CN1640852A - Carbon/carbon composite material anti-oxidation coating and preparation method thereof - Google Patents

Abstract

The invention relates to a process for coating liquid, in particular to a low-temperature anti-oxidation method for a C/C composite material. The method is characterized in that alcohol (chemically pure) is selected to replace part of distilled water as a solvent, and 20-40% of silicon dioxide, 5-25% of phosphoric acid, 40-65% of zinc dihydrogen phosphate, and 1-10% of boric acid are prepared by weight percentage; the carbon/carbon composite material is impregnated with the sol of the invention, and defects such as cracks and holes are not found on the surface of the anti-oxidation coating, the coating has good bonding with carbon, high density, and high healing ability; the introduction of a plurality of high melting point and low oxygen permeability substances improves the anti-oxygen permeability of the coating, delays the contact time between oxygen and the C/C composite material, and thus improves the anti-oxidation ability of the coating.

Description

Carbon/carbon composite anti-oxidation coating and preparation method thereof

Technical field:

The invention relates to a liquid coating process, in particular to a low-temperature anti-oxidation method for C/C composite materials.

Background technique:

Solution impregnation method, there is a phenomenon that the thermal expansion coefficient of the impregnated coating and the C/C composite material is greatly different, see Figure 1, resulting in cracks, holes and other defects, reducing the compactness of the coating, making it easy for oxygen molecules to penetrate The coating reaches the surface of the C/C material and reacts with carbon, resulting in oxidation. At the same time, it is difficult for the solution impregnation method to effectively dissolve a variety of components with different functions in one solution, and there are great limitations in composition modulation. Layer composition, which not only increases the thickness of the coating, but also increases the steps of the coating preparation process, thereby reducing the technical and economic advantages of such coatings.

Invention content:

The purpose of the present invention is to overcome the shortcomings of the existing methods and provide an anti-oxidation coating for carbon/carbon composite materials and a preparation method thereof. This method can effectively mix and dissolve a variety of raw materials with different functions of the coating components, so that the coating precursor has greater selectivity and can be adjusted as much as possible according to the performance and use environment of the C/C composite material. It is formulated to reduce the number of dipping times, reduce coating defects, improve the compactness of the coating and its compatibility with C/C composite materials, and improve the oxidation resistance of carbon/carbon composite materials.

Technical scheme of the present invention is:

1. The composition of carbon/carbon composite anti-oxidation coating is: select alcohol (chemically pure) to replace part of distilled water to do solvent, will be silicon dioxide 20～40% by weight percentage, phosphoric acid 5～25% (purity is 99% ), zinc dihydrogen phosphate 40-65% (purity is 99%), boric acid 1-10% (purity is 99%), prepared.

2. Preparation of Sol-Impregnation Coating

① Prepare 2-4% boric acid alcohol solution, and add 15-20% system ratio of TEOS;

② Prepare 20-50% phosphoric acid aqueous solution;

③Stir together the mixture of ① and ② prepared solution;

④ Prepare an aqueous solution of ammonium pentaborate with a concentration of 5-10%, and mix it with ③ sol;

⑤ Preparation of 35-55% zinc dihydrogen phosphate aqueous solution;

⑥ Mix ④ and ⑤ according to the volume ratio of 1:1～1:4;

⑦Baking the C/C composite material at 150℃～200℃, and then immersing in ⑥ for 24h;

⑧Take out the impregnated C/C composite material and let it dry naturally;

⑨Raise the temperature at 0.5°C/1°C/min to 150°C-200°C, and bake for 1-4 hours.

Advantages and positive effects of the invention:

1. This invention simplifies the preparation process of C/C composite anti-oxidation coating, increases the composition of coating precursor, inhibits the rapid reaction of coating precursor composition in solution state, and improves the relationship between coating precursor and C/C wettability of composite materials.

2. The introduction of low-melting-point substances in the coating improves the self-healing ability of the C/C composite coating and reduces the difference in thermal expansion coefficient between the coating and the C/C composite. No defects such as cracks and holes were found on the surface of the oxide coating. The coating has good bonding with carbon, high density and high healing ability. The introduction of various substances with high melting point and low oxygen permeability improves the oxygen penetration resistance of the coating and delays the contact time between oxygen and C/C composites, thereby improving the oxidation resistance of the coating.

