Stealthy ultra-high temperature thermal protection coating and preparation method and application thereof

Abstract

The application discloses a stealthy ultrahigh-temperature thermal protection coating as well as a preparation method and application thereof. The ultrahigh-temperature thermal protection coating is composed of a ceramicizable polymer precursor and an ultrahigh-temperature ceramic powder. The ceramicizable polymer precursor is prepared by reacting at least one metal element complex with a silicon-based polymer. During service, the polymer precursor is converted into an ultrahigh-temperature nano composite ceramic composed of transition metal carbon / nitride and Si(C / N) ceramic phases. The ultrahigh-temperature ceramic powder is composed of transition metal carbide, boride or nitride and is uniformly distributed in the polymer precursor. The coating can be directly coated on the outer surface of a high-speed aircraft structure. In the initial stage of flight, the coating can exhibit excellent electromagnetic wave absorption performance. In the high-speed flight process, the coating can be converted into an ultrahigh-temperature (nano) composite ceramic coating in situ through aerodynamic heating, thereby forming effective thermal protection for the aircraft and exhibiting the functions of stealth and thermal protection integration.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of inorganic coating materials, and particularly relates to a stealthy ultrahigh-temperature thermal protection coating material and a preparation method and application thereof. BACKGROUND

[0002] When a hypersonic vehicle flies at high speed, the nose cone and the leading edge of the wing and other parts thereof need to withstand high temperature of up to 1000℃ or above due to aerodynamic heating and strong thermal shock and plasma ablation caused thereby. At the same time, the stereoscopic detection and attack capability of the weapon networking of early warning and interception is greatly improved, so that the hypersonic vehicle faces severe survival threats in the starting and cruising stages of flight. Therefore, the integration technology of stealth and heat protection has become the key to the development and application of future hypersonic vehicles.

[0003] Ultrahigh-temperature ceramics (UHTCs) have attracted attention from researchers at home and abroad due to their great application prospects in the field of thermal protection of hypersonic vehicles. Such ceramics have high melting point (>3000℃), high thermal stability, high hardness, high elastic modulus, high thermal conductivity and good ablation resistance, and can withstand aerodynamic ablation or gas scouring in a high-enthalpy environment of 2000℃ or above, and are suitable for thermal protection of high-temperature structural components such as the end of the hypersonic vehicle and the leading edge of the rudder wing. However, the ultrahigh-temperature ceramic thermal protection coating is mostly prepared by thermal spraying, plasma spraying and other methods, which have harsh process conditions, long preparation period and high cost, and have certain damage to the structural components, which is not conducive to large-scale application. In addition, due to the poor impedance matching of the ultrahigh-temperature thermal protection coating with the free space, the electromagnetic wave reflection is serious, and it does not have the function of electromagnetic stealth. Therefore, it is of great significance to develop a new type of stealth ultrahigh-temperature thermal protection coating and preparation technology to realize low-temperature, rapid and low-cost preparation of the stealth ultrahigh-temperature thermal protection coating, so as to develop a hypersonic vehicle with stealth function and realize large-scale application. SUMMARY

[0004] In view of the deficiencies of the prior art, a first object of the present application is to provide a stealthy ultrahigh-temperature thermal protection coating material which can be prepared at low temperature, rapidly and at low cost.

[0005] A second object of the present application is to provide a preparation method of the stealthy ultrahigh-temperature thermal protection coating material.

[0006] A third object of the present application is to provide an application of the stealthy ultrahigh-temperature thermal protection coating material.

[0007] In order to achieve the above objects, the present application provides the following technical solutions:

[0008] The application discloses a stealthy ultra-high-temperature thermal protection coating, which is composed of a ceramicizable polymer precursor and an ultra-high-temperature ceramic powder.

