Rare-earth-based high-temperature composite ceramic fireproof coating composition and application thereof

Abstract

The invention discloses a rare-earth-based high-temperature composite ceramic fireproof coating composition and application thereof. The rare-earth-based high-temperature composite ceramic fireproof coating composition comprises the following raw materials: 25-30 wt% of lanthanum carbonate precursor powder, 25-30 wt% of cerous phosphate powder, 0-10 wt% of CTE modified filler and 30-40 wt% of a water-based inorganic binder, the lanthanum carbonate precursor powder has a lamellar microstructure, the lamellar crystal thickness is 50-100 nm, and the lamellar crystal width is 3-12 [mu] m. The formed composite ceramic protective layer is composed of lanthanum oxide and a stabilized cerous pyrophosphate phase, can bear the temperature of 1200 DEG C or even higher, keeps the structure intact and has no decomposition or failure phenomenon in a high-temperature environment, provides lasting fireproof heat-insulation protection, and is suitable for aerospace, petrochemical engineering and other extreme high-temperature scenes.

Description

Technical Field

[0001] This invention belongs to the field of passive fireproofing and thermal barrier coating technology, specifically relating to a rare earth-based high-temperature composite ceramic fireproof coating composition and its application. Background Technology

[0002] In many industrial sectors, such as aerospace, petrochemicals, and steel structures, materials need to maintain their structural integrity under extreme high-temperature conditions, such as fires. Passive fire-retardant coatings are a key technology for achieving this goal. Existing organic intumescent fire-retardant coatings expand to form a carbon layer when heated, but their temperature resistance limit is typically far below 1000°C, and they fail rapidly at higher temperatures. These coatings mainly rely on the carbonization and expansion mechanism of organic components. When the temperature exceeds their thermal stability threshold, the expanded layer disintegrates, resulting in a loss of insulation and failing to meet the requirements of scenarios with higher temperature resistance. For example, in aerospace components or petrochemical equipment, fires or high-temperature accidents can instantly reach temperatures above 1000°C, at which point the failure of organic coatings directly threatens structural safety.

[0003] To meet higher temperature resistance requirements, researchers have developed ceramic-based high-temperature resistant coatings. However, these coatings typically use pre-sintered refractory powders (such as Al2O3 and ZrO2) as fillers. A major drawback of this approach is the significant difference in the coefficient of thermal expansion (CTE) between the ceramic filler and the metallic substrate (such as steel, high-temperature alloys, and aluminum alloys). This leads to substantial thermal stress at the coating-substrate interface during drastic temperature changes, easily causing cracking and peeling of the coating, thus compromising its protective function. Specifically, the CTE of ceramic materials is typically between 5 and 10 × 10⁻⁶. -6 / K, while the CTE of steel is approximately 12-15×10 -6 This difference in temperature ( / K) can trigger the propagation of microcracks during rapid heating or cooling, ultimately leading to coating peeling. In practical applications, such as when steel structures are exposed to fire, coating peeling accelerates heat conduction and oxidative corrosion of the substrate, shortening the time to structural failure.

[0004] Therefore, developing a coating that can withstand temperatures above 1200℃ and has good thermomechanical compatibility with metal substrates is a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a rare earth-based high-temperature composite ceramic fireproof coating composition.

[0006] Another object of the present invention is to provide the application of the above-mentioned rare earth-based high-temperature composite ceramic fireproof coating composition.

[0007] The technical solution of the present invention is as follows:

[0008] A rare earth-based high-temperature composite ceramic fireproof coating composition, the raw materials of which include:

[0009] Lanthanum carbonate precursor powder 25-30 wt%

[0010] 25-30 wt% cerium phosphate powder

[0011] CTE modified filler 0-10 wt%

[0012] Water-based inorganic binder 30-40 wt%

[0013] The lanthanum carbonate precursor powder has a lamellar microstructure with a thickness of 50-100 nm and a width of 3-12 μm.

[0014] In a preferred embodiment of the present invention, the aqueous inorganic binder is selected from aqueous aluminum phosphate solution, colloidal silica and alkali metal silicate solution.

