A high-temperature, high-infrared emissivity and low-thermal conductivity coating and its preparation method and application

Abstract

The present invention relates to a high-temperature, high-infrared-emissivity and low-thermal-conductivity coating and its preparation method and application, comprising: cleaning a substrate and performing sandblasting; spraying alloy powder to form a bonding layer; and using a solution plasma spraying process to spray an atomized solution containing a water-soluble strontium source, a water-soluble X source and a water-soluble zirconium source to obtain the Sr(Zr) prepared by the present invention. 1‑y X y )O z The coating has high infrared radiation performance, and its infrared emissivity at 600℃ can reach 0.986; it also has low thermal conductivity performance, and its thermal conductivity at 1000℃ can be as low as 1.63 W·m ‑1 ·K ‑1 The resulting coating is suitable for a variety of substrates and complex surface structures, and can form a uniform and continuous coating in different application scenarios such as aircraft skins, electronic device housings, and sintering furnace inner chambers, ensuring the full performance of the coating.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, in particular to a high-temperature, high-infrared emissivity and low-thermal conductivity coating and a preparation method and application thereof. Background Art

[0002] With the increasing demand for thermal management in high-temperature environments, various fields are placing higher demands on coating materials with high infrared emissivity and low thermal conductivity. Such coating materials can improve the efficiency, performance, and lifespan of equipment under extreme operating conditions through radiative heat dissipation and efficient thermal insulation. For example, when an aerospace aircraft is in high-altitude flight, the surface temperature of its skin rises significantly due to the combined effects of aerodynamic heating and solar radiation. Excessive temperatures can affect the aircraft's structural strength and flight stability, and even endanger flight safety. While traditional metal skins have a certain degree of thermal conductivity, their radiative heat dissipation performance is low, making them unable to meet the heat dissipation requirements in high-temperature environments. Therefore, a high-infrared emissivity coating is needed to reduce the skin temperature by enhancing radiative heat dissipation while ensuring coating adhesion and weather resistance. High-temperature sintering furnaces are widely used in the sintering and heat treatment of metal materials and ceramic products, with internal temperatures typically exceeding 500°C. Heat loss in sintering furnaces has long plagued industrial production. Traditional internal materials typically have high thermal conductivity, resulting in significant heat loss through the furnace walls. By coating the inner surface of the furnace with a coating material with low thermal conductivity and high infrared emissivity, heat loss can be significantly reduced at high temperatures, improving the thermal efficiency of the furnace and thus achieving energy conservation. As the integration and power density of electronic equipment continue to increase, thermal management has become a key issue to ensure the stable operation of devices. Efficient heat dissipation coatings can reduce heat accumulation in electronic components, extend equipment life and improve performance. Although traditional metal heat sinks can quickly dissipate heat, their infrared heat dissipation capabilities are limited, especially under high temperature conditions. By coating the surface of the electronic device housing with a high infrared emissivity coating, the efficiency of heat release through radiation can be significantly improved, reducing the surface temperature of the component.

[0003] Currently, commonly used high-temperature coating materials include zirconium oxide-based ceramics, aluminum-titanium composites, and other oxide coatings. These coatings can, to a certain extent, meet the basic requirements of high-temperature environments, but they still have the following problems: insufficient infrared emissivity, making it difficult to dissipate heat efficiently; high thermal conductivity, resulting in limited thermal insulation performance; and complex and costly preparation processes, making them unsuitable for large-scale industrial deployment. SrZrO3 has a high melting point and low thermal conductivity, while ion-modified SrZrO3 ceramic materials not only maintain low thermal conductivity at high temperatures but also exhibit excellent infrared radiation properties. They can be used to reduce the operating efficiency of aircraft engine components and improve the thermal management performance of sintering furnaces. By using plasma spraying to prepare ion-modified SrZrO3 coatings, their high-temperature performance can be fully utilized, providing efficient and reliable technical support for the application of thermal barrier coatings for aircraft engines and energy-saving materials for high-temperature sintering furnaces.

[0004] Based on the above problems and the excellent properties of ion-modified SrZrO3 ceramic materials, combined with advanced plasma spraying technology, further research is still needed on high-temperature, high-infrared emissivity and low thermal conductivity coatings. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention provides a high-temperature high-infrared emissivity and low-thermal conductivity coating with high infrared emissivity, low thermal conductivity, stable performance and low cost, as well as its preparation method and application, to solve the technical problems of existing high-temperature coating materials such as low infrared emissivity, high thermal conductivity, complex preparation process, high cost and difficulty in large-scale industrial promotion.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] This invention proposes a high-temperature, high-infrared emissivity and low-thermal conductivity coating and its preparation method. By employing a suitable material composition and process, the coating achieves both high infrared emissivity and low thermal conductivity at high temperatures, significantly improving its overall performance in high-temperature thermal management. This coating can be widely used in aerospace skin cooling, energy conservation in high-temperature sintering furnaces, and heat dissipation for electronic devices, providing a novel solution for improving the energy efficiency, performance, and lifespan of high-temperature equipment.

