A rare earth doped ceria material, a preparation method and application thereof, and a preparation method of an infrared stealth coating

Abstract

This invention provides a rare-earth-doped cerium oxide material, its preparation method and application, and a method for preparing an infrared stealth coating, relating to the field of infrared stealth materials technology. The rare-earth-doped cerium oxide material provided by this invention has a fluorite structure and the chemical formula Ce. 1‑ x A x O2; where 0.1≤x≤0.3, and A is Gd, Yb, or Lu. This invention increases the free carrier concentration and thus reduces infrared emissivity by doping CeO2 with a single rare earth element A (Gd, Yb, or Lu), which dissolves into the CeO2 lattice. The results of the embodiments show that the rare earth cerium oxide material provided by this invention has an average emissivity of 0.074–0.13 in the 3–5 μm wavelength range at room temperature, with an emissivity below 0.08 in the 4–5 μm wavelength range. Using the rare earth-doped cerium oxide material provided by this invention to prepare infrared stealth coatings can meet the requirements for infrared stealth.

Description

Technical Field

[0001] This invention relates to the field of infrared stealth materials technology, and in particular to a rare earth-doped cerium oxide material, its preparation method and application, and a method for preparing an infrared stealth coating. Background Technology

[0002] With the development of modern science and technology, military detection technology is becoming increasingly mature. The risk of aircraft being detected and identified by infrared sensors during flight is constantly increasing, making it crucial to improve the infrared stealth performance of materials.

[0003] The radiation process of an object can be described by the Stefan-Boltzmann formula E = σεT 4 (E is the infrared radiation energy of the object; σ is the Stefan-Boltzmann constant; ε is the emissivity of the object; T is the absolute temperature of the object) Calculate the infrared radiation signal intensity or infrared radiation energy. The amount of infrared radiation from an object can be reduced by lowering its temperature and emissivity, thereby improving its infrared stealth performance. Lowering the temperature can be achieved through the development of heat-insulating materials and phase change materials, but this method requires a large amount of material equipment, resulting in complex structures, significant geometric limitations, and loss of power, thus restricting its application. To ensure sufficient power and thrust-to-weight ratio for the aircraft, reducing surface temperature is not feasible. Therefore, applying low-infrared-emissivity materials to the object's surface to reduce its infrared radiation energy becomes crucial for improving its infrared stealth performance. According to Wien's displacement law, when the temperature exceeds 800℃, the main source band of target infrared radiation is 3–5 μm. Therefore, reducing infrared emissivity in the shortwave range becomes particularly important.

[0004] CeO2 has the characteristics of high melting point, oxidation resistance and low infrared emissivity, and is considered a candidate material for infrared stealth applications. However, its emissivity still cannot meet the requirements of infrared stealth (the lowest emissivity at room temperature in the 3-5μm band is about 0.4). Summary of the Invention

[0005] The purpose of this invention is to provide a rare earth-doped cerium oxide material, its preparation method and application, and a method for preparing an infrared stealth coating. The rare earth-doped cerium oxide material provided by this invention has low emissivity in the 3-5 μm band, which can meet the requirements of infrared stealth.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a rare-earth-doped cerium oxide material with a fluorite structure and the chemical formula shown in Formula 1: Ce 1-x A x O2 Equation 1; In Equation 1, 0.1≤x≤0.3, and A is Gd, Yb or Lu.

[0008] This invention provides a method for preparing the rare earth-doped cerium oxide material described above, comprising the following steps:

[0009] The oxide powder of A and CeO2 powder are wet ball-milled and dried to obtain a mixed powder; wherein A is Gd, Yb or Lu; the molar ratio of A to CeO2 powder in the oxide powder of A is x:(1-x);

[0010] The mixed powder is subjected to a first sintering to obtain the rare earth-doped cerium oxide material.

[0011] Preferably, the first sintering temperature is 1600℃ and the holding time is 2h.

[0012] This invention provides the application of the rare earth-doped cerium oxide material described in the above scheme or the rare earth-doped cerium oxide material prepared by the preparation method described in the above scheme in infrared stealth coatings.

[0013] This invention provides a method for preparing an infrared stealth coating, comprising the following steps:

[0014] The rare earth-doped cerium oxide powder, binder and water are mixed and ball-milled to obtain a slurry; the rare earth-doped cerium oxide material is the rare earth-doped cerium oxide material described in the above scheme or the rare earth-doped cerium oxide material prepared by the preparation method described in the above scheme.

[0015] The slurry is spray-granulated to obtain spherical granulated powder;

[0016] The spherical granulated powder is sequentially subjected to debinding, heating, and second sintering to obtain lightly sintered rare earth-doped cerium oxide particles.

[0017] The lightly sintered rare earth-doped cerium oxide particles are sprayed onto the surface of a substrate with an adhesive layer using plasma spraying to form the infrared stealth coating.

