Infrared heat shielding type rare earth hafnate-based composite ceramic coating material and preparation method thereof

Abstract

The application discloses an infrared heat shielding type rare earth hafnate-based composite ceramic coating material and a preparation method thereof, and belongs to the technical field of thermal barrier coating materials.The application aims to solve the problem that the existing rare earth hafnate ceramic material mainly in pyrochlore / defect fluorite structure has the advantages of low thermal conductivity and high temperature phase stability, but does not have shielding effect on infrared heat radiation, the prepared thermal barrier coating is penetrated by infrared heat radiation at high temperature, the metal substrate is directly radiated and heated, and the working life of the coating material is reduced.The spinel structure ceramic with low infrared transmittance, high infrared emissivity and high infrared absorptivity is used as a dispersed phase to modify the rare earth hafnate-based phase ceramic with pyrochlore / defect fluorite structure, and an infrared heat shielding type composite ceramic coating material with low thermal conductivity, high temperature phase stability and ultralow infrared transmittance is prepared, and the material has a good application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of thermal barrier coating materials, and particularly relates to an infrared heat shielding type rare earth hafnate-based composite ceramic coating material and a preparation method thereof. BACKGROUND

[0002] With the rapid development of the aerospace field, in the process of pursuing higher thrust-to-weight ratio (about 12-15), high-temperature hot-end components are also subjected to extreme high-temperature environment tests, and their structural integrity is also subjected to unprecedented challenges. Therefore, it is urgent to develop thermal barrier coatings to reduce the temperature of the surface of the high-temperature hot-end components. The traditional YSZ thermal barrier coating material has a series of serious problems such as phase change failure, poor sintering resistance and high thermal conductivity, and there is an urgent need to develop a new type of thermal barrier coating material with low thermal conductivity and good phase stability. Among the existing thermal barrier coating candidate materials, the rare earth hafnate ceramic material with a pyrochlore / defect fluorite structure has the advantages of low thermal conductivity and high-temperature phase stability, and should be able to replace YSZ as a new generation of thermal barrier coating material, but the inherent high transmittance of the material to infrared heat radiation makes the thermal barrier coating prepared therefrom extremely easy to be penetrated by infrared heat radiation at high temperature, resulting in direct radiation heating of the metal substrate, which is difficult to play a protective role of the thermal barrier coating. Obviously, the single-component rare earth hafnate material cannot meet the performance requirements of low thermal conductivity, resistance to penetration of thermal radiation, and excellent phase stability at the same time, so the strategy of second-phase composite is commonly used to improve the comprehensive performance of the material. However, the second-phase composite has the defect that the thermal conductivity and thermal-optical performance are difficult to balance, so how to improve the resistance to penetration of thermal radiation while ensuring not to reduce the heat insulation performance (low thermal conductivity) of the material has become the key to the problem. SUMMARY

[0003] The purpose of the present application is to solve the problem that the existing rare earth hafnate ceramic material with a pyrochlore / defect fluorite structure has the advantages of low thermal conductivity and high-temperature phase stability, but does not have a shielding effect on infrared heat radiation, and the thermal barrier coating prepared therefrom is penetrated by infrared heat radiation at high temperature, resulting in direct radiation heating of the metal substrate, thereby reducing the service life of the coating material, and to provide an infrared heat shielding type rare earth hafnate-based composite ceramic coating material and a preparation method thereof.

[0004] In the present application, a spinel structure ceramic with low infrared transmittance, high infrared emissivity and high infrared absorptivity is used as a dispersed phase to modify the rare earth hafnate-based phase ceramic with a pyrochlore / defect fluorite structure, and an infrared heat shielding type composite ceramic coating material with low thermal conductivity, high-temperature phase stability and ultra-low infrared transmittance is prepared.

[0005] The base phase component of an infrared heat shielding type rare earth hafnate-based composite ceramic coating material is a rare earth hafnate ceramic with a pyrochlore / defect fluorite structure, which has low thermal conductivity, high melting point, no phase change at high temperature, and good high-temperature thermal stability, and the chemical formula is A2Hf2O7, wherein the A element is selected from rare earth elements La, Nd, Sm, Eu, Gd, Y, Dy, Ho, Er or Yb; the dispersion phase component of the composite ceramic coating material is an oxide ceramic with a spinel structure, which has high infrared absorption rate, high infrared emissivity, low infrared transmittance and high melting point, and the chemical formula is AB2O4, wherein the A and B elements are selected from Fe, Cr, Mn, Ni or Cu.

[0006] A preparation method of an infrared heat shielding type rare earth hafnate-based composite ceramic coating material, which is completed by the following steps:

[0007] I. Preparation of base phase ceramic powder by solid phase sintering method:

[0008] A2O3 and HfO2 are weighed, the weighed A2O3 and HfO2 are uniformly mixed to obtain a mixed powder; the mixed powder is calcined and crushed to obtain a base phase ceramic powder;

[0009] The A element in the A2O3 in step one is selected from rare earth elements La, Nd, Sm, Eu, Gd, Y, Dy, Ho, Er or Yb;

[0010] The molar ratio of the A2O3 to HfO2 in step one is 1:2;

[0011] II. Preparation of dispersion phase ceramic powder by solid phase sintering method:

[0012] AO and B2O3 are weighed, the weighed AO and B2O3 are uniformly mixed to obtain a mixed powder; the mixed powder is calcined and crushed to obtain a dispersion phase ceramic powder;

[0013] The molar ratio of the AO to B2O3 in step two is 1:1;

[0014] The A in the AO in step two is selected from Fe, Cr, Mn, Ni or Cu;

[0015] The B in the B2O3 in step two is selected from Fe, Cr, Mn, Ni or Cu;

[0016] III. Preparation of composite ceramic bulk material:

[0017] ①. Base phase ceramic powder and dispersion phase ceramic powder are weighed, the weighed base phase ceramic powder and dispersion phase ceramic powder are uniformly mixed to obtain a mixed powder;

[0018] The molar fraction of the dispersion phase ceramic powder in the mixed powder in step three ① is 5% to 30%.