[0015] In a preferred embodiment of the present invention, the solid content of the water-based inorganic binder is 30-50%.

[0016] In a preferred embodiment of the present invention, the CTE modified filler is mullite powder.

[0017] More preferably, the mullite powder has a particle size of 300-400 mesh.

[0018] In a preferred embodiment of the present invention, the method for preparing the lanthanum carbonate precursor powder includes the following steps:

[0019] (1) Lanthanum chloride solution is added dropwise to sodium hydroxide solution to form lanthanum hydroxide colloidal precipitate;

[0020] (2) Carbon dioxide gas is introduced into the material obtained in step (1) to carry out the reaction;

[0021] (3) Filter the material obtained in step (2) and collect the precipitate;

[0022] (4) The precipitate obtained in step (3) is washed with deionized water until it is neutral and then dried under vacuum to obtain the final product.

[0023] More preferably, in step (2), the flow rate of carbon dioxide gas is 0.8-1.2 L / min, and the reaction time is 55-65 min.

[0024] A method for applying the above-mentioned rare earth-based high-temperature composite ceramic fireproof coating composition includes: uniformly coating the rare earth-based high-temperature composite ceramic fireproof coating composition onto the surface of a metal substrate to form a wet film with a thickness of 0.8-1.2 mm, followed by drying, curing and heat preservation sintering in sequence, and then cooling to room temperature to obtain a fireproof coating.

[0025] In a preferred embodiment of the present invention, the drying is performed at 80 °C for 2 h; the curing is performed at 200 °C for 1 h; and the heat-holding sintering is performed by heating to 260 °C at a rate of 10 °C / min and holding for 2 h.

[0026] In a preferred embodiment of the present invention, the metal substrate is a Q235 steel plate, a high-temperature alloy steel substrate, or an aluminum substrate.

[0027] The beneficial effects of this invention are:

[0028] 1. The rare earth-based composite ceramic protective layer formed by the present invention is composed of lanthanum oxide and stabilized cerium pyrophosphate phase, which can withstand temperatures of 1200 ℃ or even higher. It maintains structural integrity in high-temperature environments without decomposition or failure, and provides long-lasting fireproof and heat insulation protection. It is suitable for extreme high-temperature scenarios such as aerospace and petrochemical industries.

[0029] 2. This invention utilizes an in-situ reaction mechanism, where the precursor decomposes and reacts directly on the substrate surface to form a ceramic layer that is firmly bonded to the substrate, thus avoiding the interface problems of pre-formed powder. At the same time, the coefficient of thermal expansion of the ceramic layer matches that of the metal substrate (such as steel, high-temperature alloy steel, or aluminum substrate), reducing cracking and peeling caused by thermal stress. It exhibits excellent thermal shock resistance in thermal cycling tests, with only minor fine lines appearing.

[0030] 3. The present invention uses a layered lanthanum oxide framework (such as a "brick" structure) formed by a plate-like lanthanum carbonate precursor and a cerium pyrophosphate phase (such as "mortar") to impart high density, low thermal conductivity and crack resistance to the ceramic layer, thereby improving the overall thermal insulation efficiency and mechanical strength.

[0031] 4. This invention is based on an aqueous inorganic binder system (such as aqueous aluminum phosphate solution, colloidal silica or aqueous alkali metal silicate solution), which has excellent stability and rheological properties, and is easy to spray or brush. It is compatible with a variety of additives, such as CTE modified filler, to further precisely control the thermal shock resistance performance, and is suitable for different metal substrates. Attached Figure Description

[0032] Figure 1 This is a SEM image of the lanthanum carbonate precursor powder obtained in Example 1 of the present invention.

[0033] Figure 2This is a photograph of the coating obtained in Example 2 of the present invention, where the left side is a steel plate and the right side is the coating of Example 2.

[0034] Figure 3 The coating obtained in Example 3 of this invention showed only minor fine lines on its surface after thermal cycling testing.

[0035] Figure 4 The coating prepared in Comparative Example 1 showed obvious network cracks after thermal cycling test. Detailed Implementation

[0036] The technical solution of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.

