Synthesis Method of Thermosensitive Functional Composite Powder for Thermal / Environmental Barrier Coatings

Abstract

Synthesis method of temperature-sensitive functional composite powder for thermal / environmental barrier coatings. The present invention aims to solve the problem that a small amount of nano rare earth oxides are prone to uneven distribution during the powder mixing process, resulting in segregation of subsequent powder components. The synthesis method includes: First, acidifying whiskers / fibers with a mixed acid and then reacting with a coupling agent to obtain acidified-coupling-treated whiskers / fibers; Second, preparing a dispersion of acidified-treated or surface-coupling-coated nano rare earth oxide particles, adding the acidified-coupling-treated whiskers / fibers for reaction; Third, mixing the whiskers / fibers with ceramic powder, granulating and sintering. The present invention utilizes chemical grafting of nano rare earth oxides on the surface of whiskers / fibers to achieve the effect of uniformly dispersing a small amount of rare earth oxides. After adding the surface-chemically-grafted rare earth oxides to the thermal / environmental barrier coating powder, the thermal / environmental barrier coating can be prepared through powder mixing and sintering, realizing the temperature-sensitive function of the thermal / environmental barrier coating.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal protection coating materials, and particularly relates to a chemical grafting synthesis method of a temperature-sensitive functional composite powder for a thermal / environmental barrier coating. Background Art

[0002] Currently, with the continuous increase in the thrust-to-weight ratio and the turbine inlet temperature of "two engines", the importance of thermal protection coatings for protecting hot-end components has become increasingly prominent. At present, thermal protection coatings are mainly divided into two categories according to different substrates and service temperature ranges. The first type of thermal barrier coating is a functional protective coating that plays an insulating role for a superalloy substrate, and the service temperature is generally below 1200°C. The other type of environmental barrier coating is a functional protective coating that protects a ceramic matrix composite (CMC) substrate from water and oxygen environment erosion, and the service temperature is expected to reach 1200 to 1500°C. Among them, the thermal barrier coating materials are mainly yttrium-stabilized zirconia (YSZ) and lanthanum zirconate systems, and the environmental barrier coating materials are mainly barium strontium aluminum silicate (BSAS) and rare earth silicate two systems. The structure of these two thermal protection coatings mainly consists of four parts: a substrate, a bond coat, a thermally grown oxide (TGO), and a ceramic layer. The life of the thermal protection coating is directly related to the temperature of the service environment and the temperature inside the coating. The temperature difference along the coating thickness direction is an important factor leading to vertical cracks and interface peeling in the coating, but the accurate measurement of the temperature inside the coating poses a huge challenge.

[0003] For the high-temperature temperature measurement requirements inside the above coatings far exceeding 1000°C, currently the non-contact fluorescence / phosphorescence temperature measurement method has the greatest application potential. This method dopes a small amount of rare earth luminescent elements inside the thermal protection coating, and studies its correlation with temperature based on the changes in the spectral width, intensity, and lifetime of the fluorescence / phosphorescence material during high-temperature service to achieve the purpose of real-time monitoring of the service temperature of the thermal protection coating. For example, the phosphorescence temperature measurement range of the thermal barrier coating YSZ:RE is between 800 and 1200°C. However, the research on temperature-sensitive luminescent materials based on environmental barrier coating materials (rare earth silicates, BSAS) as substrates is still in its initial stage, and the related powder material synthesis methods still need to be further studied and developed.