[0008] The present invention provides a method for preparing a high-temperature, high-infrared emissivity and low-thermal conductivity coating, comprising the following steps:

[0009] (1) After polishing, sandblasting and cleaning the substrate, substrate A is obtained;

[0010] (2) Using atmospheric plasma spraying technology, the dried alloy powder is sprayed on the substrate A to form a bonding layer to obtain the substrate B;

[0011] (3) Add water-soluble strontium source, water-soluble X source and water-soluble zirconium source to deionized water, heat and stir in a water bath to obtain solution C;

[0012] (4) Using the solution plasma spraying process, the atomized solution C is sprayed on the substrate B to obtain the coating D.

[0013] Preferably, in step (1), the substrate is copper foil, carbon steel, stainless steel, iron-based high-temperature alloy or nickel-based high-temperature alloy;

[0014] Preferably, in step (1), the substrate is first polished with sandpaper, then sandblasted, and then ultrasonically cleaned with alcohol;

[0015] Preferably, in step (1), the substrate is polished with 60-mesh, 180-mesh, and 320-mesh sandpaper in sequence; the sand used in the sandblasting machine is white corundum with a specification of 60-200 mesh, and the roughness of the substrate surface after sandblasting is 2-12 μm; the volume fraction of alcohol is 75%;

[0016] Among them, after sandblasting, the pollutants on the substrate surface can be removed, the surface roughness of the substrate can be improved, the surface energy of the substrate can be activated, and the adhesion and uniformity of the coating can be improved:

[0017] Preferably, in step (2), the alloy powder is an MCrAlY alloy powder; wherein M = Ni or Co or NiCo; the alloy powder is dried at a temperature of 60-120°C for a time of 0.5-2 h;

[0018] The preferred alloy powder for the bonding layer in this invention is an MCrAlY alloy powder. Ni and Co are the primary elements of the bonding layer, providing excellent resistance to high-temperature oxidation and hot corrosion, while also improving the coating's interfacial bonding. Furthermore, the addition of Cr (18% to 22% by mass) effectively reduces the critical Al content (8% to 12% by mass) required for the formation of α-Al₂O₃, promoting the formation of a dense α-Al₂O₃ layer and mitigating the increased room-temperature brittleness associated with excessive Al content. Cr also enhances the coating's hot corrosion resistance. Thus, the MCrAlY bonding layer combines oxidation resistance, thermal expansion matching, high-temperature strength, and excellent adhesion, enhancing the coating's stability and significantly extending its service life at high temperatures.

[0019] Preferably, in step (2), before spraying, the substrate A is preheated at a temperature of 80-250°C;

[0020] More preferably, in step (2), the atmospheric plasma spraying process is specifically as follows: the alloy powder feeding rate is 40-60 g / min; the nitrogen flow rate is 20-50 L / min; the argon flow rate is 20~50 L / min; the hydrogen flow rate is 5-8 L / min; the current is 220-250 A, and the power is 85-95 kW; the traverse speed of the spray gun is 650-850 mm / s; the longitudinal step length of the spray gun is 1-4 mm / step; the spraying distance is 70-140 mm; after spraying, the thickness of the resulting bonding layer is 100-150 μm;

[0021] Preferably, in step (3), the water-soluble strontium source is any one of strontium acetate Sr(CH3COO)2, strontium nitrate Sr(NO3)2, and strontium bromate Sr(BrO3)2, or a mixture of two or more thereof;

[0022] The water-soluble X source is any one of magnesium acetate Mg(CH3COO)2, magnesium chloride MgCl2, calcium acetate monohydrate Ca(CH3COO)2·H2O, calcium chloride hexahydrate CaCl2·6H2O, manganese acetate Mn(CH3COO)2, manganese chloride MnCl2, manganese nitrate Mn(NO3)2, ferric nitrate nonahydrate Fe(NO3)3·9H2O, ferric chloride FeCl3, cobalt chloride hexahydrate CoCl2·6H2O, cobalt acetate tetrahydrate Co(CH3COO)2·4H2O, nickel acetate tetrahydrate Ni(CH3COO)2·4H2O, nickel chloride hexahydrate NiCl2·6H2O, copper nitrate trihydrate Cu(NO3)2·3H2O, copper acetate Cu(CH3COO)2, copper chloride CuCl2, zinc acetate Zn(CH3COO)2, and zinc chloride ZnCl2, or a mixture of two or more thereof;

[0023] The water-soluble zirconium source is any one of zirconium oxychloride ZrOCl2, zirconium oxynitrate ZrO(NO3)2, zirconium acetate Zr(CH3COO)4, or a mixture of two or more thereof;