[0019] 2. The mixed powder is pressed into a sheet, and then cold isostatic pressed to obtain a green body; the green body is left for a period of time to release the internal stress in the process of static pressure, and then calcined and polished to obtain the infrared heat shielding type rare earth hafnate-based composite ceramic coating material.

[0020] Principle of the present application:

[0021] The present application designs and prepares a composite material of functional ceramic dispersion phase uniformly distributed in base phase thermal barrier ceramic by solid phase sintering; the high infrared emissivity dispersion phase is used to regulate the infrared heat shielding performance of the composite ceramic material, the impurity energy level is constructed by factors such as oxygen vacancies, narrow energy band and variable valence behavior of the constituent elements in the dispersion phase structure, the carrier concentration and the transition ability of electrons after absorbing infrared radiation energy in the material are enhanced; and by controlling the size of the dispersion phase to be less than 5 μm and the molar fraction to be between 5-30%, the optical backscattering between the dispersion phase ceramic and the base phase ceramic is enhanced, so that the thermal conductivity of the composite ceramic material in the range of 25-800 ℃ is less than 2 W / (m·K), the normal temperature infrared emissivity in the 2.5-14 μm wave band is higher than 0.85, the infrared emissivity at 800 ℃ is higher than 0.65, the normal temperature absorption rate in the 200-2500 nm wave band is greater than 0.8, and the normal temperature transmittance in the 400-2500 nm wave band is less than 0.002; the composite material has low thermal conductivity and excellent infrared heat shielding performance at the same time.

[0022] Advantages of the present application:

[0023] 1. The infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared by the present application breaks through the problems of low infrared emissivity, high infrared transmittance and transparency / half-transparency to infrared heat radiation compared with the existing thermal barrier ceramic coating candidate material mainly with pyrochlore / defect fluorite structure.

[0024] 2. The present application is simple to operate, and the low thermal conductivity and high infrared heat shielding performance of the material can be realized by solid phase sintering, and the prepared material has high density, good structure and strong stability, so that the infrared heat shielding type rare earth hafnate-based composite ceramic coating material provided by the present application has good application prospect.

[0025] 3. The infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared by the present application has thermal conductivity less than 2 W / (m·K) in the range of 25-800 ℃, normal temperature infrared emissivity higher than 0.85 in the 2.5-14 μm wave band, infrared emissivity higher than 0.65 at 800 ℃, normal temperature absorption rate greater than 0.8 in the 200-2500 nm wave band, and normal temperature transmittance less than 0.002 in the 400-2500 nm wave band. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The surface optical photograph of the infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared in Example 1 of the present application and the thermal barrier ceramic single-phase material prepared in Comparative Example 1 are compared in the following figure:

[0027] Figure 2 The SEM photograph of the infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared in Example 1 of the present application is shown in the following figure:

[0028] Figure 3 The XRD pattern of the infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared in Example 1 of the present application and the thermal barrier ceramic single-phase material prepared in Comparative Example 1 are compared in the following figure:

[0029] Figure 4 The thermal conductivity of the infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared in Examples 1-4 of the present application and the single-phase ceramic material prepared in Comparative Example 1 are compared in the following figure:

[0030] Figure 5 The thermal diffusivity of the infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared in Examples 1-4 of the present application and the single-phase ceramic material prepared in Comparative Example 1 are compared in the following figure:

[0031] Figure 6 The average infrared emissivity of the infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared in Examples 1-4 of the present application and the single-phase ceramic material prepared in Comparative Example 1 are compared in the following figure:

[0032] Figure 7 The normal temperature transmittance pattern of the infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared in Examples 1-4 of the present application and the single-phase ceramic material prepared in Comparative Example 1 are compared in the following figure:

[0033] Figure 8 The normal temperature absorptance pattern of the infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared in Examples 1-4 of the present application and the single-phase ceramic material prepared in Comparative Example 1 are compared in the following figure. DETAILED DESCRIPTION

[0034] Specific embodiment one: the infrared heat shielding type rare earth hafnate-based composite ceramic coating material of the present embodiment, the base phase component is a rare earth hafnate ceramic with pyrochlore / defect fluorite structure, which has low thermal conductivity, high melting point, no phase change at high temperature and good high-temperature thermal stability, and its chemical formula is A2Hf2O7, wherein the A element is selected from rare earth elements La, Nd, Sm, Eu, Gd, Y, Dy, Ho, Er or Yb; the dispersion phase component of the composite ceramic coating material is selected from an oxide ceramic with spinel structure, which has high infrared absorptance, high infrared emissivity, low infrared transmittance and high melting point, and its chemical formula is AB2O4, wherein the A and B elements are selected from Fe, Cr, Mn, Ni or Cu.