[0004] The preparation process of the thermal protection coating powder mainly realizes the powder preparation by ball milling and mixing powders followed by subsequent powder making and solid-phase sintering due to requirements such as productivity and efficiency. However, ball milling and mixing powders cannot achieve good dispersion effects for a small amount of nanoscale raw materials, and it is easy to cause uneven composition or segregation phenomena. How to improve the dispersion problem of nanoscale raw materials is crucial for the synthesis of temperature-sensitive luminescent powders, and precise control of the composition can be achieved through chemical methods. At present, chemical modification methods for surface modification of whiskers / fibers have great application prospects. For example, inorganic small molecules (such as carbon nanotubes, graphene, etc.) or organic macromolecules (such as polyimide, etc.) are grafted onto the surface of whiskers / fibers by chemical grafting methods. However, grafting substances suitable for the thermal protection coating material system still need to be continuously explored. Introducing whiskers / fibers into the thermal protection coating for strengthening and toughening is considered an effective method to solve the insufficient toughness of ceramic materials. The embedding degree of the surface chemically modified whiskers / fibers and the matrix is improved, effectively enhancing the service stability of the coating. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem that a small amount of nano rare earth oxides are prone to uneven distribution during the powder mixing process, resulting in segregation of the subsequent powder composition. A composite powder synthesis method is provided, which uses surface chemical grafting of nano rare earth oxides on strengthening phases such as whiskers / fibers and then adds them to the powder for granulation and sintering. This synthesis method can not only ensure the dispersion of a small amount of nano rare earth oxides, realize the temperature-sensitive function of the thermal / environmental barrier coating, but also further use the rare earth oxides as grafting substances to improve the surface state of the whiskers / fibers, and finally realize the overall mechanical stability improvement of the thermal / environmental barrier coating composite material.

[0006] The synthesis method of the temperature-sensitive functional composite powder for the thermal / environmental barrier coating of the present invention is realized according to the following steps:

[0007] Step 1: Acidify the whiskers / fibers with a mixed acid of HF / HNO3. Add the acidified whiskers / fibers, 1,4-phenylene diisocyanate coupling agent, and dibutyltin dilaurate catalyst to an organic solvent, and react under the condition of a constant temperature water bath at 40 - 45 °C. After washing and drying, obtain acidified-coupled whiskers / fibers;

[0008] Step 2: Acidify the nano rare earth oxide particles or perform surface coupling coating treatment. Ultrasonically disperse the treated nano rare earth oxide particles in 1,4-dioxane (liquid) to obtain a dispersion. Add the acidified-coupled whiskers / fibers and triethylamine catalyst to the dispersion, and stir and react under the condition of a constant temperature water bath at 40 - 50 °C. After rinsing and drying, obtain whiskers / fibers with nano rare earth oxide particles grafted on the surface;

[0009] Step 3: Mix the whiskers / fibers with surface-grafted nano rare earth oxide particles, ceramic powder, and binder, perform granulation treatment, and then carry out sintering treatment. After crushing, a thermal / environmental barrier coating powder material with temperature-sensitive function is obtained;

[0010] Among them, the material of the whiskers / fibers is silicon carbide, boron nitride, alumina, aluminum borate, or YSZ (yttrium-doped zirconia); the material of the nano rare earth oxide particles is dysprosium oxide, europium oxide, erbium oxide, samarium oxide, terbium oxide, or neodymium oxide.

[0011] The present invention uses the chemical grafting method to uniformly graft nano rare earth oxide particles on the surface of whiskers / fibers, controls the grafting amount and grafting density through the ratio of whiskers / fibers to nano rare earth oxides, and adds the whiskers / fibers grafted with rare earth oxides to the thermal / environmental barrier coating powder for mixing granulation and subsequent solid-phase sintering to form a composite powder. Among them, the rare earth oxide uniformly grafted by whiskers / fibers serves as an activator for the luminescent material of the thermal / environmental barrier coating, and the activator is doped into the matrix of the thermal / environmental barrier coating to realize the synthesis of the temperature-sensitive luminescent material of the thermal / environmental barrier coating; by grafting nano rare earth oxide particles on the surface of whiskers / fibers and controlling the distribution of whiskers / fibers, the mechanical properties of whiskers / fibers are improved and the stress mismatch inside the material is alleviated, further enhancing the toughening effect of whiskers / fibers on the thermal / environmental barrier coating material.