[0009] The application provides the stealthy ultra-high-temperature thermal protection coating which is composed of a new ceramicizable polymer precursor and an ultra-high-temperature ceramic powder. The new ceramicizable polymer precursor is prepared by reacting at least one transition metal element complex with a silicon-based polymer. During service, the polymer precursor can be in-situ converted into an ultra-high-temperature nano composite ceramic composed of binary or multi-element transition metal carbon / nitride and Si(C / N) ceramic phase at a high yield. The transition metal element is selected from Ti, Zr, Hf, Nb, Ta, Mo and W. The ultra-high-temperature ceramic powder is composed of binary or multi-element transition metal carbide, boride or nitride and is uniformly distributed in the polymer precursor. The coating can be directly coated on the outer surface of a high-speed aircraft structure, and after drying and curing, it can be quickly put into use. In the initial stage of flight, the coating can exhibit excellent electromagnetic wave absorbing performance. In the high-speed flight process, after being aerodynamically heated, the coating can be in-situ converted into an ultra-high-temperature (nano) composite ceramic coating, thereby forming effective thermal protection for the aircraft and exhibiting the functions of stealth and heat protection integration.

[0010] In the preferred scheme, the mass ratio of the ceramicizable polymer precursor to the ultra-high-temperature ceramic powder in the stealthy ultra-high-temperature thermal protection coating is 1-99:1-99, preferably 30-70:30-70.

[0011] In the preferred scheme, the transition metal element in the transition metal element complex is selected from at least one of Ti, Zr, Hf and Ta, and the ligand in the transition metal element complex is selected from one of dimethylamine (NMe2), diethylamine (NEt2) and chloride, preferably dimethylamine (NMe2).

[0012] In the preferred scheme, the silicon-based polymer is selected from at least one of polysilazane, polysilaborazane and polycarbosilane, preferably at least one of polysilazane and polysilaborazane.

[0013] In the preferred scheme, the ultra-high-temperature ceramic powder is selected from at least one of binary or multi-element carbides, borides and nitrides formed by transition metal elements Ti, Zr, Hf, Ta, Nb, Mo and W, preferably at least one of HfC, ZrC, HfB2 and ZrB2.

[0014] The application discloses a preparation method of a stealthy superhigh-temperature heat protection coating.

[0015] Preferably, the organic solvent is anhydrous dimethylbenzene.

[0016] Preferably, the protective atmosphere is nitrogen.

[0017] Preferably, the reaction temperature is -50-200 DEG C, preferably 70-90 DEG C, and more preferably 80 DEG C; and the reaction time is 10-600 min, preferably 30-50 min, and more preferably 30 min.

[0018] Preferably, the superhigh-temperature ceramic powder has a particle size of 10 nm-500 microns, preferably 1 micron.

[0019] Preferably, the stirring time is 1-48 h, preferably 24 h.

[0020] The application discloses a stealthy superhigh-temperature heat protection coating.

[0021] Preferably, the high-speed aircraft structural member is selected from at least one of C / C composite material, ceramic matrix composite material, high-temperature alloy and metal matrix composite material, preferably C / C composite material, and has a density of 0.8-1.8 g / cm 3 , preferably 1.2 g / cm 3 , a porosity of 8%-40%, and preferably 30-35%.

[0022] Preferably, the drying temperature is 0 DEG C-300 DEG C, preferably 100 DEG C; and the drying time is 10 min-600 h, preferably 48 h.

[0023] Preferably, the curing mode is at least one of heating curing, ultraviolet light curing, electron beam curing and oxidation curing.

[0024] Preferably, the coating is composed of carbonitride nanocomposite ceramic and superhigh-temperature ceramic, and the carbonitride nanocomposite ceramic is composed of multi-element transition metal carbon / nitride phase and Si(C / N) phase.

[0025] Further preferably, the multi-element transition metal carbon / nitride is a face-centered cubic crystal structure, in which transition metal elements Ti, Zr, Hf, Ta, Nb, Mo, W atoms exclusively or share the cation array points of the crystal, and C, N atoms occupy the anion array points, forming binary or multi-element single-phase ultra-high temperature ceramic nanoparticles and uniformly distributing in the Si(C / N) phase.