[0035] Specific implementation two: the difference between this embodiment and specific implementation one is: a preparation method of an infrared heat shielding type rare earth hafnate-based composite ceramic coating material, which is completed according to the following steps:

[0036] I. Preparation of base phase ceramic powder by solid phase sintering method:

[0037] A2O3 and HfO2 are weighed, the weighed A2O3 and HfO2 are uniformly mixed to obtain a mixed powder; the mixed powder is calcined and crushed to obtain a base phase ceramic powder;

[0038] The A element in the A2O3 in step one is selected from rare earth elements La, Nd, Sm, Eu, Gd, Y, Dy, Ho, Er or Yb;

[0039] The molar ratio of A2O3 to HfO2 in step one is 1:2;

[0040] II. Preparation of dispersion phase ceramic powder by solid phase sintering method:

[0041] AO and B2O3 are weighed, the weighed AO and B2O3 are uniformly mixed to obtain a mixed powder; the mixed powder is calcined and crushed to obtain a dispersion phase ceramic powder;

[0042] The molar ratio of AO to B2O3 in step two is 1:1;

[0043] The A in the AO in step two is selected from Fe, Cr, Mn, Ni or Cu;

[0044] The B in the B2O3 in step two is selected from Fe, Cr, Mn, Ni or Cu;

[0045] III. Preparation of composite ceramic bulk material:

[0046] ① The base phase ceramic powder and the dispersion phase ceramic powder are weighed, and the weighed base phase ceramic powder and dispersion phase ceramic powder are uniformly mixed to obtain a mixed powder;

[0047] The molar fraction of the dispersion phase ceramic powder in the mixed powder in step three ① is 5% to 30%;

[0048] ② The mixed powder is pressed into a sheet and then cold isostatic pressed to obtain a green body; the green body is left to stand for a period of time to release internal stress during the isostatic pressing process, and then calcined and polished to obtain an infrared heat shielding type rare earth hafnate-based composite ceramic coating material. The other steps are the same as in specific implementation one.

[0049] Specific embodiment three: the difference between this embodiment and one of the specific embodiments one or two is that the mixing method in step one is: putting A2O3, HfO2, anhydrous ethanol and zirconium oxide grinding balls into a ball mill jar, then ball milling for 20h-24h, drying, sieving to obtain the mixed powder; the mass ratio of the total mass of A2O3 and HfO2 to the mass of anhydrous ethanol and zirconium oxide is 1:0.2:4; the rotation speed of the ball milling is 200r / min-600r / min, and the ball milling time is 12h-24h; the drying temperature is 80℃-120℃, and the drying time is 12h-24h; the sieving method is: sieving through a 150-300 mesh sieve. The other steps are the same as those in the specific embodiment one or two.

[0050] Specific embodiment four: the difference between this embodiment and one of the specific embodiments one to three is that the calcination temperature in step one is 1300℃-1500℃, and the calcination time is 6h-12h; the crushing in step one is: crushing using a cell wall crusher or a mortar, and sieving using a 300 mesh sieve. The other steps are the same as those in the specific embodiments one to three.

[0051] Specific embodiment five: the difference between this embodiment and one of the specific embodiments one to four is that the mixing method in step two is: putting AO, B2O3, anhydrous ethanol and zirconium oxide grinding balls into a ball mill jar, then ball milling for 20h-24h, drying, sieving to obtain the mixed powder; the mass ratio of the total mass of AO and B2O3 to the mass of anhydrous ethanol and zirconium oxide is 1:0.2:4; the rotation speed of the ball milling is 200r / min-600r / min, and the ball milling time is 12h-24h; the drying temperature is 80℃-120℃, and the drying time is 12h-24h; the sieving method is: sieving through a 150-300 mesh sieve. The other steps are the same as those in the specific embodiments one to four.

[0052] Specific embodiment six: the difference between this embodiment and one of the specific embodiments one to five is that the calcination temperature in step two is 1200℃-1400℃, and the calcination time is 3h-8h; the crushing in step two is: crushing using a cell wall crusher or a mortar, and sieving using a 300 mesh sieve. The other steps are the same as those in the specific embodiments one to five.

[0053] Specific embodiment seven: the difference between this embodiment and one of the specific embodiments one to six is that the mixing method in step three 1 is as follows: the base phase ceramic powder, the dispersion phase ceramic powder, anhydrous ethanol and zirconium oxide grinding balls are put into a ball mill tank, then ball milling for 20h-24h, drying, sieving to obtain the mixed powder; the mass ratio of the total mass of the base phase ceramic powder and the dispersion phase ceramic powder to the mass of anhydrous ethanol and zirconium oxide is 1:0.2:4; the rotation speed of the ball milling is 200r / min-600r / min, the ball milling time is 12-24h; the drying temperature is 80℃-120℃, the drying time is 12h-24h; the sieving method is: sieving through 150-300 mesh screen. The other steps are the same as those in the specific embodiments one to six.

[0054] Specific embodiment eight: the difference between this embodiment and one of the specific embodiments one to seven is that the pressing into a sheet process in step three 2 is: pressure maintaining at 8MPa-15MPa for 1min-5min; the cold isostatic pressing process in step three 2 is: increasing the pressure to 180MPa-220MPa, pressure maintaining at 180MPa-220MPa for 3min-8min, then decreasing the pressure to 0MPa; the time for increasing and decreasing the pressure is 150s-200s; the time for the green body to stand is 8h-16h. The other steps are the same as those in the specific embodiments one to seven.