[0012] The synthesis method of the temperature-sensitive functional composite powder for thermal / environmental barrier coatings of the present invention has the following beneficial effects:

[0013] (1) The present invention uses chemical grafting on the surface of whiskers / fibers to uniformly disperse a small amount of rare earth oxides. After adding the surface-chemically grafted rare earth oxides to the thermal / environmental barrier coating powder and performing powder mixing and sintering, a thermal / environmental barrier coating composite powder can be prepared to realize the temperature-sensitive function of the thermal / environmental barrier coating.

[0014] (2) The present invention uses the chemical grafting method to graft nano rare earth oxides on the surface of whiskers / fibers, and by controlling the mass ratio of whiskers / fibers to nano oxide particles, the purpose of controlling the grafting amount and grafting density is achieved. The interfacial properties between the grafted whiskers / fibers and the matrix material are improved, thereby enhancing the mechanical property stability of the thermal / environmental barrier coating material, which has good scientific significance and engineering application value. Description of the Drawings

[0015] Figure 1 SEM image of uniformly dispersed nano oxide particles on the surface of silicon carbide whiskers prepared in Example 1;

[0016] Figure 2 Macrophotograph of the surface of the thermal protection coating with modified whiskers after 150 water-cooled cyclic thermal shocks in the application example. Specific embodiments

[0017] Specific embodiment 1: The synthesis method of the temperature-sensitive functional composite powder for the thermal / environmental barrier coating in this embodiment is implemented according to the following steps:

[0018] Step 1: Acidify the whiskers / fibers with a mixed acid of HF / HNO3. Add the acidified whiskers / fibers, 1,4-phenylene diisocyanate coupling agent, and dibutyltin dilaurate catalyst into an organic solvent, and react under the condition of a constant temperature water bath at 40 - 45 °C. After washing and drying, acidified-coupled whiskers / fibers are obtained;

[0019] Step 2: Acidify the nano rare earth oxide particles or perform surface coupling coating treatment. Ultrasonically disperse the treated nano rare earth oxide particles in 1,4-dioxane (liquid) to obtain a dispersion. Add the acidified-coupled whiskers / fibers and triethylamine catalyst into the dispersion, and stir and react under the condition of a constant temperature water bath at 40 - 50 °C. After rinsing and drying, whiskers / fibers grafted with nano rare earth oxide particles on the surface are obtained;

[0020] Step 3: Mix the whiskers / fibers grafted with nano rare earth oxide particles on the surface, ceramic powder, and binder, perform granulation treatment, and then perform sintering treatment. After crushing, a thermal / environmental barrier coating powder material with temperature-sensitive function is obtained;

[0021] Among them, the material of the whiskers / fibers is silicon carbide, boron nitride, alumina, aluminum borate, or YSZ (yttria-stabilized zirconia); the material of the nano rare earth oxide particles is dysprosium oxide, europium oxide, erbium oxide, samarium oxide, terbium oxide, or neodymium oxide.

[0022] In this embodiment, a certain amount of whiskers / fibers are acidified and then coated with a coupling agent, providing surface active sites for subsequent chemical grafting of nano rare earth oxide particles. The surface treatment of the nano rare earth oxide particles includes methods such as oxidation and coupling agent coating, improving the grafting rate of the nano rare earth oxide particles. After chemical grafting, the nano rare earth oxide particles are evenly grafted on the surface of the whiskers / fibers. Combining subsequent mixing, granulation, and sintering realizes the synthesis of the temperature-sensitive functional composite powder for the thermal / environmental barrier coating. In this embodiment, the whiskers / fibers and the nano particles can be homogeneous materials or heterogeneous materials that can undergo solid solution reactions.