[0018] Preferably, the conditions for plasma spraying include: a current of 600-700A, a main argon flow rate of 45-55 SCFH, an auxiliary hydrogen flow rate of 6-7 SCFH, a carrier argon flow rate of 3-5 SCFH; a powder feed rate of 4-5 RPM; and a distance of 85-110 mm between the spray gun and the substrate.

[0019] Preferably, the binder comprises polyvinyl alcohol; the mass of the binder is 0.5% of the mass of the rare earth-doped cerium oxide powder; and the solid content of the slurry is 35-45%.

[0020] Preferably, the spray granulation is carried out in a spray dryer, wherein the inlet temperature of the spray dryer is 230-270°C, the outlet temperature is 140-150°C, and the peristaltic pump speed is 36-40 r / s.

[0021] Preferably, the temperature for discharging the adhesive is 540–570°C, and the heat preservation time is 3–3.5 h.

[0022] Preferably, the second sintering temperature is 1280–1350°C, and the holding time is 1.5–2.5 h.

[0023] This invention provides a rare-earth-doped cerium oxide material with a fluorite structure and the chemical formula shown in Formula 1: Ce 1-x A x O2, Formula 1; in Formula 1, 0.1 ≤ x ≤ 0.3, and A is Gd, Yb, or Lu. This invention increases the free carrier concentration and thus reduces infrared emissivity by doping CeO2 with a single rare earth element A (Gd, Yb, or Lu), which dissolves into the CeO2 lattice. The results of the embodiments show that the rare earth-doped cerium oxide material provided by this invention has an average emissivity of 0.074–0.13 in the 3–5 μm wavelength range at room temperature, with an emissivity of less than 0.08 in the 4–5 μm wavelength range.

[0024] The rare-earth-doped cerium oxide material provided by this invention is used to prepare an infrared stealth coating. The resulting coating has a minimum emissivity of 0.5036 at room temperature and in the 3-5 μm band, which can meet the requirements of infrared stealth.

[0025] Furthermore, compared to traditional metallic coating materials, which have poor temperature resistance and are easily oxidized at high temperatures, making them unsuitable for long-term use at high temperatures, the rare earth-doped cerium oxide material provided by this invention exhibits better stability at high temperatures. Attached Figure Description

[0026] Figure 1 Ce prepared in Example 1 0.9 Gd 0.1 XRD pattern of O2 powder;

[0027] Figure 2 Ce prepared in Example 1 0.9 Gd 0.1 Infrared emissivity spectrum of O2 powder in the 3–14 μm band;

[0028] Figure 3 Ce prepared in Example 2 0.7 Lu 0.3 XRD pattern of O2 powder;

[0029] Figure 4 Ce prepared in Example 2 0.7Lu 0.3 Infrared emissivity spectrum of O2 powder in the 3–14 μm band;

[0030] Figure 5 Ce prepared in Example 3 0.8 Yb 0.2 XRD pattern of O2 powder;

[0031] Figure 6 Ce prepared in Example 3 0.8 Yb 0.2 Infrared emissivity spectrum of O2 powder in the 3–14 μm band;

[0032] Figure 7 Ce prepared in Example 4 0.9 Lu 0.1 XRD pattern of O2 powder;

[0033] Figure 8 Ce prepared in Example 4 0.9 Lu 0.1 Infrared emissivity spectrum of O2 powder in the 3–14 μm band;

[0034] Figure 9 Ce prepared in Example 5 0.7 Gd 0.3 XRD pattern of O2 powder;

[0035] Figure 10 Ce prepared in Example 5 0.7 Gd 0.3 Infrared emissivity spectrum of O2 powder in the 3–14 μm band;

[0036] Figure 11 Infrared emissivity spectrum of Gd2Ce2O7 powder prepared for Comparative Example 1 in the 3–14 μm band;

[0037] Figure 12 SEM image of the lightly sintered rare earth-doped cerium oxide particles prepared by step (5) of Example 1;

[0038] Figure 13 (a) is a surface morphology diagram of a single particle; (b) is a magnified view of the surface morphology of a single particle; (c, d, e) are elemental analysis spectra.

[0039] Figure 14 XRD pattern of the infrared stealth coating in Application Example 1;

[0040] Figure 15 (a) is a physical image of the infrared stealth coating used in Application Example 1, (b) is a surface topography image, and (c) is a longitudinal cross-sectional topography image.

[0041] Figure 16 The infrared emissivity spectrum of the infrared stealth coating used in Example 1 is shown. Detailed Implementation

[0042] This invention provides a rare-earth-doped cerium oxide material with a fluorite structure and the chemical formula shown in Formula 1: Ce 1-x A x O2 Equation 1; In Equation 1, 0.1≤x≤0.3, and A is Gd, Yb or Lu.

[0043] In this invention, x can specifically be 0.1, 0.15, 0.2, 0.25, or 0.3. In the embodiments of this invention, it is specifically 0.1, 0.2, or 0.3.

