CN114751744A - Ceric acid rare earth based high-entropy ceramic material and preparation method thereof - Google Patents
Ceric acid rare earth based high-entropy ceramic material and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a cerium acid rare earth based high-entropy ceramic material and a preparation method thereof, and the cerium acid rare earth based high-entropy ceramic material has the following chemical general formula: RE2Ce2O7RE is at least five of rare earth elements La, Nd, Sm, Eu, Gd, Dy, Ho, Yb, Tm, Lu, Sc and Y, and the mole number of each rare earth element is the same. The invention adopts rare earth oxide RE2O3The doping is carried out, metal ions participating in the structure are all rare earth ions with unique electronic layers, so that the rare earth ions show good chemical properties in multiple fields, compared with the existing YSZ, lanthanum zirconate and other materials, the single rare earth cerate has the characteristics of high melting point, low thermal conductivity, high thermal expansion coefficient, low thermal ratio, high-temperature thermal stability and the like, and the high-entropy rare earth cerate is obtained by combining multiple rare earth ions, so that the high-entropy rare earth cerate is further formedThe heat resistance of the material is improved, and the thermal conductivity is further reduced to 0.6W/(m.K).
Description
Technical Field
The invention belongs to the technical field of high-entropy alloys, and particularly relates to a ceric acid rare earth based high-entropy ceramic material and a preparation method thereof.
Background
In recent years, High-entropy ceramics (HECs) have been drawing attention as a solid solution of a single-component compound containing three or more main components at an equimolar ratio or a nearly equimolar ratio because of their properties such as low thermal conductivity, High hardness, and High environmental resistance. High-entropy ceramics generally refer to solid solutions formed by five or more ceramic components, and have become hot spots in the ceramic field in recent years due to unique "high-entropy effect" and superior performance. Entropy is a parameter that characterizes the degree of material disorder in thermodynamics, and its concept was proposed by clausius (t. clausius) in 1854. The lower the entropy, the more stable and ordered the system; the higher the entropy, the more chaotic the system. The research of the high-entropy ceramics can be traced back to 2015 for the first time, and then more and more high-entropy ceramics, including high-entropy oxide ceramics with fluorite structures, perovskite structures and spinel structures and non-oxide high-entropy ceramics such as boride, carbide, nitride, silicide and the like emerge like spring bamboo shoots after rain, and gradually become a research hotspot.
The characteristics of the high-entropy ceramics can be summarized as four points: (1) the thermodynamic high entropy effect; (2) lattice distortion effects of the structure; (3) a kinetic retarding diffusion effect; (4) a "cocktail" effect on performance. One of the core effects of the high-entropy material is slow diffusion, wherein atom movement and effective diffusion of atoms are hindered due to lattice distortion caused by solid solution and multi-element synergistic diffusion, so that when the high-entropy material is used at high temperature, fine grains can be maintained, and slow grain growth speed is expected, and the slow diffusion effect opens up a new window for the design of the TBC material, namely the high-entropy solid solution with fine grains and slow growth speed.
The lanthanum cerate has high melting point (> 2000 ℃) and low thermal conductivity (0.60 W.m)-1·K -11000 ℃ C.), low heat ratio (0.43J. g-1. K-1) and a length of 1400 ℃ CThe phase-annealing phase-stability-maintaining ceramic material has been developed into a novel high-temperature structure ceramic material, and has good characteristics in the application fields of oxygen ion conductors, proton-conducting fuel cell components, hydrogen permeable membranes and the like. The thermal conductivity of the material is over high and is more than 1 W.m under the low temperature condition-1·K-1The prepared ceric acid rare earth based high-entropy ceramic can effectively reduce the thermal conductivity thereof under the low-temperature condition, thereby widening the application field of the ceric acid rare earth based high-entropy ceramic.
Disclosure of Invention
The invention aims to provide a ceric acid rare earth based high-entropy porous ceramic and a preparation method thereof, and the method can obtain a low-thermal conductivity material with good infrared absorption performance through the high-entropy action of the material.
