CN101811892A - Method for preparing nanowire-toughened carbon/carbon composite material ceramic coating - Google Patents

Abstract

The invention discloses a method for preparing a nanowire-toughened carbon/carbon composite material ceramic coating. The method aims to solve the technical problem that the ceramic coating prepared by a conventional method has poor denseness. The method adopts the following technical scheme that: the nanowire-toughened carborundum (SiC)-molybdenum disilicide (MoSi2)-chromium silicide (CrSi2) ceramic coating is prepared by chemical vapor deposition, the cracking trend of the coating is reduced, and the ceramic coating with a dense structure is prepared by means of the toughening effect of nanowires. The effective anti-oxidization time of the prepared ceramic coating in atmosphere at the temperature of 1,500 DEG C is improved to 140 and 155 hours from 50 hours in background technology.

Description

A preparation method of nanowire toughened carbon/carbon composite ceramic coating

technical field

The invention relates to a preparation method of a carbon/carbon composite material ceramic coating, in particular to a preparation method of a nanowire toughened carbon/carbon composite material (hereinafter referred to as C/C composite material) ceramic coating.

Background technique

Oxidation at high temperature is the most difficult bottleneck in the practical application of thermal structural C/C composites. Researchers at home and abroad have proposed many solutions, and preparing an anti-oxidation coating on its surface is an effective means. Among them, ceramics The coating has good oxidation resistance and good physical and chemical compatibility with C/C composite materials, so it is an ideal coating material for C/C composite materials. However, the brittleness of ceramic coatings is the most difficult bottleneck in its practical application. The main reason for the anti-oxidation failure of the existing ceramic coating system is that the thermal expansion coefficient of the ceramic coating and the C/C substrate does not match, so that there is a large thermal stress in the ceramic coating, resulting in the ceramic coating being exposed to high and low temperature. In order to alleviate the cracking tendency of ceramic coatings, the whisker toughened ceramic coating technology has attracted great attention of researchers.

Literature "A SiC whisker-toughened SiC-CrSi ₂ oxidation protective coating for carbon/carbon composites, Fu Qiangang, Li Hejun, Shi Xiaohong, Li Kezhi, and Zhang Wei, Huang Min. Applied Surface Science 2007(253): 3757-3760" A method for preparing SiC whisker-toughened SiC- _CrSi2 ceramic coatings is disclosed by a two-step technology combining the slurry method and the embedding method. The method first prepares porous ceramic coatings on the surface of the C/C composite material by the slurry method. SiC whisker toughened SiC coating; secondly, Si-Cr alloy was used to fill the pores in SiC whisker toughened SiC coating by embedding method. Although this technology alleviates the cracking tendency of the ceramic coating in the high and low temperature alternating process to a certain extent, the toughening effect of the whisker toughened ceramic coating is not ideal. Because SiC whiskers are easy to agglomerate in the coating and dispersed unevenly, the toughening effect is limited, and the SiC whiskers are large in size, which will hinder the diffusion of coating powder, making the coating not dense enough, and there are large holes, which greatly Reduce the oxidation resistance of the coating, for example, the weight loss rate of the coating specimen has reached 0.66% after oxidation at 1500°C for 50 hours.

Contents of the invention

In order to overcome the shortage of poor compactness of the ceramic coating prepared by the existing method, the invention provides a preparation method of the nanowire toughened C/C composite ceramic coating. The method adopts chemical vapor deposition to prepare a SiC nanowire toughened SiC-MoSi ₂ -CrSi ₂ ceramic coating, and the toughening effect of the nanowire can reduce the cracking tendency of the coating and prepare a ceramic coating with a dense structure.

The technical solution adopted by the present invention to solve the technical problem: a method for preparing a nanowire toughened C/C composite ceramic coating, which is characterized in that it includes the following steps:

1) Clean the C/C composite material after grinding and polishing, and put it in an oven for drying;

2) Weighing Si powder with a mass percentage of 10-20%, C powder with 15-30%, and _SiO powder with 55-75% respectively, and placing them in a turpentine ball mill tank, and ball milling for 2-4 hours;

3) Put the powder prepared in step 2) into the graphite crucible so that the thickness of the powder is 1/5 of the depth of the graphite crucible, then bind the C/C composite material processed in step 1) with carbon fibers and hang it on the graphite crucible Above the surface of the powder in the crucible;