[0037] Example 1

[0038] (1) Dissolve lanthanum chloride in deionized water to prepare a lanthanum chloride solution with a concentration of 1.45 mol / L;

[0039] (2) Prepare a 1.73 mol / L sodium hydroxide solution;

[0040] (3) Take 200 mL of the lanthanum chloride solution prepared in step (1) and slowly add 503 mL of the sodium hydroxide solution prepared in step (2) while stirring to generate lanthanum hydroxide colloidal precipitate;

[0041] (4) Pure carbon dioxide gas is introduced into the material obtained in step (3) at a flow rate of 1 L / min and the reaction is carried out for 60 min.

[0042] (5) After the reaction in step (4) is completed, the white precipitate is collected by filtration, then washed with deionized water until neutral, and then vacuum dried at 60 °C for 12 h to obtain lanthanum carbonate precursor powder with a plate-like microstructure. Figure 1 As shown, SEM observation revealed that the lanthanum carbonate precursor powder consisted of lamellar crystals with a thickness of 50-100 nm and a width of 3-12 μm.

[0043] Example 2

[0044] (1) 30 g of lanthanum carbonate precursor powder prepared in Example 1 and 30 g of cerium phosphate powder were slowly added to 40 g of aluminum phosphate aqueous solution (50% solid content) and dispersed evenly under high speed stirring to obtain coating A;

[0045] (2) Coating A is evenly applied to a 100 mm × 100 mm × 5 mm Q235 steel plate to form a wet film with a thickness of about 1 mm. It is then dried at 80 ℃ for 2 h, cured at 200 ℃ for 1 h, and then placed in an oven. The temperature is increased to 260 ℃ at a rate of 10 ℃ / min and held for sintering for 2 h. After cooling, it is removed and observed. Figure 2 As shown, the coating is intact, without cracks or peeling, and it bonds well with the steel substrate, forming a dense, grayish-white ceramic layer.

[0046] Example 3

[0047] (1) After mixing 25 g of lanthanum carbonate precursor powder prepared in Example 1, 25 g of cerium phosphate powder and 10 g of mullite powder (325 mesh) evenly, it was slowly added to 40 g of aluminum phosphate aqueous solution (50% solid content) and dispersed evenly under high speed stirring to obtain coating B.

[0048] (2) Coating B was uniformly applied to a 100 mm × 100 mm × 5 mm Q235 steel plate to form a wet film with a thickness of approximately 1 mm. It was then dried at 80 ℃ for 2 h, cured at 200 ℃ for 1 h, and placed in an oven. The temperature was increased to 260 ℃ at a rate of 10 ℃ / min and held for sintering for 2 h. After cooling, a thermal cycling test was performed: the temperature was rapidly increased from room temperature to 1200 ℃, held for 30 min, and then removed and air-cooled to room temperature. This process was repeated 10 times. After the test, if... Figure 3 As shown, the coating surface exhibits only minor fine lines, with no large-area cracking or peeling, demonstrating excellent thermal shock resistance.

[0049] Example 4

[0050] (1) 30 g of lanthanum carbonate precursor powder prepared in Example 1 and 30 g of cerium phosphate powder were slowly added to 40 g of colloidal silica (30% solid content) and dispersed evenly under high-speed stirring to obtain coating C;

[0051] (2) Coating C was uniformly applied to a Q235 steel plate of 100 mm × 100 mm × 5 mm to form a wet film with a thickness of about 1 mm. Then it was dried at 80 ℃ for 2 h, cured at 200 ℃ for 1 h, and then placed in an oven to heat up to 260 ℃ at a rate of 10 ℃ / min and kept at that temperature for 2 h. After cooling, it was taken out and observed. It was found that the coating was intact, without cracks or peeling, and was well bonded to the steel plate substrate, forming a grayish-white dense ceramic layer.