[0055] Specific embodiment nine: the difference between this embodiment and one of the specific embodiments one to eight is that the calcining temperature in step three 2 is 1500℃-1600℃, the calcining time is 8h-12h; the polishing in step three 2 is using sandpaper to polish the surface of the bulk ceramic to be smooth, wherein the sandpaper mesh number is 80#, 240#, 400#, 800#, 1500#, 2000#. The other steps are the same as those in the specific embodiments one to eight.

[0056] Specific embodiment ten: the difference between this embodiment and one of the specific embodiments one to nine is that the performance index of the infrared heat shielding type rare earth hafnate-based composite ceramic coating material: the thickness is 1mm, the performance index of the normal temperature transmittance is lower than 0.002 when the test wave band is 400-2500nm; the thickness is 2mm, the performance index of the normal temperature absorption rate is higher than 0.8 when the test wave band is 200-2500nm; the thickness is 2mm, the performance index of the infrared emissivity is higher than 0.85 at normal temperature and higher than 0.65 at high temperature when the test wave band is 2.5-14μm and the test temperature is 25-800℃; the thickness is 2mm, the performance index of the thermal conductivity is less than 2W / (m·K) when the test temperature is 25-800℃. The other steps are the same as those in the specific embodiments one to nine.

[0057] The beneficial effects of the present application are verified by the following embodiments:

[0058] Embodiment 1: A preparation method of an infrared heat shielding type rare earth hafnate-based composite ceramic coating material (85 mol%-La2Hf2O7 / 15 mol%-NiFe2O4), specifically completed by the following steps:

[0059] I. Preparation of base phase ceramic powder by solid phase sintering method:

[0060] La2O3 and HfO2 are weighed, the weighed La2O3 and HfO2 are uniformly mixed to obtain a mixed powder; the mixed powder is calcined at 1400°C for 8h, broken, and the base phase ceramic powder (La2Hf2O7) is obtained;

[0061] The molar ratio of La2O3 and HfO2 in step one is 1:2;

[0062] The mixing method in step one is: La2O3, HfO2, anhydrous ethanol and zirconium oxide grinding balls are put into a ball mill tank, then ball milling at a speed of 400r / min for 24h, drying at 90°C for 12h, and sieving through a 300 mesh sieve to obtain the mixed powder;

[0063] The mass ratio of the total mass of La2O3 and HfO2 to anhydrous ethanol and zirconium oxide is 1:0.2:4;

[0064] The breaking in step one is: breaking using a cell wall breaker and sieving using a 300 mesh sieve;

[0065] II. Preparation of dispersion phase ceramic powder by solid phase sintering method:

[0066] NiO and Fe2O3 are weighed, the weighed NiO and Fe2O3 are uniformly mixed to obtain a mixed powder; the mixed powder is calcined at 1200°C for 3h, broken, and the dispersion phase ceramic powder (NiFe2O4) is obtained;

[0067] The molar ratio of NiO and Fe2O3 in step two is 1:1;

[0068] The mixing method in step two is: NiO, Fe2O3, anhydrous ethanol and zirconium oxide grinding balls are put into a ball mill tank, then ball milling at a speed of 400r / min for 24h, drying at 90°C for 12h, and sieving through a 300 mesh sieve to obtain the mixed powder;

[0069] The mass ratio of the total mass of NiO and Fe2O3 to anhydrous ethanol and zirconium oxide is 1:0.2:4;

[0070] The breaking in step two is: breaking using a cell wall breaker and sieving using a 300 mesh sieve;

[0071] III. Preparation of composite ceramic bulk material:

[0072] ①, the base phase ceramic powder (La2Hf2O7) and dispersion phase ceramic powder (NiFe2O4) are weighed and mixed uniformly to obtain a mixed powder;

[0073] The molar ratio of the base phase ceramic powder (La2Hf2O7) and the dispersion phase ceramic powder (NiFe2O4) in step three ① is 85:15;

[0074] The mixing method in step three ① is as follows: the base phase ceramic powder, the dispersion phase ceramic powder, anhydrous ethanol and zirconium oxide grinding balls are put into a ball mill tank, then ball milling at a speed of 400 r / min for 24 h, drying at 90℃ for 12 h, and sieving through a 300 mesh sieve to obtain the mixed powder;

[0075] The mass ratio of the total mass of the base phase ceramic powder and the dispersion phase ceramic powder to the mass of anhydrous ethanol and zirconium oxide is 1:0.2:4;

[0076] ②, the mixed powder is pressed into a sheet under 10 MPa for 3 min, and then cold isostatic pressing is performed to obtain a green body; the green body is left to stand for 12 h to release the internal stress during the static pressure process, then calcined at 1550℃ for 10 h, and finally polished to obtain an infrared heat shielding rare earth hafnate-based composite ceramic coating material;

[0077] The cold isostatic pressing process in step three ② is as follows: the pressure is raised to 200 MPa, and the pressure is maintained at 200 MPa for 5 min, and then the pressure is reduced to 0 MPa; the time for raising and reducing the pressure is 180 s;

[0078] The polishing in step three ② is polishing the surface of the bulk ceramic to smoothness using sandpaper, wherein the sandpaper mesh is 80#, 240#, 400#, 800# and 1500#.

[0079] Example 2: The difference between this example and Example 1 is that the molar ratio of the base phase ceramic powder (La2Hf2O7) and the dispersion phase ceramic powder (NiFe2O4) in step three ① is 70:30, and the product obtained is an infrared heat shielding rare earth hafnate-based composite ceramic coating material (70mol%-La2Hf2O7 / 30mol%-NiFe2O4). The other steps and parameters are the same as those of Example 1.