[0044] This invention increases the free carrier concentration and thus reduces the infrared emissivity of cerium oxide by doping CeO2 with a single rare earth element A (Gd, Yb or Lu), which dissolves into the CeO2 lattice.

[0045] This invention provides a method for preparing the rare earth-doped cerium oxide material described above, comprising the following steps:

[0046] The oxide powder of A and CeO2 powder are wet ball-milled and dried to obtain a mixed powder; wherein A is Gd, Yb or Lu; the molar ratio of A to CeO2 powder in the oxide powder of A is x:(1-x);

[0047] The mixed powder is subjected to a first sintering to obtain the rare earth-doped cerium oxide material.

[0048] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0049] In this invention, oxide powder of A and CeO2 powder are subjected to wet ball milling (referred to as the first wet ball milling) and dried to obtain a mixed powder.

[0050] In this invention, A is Gd, Yb, or Lu; when A is Gd, the oxide powder of A is Gd2O3 powder; when A is Yb, the oxide powder of A is Yb2O3 powder; when A is Lu, the oxide powder of A is Lu2O3 powder.

[0051] In this invention, the average particle size of both the oxide powder of A and the CeO2 powder is preferably 500 nm, and the purity is preferably greater than 99.9%. In this invention, the molar ratio of A to CeO2 powder in the oxide powder of A is x:(1-x), where 0.1≤x≤0.3.

[0052] Before the first wet ball milling, the present invention preferably further includes removing the water of crystallization from the oxide powder of A and the CeO2 powder. In the present invention, when the oxide powder of A is Gd2O3 powder, Yb2O3 powder, or Lu2O3 powder, removing the water of crystallization from the Gd2O3 powder, Yb2O3 powder, or Lu2O3 powder preferably includes: placing the Gd2O3 powder, Yb2O3 powder, or Lu2O3 powder in an alumina crucible, heating it to 1000℃ at a heating rate of 3-7℃ / min and holding it at that temperature for 2 hours, and then cooling it with the furnace. Removing the water of crystallization from the CeO2 powder preferably includes: placing the CeO2 powder in an alumina crucible, heating it to 400℃ at a heating rate of 3-7℃ / min and holding it at that temperature for 2 hours, and then cooling it with the furnace. The present invention's removal of the water of crystallization from the raw material powder can ensure the accuracy of the stoichiometry in the preparation of rare earth-doped cerium oxide materials.

[0053] In this invention, the grinding media for the first wet ball mill preferably includes zirconia balls with diameters of 8mm, 5mm, and 3mm; wherein the mass ratio of the 8mm, 5mm, and 3mm zirconia balls is preferably 1:2:(1-2); the ball-to-material ratio for the first wet ball mill is preferably (3-5):1, more preferably (3.5-4.5):1. In this invention, the dispersion medium for the first wet ball mill is preferably anhydrous ethanol; the amount of anhydrous ethanol used is not particularly important, as long as it is sufficient to disperse the raw material powder evenly. In this invention, the rotational speed of the first wet ball mill is preferably 220-280 rpm, more preferably 240-260 rpm; the milling time is preferably 5-7 hours, more preferably 5.5-6 hours.

[0054] In this invention, the drying temperature is preferably 60-80°C, more preferably 65-75°C, and even more preferably 70°C; the drying time is preferably 8-15 hours, more preferably 10-13 hours, and even more preferably 12 hours.

[0055] After obtaining the mixed powder, the present invention performs a first sintering on the mixed powder to obtain the rare earth-doped cerium oxide material.

[0056] In this invention, the mixed powder is preferably first ground, then passed through a 120-mesh sieve, and the undersize material is used for a first sintering. In this invention, the preferred temperature for the first sintering is 1600℃, and the preferred holding time is 2 hours. In this invention, the preferred rate of heating to the first sintering temperature is 3-6℃ / min, more preferably 4-5℃ / min. In this invention, the first sintering is preferably carried out in an air atmosphere. During the first sintering process, CeO2 and the oxide of A undergo solid solution reaction to form a solid solution Ce. 1-x A x O2.

[0057] This invention provides the application of the rare earth-doped cerium oxide material described in the above scheme or the rare earth-doped cerium oxide material prepared by the preparation method described in the above scheme in infrared stealth coatings.

[0058] This invention provides a method for preparing an infrared stealth coating, comprising the following steps:

[0059] The rare earth-doped cerium oxide powder, binder and water are mixed and ball-milled to obtain a slurry;

[0060] The slurry is spray-granulated to obtain spherical granulated powder; the rare earth doped cerium oxide material is the rare earth doped cerium oxide material described in the above technical solution or the rare earth doped cerium oxide material prepared by the preparation method described in the above solution.

[0061] The spherical granulated powder is sequentially subjected to debinding, heating, and second sintering to obtain lightly sintered rare earth-doped cerium oxide particles.

[0062] The lightly sintered rare earth-doped cerium oxide particles are sprayed onto the surface of a substrate with an adhesive layer using plasma spraying to form the infrared stealth coating.