[0024] Preferably, in step (3), the water bath heating temperature is 30-80°C, and the water bath heating stirring time is 2-6 h;

[0025] Preferably, in step (3), the molar ratio of strontium ions, X ions and zirconium ions in the water-soluble strontium source, the water-soluble X source and the water-soluble zirconium source is (1-1.3):(0.05-0.5):(0.5-0.95); the sum of the concentrations of metal cations in solution C is 1.6-3.2 mol / L;

[0026] More preferably, in step (3), the molar ratio of strontium ions, X ions and zirconium ions in the water-soluble strontium source, the water-soluble X source and the water-soluble zirconium source is 1:(0.15-0.25):(0.85-0.75); the total concentration of metal cations in solution C is 2.0-2.8 mol / L;

[0027] The present invention limits the molar ratio of strontium ions, X ions, and zirconium ions in solution C to a specific range, and also limits the concentration of metal cations in solution C to 1.6 to 3.2 mol / L. At this point, the surface tension and viscosity of the solution are optimal, facilitating solution transport during subsequent solution plasma spraying and ensuring the production of high-quality coatings. Furthermore, the coating material prepared by solution plasma spraying of solution C under these conditions does not produce any second-phase products, resulting in a single perovskite-phase coating. This phase structure significantly improves the coating's infrared emissivity and imparts low thermal conductivity.

[0028] Preferably, in the step (4), before spraying, the solution C is first filtered through a 200-400 mesh filter screen to remove possible impurities in the solution, and then sent to the atomization treatment; and the substrate B is preheated at a preheating temperature of 80-350°C;

[0029] More preferably, in step (4), the solution plasma spraying process is specifically as follows: the liquid feeding rate for the atomization treatment of solution C is 10-60 mL / min; the atomizing air flow of the atomizing nozzle is 7-25 L / min; the total gas flow rate is 220-240 L / min; and in the gas, the volume fraction of argon is 50-85%, the volume fraction of hydrogen is 5-25%, and the volume fraction of nitrogen is 5-25%; the current is 210-220 A, and the power is 70-125 kW; the traverse speed of the spray gun is 600-900 mm / s, and the longitudinal step length of the spray gun is 1-3 mm / step; the spraying distance is 60-120 mm; after spraying, the thickness of the obtained coating is 100-300 μm;

[0030] The present invention limits the atmospheric plasma spraying process and the solution plasma spraying process to a specific range, wherein, if the spraying distance is too high, the coating structure gradually becomes loose, the thickness gradually decreases, and there are more and more unmelted particles and pores in the coating; if the spraying distance is too low, a large number of cracks are easily generated in the coating structure; if the longitudinal step of the spray gun is too low, the substrate temperature is too high, resulting in increased thermal stress between the coating and the substrate, and eventually the coating is prone to shedding and failure; if the longitudinal step of the spray gun is too high, the substrate temperature is too low, resulting in reduced coating bonding strength and shortened coating life; if the gas flow rate and powder feeding are too low, the coating deposition efficiency will be low and the coating thickness will be reduced; if the gas flow rate and powder feeding are too high, the coating deposition efficiency will be too high and the coating structure will deteriorate; if the lateral movement speed of the spray gun is too low, the coating will produce lateral cracks, affecting the coating life; if the lateral movement speed of the coating is too high, the coating deposition efficiency will be too low and the melting will be incomplete.

[0031] Within the process parameters defined in this invention for atmospheric plasma spraying and solution plasma spraying, when the spraying distance is long, the solution precursor requires more time to reach the substrate surface, resulting in reduced kinetic energy and insufficient impact force. Furthermore, during the impact process, the temperature of the molten particles decreases, ultimately resulting in poor adhesion to the substrate surface and a decrease in coating thickness. When the spraying distance is too close, the sample temperature becomes too high due to the proximity to the sample, resulting in incompletely decomposed deposits, which ultimately affect the coating structure and lead to coating failure. The coating deposition thickness decreases with increasing spraying distance, increases with increasing total gas flow rate, and decreases with increasing longitudinal stepping of the spray gun.

[0032] In this process, a soluble precursor is dissolved in water to produce a precursor solution (Solution C). This solution is then delivered to an atomizing nozzle via a liquid delivery device. Under gas pressure, the liquid is atomized into fine particles and injected into a plasma arc. After undergoing a series of physical and chemical processes within the arc (evaporation, decomposition, precipitation, pyrolysis, sintering, and melting), the droplets containing oxide particles solidify and form a nano- or submicron coating on the substrate surface. The resulting coating exhibits the following characteristics: (i) ultrafine lamellar crystals (0.5-5 μm in diameter); (ii) interconnected nano- and micron-sized pores; (iii) closely spaced vertical cracks that extend through the thickness of the coating; and (iv) inter-pass boundaries (IPBs). The coatings produced using this process exhibit excellent cyclic durability, a high cycle life, low thermal conductivity, and low cost.

