid, then add the mass ratio of 5:2 (H ₂ O:B ₄ C) The B ₄ C powder was ball milled for 48 hours to obtain a uniformly mixed B ₄ C slurry.

Step 3, vacuum pressure slurry impregnation:

Put the three-dimensional needle-punched carbon fiber prefabricated body obtained in step 1 into the impregnation tank, and after evacuating for 30 minutes, inject B ₄ C slurry, pressurize to 1.5MPa with inert gas, take it out after impregnation for about 60 minutes, and place it under the condition of 150°C Dry for 4 hours to obtain a three-dimensional needle-punched carbon fiber preform containing B ₄ C powder.

Step 4, preparation of C/C composite material containing B ₄ C:

Using propylene as a precursor, PyC was deposited in a three-dimensional needle-punched C fiber preform at a deposition temperature of 930 °C.

The deposition time was 300h, and a C/C composite material containing B ₄ C powder with a density of 1.6g/cm ³ was prepared. The deposited C/C composite material containing B ₄ C is subjected to vacuum high-temperature heat treatment, the treatment temperature is 2500° C., and the holding time is 1 h.

Step 5, reactive melt impregnation:

The C/C composite material containing B ₄ C powder obtained in step 4 is prepared by reactive melt infiltration process under vacuum condition to prepare B ₄ C modified C/C-SiC brake material. The reaction melt is Fe-Si alloy, the pressure in the furnace is lower than 50Pa, the reaction temperature is 1500°C, and the holding time is 2h.

Claims (5)

1. A preparation method of B ₄ C modified C/C-SiC brake material, characterized in that the steps are as follows: Step 1: Add B ₄ C powder to the aqueous solution of carboxymethyl cellulose sodium CMC with a mass fraction of 0.5% to 1.5%, and prepare the B ₄ C slurry for more than 24 to 48 hours; Step 2: Under vacuum conditions, immerse the ^three -dimensional needle-punched carbon fiber felt with a density of 0.4-0.6g/cm3 into the B ₄ C slurry, then pass in an inert gas to pressurize to 0.5-3MPa, hold the pressure for 30-60min, and then Take out and dry to obtain a three-dimensional needle-punched carbon fiber preform containing B ₄ C powder; Step 3: Deposit pyrolytic carbon on the three-dimensional needle-punched carbon fiber preform by chemical vapor infiltration CVI or PIP by carbon-containing polymer impregnation and cracking method to obtain C/C composite material; then conduct vacuum high-temperature heat treatment; Step 4: Siliconize the C/C composite material in a high-temperature vacuum furnace, the reaction melt is an alloy containing Si, the pressure in the furnace is lower than 50Pa, the reaction temperature is 1300-1900°C, the holding time is 0.5-4h, Cool naturally to room temperature to obtain B ₄ C modified C/C-SiC brake material. 2. The method for preparing B ₄ C modified C/C-SiC brake material according to claim 1, characterized in that: the mass ratio added in the step 1 is 5:1～2(H ₂ O:B ₄ C ) of B ₄ C powder. The Si-containing alloy is Si or Si-Zr alloy, Fe-Si alloy, Si-Al alloy. 3. according to the preparation method of B ₄ C modified C/C-SiC brake material described in claim 1 or 2, it is characterized in that: the density of the C/C composite material containing B ₄ C powder prepared in said step 3 It is 1.3-1.7g/cm ³ , and the process parameters are as follows: propylene is used as the precursor, and PyC is deposited in the three-dimensional needle-punched C fiber preform, the deposition temperature is 930°C, and the deposition time is 300h. 4. The method for preparing B ₄ C modified C/C-SiC brake material according to claim 1 or 2, characterized in that: the treatment temperature of the vacuum high temperature heat treatment in the step 3 is 2500°C, and the holding time is 1h. 5 . The method for preparing B ₄ C modified C/C-SiC brake material according to claim 1 or 2, characterized in that: the particle size of the B ₄ C powder is less than 5 um.