4) Put the graphite crucible into the vacuum reaction furnace. After vacuuming the vacuum furnace, pass argon to normal pressure, raise the furnace temperature from room temperature to 1600-1700°C at a heating rate of 5-10°C/min, and keep warm. 1 to 3 hours; then turn off the power and cool down to room temperature naturally, and protect with argon during the whole process;

5) Weigh Si powder with a mass percentage of 40-65%, C powder with 5-10%, _MoSi2 powder with 20-30%, and Cr powder with 10-20%, and place them in a turpentine ball mill jar, and mix them by ball milling Treat for 2 to 4 hours;

6) Put half of the powder prepared in step 5) into a graphite crucible, then put the C/C composite material containing SiC nanowires on the surface prepared in step 4), and then put the other half of the embedding powder to cover the surface containing C/C composite coverage of SiC nanowires;

7) Put the graphite crucible into the vacuum reaction furnace. After vacuuming the vacuum furnace, pass argon to normal pressure, raise the furnace temperature from room temperature to 2100-2300°C at a heating rate of 5-10°C/min, and keep warm. 1 to 3 hours; then turn off the power and cool down to room temperature naturally, and protect with argon during the whole process.

The beneficial effects of the present invention are: due to the SiC nanowire toughened SiC-MoSi ₂ -CrSi ₂ ceramic coating prepared by chemical vapor deposition, the cracking tendency of the coating is reduced by virtue of the toughening effect of the nanowire, and a compact structure is prepared. ceramic coating. The effective anti-oxidation time of the prepared ceramic coating in air at 1500 DEG C is increased from 50 hours in the background technology to 140-155 hours.

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

Description of drawings

FIG. 1 is a scanning electron micrograph of the surface of SiC nanowires prepared in Example 2 of the present invention.

Fig. 2 is a scanning electron micrograph of the surface of the SiC nanowire toughened ceramic coating prepared in Example 2 of the present invention.

Fig. 3 is a scanning electron micrograph of the cross-section of the SiC nanowire toughened ceramic coating prepared in Example 2 of the present invention.

Fig. 4 is the oxidation weight loss curve at 1500°C of the C/C composite material with SiC nanowire toughened ceramic coating on the surface prepared in Example 2 of the present invention.

Detailed ways

Example 1: The C/C composite material was sequentially polished and polished with No. 400, No. 800 and No. 1000 sandpaper respectively, washed with absolute ethanol, and dried in an oven for later use.

Weigh 10g of Si powder, 25g of C powder and 65g of _SiO2 powder respectively. Place in a turpentine ball mill jar, take different numbers of agate balls with different diameters into the rosin ball mill jar, and perform ball milling and mixing treatment on a planetary ball mill for 2 hours, and use it as a powder for later use.

Put the powder into the graphite crucible so that the thickness of the powder is one-fifth of the depth of the graphite crucible, then bind the dried C/C composite material with a bundle of 3K carbon fibers and hang it above the surface of the powder , and then put the graphite crucible into the vacuum reactor. After evacuating for 30 minutes, make the vacuum degree reach -0.09MPa, keep the vacuum for 30 minutes, and observe whether the indication of the vacuum gauge changes. If there is no change, it means that the system is well sealed. Blow argon to normal pressure. This process is repeated three times. Afterwards, the furnace temperature was raised to 1600° C. at a heating rate of 5° C./min, and then kept for 2 hours. Then turn off the power and cool down to room temperature naturally, and protect with argon during the whole process. Then the graphite crucible is taken out, and the carbon fibers on the C/C composite material are cleaned to obtain a C/C composite material with SiC nanowires on the surface.

Weigh 40g of Si powder, 10g of C powder, 30g of MoSi ₂ powder, and 20g of Cr powder. Place in a turpentine ball mill jar, put agate balls of different numbers and diameters into the rosin ball mill jar, and perform ball milling and mixing treatment on a planetary ball mill for 3 hours, and use it as an embedding material for later use.

Put half of the above-mentioned embedding material into the graphite crucible, put it into the prepared C/C composite material containing SiC nanowires on the surface, then put the other half of the embedding material, and shake the graphite crucible slightly to make the embedding material evenly The C/C composite material containing SiC nanowires on the surface is embedded, and then the graphite crucible is placed in a vacuum reactor. After evacuating for 30 minutes, make the vacuum degree reach -0.09MPa, keep the vacuum for 30 minutes, and observe whether the indication of the vacuum gauge changes. If there is no change, it means that the system is well sealed. Blow argon to normal pressure. This process is repeated three times. Afterwards, the furnace temperature was raised to 2100° C. at a heating rate of 7° C./min, and then kept for 2 hours. Then turn off the power and cool down to room temperature naturally, and protect with argon during the whole process. Then the graphite crucible is taken out, and the embedding powder is cleaned to obtain a C/C composite material containing SiC nanowire toughened SiC-MoSi ₂ -CrSi ₂ ceramic coating.