[0033] Preferably, the molecular formula of the material involved in the obtained coating D is Sr(Zr 1-y X y )O z, X is Mg, Ca, Mn, Fe, Co, Ni, Cu or Zn; y is 0.05 to 0.5, and z is 2.5 to 2.9375.

[0034] More preferably, the molecular formula of the material involved in the obtained coating D is Sr(Zr 1-y X y )O z , X is Mn, Fe or Ni; y is 0.15-0.25, and z is 2.75-2.85.

[0035] Among them, the present invention uses X element to modify SrZrO3, which is beneficial to increase oxygen vacancies, and the Fermi level passes through the conduction band, so that the material has the characteristics of an n-type semiconductor, and the transition type is an indirect transition. With the doping of X element, the static dielectric constant and refractive index tend to decrease. The doping of X element improves the stability of the strontium zirconate system. In particular, the present invention Sr(Zr 1-y X y )O z X is preferably Mn, Fe or Ni. Compared with other ions, the incorporation of Mn, Fe and Ni ions can reduce the band gap of the crystal to a greater extent, thereby improving the carrier absorption of the crystal in the short infrared band, thereby increasing the infrared emissivity of the obtained coating and reducing its thermal conductivity.

[0036] The present invention provides a high-temperature, high-infrared emissivity and low-thermal conductivity coating, which is prepared by the preparation method.

[0037] The present invention provides an application of a high-temperature, high-infrared emissivity and low-thermal conductivity coating, wherein the high-temperature, high-infrared emissivity and low-thermal conductivity coating is used for aircraft skins, sintering furnace interiors or electronic device housings.

[0038] Specifically, the high-temperature, high-infrared emissivity and low-thermal conductivity coating is used as a thermal barrier coating for an aircraft engine combustion chamber, or for the inner surface of a high-temperature sintering furnace.

[0039] The technical solution of the present invention achieves the following beneficial technical effects:

[0040] 1. The present invention uses atmospheric plasma spraying technology to prepare MCrAlY alloy powder bonding layer, uses water-soluble strontium source, water-soluble X source and water-soluble zirconium source to prepare precursor solution, and uses solution plasma spraying technology to prepare Sr (Zr 1-y X y )O z coating, and finally achieved Sr(Zr 1-y X y )O zThe preparation method of the coating with high infrared radiation and low thermal conductivity has the advantages of low cost, simple process and large-scale industrial promotion.

[0041] 2. Sr(Zr) prepared by the present invention 1-y X y )O z The coating has high infrared radiation performance. Its infrared emissivity in the range of 1-22 μm from room temperature to 600°C is between 0.872 and 0.986, and can reach 0.986 at 600°C. It also has low thermal conductivity. Its thermal conductivity is 3.1~1.63 W·m in the range of room temperature to 1400°C. -1 ·K -1 , which can be as low as 1.63 W·m at 1000℃ -1 ·K -1 , can be used for heat dissipation of aerospace skins, energy saving in high-temperature sintering furnaces, and heat dissipation of electronic devices.

[0042] 3. The present invention uses MCrAlY alloy powder as a bonding layer, combines atmospheric plasma spraying technology and solution plasma spraying technology to prepare Sr (Zr 1-y X y )O z The coating is suitable for a variety of substrates and complex surface structures. It can form coatings in different application scenarios such as aircraft skins, electronic device housings, and sintering furnace inner chambers to ensure the full performance of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The Sr(Zr) prepared in Example 1 of the present invention 0.75 Ni 0.25 )O 2.75 Microscopic morphology of the coating;

[0044] Figure 2 Sr(Zr) prepared in Examples 1-3 of the present invention 1-y X y )O z Infrared emissivity of the coating in the 1-22 μm band from room temperature to 600°C.

[0045] Figure 3 Sr(Zr) prepared in Examples 1-3 of the present invention 1-y X y )O z Thermal conductivity of the coating from room temperature to 1400°C. DETAILED DESCRIPTION

[0046] Example 1

[0047] This embodiment relates to a method for preparing a high-temperature, high-infrared emissivity and low-thermal conductivity coating, comprising the following steps:

[0048] (1) The stainless steel substrate was polished with 60-mesh, 180-mesh, and 320-mesh sandpaper in sequence, and then placed in a sandblasting machine for sandblasting with 100-mesh white corundum. Subsequently, it was ultrasonically cleaned with 75% (v / v) alcohol to obtain a stainless steel substrate A.