[0026] Further preferably, the Si(C / N) phase is selected from at least one of silicon carbonitride, silicon carbide, and silicon nitride.

[0027] Further preferably, the yield of the stealth ultra-high temperature thermal protection coating is 50-95%.

[0028] Principles and advantages

[0029] The present application is a stealth ultra-high temperature thermal protection coating which can be directly and quickly coated on the outer surface of a high-speed aircraft structure and can be in-situ converted into a heat-resistant ceramic coating with high yield by introducing ultra-high temperature ceramic powder, with the aid of the strong designability, high ceramic yield, and adjustable rheological properties of the new ultra-high temperature ceramic precursor molecular structure. The coating can be used after coating, drying, and curing, and the process is simple and low in cost. The drying and curing can be performed at room temperature without damaging the structure. During the initial flight stage of the aircraft, the flight speed is low and the surface temperature of the aircraft is not high (<1000℃). The coating mainly has the following two composition states: (1) polymer + ultra-high temperature ceramic powder; (2) SiMe(C / N) amorphous ceramic + ultra-high temperature ceramic powder (Me is one or more of Ti, Zr, Hf, Ta, Nb, Mo, and W). In the above two states, the polymer and amorphous ceramic have good impedance matching with free space, and the ultra-high temperature ceramic powder has excellent electrical conductivity, which can achieve electromagnetic wave absorption through electrical loss mechanism, thereby realizing electromagnetic stealth function in the initial flight stage. During the high-speed cruising and attack stage of the aircraft, the surface temperature of the aircraft is high due to strong aerodynamic heating (>1500℃). At this time, the coating is composed of crystalline ultra-high temperature nano-composite ceramic + ultra-high temperature ceramic powder, and exhibits excellent oxidation resistance and ablation resistance, thereby realizing the stealth and heat protection function of the aircraft in the high-speed cruising and attack stage.

[0030] The stealth ultrahigh-temperature thermal protection coating designed and prepared in the application avoids the defects of high process temperature, long preparation period, high cost and damage to the thermal protection structural member in traditional preparation methods such as thermal spraying and plasma spraying, realizes low-temperature, rapid and low-cost preparation of the ultrahigh-temperature thermal protection coating, can effectively avoid the damage to the thermal protection structural member in the high-temperature preparation process, reduces the requirement on the production equipment, improves the production efficiency, and provides material and technical support for the development and large-scale application of the stealth high-speed aircraft. The coating is composed of a new polymer precursor and an ultrahigh-temperature ceramic powder and can exhibit excellent electromagnetic stealth function in the aircraft launching and flight starting stage. Through the experimental verification of the coating, it is found that the linear ablation rate of the C / C composite material coated with the ultrahigh-temperature thermal protection coating is 0.00518 mm / s and the mass ablation rate is 12.4 mg / s after ablation at ≤2500 ℃ for 60 s. The coating has wave absorption performance in a certain frequency range, and the lowest reflection coefficient is-18.07 dB. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The preparation process flow chart of the ultrahigh-temperature thermal protection coating of the application.

[0032] Figure 2 The schematic diagram of the ultrahigh-temperature thermal protection coating prepared in the application.

[0033] Figure 3 The schematic diagram of the C / C composite material coated with the coating in the application.

[0034] Figure 4 The macroscopic morphology diagram of the ultrahigh-temperature thermal protection coating sample dried and cured in Example 1 of the application.

[0035] Figure 5 The SEM diagram of the ultrahigh-temperature thermal protection coating sample dried and cured in Example 1 of the application.

[0036] Figure 6 The XRD diagram of the polymer precursor obtained in Example 1 of the application after heat treatment.

[0037] Figure 7 The TEM diagram of the polymer precursor obtained in Example 1 of the application after heat treatment.

[0038] Figure 8 The macroscopic morphology diagram of the material obtained in Example 1 of the application after ablation.