In order to achieve the above object, according to one aspect of the present invention, there is provided a rare earth ceric acid-based high entropy ceramic material having the following chemical formula: RE2Ce2O7Wherein RE is at least five rare earth elements selected from La, Nd, Sm, Eu, Gd, Dy, Ho, Yb, Tm, Lu, Sc and Y, and the mole number of each rare earth element is the same.
According to the invention, the structural formula of the ceric acid rare earth-based high-entropy ceramic material is (La)0.4Gd0.4Er0.4Tm0.4Yb0.4)Ce2O7、(La0.4Nd0.4Sm0.4Eu0.4Gd0.4)Ce2O7Or (La)0.4Dy0.4Ho0.4Lu0.4Y0.4)Ce2O7。
According to the invention, the ceric acid rare earth based high-entropy ceramic material is a compact ceramic material or a porous ceramic material, wherein the aperture of the through hole is 5 nm-50 μm.
According to the invention, the thermal conductivity of the ceric acid rare earth-based high-entropy ceramic material is 0.6W/mK-0.9W/mK.
According to another aspect of the present invention, there is provided a method for preparing a ceric acid rare earth based high-entropy ceramic material, comprising the steps of: s1, mixing cerium oxide and at least five rare earth oxides RE2O3The components are mixed and then are mixed,adding absolute ethyl alcohol and a binder, and performing high-energy ball milling; wherein, rare earth oxide RE2O3The rare earth elements in (1) are selected from at least five of La, Nd, Sm, Eu, Gd, Dy, Ho, Yb, Tm, Lu, Sc and Y; s2, drying, sieving and tabletting the mixture obtained in the step S1 to obtain a compact blank A; s3, pre-sintering the compact blank A, preserving heat, and crushing to obtain ceric acid rare earth base high-entropy ceramic powder; s4, performing high-energy ball milling on the ceric acid rare earth based high-entropy ceramic powder obtained in the step S3, absolute ethyl alcohol and a binder; or mixing the ceric acid rare earth based high-entropy ceramic powder with a pore-forming agent, absolute ethyl alcohol and a binder, and then carrying out high-energy ball milling to obtain a mixture; s5, drying, sieving and briquetting the mixture obtained in the step S4 to obtain a compact blank B, and sintering and insulating the blank B to obtain the ceric acid rare earth based high-entropy compact or porous ceramic.
According to the invention, in step S1, the cerium oxide and the metal ions in the five rare earth oxides satisfy Ce4+With the total RE3+The molar ratio is 1: 1. Preferably, the molar ratio of the rare earth elements in the five rare earth oxides is 1:1:1:1: 1.
According to the invention, the binder is PVP, PVB or polyethylene glycol. Preferably, the mass ratio of the adhesive to the mixture powder/the ceric acid rare earth based high-entropy ceramic powder is (0.03-0.08):1, and the volume mass ratio of the ethanol to the mixture powder/the ceric acid rare earth based high-entropy ceramic powder is (1-10): 3.
According to the invention, the rotation speed of the high-energy ball milling in the step S1 is 800-1100 rpm, and the time is 2-6 hours; the high-energy ball milling mode is that the interval is 1 minute every 4 minutes of work, and the positive rotation and the negative rotation are sequentially alternated. Preferably, the grinding balls in the high-energy ball milling in the step S1 are zirconia balls, and the mass ratio of the zirconia balls to the powder raw material is (2-10): 1; the diameter of the zirconia ball is 3 mm.
According to the invention, the drying temperature in the step S2 and the step S5 is 60-90 ℃, and the drying time is 12-24 hours; preferably, the aperture of the sieved screen mesh is 50-200 meshes. Preferably, the pressure of the briquetting during tabletting is 5-15 MPa, and the pressing time of the briquetting is 10-20 s. Preferably, the pre-sintering temperature in the step S3 is 800-1200 ℃, the heating rate is 2 ℃/min, the heat preservation time is 6-24 hours, and the heat preservation time is 8-12 hours.