[0049] (2) NiCrAlY alloy powder (purchased from Beikuang New Materials Technology Co., Ltd., model: KF-110) was placed in a drying oven, the temperature was set to 80 °C, and dried for 1.5 h; the dried NiCrAlY alloy powder was placed in a powder feeder, and the feeding rate of the NiCrAlY alloy powder was 40 g / min;

[0050] A plasma spray system was used to preheat the stainless steel substrate A. After preheating, atmospheric plasma spraying was performed using the plasma spray system. The spraying process settings were nitrogen flow rate of 25 L / min, argon flow rate of 25 L / min, hydrogen flow rate of 8 L / min, current of 220 A, power of 85 kW, traverse speed of the spray gun of 700 mm / s, longitudinal step length of the spray gun of 1 mm / step, and spraying distance of 75 mm. Before spraying, the preheating temperature of the substrate material A was 150°C. A bonding layer with a thickness of about 100 μm was obtained to obtain substrate B.

[0051] (3) Sr(NO3)2, Ni(CH3COO)2·4H2O, and Zr(C2H3O2)4 were added to deionized water at a molar ratio of 1:0.25:0.75, heated in a 50°C water bath, and stirred thoroughly for 1 h to obtain a uniformly mixed solution C. The total concentration of all metal cations in solution C was 2.2 mol / L.

[0052] (4) Filter the prepared solution C through a 325-mesh sieve and pour it into a liquid feeding barrel; feed the solution C into the atomizing nozzle through an axial liquid feeding device, and the liquid feeding rate for the atomization treatment of the solution C is 15 mL / min;

[0053] Solution plasma spraying was performed using a plasma spraying system. The spraying process was set with an atomizing airflow of 8 L / min for the atomizing nozzle; a total gas flow of 240 L / min, and the volume fraction of argon, hydrogen, and nitrogen was 75%, 13%, and 12% in the gas; the current was 220 A, and the power was 85 kW; the traverse speed of the spray gun was 700 mm / s, and the longitudinal step length of the spray gun was 1 mm / step; the spraying distance was 75 mm; before spraying, the preheating temperature of the substrate B was 150°C; the obtained coating with high infrared emissivity and low thermal conductivity had a thickness of approximately 220 μm (excluding the thickness of the bonding layer).

[0054] Figure 1 The Sr(Zr 0.75 Ni 0.25 )O 2.75 The surface micromorphology of the coating shows that it is composed of micron-sized particles.

[0055] After testing, the Sr(Zr 0.75 Ni 0.25 )O 2.75 The infrared emissivity of the coating in the 1-22 μm band from room temperature to 600 °C is 0.924-0.986, of which 0.986 at 600 °C. The thermal conductivity is 2.6-1.63 W·m in the room temperature to 1400 °C. -1 ·K -1 , among which the thermal conductivity is the lowest at 1000 ℃, which is 1.63 W·m -1 ·K -1 .

[0056] Example 2

[0057] This embodiment relates to a method for preparing a high-temperature, high-infrared emissivity and low-thermal conductivity coating, comprising the following steps:

[0058] (1) The stainless steel substrate was polished with 60-mesh, 180-mesh, and 320-mesh sandpaper in sequence, and then placed in a sandblasting machine for sandblasting with 80-mesh white corundum. Subsequently, it was ultrasonically cleaned with 75% (v / v) alcohol to obtain stainless steel substrate A.

[0059] (2) Place NiCrAlY alloy powder (KF-110) in a drying oven at 85°C for 2 h; place the baked NiCrAlY alloy powder in a powder feeder at a feeding rate of 52 g / min;

[0060] Atmospheric plasma spraying was performed using a plasma spraying system. The spraying process settings were nitrogen flow rate of 30 L / min, argon flow rate of 30 L / min, hydrogen flow rate of 5 L / min, current of 220 A, power of 95 kW, traverse speed of the spray gun of 750 mm / s, longitudinal step length of the spray gun of 1.5 mm / step, and spraying distance of 75 mm. Before spraying, the substrate material A was preheated to 120°C. A bonding layer with a thickness of about 120 μm was obtained, obtaining substrate B.

[0061] (3) Sr(NO3)2, Fe(NO3)3·9H2O, and Zr(C2H3O2)4 were added to deionized water at a molar ratio of 1:0.15:0.85, heated in a 65°C water bath, and stirred thoroughly for 1.5 h to obtain a uniformly mixed solution C. The total concentration of all metal cations in solution C was 2.5 mol / L.

[0062] (4) Filter the prepared solution C through a 340-mesh sieve and pour it into a liquid feeding bucket; feed the solution C into the atomizing nozzle through an axial liquid feeding device, and the liquid feeding rate for the atomization treatment of the solution C is 25 mL / min;

[0063] Solution plasma spraying was carried out using a plasma spraying system. The spraying process settings were as follows: the atomizing airflow of the atomizing nozzle was 18 L / min; the total gas flow rate was 235 L / min, and the volume fraction of argon was 78%, the volume fraction of hydrogen was 11%, and the volume fraction of nitrogen was 11%. The current was 210 A and the power was 90 kW. The traverse speed of the spray gun was 750 mm / s, and the longitudinal step length of the spray gun was 1.5 mm / step. The spraying distance was 80 mm. Before spraying, the preheating temperature of the substrate B was 180°C. The obtained coating with high infrared emissivity and low thermal conductivity had a thickness of approximately 150 μm.