[0063] This invention involves ball milling a mixture of rare-earth-doped cerium oxide powder, a binder, and water to obtain a slurry. In this invention, the rare-earth-doped cerium oxide powder is preferably obtained by wet ball milling (referred to as the second wet ball milling) and drying of the rare-earth-doped cerium oxide material. The grinding media of the second wet ball milling preferably includes zirconia balls with diameters of 8mm, 5mm, and 3mm; wherein the mass ratio of 8mm, 5mm, and 3mm zirconia balls is preferably 1:2:(1-2); the ball-to-material ratio of the second wet ball milling is preferably (4-5):1. In this invention, the dispersion medium of the second wet ball milling is preferably anhydrous ethanol; the amount of anhydrous ethanol used is not particularly important, as long as it is sufficient to disperse the raw material powder evenly. In this invention, the rotation speed of the second wet ball milling is preferably 300-400 rpm, more preferably 330-370 rpm; the ball milling time is preferably 8-12 hours, more preferably 10 hours.

[0064] In this invention, the drying temperature is preferably 60–80°C, more preferably 65–75°C; the drying time is preferably 10–13 h, more preferably 11–12 h. In this invention, the particle size of the rare earth-doped cerium oxide material powder is preferably less than 120 mesh (i.e., 120 mesh undersize).

[0065] In this invention, the binder preferably comprises polyvinyl alcohol; the mass of the binder is preferably 0.5% of the mass of the rare earth-doped cerium oxide powder; this invention does not have special requirements for the amount of water used, but it is preferred that the solid content of the slurry be 35-45%. In this invention, the solid content of the slurry is further preferably 38-42%.

[0066] In this invention, the mixing ball milling is preferably carried out in a planetary ball mill; the grinding balls used in the mixing ball milling are preferably zirconia grinding balls with diameters of 8 mm, 5 mm, and 3 mm, and the mass ratio of grinding balls with diameters of 8 mm, 5 mm, and 3 mm is preferably 1:2:1. In this invention, the ball-to-material ratio of the mixing ball milling is preferably (3-5):1, the ball milling speed is preferably 300-350 rpm, and the ball milling time is preferably 2-2.5 h.

[0067] After obtaining the slurry, the present invention performs spray granulation on the slurry to obtain spherical granulated powder.

[0068] In this invention, the spray granulation is preferably carried out in a spray dryer. The inlet temperature of the spray dryer is preferably 230–270°C, more preferably 240–260°C; the outlet temperature is preferably 140–150°C, more preferably 150°C; and the peristaltic pump speed is preferably 36–40 r / s, more preferably 38–40 r / s. This invention obtains spherical particles with good sphericity and complete particle shape through spray granulation, which facilitates the preparation of subsequent spray coatings.

[0069] After obtaining spherical granulated powder, the present invention sequentially performs debinding, heating and second sintering on the spherical granulated powder to obtain lightly sintered rare earth doped cerium oxide particles.

[0070] In this invention, the adhesive removal temperature is preferably 540–570°C, more preferably 550–560°C; the holding time for adhesive removal is preferably 3–3.5 h; the rate of heating to the adhesive removal temperature is preferably 1–2°C / min; and the adhesive removal is carried out in an air atmosphere. This invention reduces the influence of the adhesive on the performance of the sprayed coating by removing the adhesive.

[0071] In this invention, the rate at which the self-dispensing temperature rises to the second sintering temperature is preferably 4–6 °C / min. The second sintering temperature is preferably 1280–1350 °C, more preferably 1300–1320 °C; the holding time is preferably 1.5–2.5 h, more preferably 2 h; and the second sintering is preferably carried out in an air atmosphere. This invention, through the second sintering, causes slight sintering of the rare-earth-doped cerium oxide particles, thereby making the bonding between small particles tighter, making the spherical powder less prone to breakage, and facilitating the preparation of the spray coating.

[0072] After obtaining lightly sintered rare earth doped cerium oxide particles, the present invention uses plasma spraying to spray the lightly sintered rare earth doped cerium oxide particles onto the substrate surface with an adhesive layer to form the infrared stealth coating.

[0073] This invention does not have special requirements for the preparation of the substrate with the adhesive layer; a method well-known in the art can be used to prepare the adhesive layer on the substrate surface. This invention also does not have special requirements for the substrate and the adhesive layer; a substrate and adhesive well-known in the art can be used. In an embodiment of this invention, the adhesive layer is specifically NiCrCoAlY. Specifically, in this invention, lightly sintered rare-earth-doped cerium oxide particles are sprayed onto the surface of the adhesive layer.

[0074] Before plasma spraying, the present invention preferably uses a standard sieve to control the particle size of lightly sintered rare earth doped cerium oxide particles, taking the undersize of a standard sieve with a pore size of 50 μm and the oversize of a standard sieve with a pore size of 90 μm, thereby obtaining lightly sintered rare earth doped cerium oxide particles with a particle size range of 50 to 90 μm for plasma spraying.