[0023] In this embodiment, the grafting amount and grafting density are adjusted by controlling the mass ratio of the whiskers / fibers and the nano rare earth oxide particles during the chemical grafting process to achieve the purpose of surface modification of the whiskers / fibers. By enhancing the mechanical properties of the whiskers / fibers, the stress mismatch inside the material is alleviated, further enhancing the toughening effect of the whiskers / fibers on the thermal / environmental barrier coating material.

[0024] This embodiment proposes a composite powder synthesis method that uses whiskers / fibers and other reinforcing phases to chemically graft nano rare earth oxides on the surface and then add them to the powder for granulation and sintering, so as to solve the problem of dispersion segregation of a small amount of rare earth oxides in the powder materials of thermal / environmental barrier coatings and achieve the temperature-sensitive function of thermal / environmental barrier coatings; and the chemical grafting on the surface improves the interfacial embedding force between whiskers / fibers and other reinforcing phases and the matrix material, thereby enhancing the high-temperature strength and toughness of thermal / environmental barrier coatings.

[0025] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that in Step 1, a mixed acid of HF / HNO3 is used to acidify the whiskers / fibers at 70 °C for 30 min.

[0026] In this embodiment, the mass ratio of HF / HNO3 in the mixed acid is 4:6.

[0027] Specific Embodiment 3: The difference between this embodiment and Specific Embodiment 1 or 2 is that in Step 1, the mass ratio of the acidified whiskers / fibers to the 1,4-phenylene diisocyanate coupling agent is 1:(1-2).

[0028] Specific Embodiment 4: The difference between this embodiment and any one of Specific Embodiments 1 to 3 is that in Step 1, the reaction is carried out for 20-24 h under the condition of a constant temperature water bath at 40-45 °C.

[0029] Specific Embodiment 5: The difference between this embodiment and any one of Specific Embodiments 1 to 4 is that in Step 2, the surface coupling and coating treatment of the nano rare earth oxide particles is to react the nano rare earth oxide particles with the 1,4-phenylene diisocyanate coupling agent for 20-24 h under the condition of a constant temperature water bath at 40-45 °C.

[0030] Specific Embodiment 6: The difference between this embodiment and any one of Specific Embodiments 1 to 5 is that in Step 2, the mass ratio of the acidified-coupled whiskers / fibers to the nano rare earth oxide particles is controlled to be (4-12):1.

[0031] Specific Embodiment 7: The difference between this embodiment and any one of Specific Embodiments 1 to 6 is that in Step 2, the stirring reaction is carried out for 20-24 h under the condition of a constant temperature water bath at 40-50 °C.

[0032] Specific Embodiment 8: The difference between this embodiment and any one of Specific Embodiments 1 to 7 is that in Step 3, the ceramic powder is a thermal barrier coating material or an environmental barrier coating material, and the thermal barrier coating material is YSZ, modified YSZ, lanthanum zirconate or modified lanthanum zirconate; the environmental barrier coating material is yttrium silicate, modified rare earth silicate, BSAS (barium strontium aluminum silicate) or modified BSAS.

[0033] Specific Embodiment Nine: The difference between this embodiment and any one of Specific Embodiments One to Eight is that in Step 3, the mass ratio of the whiskers / fibers with surface-grafted nano rare earth oxide particles to the ceramic powder is (1-2):(8-16).

[0034] Specific Embodiment Ten: The difference between this embodiment and any one of Specific Embodiments One to Nine is that in Step 3, the granulation treatment described uses dry pressing granulation, isostatic pressing granulation, or spray granulation.

[0035] Specific Embodiment Eleven: The difference between this embodiment and any one of Specific Embodiments One to Ten is that in Step 3, sintering treatment is carried out at a temperature of 1300-1600°C for 5-10 h.

[0036] In this embodiment, the whiskers / fibers with surface chemically grafted nano rare earth oxide particles are used as the second-phase additive for toughening and strengthening, and added to the thermal / environmental barrier coating material. The whiskers / fibers grafted with nano rare earth oxide particles can improve the high and low temperature mechanical stability of the matrix material and realize the temperature-sensitive function of the thermal / environmental barrier coating.