Oxidation experiments show that the SiC nanowire toughened SiC-MoSi ₂ -CrSi ₂ ceramic coating has an effective anti-oxidation time of 140 hours in air at 1500°C.

Example 2: The C/C composite material was sequentially polished and polished with No. 400, No. 800 and No. 1000 sandpaper respectively, washed with absolute ethanol, and dried in an oven for later use.

Weigh 15g of Si powder, 30g of C powder and 75g of _SiO2 powder respectively. Place in a turpentine ball mill jar, put agate balls of different numbers and different diameters into the rosin ball mill jar, and perform ball milling and mixing treatment on a planetary ball mill for 3 hours, and use it as a powder for later use.

Put the powder into the graphite crucible so that the thickness of the powder is one-fifth of the depth of the graphite crucible, then bind the baked C/C composite material with a bundle of 3K carbon fibers and hang it above the surface of the powder, Then put the graphite crucible into the vacuum reactor. After evacuating for 30 minutes, make the vacuum degree reach -0.09MPa, keep the vacuum for 30 minutes, and observe whether the indication of the vacuum gauge changes. If there is no change, it means that the system is well sealed. Blow argon to normal pressure. This process is repeated three times. Afterwards, the furnace temperature was raised to 1650° C. at a heating rate of 7° C./min, and then kept at a temperature of 3 hours. Then turn off the power and cool down to room temperature naturally, and protect with argon during the whole process. Then the graphite crucible is taken out, and the carbon fibers on the C/C composite material are cleaned to obtain a C/C composite material with SiC nanowires on the surface.

50g of Si powder, 8g of C powder, 27g of MoSi ₂ powder and 15g of Cr powder were weighed respectively. Place in a turpentine ball mill jar, put agate balls of different numbers and diameters into the rosin ball mill jar, and perform ball milling and mixing treatment on a planetary ball mill for 4 hours, and use it as an embedding material for later use.

Put half of the above-mentioned embedding material into the graphite crucible, put it into the prepared C/C composite material containing SiC nanowires on the surface, then put the other half of the embedding material, and shake the graphite crucible slightly to make the embedding material evenly The C/C composite material containing SiC nanowires on the surface is embedded, and then the graphite crucible is placed in a vacuum reactor. After evacuating for 30 minutes, make the vacuum degree reach -0.09MPa, keep the vacuum for 30 minutes, and observe whether the indication of the vacuum gauge changes. If there is no change, it means that the system is well sealed. Blow argon to normal pressure. This process is repeated three times. Afterwards, the furnace temperature was raised to 2200° C. at a heating rate of 10° C./min, and then kept for 3 hours. Then turn off the power and cool down to room temperature naturally, and protect with argon during the whole process. Then the graphite crucible is taken out, and the embedding powder is cleaned to obtain a C/C composite material containing SiC nanowire toughened SiC-MoSi ₂ -CrSi ₂ ceramic coating.

It can be seen from Figure 1 that the orientation of SiC nanowires on the surface of the C/C composite obtained by chemical vapor deposition is randomly distributed, forming a loose porous structure. It can be seen from Figure 2 that the prepared SiC nanowire toughened ceramic coating has a compact structure without obvious defects such as holes and cracks. It can be seen from Figure 3 that the as-prepared SiC nanowires have disordered orientation and uniform dispersion in the ceramic coating. It can be seen from Figure 4 that the oxidation resistance of the SiC nanowire toughened SiC-MoSi ₂ -CrSi ₂ ceramic coating is significantly improved, and the effective oxidation resistance time in air at 1500°C reaches 155 hours.

Example 3: The C/C composite material was sequentially polished and polished with No. 400, No. 800 and No. 1000 sandpaper respectively, washed with absolute ethanol, and dried in an oven for later use.

Weigh 20g of Si powder, 15g of C powder and 55g of _SiO2 powder respectively. Place in a turpentine ball mill jar, put agate balls of different numbers and different diameters into the turpentine ball mill jar, and carry out ball milling and mixing treatment on a planetary ball mill for 4 hours, and use it as a powder for later use.