[0064] After testing, the Sr(Zr 0.85 Fe 0.15 )O 2.85 The infrared emissivity of the coating in the 1-22 μm band is 0.902-0.989 from room temperature to 600°C, of which 0.989 at 600°C. The thermal conductivity is 2.94-1.72 W·m in the room temperature to 1400°C. -1 ·K -1 , among which the thermal conductivity is the lowest at 800℃, which is 1.72 W·m -1 ·K -1 .

[0065] Example 3

[0066] This embodiment relates to a method for preparing a high-temperature, high-infrared emissivity and low-thermal conductivity coating, comprising the following steps:

[0067] (1) The stainless steel substrate was polished with 60-mesh, 180-mesh, and 320-mesh sandpaper in sequence, and then placed in a sandblasting machine and sandblasted with 120-mesh white corundum for surface treatment; subsequently, ultrasonic cleaning was performed with 75% (v / v) alcohol to obtain a stainless steel substrate A;

[0068] (2) NiCrAlY alloy powder (KF-110) was placed in a drying oven at 82°C and dried for 3 h. The dried NiCrAlY alloy powder was placed in a powder feeder at a feeding rate of 58 g / min.

[0069] A plasma spraying system was used for atmospheric plasma spraying. The spraying process settings were nitrogen flow rate of 28 L / min, argon flow rate of 28 L / min, hydrogen flow rate of 8 L / min, current of 220 A, power of 88 kW, traverse speed of the spray gun of 700 mm / s, longitudinal step length of the spray gun of 2 mm / step, spraying distance of 100 mm, and pre-treatment of the substrate material A before spraying.

[0070] The heating temperature was 140°C; a bonding layer with a thickness of about 124 μm was obtained, thereby obtaining substrate B;

[0071] (3) Sr(CH3COO)2, Mn(NO3)2, and Zr(C2H3O2)4 were added to deionized water at a molar ratio of 1:0.18:0.82, heated in a 60°C water bath, and stirred for 2 h to obtain a uniformly mixed solution C. The total concentration of all metal cations in solution C was 2.0 mol / L.

[0072] (4) Filter the prepared solution C through a 330-mesh sieve and pour it into a liquid feeding bucket; feed the solution C into the atomizing nozzle through an axial liquid feeding device, and the liquid feeding rate for the atomization treatment of the solution C is 35 mL / min;

[0073] Solution plasma spraying was carried out using a plasma spraying system. The spraying process settings were as follows: the atomizing airflow of the atomizing nozzle was 24 L / min; the total gas flow rate was 220 L / min, and the volume fraction of argon was 76%, the volume fraction of hydrogen was 14%, and the volume fraction of nitrogen was 10%; the current was 220 A, and the power was 88 kW; the traverse speed of the spray gun was 720 mm / s, and the longitudinal step length of the spray gun was 1.3 mm / step; the spraying distance was 100 mm; before spraying, the preheating temperature of the substrate B was 160°C; the obtained coating with high infrared emissivity and low thermal conductivity had a thickness of approximately 210 μm.

[0074] After testing, the Sr(Zr 0.82 Mn 0.18 )O 2.82 The infrared emissivity of the coating in the 1-22 μm band is 0.89-0.985 from room temperature to 600°C, of which 0.985 at 600°C. The thermal conductivity is 3.1-1.9 W·m from room temperature to 1400°C. -1 ·K -1 , the thermal conductivity is the lowest at 1000℃, which is 1.93 W·m -1 ·K -1 .

[0075] Figure 2 and Figure 3 The infrared emissivity and thermal conductivity curves of the coatings prepared in Examples 1-3 at different temperatures are shown. It can be seen from the figure that the infrared emissivity of the coatings prepared in the examples gradually increases with increasing temperature, and the thermal conductivity shows a trend of first decreasing and then increasing with increasing temperature. When the temperature reaches about 1000°C, the thermal conductivity reaches the minimum value.

[0076] Comparative Example 1

[0077] This comparative example provides a method for preparing a coating, which differs from Example 1 in that the specific process parameters of atmospheric plasma spraying involved in step (2) of this comparative example are different.

[0078] The atmospheric plasma spraying process involved in step (2) of this comparative example is specifically as follows: the alloy powder feeding rate is 22 g / min; the nitrogen flow rate is 18 L / min; the argon flow rate is 52 L / min; the hydrogen flow rate is 15 L / min; the current is 200 A, and the power is 60 kW; the lateral movement speed of the spray gun is 400 mm / s, and the longitudinal step length of the spray gun is 4.5 mm / step; the spraying distance is 150 mm; a bonding layer with a thickness of about 40 μm is obtained to obtain substrate B; the other steps and parameters are the same as those in Example 1.