[0052] Example 5

[0053] (1) 30 g of lanthanum carbonate precursor powder prepared in Example 1 and 30 g of cerium phosphate powder were slowly added to 40 g of sodium silicate (35% solid content) and dispersed evenly under high speed stirring to obtain coating D;

[0054] (2) Coating D was uniformly applied to an aluminum substrate of 100 mm × 100 mm × 5 mm to form a wet film with a thickness of about 1 mm. Then it was dried at 80 ℃ for 2 h, cured at 200 ℃ for 1 h, and then placed in an oven and heated to 260 ℃ at a rate of 10 ℃ / min and kept at that temperature for 2 h. After cooling, it was taken out and observed. The coating was intact, without cracks or peeling, and was well bonded to the aluminum substrate, forming a grayish-white dense ceramic layer.

[0055] Comparative Example 1

[0056] (1) 60 g of pre-sintered cerium oxide (CeO2) powder (325 mesh) was added to 40 g of aluminum phosphate aqueous solution and stirred at high speed to disperse evenly to obtain the comparative coating.

[0057] (2) Prepare a sample using the same method as in Example 2, and perform the thermal cycling test in Example 3 together with the sample from Example 2. After the test, as follows: Figure 4 The coating formed by the comparative paint shown in the figure exhibits obvious network cracks and edge peeling, while the coating of Example 2 maintains better integrity.

[0058] This indicates that the in-situ generation mechanism and optimized CTE matching of the present invention significantly improve the thermomechanical stability and adhesion of the coating.

[0059] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A rare earth based high temperature composite ceramic fireproof coating composition characterized by: The raw materials include: lanthanum carbonate precursor powder 25-30 wt%; cerium phosphate powder 25-30 wt%; CTE-modifying filler 0-10 wt%; aqueous inorganic binder 30-40 wt%; The lanthanum carbonate precursor powder has a flaky microstructure, with the thickness of the flake being 50-100 nm and the width being 3-12 μm.

2. A rare earth based high temperature composite ceramic fireproof coating composition as claimed in claim 1, wherein: The aqueous inorganic binder is selected from the group consisting of an aqueous aluminum phosphate solution, colloidal silicon dioxide and an alkali metal silicate solution.

3. A rare earth based high temperature composite ceramic fireproof coating composition as claimed in claim 1, wherein: The solid content of the aqueous inorganic binder is 30-50%.

4. A rare earth based high temperature composite ceramic fireproof coating composition as claimed in claim 1, wherein: The CTE-modifying filler is mullite powder.

5. A rare earth based high temperature composite ceramic fireproof coating composition as claimed in claim 4, wherein: The particle size of the mullite powder is 300-400 mesh.

6. A rare earth based high temperature composite ceramic fireproof paint composition as claimed in any one of claims 1 to 5, characterized by: The preparation method of the lanthanum carbonate precursor powder includes the following steps: (1) drop lanthanum chloride solution into sodium hydroxide solution to form lanthanum hydroxide colloidal precipitate; (2) introduce carbon dioxide gas into the material obtained in step (1) to react; (3) perform suction filtration on the material obtained in step (2) to collect the precipitate; (4) wash the precipitate obtained in step (3) with deionized water to neutralization and vacuum drying, and the lanthanum carbonate precursor powder is obtained.

7. A rare earth based high temperature composite ceramic fireproof coating composition as claimed in claim 6, wherein: In step (2), the flow rate of the introduced carbon dioxide gas is 0.8-1.2 L / min, and the reaction time is 55-65 min.

8. A method of using the high temperature composite ceramic fireproof coating composition according to any one of claims 1 to 7, characterized in that: The high-temperature composite ceramic fireproof coating composition is uniformly coated on the surface of a metal substrate to form a wet film with a thickness of 0.8-1.2 mm, followed by drying, curing and heat soaking sintering in sequence, and then cooling to room temperature to obtain a fireproof coating. The drying is performed at 80 ℃ for 2 h; the curing is performed at 200 ℃ for 1 h; the heat soaking sintering is performed at a rate of 10 ℃ / min to 260 ℃, and then heat soaking sintering for 2 h.

9. The method of claim 8, wherein: The metal substrate is a Q235 steel plate, a high-temperature alloy steel substrate or an aluminum substrate.

10. The method of claim 8, wherein: ​

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