[0037] Example 1: The synthesis method of the temperature-sensitive functional composite powder for the thermal / environmental barrier coating in this example is implemented according to the following steps:

[0038] Step 1: The silicon carbide whiskers with an aspect ratio greater than 20 (the whisker length is 10-50 μm) are acidified with a mixed acid of HF / HNO3 at 70°C for 30 min. 0.5 g of the acidified whiskers, 1 g of 1,4-phenylene diisocyanate coupling agent, and 2.5 ml of dibutyltin dilaurate catalyst are added to 50 ml of xylene, and magnetically stirred (450 revolutions per minute) in a 40°C constant temperature water bath for 24 h. After washing and drying, acidified-coupled treated whiskers are obtained.

[0039] Step 2: According to the mass parts, 1 part of nano europium oxide particles (particle size less than 40 nm) and 2 parts of 1,4-phenylene diisocyanate coupling agent are magnetically stirred (450 revolutions per minute) in a 40°C constant temperature water bath for 24 h to obtain surface-coupled coated nano europium oxide particles. Then, they are added to 1,4-dioxane (liquid) and ultrasonically dispersed at 50°C for 2 hours to form a dispersion liquid. Then, 10 parts of acidified-coupled treated whiskers and a small amount of triethylamine (1 ml of triethylamine is added to every 10 ml of the reaction solution) are magnetically stirred (450 revolutions per minute) in a 40°C constant temperature water bath for 24 h. After rinsing and drying, whiskers with surface-grafted nano rare earth oxide particles are obtained.

[0040] Step 3: Add 100 g of whiskers with surface-grafted nano rare earth oxide particles and 900 g of (YHoErYbLu)2Si2O7 ceramic powder into deionized water with the same mass as the powder and 1-2% PVA (polyvinyl alcohol) to form a precursor slurry. Granulate the precursor slurry through a spray granulator to obtain initial powder. Sinter the initial powder at a temperature of 1400 °C for 10 h, and then crush it to obtain an environmental barrier coating powder material with temperature-sensitive function.

[0041] In the application example, the surface-chemically modified whiskers / fibers are added to the original powder of the environmental barrier coating, that is, the whiskers with surface-grafted nano rare earth oxide particles prepared in Example 1 are added to the (YHoErYbLu)2Si2O7 environmental barrier ceramic powder. After spray granulation and sintering, composite ceramic powder is formed. Then, the composite ceramic powder is sprayed and deposited on the bonding layer through an atmospheric plasma spraying process, and a temperature-sensitive ceramic layer with a thickness of 20-50 μm is stacked on the surface of the bonding layer. Subsequently, an environmental barrier ceramic layer with a thickness of 200 μm is prepared on the surface of the temperature-sensitive ceramic layer. The thermal protection coating added with modified whiskers has excellent thermal shock resistance. As Figure 2 shown in the figure is the macroscopic morphology of the coating surface after 150 water-cooled cyclic thermal shocks. It can be seen from the figure that after the coating serves under severe extremely cold and extremely hot conditions, the surface is basically intact, and only a small amount of peeling appears at the edge. This indicates that the thermal protection coating added with modified whiskers has good practical engineering application value and is suitable for industrial promotion.

[0042] In this example, nano rare earth oxide particles are grafted on the surface of the whiskers, which not only solves the agglomeration of nano rare earth oxide particles and realizes the luminescence performance of the thermal / environmental barrier coating, but also is added to the thermal / environmental barrier coating as a toughening and strengthening phase.