[0080] Example 3: A method for preparing an infrared heat shielding rare earth hafnate-based composite ceramic coating material (85mol%-Gd2Hf2O7 / 15mol%-NiFe2O4), which is completed according to the following steps:

[0081] I. Preparation of base phase ceramic powder by solid phase sintering method:

[0082] Gd2O3 and HfO2 are weighed, the weighed Gd2O3 and HfO2 are mixed uniformly to obtain a mixed powder; the mixed powder is calcined at 1400 DEG C for 8h, and is broken to obtain a base phase ceramic powder (Gd2Hf2O7);

[0083] The molar ratio of Gd2O3 to HfO2 in step one is 1:2;

[0084] The mixing method in step one is that Gd2O3, HfO2, anhydrous ethanol and zirconium oxide grinding balls are put into a ball mill tank, then ball milling is carried out at a rotating speed of 400r / min for 24h, and then drying is carried out at 90 DEG C for 12h, and then sieving is carried out through a 300 mesh screen to obtain a mixed powder;

[0085] The mass ratio of the total mass of Gd2O3 and HfO2 to the mass of anhydrous ethanol and zirconium oxide is 1:0.2:4;

[0086] The breaking in step one is that breaking is carried out by using a wall breaking machine, and sieving is carried out by using a 300 mesh screen;

[0087] II. Preparing a dispersion phase ceramic powder by a solid phase sintering method:

[0088] NiO and Fe2O3 are weighed, the weighed NiO and Fe2O3 are mixed uniformly to obtain a mixed powder; the mixed powder is calcined at 1200 DEG C for 3h, and is broken to obtain a dispersion phase ceramic powder (NiFe2O4);

[0089] The molar ratio of NiO to Fe2O3 in step two is 1:1;

[0090] The mixing method in step two is that NiO, Fe2O3, anhydrous ethanol and zirconium oxide grinding balls are put into a ball mill tank, then ball milling is carried out at a rotating speed of 400r / min for 24h, and then drying is carried out at 90 DEG C for 12h, and then sieving is carried out through a 300 mesh screen to obtain a mixed powder;

[0091] The mass ratio of the total mass of NiO and Fe2O3 to the mass of anhydrous ethanol and zirconium oxide is 1:0.2:4;

[0092] The breaking in step two is that breaking is carried out by using a wall breaking machine, and sieving is carried out by using a 300 mesh screen;

[0093] III. Preparing a composite ceramic bulk material:

[0094] ①, base phase ceramic powder (Gd2Hf2O7) and dispersion phase ceramic powder (NiFe2O4) are weighed, the weighed base phase ceramic powder and dispersion phase ceramic powder are mixed uniformly to obtain a mixed powder;

[0095] The molar ratio of the base phase ceramic powder (Gd2Hf2O7) and the dispersion phase ceramic powder (NiFe2O4) described in step three 1 is 85:15;

[0096] The mixing method described in step three 1 is: the base phase ceramic powder, the dispersion phase ceramic powder, anhydrous ethanol and zirconium oxide grinding balls are put into a ball mill tank, then ball milling at a speed of 400 r / min for 24 h, drying at 90℃ for 12 h, and then sieving through a 300 mesh sieve to obtain the mixed powder;

[0097] The mass ratio of the total mass of the base phase ceramic powder and the dispersion phase ceramic powder to the mass of anhydrous ethanol and zirconium oxide is 1:0.2:4;

[0098] ②, the mixed powder is pressed into a sheet under the pressure of 10 MPa for 3 min, and then cold isostatic pressing to obtain a green body; the green body is left to release the internal stress during the static pressure process for 12 h, and then calcined at 1550℃ for 10 h, and finally polished to obtain the infrared heat shielding type rare earth hafnate-based composite ceramic coating material;

[0099] The process of cold isostatic pressing described in step three 2 is: the pressure is raised to 200 MPa, and the pressure is kept at 200 MPa for 5 min, and then the pressure is reduced to 0 MPa; the time for raising and reducing the pressure is 180 s;

[0100] The polishing described in step three 2 is using sandpaper to polish the surface of the bulk ceramic to be smooth, wherein the sandpaper mesh is 80#, 240#, 400#, 800# and 1500#.

[0101] Example 4: a preparation method of an infrared heat shielding type rare earth hafnate-based composite ceramic coating material (85mol%-La2Hf2O7 / 15mol%-NiCr2O4), which is completed according to the following steps:

[0102] I. Preparation of base phase ceramic powder by solid phase sintering method:

[0103] La2O3 and HfO2 are weighed and mixed uniformly to obtain a mixed powder; the mixed powder is calcined at 1400℃ for 8 h, and then broken to obtain the base phase ceramic powder (La2Hf2O7);

[0104] The molar ratio of La2O3 and HfO2 described in step one is 1:2;

[0105] The mixing method described in step one is: La2O3, HfO2, anhydrous ethanol and zirconium oxide grinding balls are put into a ball mill tank, then ball milling at a speed of 400 r / min for 24 h, drying at 90℃ for 12 h, and then sieving through a 300 mesh sieve to obtain the mixed powder;

[0106] The mass ratio of the total mass of La2O3 and HfO2 to the mass of anhydrous ethanol and zirconium oxide is 1:0.2:4;

[0107] The crushing in step one is crushing by using a blender and sieving by using a 300-mesh screen;

[0108] II. Preparing a dispersion phase ceramic powder by a solid phase sintering method:

[0109] NiO and Cr2O3 are weighed, the weighed NiO and Cr2O3 are uniformly mixed to obtain a mixed powder; the mixed powder is calcined at 1200 DEG C for 3h, crushed to obtain a dispersion phase ceramic powder (NiCr2O4);

[0110] The molar ratio of NiO to Cr2O3 in step two is 1:1;

[0111] The mixing method in step two is: putting NiO, Cr2O3, anhydrous ethanol and zirconium oxide grinding balls into a ball mill tank, then ball milling at a speed of 400r / min for 24h, drying at 90 DEG C for 12h, and sieving through a 300-mesh screen to obtain a mixed powder;

[0112] The mass ratio of the total mass of NiO and Cr2O3 to the mass of anhydrous ethanol and zirconium oxide is 1:0.2:4;

[0113] The crushing in step two is crushing by using a blender and sieving by using a 300-mesh screen;

[0114] III. Preparing a composite ceramic bulk material:

[0115] 1. Weighing base phase ceramic powder (La2Hf2O7) and dispersion phase ceramic powder (NiCr2O4), and uniformly mixing the weighed base phase ceramic powder and dispersion phase ceramic powder to obtain a mixed powder;

[0116] The molar ratio of base phase ceramic powder (La2Hf2O7) to dispersion phase ceramic powder (NiCr2O4) in step three 1 is 85:15;

[0117] The mixing method in step three 1 is: putting base phase ceramic powder, dispersion phase ceramic powder, anhydrous ethanol and zirconium oxide grinding balls into a ball mill tank, then ball milling at a speed of 400r / min for 24h, drying at 90 DEG C for 12h, and sieving through a 300-mesh screen to obtain a mixed powder;

[0118] The mass ratio of the total mass of base phase ceramic powder and dispersion phase ceramic powder to the mass of anhydrous ethanol and zirconium oxide is 1:0.2:4;

[0119] ②, the mixed powder is pressed into a sheet at 10 MPa for 3 min, and then cold isostatic pressed to obtain a green body; the green body is left for 12 h to release the internal stress in the static pressure process, and then calcined at 1550 DEG C for 10 h, and finally polished to obtain the infrared heat shielding rare earth hafnate-based composite ceramic coating material;

[0120] The cold isostatic pressing process in step three ② is: pressurized to 200 MPa, pressurized at 200 MPa for 5 min, and then depressurized to 0 MPa; the pressurization and depressurization time is 180 s;

[0121] The polishing in step three ② is polishing the surface of the bulk ceramic to smooth using sandpaper, wherein the sandpaper mesh is 80#, 240#, 400#, 800# and 1500#.

[0122] Preparation method of the La2Hf2O7 single-phase ceramic material is completed according to the following steps:

[0123] I. Preparation of La2Hf2O7 ceramic powder:

[0124] La2O3 and HfO2 are weighed, and the weighed La2O3 and HfO2 are mixed uniformly to obtain a mixed powder; the mixed powder is calcined at 1400 DEG C for 8 h, and then broken to obtain La2Hf2O7 ceramic powder;

[0125] The molar ratio of La2O3 and HfO2 in step one is 1:2;

[0126] The mixing method in step one is: La2O3, HfO2, anhydrous ethanol and zirconium oxide grinding balls are put into a ball mill tank, then ball milled at a speed of 400 r / min for 24 h, and then dried at 90 DEG C for 12 h, and sieved through a 300 mesh screen to obtain a mixed powder;

[0127] The mass ratio of the total mass of La2O3 and HfO2 to anhydrous ethanol and zirconium oxide is 1:0.2:4;

[0128] The breaking in step one is: broken by using a wall breaking machine, and sieved by using a 300 mesh screen;

[0129] II. Preparation of ceramic bulk material:

[0130] The La2Hf2O7 ceramic powder is ball milled, dried, sieved, pressed into a sheet, cold isostatic pressed, calcined and polished to obtain a La2Hf2O7 single-phase ceramic material;

[0131] The ball milling method in step two 1 is as follows: the La2Hf2O7 ceramic powder, anhydrous ethanol and zirconia grinding balls are put into a ball mill tank, and then ball milling is carried out at a rotating speed of 400 r / min for 24 h; the mass ratio of the La2Hf2O7 ceramic powder, anhydrous ethanol and zirconia is 1:0.2:4;

[0132] The drying in step two 1 is drying at 90℃ for 12 h; the sieving is sieving through a 300-mesh sieve;

[0133] The pressing into a sheet in step two 1 is pressing into a sheet under the pressure of 10 MPa for 3 min;

[0134] The cold isostatic pressing in step two 1 is as follows: the pressure is increased to 200 MPa, the pressure is kept at 200 MPa for 5 min, and then the pressure is decreased to 0 MPa; the time for increasing and decreasing the pressure is 180 s, and a green body is obtained; the green body is left to stand for 12 h to release the internal stress in the static pressure process;

[0135] The calcining in step two 1 is calcining at 1550℃ for 10 h;

[0136] The polishing in step two 1 is polishing the surface of the bulk ceramic to be smooth by using sandpaper, wherein the mesh number of the sandpaper is 80#, 240#, 400#, 800# and 1500#.

[0137] Figure 1 A surface optical photograph comparison chart of the infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared in Example 1 and the thermal barrier ceramic single-phase material prepared in Comparative Example 1;

[0138] From Figure 1 It can be seen that the prepared infrared heat shielding type rare earth hafnate-based composite ceramic coating material has good density, a smooth surface, no obvious pores and cracks; and the composite material has obvious color difference with the single-phase material in macroscopic view.