[0075] In this invention, the preferred conditions for plasma spraying include: a current of 600–700 A, a main argon flow rate of 45–55 SCFH, an auxiliary hydrogen flow rate of 6–7 SCFH, and a carrier argon flow rate of 3–5 SCFH; a powder feed rate of 4–5 RPM; and a distance of 85–110 mm between the spray gun and the substrate. Further, the plasma spraying current is more preferably 620–680 A, and more preferably 640–660 A; the main argon flow rate is more preferably 48–53 SCFH, and more preferably 49–50 SCFH; the carrier argon flow rate is more preferably 3.5–4.5 SCFH, and more preferably 4 SCFH; and the distance between the spray gun and the substrate is more preferably 90–105 mm, and more preferably 90–100 mm.

[0076] In this invention, the thickness of the infrared stealth coating is preferably 150-250 μm, more preferably 170-230 μm, and even more preferably 190-200 μm.

[0077] The following detailed description, in conjunction with embodiments, illustrates the rare-earth-doped cerium oxide materials, their preparation methods, and applications provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0078] Example 1

[0079] Ce 0.9 Gd 0.1 Preparation of O2 powder:

[0080] Gd₂O₃ raw material powder was heat-treated at 1000℃ for 2 hours and then cooled to 70℃ in the furnace. CeO₂ raw material powder was heat-treated at 400℃ for 2 hours and then cooled to 70℃ in the furnace. Then, according to Ce… 0.9 Gd 0.1 The O2 ratio is as follows: Gd2O3 and CeO2 are placed in a ball mill jar and ball milled with anhydrous ethanol as the medium to obtain a slurry; wherein the diameter of the zirconia grinding balls is Φ8mm, Φ5mm and Φ3mm, the mass ratio is 1:2:1, the ball-to-material mass ratio is 4:1, the ball milling time is 6h and the rotation speed is 250rpm.

[0081] The above slurry was poured into an evaporating dish and dried in an oven at 70°C for 12 hours to remove anhydrous ethanol, resulting in a mixed powder.

[0082] The mixed powder was ground thoroughly in a mortar until no agglomerates remained, then passed through a 120-mesh sieve. The powder was then placed in an alumina crucible and placed in a muffle furnace. Under air atmosphere, the temperature was increased to 1600℃ at a heating rate of 5℃ / min and held for 2 hours. After cooling to room temperature with the furnace, Ce was obtained. 0.9 Gd 0.1 O2 powder.

[0083] The above powder was subjected to XRD analysis, and the XRD pattern was obtained as follows: Figure 1 As shown. According to Figure 1 It can be seen that the diffraction peaks of the powder are consistent with the CeO2 standard card PDF#81-0792, and no other impurity peaks appear. Therefore, it can be proved that Gd has been completely dissolved into the CeO2 lattice and has a fluorite structure.

[0084] Emissivity at room temperature was measured using the reflectance method. The instrument was a Bruker Innovio R Fourier transform infrared spectrometer from BRUKER, Germany. The reflectance spectrum of the gold mirror was measured before each measurement to subtract the background, and the error was less than 0.1%. 0.9 Gd 0.1 The infrared emissivity spectrum of O2 powder in the 3–14 μm wavelength range is shown below. Figure 2 The average emissivity of this powder is 0.12 in the 3–5 μm band, with an emissivity of less than 0.08 in the 4–5 μm band.

[0085] Example 2

[0086] Ce 0.7 Lu 0.3 Preparation of O2 powder:

[0087] Lu2O3 raw material powder was heat-treated at 1000℃ for 2 hours and then cooled to 70℃ in the furnace. CeO2 raw material powder was heat-treated at 400℃ for 2 hours and then cooled to 70℃ in the furnace. (The last part, "CeO2 raw material powder," appears to be an error and doesn't need a direct translation.) 0.7 Lu 0.3The O2 ratio is as follows: Lu2O3 and CeO2 are placed in a ball mill jar and ball milled with anhydrous ethanol as the medium to obtain a slurry; wherein the diameter of the zirconia grinding balls is Φ8mm, Φ5mm and Φ3mm, the mass ratio is 1:2:1, the ball-to-material mass ratio is 4:1, the ball milling time is 6h and the rotation speed is 250rpm.

[0088] The above slurry was poured into an evaporating dish and dried in an oven at 70°C for 12 hours to remove anhydrous ethanol, resulting in a mixed powder.

[0089] The mixed powder was ground thoroughly in a mortar until no agglomerates remained, then passed through a 120-mesh sieve. The powder was then placed in an alumina crucible and placed in a muffle furnace. Under air atmosphere, the temperature was increased to 1600℃ at a heating rate of 5℃ / min and held for 2 hours. After cooling to room temperature with the furnace, Ce was obtained. 0.7 Lu 0.3 O2 powder.