Put the powder into the graphite crucible so that the thickness of the powder is one-fifth of the depth of the graphite crucible, then bind the baked C/C composite material with a bundle of 3K carbon fibers and hang it above the surface of the powder, Then put the graphite crucible into the vacuum reactor. After evacuating for 30 minutes, make the vacuum degree reach -0.09MPa, keep the vacuum for 30 minutes, and observe whether the indication of the vacuum gauge changes. If there is no change, it means that the system is well sealed. Blow argon to normal pressure. This process is repeated three times. Afterwards, the furnace temperature was raised to 1700° C. at a heating rate of 10° C./min, and then kept for 1 hour. Then turn off the power and cool down to room temperature naturally, and protect with argon during the whole process. Then the graphite crucible is taken out, and the carbon fibers on the C/C composite material are cleaned to obtain a C/C composite material with SiC nanowires on the surface.

65g of Si powder, 5g of C powder, 20g of MoSi ₂ powder and 10g of Cr powder were weighed respectively. Place in a turpentine ball mill jar, put agate balls of different numbers and diameters into the rosin ball mill jar, and perform ball milling and mixing treatment on a planetary ball mill for 2 hours, and use it as an embedding material for later use.

Put half of the above-mentioned embedding material into the graphite crucible, put it into the prepared C/C composite material containing SiC nanowires on the surface, then put the other half of the embedding material, and shake the graphite crucible slightly to make the embedding material evenly The C/C composite material containing SiC nanowires on the surface is embedded, and then the graphite crucible is placed in a vacuum reactor. After evacuating for 30 minutes, make the vacuum degree reach -0.09MPa, keep the vacuum for 30 minutes, and observe whether the indication of the vacuum gauge changes. If there is no change, it means that the system is well sealed. Blow argon to normal pressure. This process is repeated three times. Afterwards, the furnace temperature was raised to 2300° C. at a heating rate of 5° C./min, and then kept for 1 hour. Then turn off the power and cool down to room temperature naturally, and protect with argon during the whole process. Then the graphite crucible is taken out, and the embedding powder is cleaned to obtain a C/C composite material containing SiC nanowire toughened SiC-MoSi ₂ -CrSi ₂ ceramic coating.

Oxidation experiments show that the SiC nanowire-toughened SiC-MoSi ₂ -CrSi ₂ ceramic coating has an effective anti-oxidation time of 150 hours in air at 1500°C.

In all embodiments, the purity of Si powder is 99.5%, and particle size is 300 orders, and the purity of C powder is 99%, and particle size is 320 orders, and the purity of _SiO2 powder is analytically pure, and particle size is 300 orders, and the purity of _MoSi2 powder is 99%, the particle size is 300 mesh, the purity of Cr powder is high purity, and the particle size is 200 mesh.

Claims (1)

1. the preparation method of a nanowire-toughened carbon/carbon/carbon/carbon composite material ceramic coating is characterized in that comprising the steps:

1) with cleaning behind the C/C matrix material sanding and polishing, puts into baking oven and dry;

2) taking by weighing mass percent respectively is 10～20% Si powder, 15～30% C powder, 55～75% SiO ₂Powder places the rosin ball grinder, ball milling combination treatment 2～4 hours;

3) with step 2) powder of preparation puts into plumbago crucible, and making its powder thickness is 1/5 of the plumbago crucible degree of depth, is suspended on the top on powder surface in the plumbago crucible after the C/C matrix material that step 1) is handled bundlees with the charcoal fiber again;

4) plumbago crucible is put into the vacuum reaction stove, vacuum oven is carried out vacuum-treat after, logical argon gas rises to 1600～1700 ℃ with furnace temperature from room temperature with 5～10 ℃/min heat-up rate to normal pressure, is incubated 1～3 hour; Powered-down naturally cools to room temperature subsequently, logical argon shield in the whole process;

5) taking by weighing mass percent respectively is 40～65% Si powder, 5～10% C powder, 20～30% MoSi ₂Powder, 10～20% Cr powder places the rosin ball grinder, ball milling combination treatment 2～4 hours;

6) half puts into plumbago crucible with the powder of step 5) preparation, puts into the C/C matrix material that contains the SiC nano wire through the surface of step 4) preparation again, puts into the C/C matrix material that second half embedding powder contains the SiC nano wire with the surface subsequently and covers;

7) plumbago crucible is put into the vacuum reaction stove, vacuum oven is carried out vacuum-treat after, logical argon gas rises to 2100～2300 ℃ with furnace temperature from room temperature with 5～10 ℃/min heat-up rate to normal pressure, is incubated 1～3 hour; Powered-down naturally cools to room temperature subsequently, logical argon shield in the whole process.

Images