[0139] Figure 2 An SEM chart of the infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared in Example 1;

[0140] From Figure 2 It can be seen that the composite ceramic material in which NiFe2O4 is dispersedly distributed in La2Hf2O7 is successfully prepared in Example 1, and the grain size of the dispersed-phase ceramic NiFe2O4 is within 5 μm, and the grain size of the base-phase ceramic La2Hf2O7 is within 15 μm.

[0141] Figure 3 An XRD chart of the infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared in Example 1 and the thermal barrier ceramic single-phase material prepared in Comparative Example 1;

[0142] From Figure 3 It can be seen that: the infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared in Example 1 exists La2Hf2O7 and NiFe2O4 two phases, which shows that La2Hf2O7 and NiFe2O4 can coexist in a complex phase structure, and cannot form a single phase material by solid solution, and the optical scattering of the multi-phase interface also provides a condition for improving the emissivity of the composite material.

[0143] Figure 4 The thermal conductivity comparison chart of the infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared in Examples 1-4 and the single-phase ceramic material prepared in Comparative Example 1;

[0144] Figure 5 The thermal diffusivity comparison chart of the infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared in Examples 1-4 and the single-phase ceramic material prepared in Comparative Example 1;

[0145] The thermal conductivity and thermal diffusivity of the prepared sample material were measured by LFA457 laser thermal conductivity instrument. It can be seen that the thermal conductivity and thermal diffusivity of the composite material prepared in Examples 1-4 are obviously reduced, and the reduction of Example 1 is the most obvious. The thermal conductivity at room temperature is 1.89 W / (m·K), the high-temperature thermal conductivity is reduced to 1.55 W / (m·K), the thermal diffusivity at room temperature is 0.87 mm 2 ·s -1 , and the high-temperature thermal diffusivity is only 0.52 mm 2 ·s -1 , which lays a foundation for the excellent infrared heat shielding effect of the composite material.

[0146] Figure 6 The average infrared emissivity comparison chart of the infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared in Examples 1-4 and the single-phase ceramic material prepared in Comparative Example 1;

[0147] The Bruker VERTEX 70 Fourier transform infrared spectrometer and the high-temperature emissivity tester made by the research group were used to measure the room temperature and high temperature infrared emissivity of the prepared sample material. It can be seen that the room temperature infrared emissivity of the composite material prepared in Examples 1-4 in the 2.5-14 μm wave band is higher than 0.8, and the high temperature emissivity is higher than 0.6, which is obviously higher than the single-phase material prepared in Comparative Example 1, and lays a foundation for the excellent infrared heat shielding effect of the composite material.

[0148] Figure 7 The room temperature transmittance spectrum of the infrared heat shielding type rare earth hafnate-based composite ceramic coating material prepared in Examples 1-4 and the single-phase ceramic material prepared in Comparative Example 1;

[0149] The transmittance of the prepared sample materials at room temperature was measured by using PerkinElmer LAMBDA 1050 spectrophotometer. It can be seen that the transmittance of the composite materials prepared in Examples 1-4 at the wavelength of 400-2500 nm is lower than 0.002, which is obviously lower than that of the single-phase material prepared in Comparative Example 1, thereby proving that the composite ceramic material prepared in the examples has excellent infrared heat shielding effect.

[0150] Figure 8 The transmittance of the prepared sample materials at room temperature was measured by using PerkinElmer LAMBDA 1050 spectrophotometer. It can be seen that the transmittance of the composite materials prepared in Examples 1-4 at the wavelength of 400-2500 nm is lower than 0.002, which is obviously lower than that of the single-phase material prepared in Comparative Example 1, thereby proving that the composite ceramic material prepared in the examples has excellent infrared heat shielding effect.

[0151] The transmittance of the prepared sample materials at room temperature was measured by using PerkinElmer LAMBDA 1050 spectrophotometer. It can be seen that the transmittance of the composite materials prepared in Examples 1-4 at the wavelength of 400-2500 nm is lower than 0.002, which is obviously lower than that of the single-phase material prepared in Comparative Example 1, thereby proving that the composite ceramic material prepared in the examples has excellent infrared heat shielding effect.