According to the invention, in the step S3, a high-energy ball mill is adopted for crushing treatment, the rotating speed is 800-1100 rpm, and the time is 10 minutes. Preferably, zirconia balls are adopted for high-energy ball milling in the step S4, the mass ratio of the zirconia balls to the cerium acid rare earth based high-entropy ceramic powder is (2-10):1, and the diameter of the zirconia balls is about 1 cm. Preferably, the pore-forming agent in step S4 is one or more of cellulose nanofiber, cellulose nanocrystal and cellulose powder. Preferably, the diameter of the cellulose nanofiber is 4-10 nm, and the length of the cellulose nanofiber is 1-3 μm; preferably, the diameter is 4 to 8nm and the length is 1.5 to 2 μm. Preferably, the diameter of the cellulose nanocrystal is 5-20 nm, and the length of the cellulose nanocrystal is 50-200 nm. Preferably, the particle size of the cellulose powder is less than or equal to 25 μm. Preferably, the mass ratio of the pore-forming agent to the tungstic acid-based high-entropy ceramic powder is (0-0.5): 1. Preferably, the sintering temperature in the step S5 is 1000-1700 ℃, the heating rate is 2 ℃/min at 1400-1600 ℃, and the heat preservation time is 6-24 hours.
The invention has the beneficial effects that:
1) the invention adopts rare earth oxide RE2O3The cerium acid rare earth base high-entropy ceramic material is prepared by doping, and metal ions participating in the structure are all rare earth ions which have unique electronic layers, so that the cerium acid rare earth base high-entropy ceramic material has good chemical properties in multiple fields. Compared with the existing thermal barrier materials such as YSZ and lanthanum zirconate, the single rare earth cerate has the characteristics of high melting point, low thermal conductivity, high thermal expansion coefficient, low thermal ratio, high-temperature thermal stability and the like, and the high-entropy rare earth cerate is obtained by combining various rare earth ions, so that on one hand, the heat resistance of the material is improved, and the form of the material is not changed under the condition of heat preservation at 1700 ℃ for 24 hours. On the other hand, the thermal conductivity is further reduced to 0.8W/(m.k) by making the ceric acid rare earth-based ceramic highly entropic.
2) The cerium acid rare earth based high-entropy ceramic prepared by the invention can be a compact structure, the heat conductivity coefficient of the high-entropy ceramic with the compact structure is obviously reduced, the porous ceramic can be formed by utilizing cellulose for pore forming on the basis, through holes are easy to form by taking the cellulose as a pore-forming agent, the heat conductivity coefficient of the material is further reduced by the formation of the through holes, in addition, the carbon content of the cellulose is low, and the carbonization of the ceramic material can be effectively prevented.
3) The invention adopts a solid-phase synthesis method, and the obtained powder has fine and uniform crystal grains, simple preparation process and high purity and has the potential of large-scale industrial production.
Drawings
FIG. 1 is a process flow chart of the high-entropy and high-entropy preparation of ceric acid rare earth-based porous ceramics by the high-temperature solid-phase method.
FIG. 2 shows (La) synthesized in example 1 of the present invention0.4Gd0.4Er0.4Tm0.4Yb0.4)Ce2O7XRD pattern of high entropy ceramic powder.
FIG. 3 shows (La) synthesized in example 1 of the present invention0.4Gd0.4Er0.4Tm0.4Yb0.4)Ce2O7EDS element distribution diagram of high entropy ceramics.
FIG. 4 shows (La) synthesized in example 2 of the present invention0.4Nd0.4Sm0.4Eu0.4Gd0.4)Ce2O7XRD pattern of high entropy ceramic powder.