[0090] The above powder was subjected to XRD analysis, and the XRD pattern was obtained as follows: Figure 3 As shown. According to Figure 3 It can be seen that the diffraction peaks of the powder are consistent with the CeO2 standard card PDF#81-0792, and no other impurity peaks appear. Therefore, it can be proved that Lu has been completely dissolved into the CeO2 lattice and has a fluorite structure.

[0091] Emissivity at room temperature was measured using the reflectance method. The instrument was a Bruker Innovio R Fourier transform infrared spectrometer from BRUKER, Germany. The reflectance spectrum of the gold mirror was measured before each measurement to subtract the background, and the error was less than 0.1%. 0.9 Gd 0.1 The infrared emissivity spectrum of O2 powder in the 3–14 μm wavelength range is shown below. Figure 4 The average emissivity of this powder in the 3–5 μm wavelength range is 0.098.

[0092] Example 3

[0093] Ce 0.8 Yb 0.2 Preparation of O2 powder:

[0094] Yb₂O₃ raw material powder was heat-treated at 1000℃ for 2 hours and then cooled to 70℃ in the furnace. CeO₂ raw material powder was heat-treated at 400℃ for 2 hours and then cooled to 70℃ in the furnace. Then, according to Ce… 0.8 Yb 0.2 The O2 ratio was determined by placing Yb2O3 and CeO2 in a ball mill jar and ball milling them with anhydrous ethanol as the medium to obtain a slurry. The diameters of the zirconia milling balls were Φ8mm, Φ5mm, and Φ3mm, with a mass ratio of 1:2:1 and a ball-to-material mass ratio of 4:1. The ball milling time was 6 hours and the rotation speed was 250 rpm.

[0095] The above slurry was poured into an evaporating dish and dried in an oven at 70°C for 12 hours to remove anhydrous ethanol, resulting in a mixed powder.

[0096] The mixed powder was ground thoroughly in a mortar until no agglomerates remained, then passed through a 120-mesh sieve. The powder was then placed in an alumina crucible and placed in a muffle furnace. Under air atmosphere, the temperature was increased to 1600℃ at a heating rate of 5℃ / min and held for 2 hours. After cooling to room temperature with the furnace, Ce was obtained. 0.8 Yb 0.2 O2 powder.

[0097] The above powder was subjected to XRD analysis, and the XRD pattern was obtained as follows: Figure 5 As shown. According to Figure 5 It can be seen that the diffraction peaks of the powder are consistent with the CeO2 standard card PDF#81-0792, and no other impurity peaks appear. Therefore, it can be proved that Yb has been completely dissolved into the CeO2 lattice and has a fluorite structure.

[0098] Emissivity at room temperature was measured using the reflectance method. The instrument was a Bruker Innovio R Fourier transform infrared spectrometer from BRUKER, Germany. The reflectance spectrum of the gold mirror was measured before each measurement to subtract the background, and the error was less than 0.1%. 0.8 Yb 0.2 The infrared emissivity spectrum of O2 powder in the 3–14 μm wavelength range is shown below. Figure 6 The average emissivity of this powder in the 3–5 μm wavelength range is 0.094.

[0099] Example 4

[0100] Ce 0.9 Lu 0.1 Preparation of O2 powder:

[0101] Lu2O3 raw material powder was heat-treated at 1000℃ for 2 hours and then cooled to 70℃ in the furnace. CeO2 raw material powder was heat-treated at 400℃ for 2 hours and then cooled to 70℃ in the furnace. (The last part, "CeO2 raw material powder," appears to be an error and doesn't need a direct translation.) 0.9 Lu 0.1 The O2 ratio is as follows: Lu2O3 and CeO2 are placed in a ball mill jar and ball milled with anhydrous ethanol as the medium to obtain a slurry; wherein the diameter of the zirconia grinding balls is Φ8mm, Φ5mm and Φ3mm, the mass ratio is 1:2:1, the ball-to-material mass ratio is 4:1, the ball milling time is 6h and the rotation speed is 250rpm.

[0102] The above slurry was poured into an evaporating dish and dried in an oven at 70°C for 12 hours to remove anhydrous ethanol, resulting in a mixed powder.

[0103] The mixed powder was ground thoroughly in a mortar until no agglomerates remained, then passed through a 120-mesh sieve. The powder was then placed in an alumina crucible and placed in a muffle furnace. Under air atmosphere, the temperature was increased to 1600℃ at a heating rate of 5℃ / min and held for 2 hours. After cooling to room temperature with the furnace, Ce was obtained. 0.9 Lu 0.1 O2 powder.

[0104] The above powder was subjected to XRD analysis, and the XRD pattern was obtained as follows: Figure 7 As shown. According to Figure 7 It can be seen that the diffraction peaks of the powder are consistent with the CeO2 standard card PDF#81-0792, and no other impurity peaks appear. Therefore, it can be proved that Lu has been completely dissolved into the CeO2 lattice and has a fluorite structure.