Claims

1. A method for preparing an infrared heat-shielding rare-earth hafnate-based composite ceramic coating material, characterized in that The base phase component of the composite ceramic coating material is a rare earth hafnate ceramic with pyrochlore / defect fluorite structure, which has low thermal conductivity, high melting point, no phase change at high temperature, and good high-temperature thermal stability, and the chemical formula is A2Hf2O7, wherein the A element is selected from rare earth elements La, Nd, Sm, Eu, Gd, Y, Dy, Ho, Er or Yb; the dispersion phase component of the composite ceramic coating material is an oxide ceramic with spinel structure, which has high infrared absorption rate, high infrared emissivity, low infrared transmittance and high melting point, and the chemical formula is AB2O4, wherein the A and B elements are selected from Fe, Cr, Mn, Ni or Cu; The preparation method is specifically completed by the following steps: I. Preparation of base phase ceramic powder by solid phase sintering method: Take A2O3 and HfO2, mix the taken A2O3 and HfO2 uniformly to obtain a mixed powder; calcine and crush the mixed powder to obtain a base phase ceramic powder; In step one, the A element in A2O3 is selected from rare earth elements La, Nd, Sm, Eu, Gd, Y, Dy, Ho, Er or Yb; In step one, the molar ratio of A2O3 to HfO2 is 1:2; II. Preparation of dispersion phase ceramic powder by solid phase sintering method: Take AO and B2O3, mix the taken AO and B2O3 uniformly to obtain a mixed powder; calcine and crush the mixed powder to obtain a dispersion phase ceramic powder; In step two, the molar ratio of AO to B2O3 is 1:1; In step two, the A in AO is selected from Fe, Cr, Mn, Ni or Cu; In step two, the B in B2O3 is selected from Fe, Cr, Mn, Ni or Cu; III. Preparation of composite ceramic bulk material: ①Take the base phase ceramic powder and the dispersion phase ceramic powder, mix the taken base phase ceramic powder and dispersion phase ceramic powder uniformly to obtain a mixed powder; In step III ①, the molar fraction of the dispersion phase ceramic powder in the mixed powder is 5% to 30%; ②Press the mixed powder into a sheet, then cold isostatic press to obtain a green body; let the green body stand for a period of time to release the internal stress in the isostatic pressing process, then calcine and polish to obtain an infrared heat shielding type rare earth hafnate-based composite ceramic coating material; In step III ②, the calcining temperature is 1500°C to 1600°C, and the calcining time is 8h to 12h; The performance indicators of the infrared heat shielding type rare earth hafnate-based composite ceramic coating material are as follows: the thickness is 1mm, the performance indicator of the transmittance at room temperature is less than 0.002 when the test wavelength range is 400-2500nm; the thickness is 2mm, the performance indicator of the absorption rate at room temperature is higher than 0.8 when the test wavelength range is 200-2500nm; the thickness is 2mm, the performance indicator of the infrared emissivity is higher than 0.85 at room temperature and higher than 0.65 at high temperature when the test wavelength range is 2.5-14μm and the test temperature is 25-800°C; the thickness is 2mm, the performance indicator of the thermal conductivity is less than 2W / (m·K) when the test temperature is 25-800°C.

2. The preparation method of an infrared heat-shielding rare earth hafnium salt-based composite ceramic coating material according to claim 1, characterized in that... The mixing method in step one is: putting A2O3, HfO2, anhydrous ethanol and zirconium oxide grinding balls into a ball mill jar, then ball milling for 20h-24h, drying, sieving to obtain mixed powder; the mass ratio of the total mass of A2O3 and HfO2 to the mass of anhydrous ethanol and zirconium oxide is 1:0.2:4; the rotation speed of ball milling is 200r / min-600r / min, and the ball milling time is 12h-24h; the drying temperature is 80℃-120℃, and the drying time is 12h-24h; the sieving method is: sieving through 150-300 mesh sieve.

3. The preparation method of an infrared heat-shielding rare earth hafnium salt-based composite ceramic coating material according to claim 1, characterized in that... The calcination temperature in step one is 1300℃-1500℃, and the calcination time is 6h-12h; the crushing in step one is: crushing using a cell wall breaker or a mortar, and sieving using a 300 mesh sieve.

4. The preparation method of an infrared heat-shielding rare earth hafnium salt-based composite ceramic coating material according to claim 1, characterized in that... The mixing method in step two is: putting AO, B2O3, anhydrous ethanol and zirconium oxide grinding balls into a ball mill jar, then ball milling for 20h-24h, drying, sieving to obtain mixed powder; the mass ratio of the total mass of AO and B2O3 to the mass of anhydrous ethanol and zirconium oxide is 1:0.2:4; the rotation speed of ball milling is 200r / min-600r / min, and the ball milling time is 12h-24h; the drying temperature is 80℃-120℃, and the drying time is 12h-24h; the sieving method is: sieving through 150-300 mesh sieve.

5. The preparation method of an infrared heat-shielding rare earth hafnium salt-based composite ceramic coating material according to claim 1, characterized in that... The calcination temperature in step two is 1200℃-1400℃, and the calcination time is 3h-8h; the crushing in step two is: crushing using a cell wall breaker or a mortar, and sieving using a 300 mesh sieve.

6. The preparation method of an infrared heat-shielding rare earth hafnium salt-based composite ceramic coating material according to claim 1, characterized in that... The mixing method in step three ① is: putting base phase ceramic powder, dispersion phase ceramic powder, anhydrous ethanol and zirconium oxide grinding balls into a ball mill jar, then ball milling for 20h-24h, drying, sieving to obtain mixed powder; the mass ratio of the total mass of base phase ceramic powder and dispersion phase ceramic powder to the mass of anhydrous ethanol and zirconium oxide is 1:0.2:4; the rotation speed of ball milling is 200r / min-600r / min, and the ball milling time is 12-24h; the drying temperature is 80℃-120℃, and the drying time is 12h-24h; the sieving method is: sieving through 150-300 mesh sieve.

7. The preparation method of an infrared heat-shielding rare earth hafnium salt-based composite ceramic coating material according to claim 1, characterized in that... The pressing into a sheet process in step three ② is: keeping pressure at 8MPa-15MPa for 1min-5min; the cold isostatic pressing process in step three ② is: increasing pressure to 180MPa-220MPa, keeping pressure at 180MPa-220MPa for 3min-8min, and then decreasing pressure to 0MPa; the time for increasing and decreasing pressure is 150s-200s; the time for the green body to stand is 8h-16h.

8. The preparation method of an infrared heat-shielding rare earth hafnium salt-based composite ceramic coating material according to claim 1, characterized in that... The polishing in step three ② is: using sandpaper to polish the surface of the block ceramic to be smooth, wherein the sandpaper mesh number is 80#, 240#, 400#, 800#, 1500#, 2000#.

Images