[0079] After testing, the Sr(Zr 0.75 Ni 0.25 )O 2.75 The infrared emissivity of the coating in the 1-22 μm band is 0.732-0.812 from room temperature to 600°C, of which 0.812 at 600°C. The thermal conductivity is 3.3-2.7 W·m from room temperature to 1400°C. -1 ·K -1 , the thermal conductivity is the lowest at 1000℃, which is 2.71W·m -1 ·K -1 .

[0080] Comparative Example 2

[0081] This comparative example provides a method for preparing a coating, which differs from Example 1 in that, in solution C involved in step (3) of this comparative example, Ni(CH3COO)2·4H2O is replaced by Ca(CH3COO)2·H2O.

[0082] In step (3) of this comparative example, Sr(NO3)2, Ca(CH3COO)2·H2O, and Zr(C2H3O2)4 were added to deionized water in a molar ratio of 1:0.25:0.75. The other steps and parameters were the same as those in Example 1.

[0083] After testing, the Sr(Zr 0.75 Ca 0.25 )O 2.75 The infrared emissivity of the coating in the 1-22 μm band is 0.776-0.846 from room temperature to 600°C, of which 0.846 at 600°C. The thermal conductivity is 3.9-2.9 W·m in the room temperature to 1400°C. -1 ·K -1 , the thermal conductivity is the lowest at 1000℃, which is 2.9W·m -1 ·K -1 .

[0084] Comparative Example 3

[0085] This comparative example provides a method for preparing a coating, which differs from Example 1 in that the ratio of the amounts of Sr(NO3)2, Ni(CH3COO)2·4H2O, and Zr(C2H3O2)4 in solution C involved in step (3) of this comparative example is different.

[0086] In step (3) of this comparative example, Sr(NO3)2, Ni(CH3COO)2·4H2O, and Zr(C2H3O2)4 were added to deionized water at a molar ratio of 1.8:1:1. The other steps and parameters were the same as those in Example 1.

[0087] After testing, the Sr(Zr 0.75 Ni 0.25 )O 2.75 The infrared emissivity of the coating in the 1-22 μm band is 0.634-0.759 from room temperature to 600°C, of which 0.759 at 600°C. The thermal conductivity is 5.3-4.5 W·m from room temperature to 1400°C. -1 ·K -1 , the thermal conductivity is the lowest at 1000℃, which is 4.5W·m -1 ·K -1 .

[0088] Comparative Example 4

[0089] This comparative example provides a method for preparing a coating, which differs from Example 1 in that the total concentration of all metal cations in solution C involved in step (3) of this comparative example is different.

[0090] The total concentration of all metal cations in solution C in step (3) of this comparative example is 3.8 mol / L, and the other steps and parameters are the same as those in Example 1.

[0091] After testing, the Sr(Zr 0.75 Ni 0.25 )O 2.75 The infrared emissivity of the coating in the 1-22 μm band is 0.811-0.876 from room temperature to 600°C, of which 0.876 at 600°C. The thermal conductivity is 3.9-2.9 W·m from room temperature to 1400°C. -1 ·K -1 , the thermal conductivity is the lowest at 1000℃, which is 2.9W·m -1 ·K -1 .

[0092] Comparative Example 5

[0093] This comparative example provides a method for preparing a coating, which differs from Example 1 in that the specific process parameters of the solution plasma spraying involved in step (4) of this comparative example are different.

[0094] The solution plasma spraying process in step (4) of this comparative example is as follows: the liquid feeding rate for the atomization treatment of solution C is 66 mL / min; the atomizing air flow of the atomizing nozzle is 30 L / min; the total flow rate of the gas is 400 L / min; and the volume fraction of argon in the gas is 90%, the volume fraction of hydrogen is 4%, and the volume fraction of nitrogen is 6%; the current is 250 A, and the power is 60 kW; the lateral movement speed of the spray gun is 400 mm / s, and the longitudinal step length of the spray gun is 0.5 mm / step; the spraying distance is 50 mm; after spraying, the total thickness of the obtained coating is 77 μm; the other steps and parameters are the same as those in Example 1.

[0095] After testing, the Sr(Zr 0.75 Ni 0.25 )O 2.75 The infrared emissivity of the coating in the 1-22 μm band is 0.634-0.759 from room temperature to 600°C, of which 0.759 at 600°C. The thermal conductivity is 5.3-4.5 W·m from room temperature to 1400°C. -1 ·K -1 , the thermal conductivity is the lowest at 1000℃, which is 4.5W·m -1 ·K-1 .