[0039] Figure 9 The ablation temperature curve of the material obtained in Example 1 of the application.

[0040] Figure 10 The XRD diagram of the material obtained in Example 1 of the application after ablation.

[0041] Figure 11 This is a SEM image of the material obtained in Example 1 of the present invention after ablation.

[0042] Figure 12 This is a macroscopic morphology diagram of the dried and cured coating sample from Embodiment 2 of the present invention.

[0043] Figure 13 This is a macroscopic morphology diagram of the material obtained in Example 2 of the present invention after ablation.

[0044] Figure 14 This is the ablation temperature curve of the material obtained in Example 2 of the present invention.

[0045] Figure 15 This is the XRD pattern of the material obtained in Example 2 of the present invention after ablation.

[0046] Figure 16 This is a three-dimensional graph of the coating reflectance coefficient, material thickness, and frequency obtained in Example 3 of the present invention.

[0047] Figure 17 This is a reflection coefficient-frequency diagram of a certain thickness of the coating obtained in Example 3 of the present invention. Detailed Implementation

[0048] The following embodiments further illustrate this description. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the invention.

[0049] Example 1

[0050] According to 83(Ti) 0.1 Zr 0.3 Hf 0.5 Ta 0.1 C x N 1-x -17SiC y N 1-y The stoichiometric ratios of 0.980 g tetra(dimethylamino)titanium (Ⅳ), 3.509 g tetra(dimethylamino)zirconium (Ⅳ), 7.756 g tetra(dimethylamino)hafnium (Ⅳ), and 1.754 g penta(dimethylamino)tantalum (Ⅳ) were weighed and dissolved in 5 ml of anhydrous toluene. 3.00 g polysilazane (PSZ) was weighed and dissolved in 5 ml of anhydrous toluene. The two mixtures were thoroughly mixed, stirred at room temperature for 30 min, heated to 80°C and stirred continuously for 3 h, and then allowed to cool naturally for 12 h. Subsequently, 27 g HfC and 27 g HfB2 were added to the above precursor polymer, and the mixture was stirred continuously for 12 h to obtain a heat-protective coating. Figure 2 (As shown). The ultra-high temperature thermal protective coating prepared above was uniformly brushed onto a surface with a density of 1.2~1.6 g / cm³. 3 Porous C / C composite materials with a diameter of 29 mm and a thickness of 10 mm (such as...)Figure 3 The surface (as shown) was dried at room temperature for 24 hours to obtain the following result. Figure 4 The sample shown, after SEM analysis, showed that the added ultra-high temperature ceramic powder was uniformly dispersed in the polymer precursor (e.g., Figure 5 ).

[0051] The polymer precursor prepared above, after pyrolysis at 1100℃ and heat treatment at 1600℃, has the following phase composition: Figure 6 As shown; its microstructure is as follows Figure 7 As shown. After heat treatment, the polymer precursor is transformed into a nano-composite ceramic structure, containing high-entropy nano-(Ti) grains with a nanoscale grain structure. 0.1 Zr 0.3 Hf 0.5 Ta 0.1 C x N 1-x The coating contains both silicon nitride and β-Si3N4 phases. The silicon nitride phase comprises approximately 20 wt%, and after high-temperature heat treatment of the polymer, the ceramic yield is approximately 65%. Calculations show that, during use, the total content of the ultra-high temperature ceramic phase in this thermal protection coating, after pneumatic heating conversion, is approximately 96.9 wt%.

[0052] The C / C composite material with the aforementioned ultra-high temperature thermal protective coating, after passing the plasma ablation test, exhibits the following macroscopic surface morphology: Figure 8 As shown, the ablation temperature curve is as follows: Figure 9 .like Figure 10 XRD pattern shows that the sample surface after ablation is mainly composed of MO2 (M = Ti, Zr, Hf, Ta). Figure 11 SEM images after ablation show that the polymer precursor was ablated and oxidized in situ to form a SiO2 glass phase and ultra-high temperature nano-oxides. After ablation at the highest temperature of 2447℃ for 60 s, the mass ablation rate was 12.4 mg / s and the linear ablation rate was 0.00518 mm / s.