Claims

1. Synthesis method of temperature-sensitive functional composite powder for thermal / environmental barrier coatings, characterized in that The synthesis method is realized according to the following steps: Step 1: Acidify the whiskers / fibers with a mixed acid of HF / HNO3. Add the acidified whiskers / fibers, 1,4-phenylene diisocyanate coupling agent and dibutyltin dilaurate catalyst into an organic solvent, and react under the condition of a constant temperature water bath at 40 - 45 °C. After washing and drying, acidified-coupled whiskers / fibers are obtained; Step 2: Acidify the nano rare earth oxide particles or perform surface coupling coating treatment. Ultrasonically disperse the treated nano rare earth oxide particles in 1,4-dioxane to obtain a dispersion. Add the acidified-coupled whiskers / fibers and triethylamine catalyst into the dispersion, and stir and react under the condition of a constant temperature water bath at 40 - 50 °C. After rinsing and drying, whiskers / fibers grafted with nano rare earth oxide particles on the surface are obtained; Step 3: Mix the whiskers / fibers grafted with nano rare earth oxide particles on the surface, ceramic powder and binder, perform granulation treatment, and then perform sintering treatment. After crushing, a thermal / environmental barrier coating powder material with temperature-sensitive function is obtained; Among them, the material of the whiskers / fibers is silicon carbide, boron nitride, aluminum oxide, aluminum borate or YSZ; the material of the nano rare earth oxide particles is dysprosium oxide, europium oxide, erbium oxide, samarium oxide, terbium oxide or neodymium oxide.

2. The synthesis method of the temperature-sensitive functional composite powder for thermal / environmental barrier coatings according to claim 1, characterized in that In Step 1, the whiskers / fibers are acidified with a mixed acid of HF / HNO3 at 70 °C for 30 min.

3. The synthesis method of the temperature-sensitive functional composite powder for thermal / environmental barrier coatings according to claim 1, wherein In Step 1, the mass ratio of the acidified whiskers / fibers to the 1,4-phenylene diisocyanate coupling agent is 1:(1 - 2).

4. The synthesis method of the temperature-sensitive functional composite powder for thermal / environmental barrier coatings according to claim 1, wherein In Step 1, the reaction is carried out for 20 - 24 h under the condition of a constant temperature water bath at 40 - 45 °C.

5. The synthesis method of the temperature-sensitive functional composite powder for thermal / environmental barrier coatings according to claim 1, characterized in that In Step 2, the surface coupling coating treatment of the nano rare earth oxide particles is to react the nano rare earth oxide particles with the 1,4-phenylene diisocyanate coupling agent for 20 - 24 h under the condition of a constant temperature water bath at 40 - 45 °C.

6. The synthesis method of the temperature-sensitive functional composite powder for thermal / environmental barrier coatings according to claim 1, characterized in that In Step 2, the mass ratio of the acidified-coupled whiskers / fibers to the nano rare earth oxide particles is controlled to be (4 - 12):

1.

7. The synthesis method of the temperature-sensitive functional composite powder for thermal / environmental barrier coatings according to claim 1, characterized in that In Step 3, the ceramic powder is a thermal barrier coating material or an environmental barrier coating material. The thermal barrier coating material is YSZ, modified YSZ, lanthanum zirconate or modified lanthanum zirconate; The environmental barrier coating material is yttrium silicate, modified rare earth silicate, BSAS or modified BSAS.

8. The synthesis method of the temperature-sensitive functional composite powder for thermal / environmental barrier coatings according to claim 1, characterized in that In Step 3, the mass ratio of the whiskers / fibers grafted with nano rare earth oxide particles on the surface to the ceramic powder is (1 - 2):(8 - 16).

9. The synthesis method of the temperature-sensitive functional composite powder for thermal / environmental barrier coatings according to claim 1, characterized in that In Step 3, the granulation treatment adopts dry pressing granulation, static pressing granulation or spray granulation.

10. The synthesis method of the temperature-sensitive functional composite powder for thermal / environmental barrier coatings according to claim 1, characterized in that In Step 3, sintering treatment is carried out at a temperature of 1300 - 1600 °C for 5 - 10 h.

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