[0096] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the claims of this patent application.

Claims

1. A method for preparing a high-temperature, high-infrared emissivity and low-thermal conductivity coating, characterized in that: The steps include: (1) After polishing, sandblasting and cleaning the substrate, substrate A is obtained; (2) Using an atmospheric plasma spraying process, the dried alloy powder is sprayed on the substrate A to form a bonding layer to obtain a substrate B; the alloy powder is an MCrAlY type alloy powder; wherein M=Ni or Co or NiCo; the atmospheric plasma spraying process is specifically as follows: the alloy powder feeding rate is 40-60 g / min; the nitrogen flow rate is 20-50 L / min; the argon flow rate is 20~50 L / min; the hydrogen flow rate is 5-8 L / min; the current is 220-250 A, and the power is 85-95 kW; the traverse speed of the spray gun is 650-850 mm / s; the longitudinal step length of the spray gun is 1-4 mm / step; the spraying distance is 70-140 mm; after spraying, the thickness of the resulting bonding layer is 100-150 μm; (3) Add a water-soluble strontium source, a water-soluble X source, and a water-soluble zirconium source to deionized water, heat in a water bath, and stir to obtain solution C; the water-soluble X source is any one of manganese acetate, manganese chloride, manganese nitrate, ferric nitrate nonahydrate, ferric chloride, nickel acetate tetrahydrate, and nickel chloride hexahydrate, or a mixture of two or more thereof; the molar ratio of strontium ions, X ions, and zirconium ions in the water-soluble strontium source, the water-soluble X source, and the water-soluble zirconium source is (1-1.3):(0.05-0.5):(0.5-0.95); the sum of the concentrations of metal cations in solution C is 1.6-3.2 mol / L; (4) Using a solution plasma spraying process, the atomized solution C is sprayed on the substrate B to obtain a coating D; the solution plasma spraying process is specifically as follows: the liquid feeding rate for the atomization treatment of solution C is 10-60 mL / min; the atomizing air flow of the atomizing nozzle is 7-25 L / min; the total gas flow rate is 220-240 L / min; and in the gas, the volume fraction of argon is 50-85%, the volume fraction of hydrogen is 5-25%, and the volume fraction of nitrogen is 5-25%; the current is 210-220 A, and the power is 70-125kW; the lateral movement speed of the spray gun is 600-900 mm / s, and the longitudinal step length of the spray gun is 1-3 mm / step; the spraying distance is 60-120 mm; after spraying, the thickness of the obtained coating is 100-300 μm; the molecular formula of the material involved in the obtained coating D is Sr(Zr 1-y X y )O z , X is Mn, Fe or Ni; y is 0.15-0.25, and z is 2.75-2.

85.

2. The preparation method according to claim 1, wherein In the step (1), the substrate is copper foil, carbon steel, stainless steel, iron-based high-temperature alloy or nickel-based high-temperature alloy; Before cleaning, the substrate was polished with 60-mesh, 180-mesh, and 320-mesh sandpaper in sequence, then sandblasted with 60-200-mesh white corundum, and then ultrasonically cleaned with 75% volume fraction alcohol.

3. The preparation method according to claim 1, wherein In the step (2), the alloy powder is dried at a temperature of 60-120°C for 0.5-2 hours; before spraying, the substrate A is preheated at a temperature of 80-250°C.

4. The preparation method according to claim 1, wherein In the step (3), the water-soluble strontium source is any one of strontium acetate, strontium nitrate, and strontium bromate, or a mixture of two or more thereof; the water-soluble zirconium source is any one of zirconium oxychloride, zirconium oxynitrate, and zirconium acetate, or a mixture of two or more thereof.

5. The preparation method according to claim 1, wherein The water bath heating temperature is 30~80℃, and the water bath heating stirring time is 2~6 h.

6. The preparation method according to claim 1, wherein In step (3), the molar ratio of strontium ions, X ions and zirconium ions in the water-soluble strontium source, the water-soluble X source and the water-soluble zirconium source is 1:(0.15-0.25):(0.85-0.75); and the total concentration of metal cations in solution C is 2.0-2.8 mol / L.

7. The preparation method according to claim 1, wherein In the step (4), before spraying, the solution C is first filtered through a 200-400 mesh filter sieve and then sent to an atomization process; and the substrate B is preheated at a preheating temperature of 80-350°C.

8. A high-temperature, high-infrared emissivity and low-thermal conductivity coating, characterized in that: The high-temperature, high-infrared emissivity and low-thermal conductivity coating is prepared by the preparation method according to any one of claims 1 to 7.

9. Application of a high-temperature, high-infrared-emissivity, and low-thermal-conductivity coating, wherein the high-temperature, high-infrared-emissivity, and low-thermal-conductivity coating according to claim 8 is applied to aircraft skins, sintering furnace interiors, or electronic device housings.

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