[0053] Example 2

[0054] According to 70ZrC x N 1-x -30SiC y N 1-y 7 g of tetra(dimethylamino)zirconium(IV) was dissolved in 5 ml of anhydrous toluene, and 3.00 g of PSZ was dissolved in 5 ml of anhydrous toluene. The two were mixed thoroughly and stirred at room temperature for 30 min. The mixture was then heated to 80 °C and stirred continuously for 3 h, followed by natural cooling and standing for 12 h. Subsequently, 6.5 g of ZrC and 6.5 g of ZrB2 were added to the precursor polymer, and the mixture was stirred continuously for 12 h. The resulting ultra-high temperature thermal protective coating was then uniformly brushed onto a surface with a density of 1.2–1.6 g / cm³. 3, the surface of the porous C / C composite material with a diameter of 29 mm and a thickness of 10 mm is dried at room temperature for 24 h to obtain a sample as shown in Figure 12 .

[0055] The polymer precursor prepared above has a silicon nitride phase of about 30 wt%, and after high-temperature heat treatment of the polymer, the ceramic yield is about 65%. It is calculated that the total content of the ultra-high-temperature ceramic phase of the ultra-high-temperature thermal protection coating after conversion by aerodynamic heating during use is about 90.0 wt%.

[0056] The C / C composite material coated with the above ultra-high-temperature thermal protection coating is subjected to plasma ablation test, and the surface macro-morphology thereof is as shown in Figure 13 , and the temperature curve is as shown in Figure 14 . The XRD diagram of the ablated sample is as shown in Figure 15 . The surface of the ablated sample is mainly ZrO2. After ablation at the highest temperature of 2292℃ for 60 s, the mass ablation rate is 33.74 mg / s, and the linear ablation rate is 0.0167 mm / s.

[0057] Example 3

[0058] According to 20ZrC x N 1-x -80SiC y N 1-y 2 g of tetrakis(dimethylamino)zirconium (IV) is weighed and dissolved in 5 ml of anhydrous toluene, 8.00 g of PSZ is weighed and dissolved in 5 ml of anhydrous toluene, and the two are mixed uniformly, stirred at room temperature for 30 min, heated to 80℃ and continuously stirred for 3 h, and naturally cooled and placed for 12 h. Subsequently, 40 g of ZrC is added to the above precursor polymer, and continuously stirred for 12 h. After drying and curing of the above prepared ultra-high-temperature thermal protection coating, it is ground into powder, a small amount of paraffin is added according to a mass ratio of 8:2, and a cylindrical block is pressed. It is calculated that the total content of the ultra-high-temperature ceramic phase of the ultra-high-temperature thermal protection coating after conversion by aerodynamic heating during use is about 90.0 wt%.

[0059] The above cylindrical block is subjected to wave absorption performance test, and the three-dimensional graph of the wave absorption performance is as shown in Figure 16 , and the effective absorption width exists in the range of 11 GHz, 17.5~18 GHz (as shown in Figure 17 ), indicating that the coating can play a certain wave absorption protection after curing, and the lowest reflection coefficient thereof in a certain frequency range is -18.07 dB.

[0060] Comparative Example 1

[0061] 2.8 g of PSZ is weighed and dissolved in 5 ml of anhydrous toluene, mixed uniformly, 4.5 g of HfC and 4.5 g of HfB2 are added into the above polymer, and stirring is continued for 12 h. The prepared ultra-high temperature thermal protection coating is uniformly brushed on the surface of a porous C / C composite material with a density of 1.2-1.6 g / cm 3 , a diameter of 29 mm, and a thickness of 10 mm, and dried at room temperature for 24 h.

[0062] The yield of PSZ ceramic is about 40 %. It is calculated that the total content of the ultra-high temperature ceramic phase of the ultra-high temperature thermal protection coating converted by aerodynamic heating during use is 90.0 wt %.