[0105] Emissivity at room temperature was measured using the reflectance method. The instrument was a Bruker Innovio R Fourier transform infrared spectrometer from BRUKER, Germany. The reflectance spectrum of the gold mirror was measured before each measurement to subtract the background, and the error was less than 0.1%. 0.9 Lu 0.1 The infrared emissivity spectrum of O2 powder in the 3–14 μm wavelength range is shown below. Figure 8 The average emissivity of this powder is 0.074 in the 3–5 μm band, with the emissivity in the 4–5 μm band being less than 0.05.

[0106] Example 5

[0107] Ce 0.7 Gd 0.3 Preparation of O2 powder:

[0108] The only difference from Example 1 is that x is replaced with 0.3.

[0109] The above powder was subjected to XRD analysis, and the XRD pattern was obtained as follows: Figure 9 As shown. According to Figure 9 It can be seen that the diffraction peaks of the powder are consistent with the CeO2 standard card PDF#81-0792, and no other impurity peaks appear. Therefore, it can be proved that Gd has been completely dissolved into the CeO2 lattice and has a fluorite structure.

[0110] Ce 0.7 Gd 0.3 The infrared emissivity spectrum of O2 powder in the 3–14 μm wavelength range is shown below. Figure 10 The average emissivity of this powder in the 3–5 μm wavelength range is 0.13.

[0111] Comparative Example 1

[0112] The only difference from Example 1 is that x = 0.5. However, when the doping content is 0.5%, the chemical formula is generally written as RE2Ce2O7 (RE is rare earth), and the atomic ratio of RE to Ce is 1:1, that is, x is 0.5.

[0113] Preparation of Gd2Ce2O7 powder:

[0114] The infrared emissivity spectrum of Gd₂Ce₂O₇ powder in the 3–14 μm wavelength band is shown below. Figure 11 The average emissivity of this powder in the 3-5 μm wavelength range is 0.16, which is higher than the emissivity of the powder doped with 0.1-0.3.

[0115] Application Example 1

[0116] (1) In order to obtain powder that meets the spray granulation standard, the sieved Ce 0.8 Yb 0.2 O2 powder was placed in a ball mill jar, using anhydrous ethanol as the dispersant. Zirconia ball milling balls with a diameter ratio of 8 mm:5 mm:3 mm and a mass ratio of 1:2:1 were used. The milling speed was 350 rpm, and the milling time was 10 hours. The resulting slurry was placed in a large beaker and dried in a 70°C oven for 12 hours to remove the anhydrous ethanol, yielding Ce powder that meets the spray granulation standards. 0.8 Yb 0.2 O2 powder.

[0117] (2) Using deionized water as the dispersant, the mass of the binder polyvinyl alcohol (PVA) is Ce. 0.8 Yb 0.2 0.5 wt% O2 powder was processed using a planetary ball mill to remove Ce. 0.8 Yb 0.2 O2 powder and PVA were mixed evenly. Zirconia grinding balls were used with a diameter ratio of 8 mm:5 mm:3 mm, a mass ratio of 1:2:1, a ball-to-material ratio of 4:1, a grinding speed of 300 rpm, and a grinding time of 2.5 h to obtain a slurry with a solid content of 40%.

[0118] (3) Spray granulation is carried out using a spray dryer. The fan of the spray dryer is turned on in advance for preheating. The inlet temperature is 250℃, the outlet temperature is 150℃, and the speed of the peristaltic pump is 40r / s to obtain spherical granulated powder.

[0119] (4) Place the spherical granulated powder into a corundum crucible, heat it to 550°C at a heating rate of 2°C / min and hold it for 3 hours to remove PVA and reduce the influence of the binder on the performance of the sprayed coating. Heat it to 1300°C at a heating rate of 5°C / min and hold it for 2 hours. Then cool it to 25°C with the furnace to obtain lightly sintered rare earth doped cerium oxide particles.

[0120] (5) The particle size of light sintered rare earth doped cerium oxide particles is controlled by using a standard sieve. The undersize of a standard sieve with a pore size of 50 μm is taken, and the oversize of a standard sieve with a pore size of 90 μm is taken, so as to obtain light sintered rare earth doped cerium oxide particles with a particle size range of 50 to 90 μm.

[0121] (6) The plasma spraying equipment used is an F4 model spray gun, and the substrate is a high-temperature alloy substrate. The substrate is sandblasted before spraying. To reduce the thermal mismatch between the ceramic coating and the substrate, NiCrCoAlY is selected as the adhesive layer. The preferred plasma spraying conditions include: current 650A, main gas argon flow rate of 50SCFH, auxiliary gas hydrogen flow rate of 6.5SCFH, carrier gas argon flow rate of 4SCFH; powder feed rate of 4.3RPM; and a distance of 90mm between the spray gun and the substrate to form an infrared stealth coating.