3. The oxidation weight loss rate of the C/C composite material impregnated in a single solution or composite solution at 650°C and 50h is 19%, while the oxidation weight loss rate of the sample prepared by sol impregnation at 650°C and 50h is 1.89%, which fully embodies the anti-oxidation of the present invention The effect is remarkable.

Description of drawings:

Figure 1: Effect diagram of carbon/carbon composite anti-oxidation coating prepared by existing solution impregnation method

Figure 2: Effect diagram of the carbon/carbon composite anti-oxidation coating prepared by the sol impregnation method of the present invention

Detailed ways:

Example 1

Preparation of sol dip coating:

① Weigh 1.5g of boric acid, dissolve it in 50ml of absolute ethanol, and take 10ml of TEOS and dissolve it in 1 solution.

② Dilute 30ml of 85% phosphoric acid solution into 20ml of deionized water.

③Mix the solutions prepared in 2 and 3 together and stir to make a sol.

④ Dissolve 10g of ammonium pentaborate in 100ml of deionized water, mix 10ml of the solution with the sol prepared in 3, and stir until it stands still and becomes transparent.

⑤ Prepare 40 (wt)% zinc dihydrogen phosphate aqueous solution.

⑥ Mix the sol prepared in 4 with the solution in 5 at a volume ratio of 1:1, and stir until the sol is transparent.

⑦ Bake the prepared C/C composite material sample at 150°C for 2 hours, and quickly immerse it in the prepared sol for 24 hours.

⑧Take out the impregnated C/C composite material sample and place it on the carbon felt, and place it in a drying oven to dry naturally for 24 hours.

⑨Put the sample in 8 in a drying oven at a rate of 0.5°C/min and gradually increase to 180°C, bake for 3 hours and then cool in the oven.

Example 2:

Preparation of sol dip coating:

①Weigh 1.0g of boric acid, dissolve it in 50ml of absolute ethanol, and dissolve 10ml of TEOS in it.

② Dilute 10ml of 85% phosphoric acid solution into 20ml of deionized water.

③ Mix the solutions prepared in 2 and 3 together, stir until transparent to form a sol, and let stand for 24 hours.

④Weigh 10g of ammonium pentaborate and dissolve it in 100ml of deionized water, add 10ml of the solution into the sol in 3, and stir until transparent.

⑤ Prepare 40 (wt)% zinc dihydrogen phosphate aqueous solution.

⑥ Mix the sol prepared in 4 with the solution in 5 according to the volume ratio of 2:3, and stir until the sol is transparent.

⑦ Bake the prepared C/C composite material sample at 180°C for 2 hours, and quickly immerse it in the prepared sol for 24 hours.

⑧Take out the impregnated C/C composite material sample and place it on the carbon felt, and place it in a drying oven to dry naturally for 24 hours.

⑨Put the sample in 8 in a drying oven at a rate of 0.5°C/min and gradually raise it to 180°C for 3 hours, and finally cool down with the furnace.

Example 3:

Preparation of sol dip coating:

①Weigh 1.5g of boric acid, dissolve it in 50ml of absolute ethanol, and dissolve 10ml of TEOS in it.

② Dilute 10ml of 85% phosphoric acid solution into 20ml of deionized water.

③Mix the solutions prepared in 2 and 3 together and stir until transparent to form a sol.

④Weigh 10g of ammonium pentaborate and dissolve it in 100ml of deionized water, add 10ml of the solution into the sol in 3, and stir until transparent.

⑤ Prepare 40 (wt)% zinc dihydrogen phosphate aqueous solution.

⑥ Mix the sol prepared in 4 with the solution in 5 at a volume ratio of 1:3, and stir until the sol is transparent.

⑦ Bake the prepared C/C composite material sample at 180°C for 2 hours, and quickly immerse it in the prepared sol for 24 hours.

⑧Take out the impregnated C/C composite material sample and place it on the carbon felt, and place it in a drying oven to dry naturally for 24 hours.

⑨Put the sample in 8 in a drying oven and bake for 3 hours at a rate of 0.5°C/min to 180°C gradually, and finally cool in the oven.

Example 4:

Preparation of sol dip coating:

①Weigh 1.5g of boric acid, dissolve it in 50ml of absolute ethanol, and dissolve 10ml of TEOS in it.

② Dilute 5ml of 85% phosphoric acid solution into 20ml of deionized water.

③Mix the solutions prepared in 2 and 3 together and stir until transparent to form a sol.