[0063] The C / C composite material with the above brushed ultra-high temperature thermal protection coating is tested by plasma ablation, and the mass ablation rate thereof is 15.6 mg / s and the linear ablation rate thereof is 0.0073 mm / s after ablation at a maximum temperature of 2578 ℃ for 60 s.

[0064] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and principle of the present application shall be covered within the protection scope of the present application.

Claims

1. A stealth ultra-high temperature thermal protection coating, characterized in that: The stealth ultra-high temperature thermal protection coating is composed of a ceramicizable polymer precursor and an ultra-high temperature ceramic powder, wherein the ceramicizable polymer precursor is prepared by reacting at least one transition metal element complex with a silicon-based polymer; The transition metal element in the transition metal element complex is at least one of Ti, Zr, Hf, and Ta, and the ligand in the transition metal element complex is one of dimethylamine, diethylamine, and chloride; The silicon-based polymer is at least one of polysilazane and polysilaborazane; The ultra-high temperature ceramic powder is at least one of binary or multi-element carbides, borides, and nitrides formed by transition metal elements Ti, Zr, Hf, Ta, Nb, Mo, and W; The preparation method of the stealth ultra-high temperature thermal protection coating is as follows: the transition metal element complex and the silicon-based polymer are dissolved in an organic solvent, and reacted under a protective atmosphere to obtain the ceramicizable polymer precursor; the ultra-high temperature ceramic powder is added into the ceramicizable polymer precursor and stirred to obtain the coating; the reaction temperature is -50-200 ℃, and the reaction time is 10-600 min.

2. The stealth ultra-high temperature thermal protection paint according to claim 1, characterized in that: The mass ratio of the ceramicizable polymer precursor to the ultra-high temperature ceramic powder in the stealth ultra-high temperature thermal protection coating is 1-99:1-99.

3. The stealthy ultra-high temperature thermal protection paint according to claim 1 or 2, characterized in that: The organic solvent is anhydrous xylene; The protective atmosphere is nitrogen.

4. The stealthy ultra-high temperature thermal protection paint according to claim 1 or 2, characterized in that: The particle size of the ultra-high temperature ceramic powder is 10 nm-500 μm. The stirring time is 1-48 h.

5. Use of a stealth ultra-high temperature thermal protection coating according to any one of claims 1 to 4, characterized in that: The stealth ultra-high temperature thermal protection coating is obtained by brushing the coating on the surface of a high-speed aircraft structural member, drying, and curing.

6. Use of a stealth ultra-high temperature thermal protection coating according to claim 5, characterized in that: The high-speed aircraft structural member is at least one of C / C composite material, ceramic matrix composite material, high-temperature alloy, and metal matrix composite material.

7. Use of a stealth ultra-high temperature thermal protection coating according to claim 5, characterized in that: The drying temperature is 0 ℃-300 ℃, and the drying time is 10 min-600 h. The curing mode is at least one of heating curing, ultraviolet light curing, electron beam curing, and oxidation curing.

8. Use of a stealth ultra-high temperature thermal protection coating according to claim 5, characterized in that: The coating is composed of carbonitride nanocomposite ceramic and ultra-high temperature ceramic, wherein the carbonitride nanocomposite ceramic is composed of multi-element transition metal carbon / nitride phase and Si(C / N) phase; The multi-element transition metal carbon / nitride is a face-centered cubic crystal structure, wherein transition metal elements Ti, Zr, Hf, Ta, Nb, Mo, and W atoms exclusively or share the cation array points of the crystal, and C and N atoms occupy the anion array points to form binary or multi-element single-phase ultra-high temperature ceramic nanoparticles and uniformly distribute in the Si(C / N) phase; The Si(C / N) phase is at least one of silicon carbonitride, silicon carbide, and silicon nitride; The yield of the stealth ultra-high temperature thermal protection coating is 50-95 %.

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