[0122] Characterization:

[0123] The surface morphology of the lightly sintered rare earth-doped cerium oxide particles described in step (5) was observed, such as... Figure 12 As shown, the lightly sintered rare earth-doped cerium oxide particles are spherical, and their magnification allows for observation (e.g.) Figure 13 As shown in the figure, sintering necks appear on the surface of the sintered particles, resulting in a tighter bond and enhanced cohesive strength on the surface of the lightly sintered rare earth-doped cerium oxide particles. The spherical particles have intact surfaces without obvious cracks.

[0124] The flowability and loose density of the oxide ceramic particles prepared according to step (5) of GB / T 39696-2020 and GB / T 31057.1-2014 were tested. The flowability was found to be 53.48 s / 50 g, and the loose density was found to be 1.2648 g / cm³. 3 .

[0125] The infrared stealth coating prepared above was subjected to XRD detection, and the results are as follows: Figure 14 As shown, the diffraction peaks of the infrared stealth coating are consistent with those of the CeO2 standard card PDF#81-0792, and no other impurity peaks appear. Therefore, it can be proved that the granulation, sintering and spraying processes do not cause changes in the phase structure.

[0126] Figure 15 (a) shows the physical image of the prepared infrared stealth coating, and (b) shows the SEM image of the surface of the infrared stealth coating. As can be seen from the images, the coating surface is intact and relatively smooth. The longitudinal section of the coating was observed using SEM, and the resulting SEM image is shown below. Figure 15 As shown in (c), the arrow indicates the thickness of the coating. As can be seen from the figure, the thickness of the infrared stealth coating is about 200 μm. The coating has good adhesion to the substrate, and the uneven surface of the substrate helps to improve the adhesion strength of the coating.

[0127] Emissivity was measured using a Bruker INVENIOR FTIR Fourier transform infrared spectrometer from BRUKER GmbH, Germany, to determine the reflectivity of the infrared stealth coating in Application Example 1. Because the prepared coating is opaque, for opaque materials, the sum of its absorptivity (α) and reflectivity (ρ) is 1. According to Kirchhoff's law, under thermal equilibrium conditions, the emissivity of a material is equal to its absorptivity, thus allowing the calculation of the material's emissivity value. The test temperature was room temperature, and the test wavelength was 3–14 μm. The emissivity spectrum of the coating under these test conditions is shown below. Figure 16 As shown in the figure. Among them, the lowest value in the 3-5μm band is 0.5036.

[0128] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. Use of a rare earth doped ceria material in an infrared stealth coating, characterized in that, The rare earth doped ceria material is fluorite structured with the chemical formula Ce 0.9 Lu 0.1 O2; The preparation method of the rare earth-doped cerium oxide material includes the following steps: Lu2O3 powder and CeO2 powder were wet ball-milled and dried to obtain a mixed powder; the molar ratio of Lu to CeO2 powder in the Lu2O3 powder was 0.1:0.

9. The mixed powder is subjected to a first sintering to obtain the rare earth-doped cerium oxide material; the first sintering temperature is 1600℃ and the holding time is 2 h.

2. A method for preparing an infrared stealth coating, characterized in that, Includes the following steps: The rare earth-doped cerium oxide powder, binder and water are mixed and ball-milled to obtain a slurry; The slurry is spray-granulated to obtain spherical granulated powder; The spherical granulated powder is sequentially subjected to debinding, heating, and second sintering to obtain lightly sintered rare earth-doped cerium oxide particles. The lightly sintered rare earth-doped cerium oxide particles are sprayed onto the surface of a substrate with an adhesive layer using plasma spraying to form the infrared stealth coating. The rare earth doped ceria material is fluorite structured with the chemical formula Ce 0.9 Lu 0.1 O2; The preparation method of the rare earth-doped cerium oxide material includes the following steps: Lu2O3 powder and CeO2 powder were wet ball-milled and dried to obtain a mixed powder; the molar ratio of Lu to CeO2 powder in the Lu2O3 powder was 0.1:0.

9. The mixed powder is subjected to a first sintering to obtain the rare earth-doped cerium oxide material; the first sintering temperature is 1600℃ and the holding time is 2 h.

3. The preparation method according to claim 2, characterized in that, The conditions for plasma spraying include: current of 600-700 A, main argon flow rate of 45-55 SCFH, auxiliary hydrogen flow rate of 6-7 SCFH, carrier argon flow rate of 3-5 SCFH; powder feed rate of 4-5 RPM; and distance between the spray gun and the substrate of 85-110 mm.

4. The preparation method according to claim 2, characterized in that, The binder comprises polyvinyl alcohol; the mass of the binder is 0.5% of the mass of the rare earth-doped cerium oxide powder; the solid content of the slurry is 35-45%.

5. The preparation method according to claim 2, characterized in that, The temperature for discharging the adhesive is 540~570℃, and the holding time is 3~3.5 h.

6. The preparation method according to claim 2, characterized in that, The second sintering temperature is 1280~1350℃, and the holding time is 1.5~2.5 h.

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