④Weigh 10g of ammonium pentaborate and dissolve it in 100ml of deionized water, add 10ml of the solution into the sol in 3, and stir until transparent.

⑤ Prepare 50 (wt)% zinc dihydrogen phosphate aqueous solution.

⑥ Mix the sol prepared in 4 with the solution in 5 at a volume ratio of 1:1, and stir until the sol is transparent.

⑦ Bake the prepared C/C composite material sample at 150°C for 2 hours, and quickly immerse it in the prepared sol for 24 hours.

⑧Take out the impregnated C/C composite material sample and place it on the carbon felt, and place it in a drying oven to dry naturally for 24 hours.

⑨Put the sample in 8 in a drying oven and bake at a rate of 0.5°C/min to 200°C for 3 hours, and finally cool in the oven.

Example 5:

Preparation of sol dip coating:

①Weigh 1.5g of boric acid, dissolve it in 50ml of absolute ethanol, and dissolve 10ml of TEOS in it.

② Dilute 5ml of 85% phosphoric acid solution into 20ml of deionized water.

③Mix the solutions prepared in 2 and 3 together and stir until transparent to form a sol.

④Weigh 10g of ammonium pentaborate and dissolve it in 100ml of deionized water, add 10ml of the solution into the sol in 3, and stir until transparent.

⑤ Prepare 40 (wt)% zinc dihydrogen phosphate aqueous solution.

⑥ Mix the sol prepared in 4 with the solution in 5 at a volume ratio of 1:3, and stir until the sol is transparent.

⑦ Bake the prepared C/C composite material sample at 180°C for 2 hours, and quickly immerse it in the prepared sol for 24 hours.

⑧Take out the impregnated C/C composite material sample and place it on the carbon felt, and place it in a drying oven to dry naturally for 24 hours.

⑨Put the sample in 8 in a drying oven and bake for 3 hours at a rate of 0.5°C/min to 180°C gradually, and finally cool in the oven.

Embodiment 6:

Preparation of sol dip coating:

① Weigh 1.3g of boric acid, dissolve it in 50ml of absolute ethanol, and dissolve 10ml of TEOS in it.

② Dilute 10ml of 85% phosphoric acid solution into 20ml of deionized water.

③Mix the solutions prepared in 2 and 3 together and stir until transparent to form a sol.

④Weigh 10g of ammonium pentaborate and dissolve it in 100ml of deionized water, add 10ml of the solution into the sol in 3, and stir until transparent.

⑤ Prepare 40 (wt)% zinc dihydrogen phosphate aqueous solution.

⑥ Mix the sol prepared in 4 with the solution in 5 at a volume ratio of 1:3, and stir until the sol is transparent.

⑦ Bake the prepared C/C composite material sample at 180°C for 2 hours, and quickly immerse it in the prepared sol for 24 hours.

⑧Take out the impregnated C/C composite material sample and place it on the carbon felt, and place it in a drying oven to dry naturally for 24 hours.

⑨Put the sample in 8 in a drying oven and bake at a rate of 0.5°C/min to 200°C for 3 hours, and finally cool in the oven.

Claims (2)

1. carbon/carbon composite oxidation resistant coating, it is characterized in that: select for use alcohol (chemical pure) instead of part distilled water to make solvent, to be silicon-dioxide 20～40% by weight percentage, phosphoric acid 5～25% (purity is 99%), primary zinc phosphate 40～65% (purity is 99%), boric acid 1～10% (purity is 99%), formulated.

2. the anti-oxidant preparation method of carbon/carbon composite is characterized in that:

1. prepare 2～4% boric acid spirit solutions, and add the TEOS of 15～20% systems ratio;

2. prepare 20～50% phosphate aqueous solutions;

3. will be 1., 2. prepare the stirring that is mixed of solution;

4. the ammonium pentaborate aqueous solution for preparing 5～10% concentration, and mix with 3. colloidal sol;

5. prepare 35～55% phosphoric acid dihydro zinc aqueous solution;

6. by 1: 1～1: 4 volume ratio will 4., 5. mixing;

7. at 150 ℃～200 ℃ baking C/C matrix materials, immerse 6. middle 24h then;

8. take out dipping C/C matrix material, seasoning;

9. 0.5 ℃/1 ℃/min is warming up to 150 ℃～200 ℃, baking 1～4h.

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