FIG. 5 shows (La) synthesized in example 2 of the present invention0.4Nd0.4Sm0.4Eu0.4Gd0.4)Ce2O7EDS element distribution diagram of high entropy ceramics.
FIG. 6 shows (La) synthesized in example 3 of the present invention0.4Dy0.4Ho0.4Lu0.4Y0.4)Ce2O7XRD pattern of high entropy ceramic powder.
FIG. 7 shows (La) synthesized in example 3 of the present invention0.4Dy0.4Ho0.4Lu0.4Y0.4)Ce2O7EDS element distribution diagram of high entropy ceramics.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and embodiments. It should be emphasized that the specific embodiments described herein are merely illustrative of the invention, are some, not all, and therefore do not limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention provides a ceric acid rare earth based high-entropy ceramic material which has the following chemical general formula: RE2Ce2O7Wherein RE is at least five selected from lanthanum (La), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), ytterbium (Yb), thulium (Tm), lutetium (Lu) scandium (Sc) and yttrium (Y), and the mole number of each rare earth element is the same.
Preferably, the cerium oxide in step S1 satisfies the following conditions with metal ions in at least five rare earth oxides: ce4+And RE3+The overall molar ratio was 1: 1. More preferably, the five rare earth oxides satisfy an ionic molar ratio of 1:1:1:1: 1. For example, the structural formula of the cerium acid rare earth based high-entropy ceramic material can be (La) 0.4Gd0.4Er0.4Tm0.4Yb0.4)Ce2O7、(La0.4Nd0.4Sm0.4Eu0.4Gd0.4)Ce2O7Or (La)0.4Dy0.4Ho0.4Lu0.4Y0.4)Ce2O7。
The ceric acid rare earth based high-entropy ceramic material can be a porous ceramic material or a non-porous compact ceramic material. When the ceric acid rare earth based high-entropy ceramic material is a porous ceramic material, the pores are through holes, and the pore diameter is 5 nm-50 mu m. More preferably, the aperture of the through hole is 0.2 to 50 μm.
According to another aspect of the invention, the invention also provides a preparation method of the ceric acid rare earth based high-entropy porous ceramic material, which comprises the following steps:
s1, mixing cerium oxide (CeO)2) And at least five rare earth oxides (RE)2O3) Mixing, adding anhydrous ethanol anda binder, and performing high-energy ball milling;
s2, drying, sieving and tabletting the mixture obtained in the step S1 to obtain a compact blank A;
s3, pre-sintering the compact blank A, preserving heat, and crushing to obtain ceric acid rare earth based high-entropy ceramic powder;
s4, performing high-energy ball milling on the ceric acid rare earth based high-entropy ceramic powder obtained in the step S3, ethanol and a binder; or mixing the ceric acid rare earth based high-entropy ceramic powder with pore-forming agent ethanol and a binder, and then performing high-energy ball milling to obtain a mixture;
s5, drying, sieving and briquetting the mixture prepared in the step S4 to obtain a compact blank B, and sintering and insulating the compact blank B to obtain the ceric acid rare earth based high-entropy compact or porous ceramic.
Wherein the rare earth oxide in step S1 is selected from at least five of lanthanum (La), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), ytterbium (Yb), thulium (Tm), lutetium (Lu) scandium (Sc), and yttrium (Y), expressed as RE, none of which is Ce-free.
According to an embodiment of the invention, the added binder is PVP, PVB or polyethylene glycol. Preferably, the mass ratio of the adhesive to the mixture powder/the ceric acid rare earth based high-entropy ceramic powder is (0.03-0.08):1, and the volume mass ratio of the ethanol to the mixture powder/the ceric acid rare earth based high-entropy ceramic powder (mL/g) is (1-10): 3.
According to the invention, the high-energy ball mill has the rotating speed of 800-1100 rpm and the time of 2-6 hours. The high-energy ball milling mode is that the intermittent operation lasts for 1 minute after 4 minutes of work, and the positive rotation and the negative rotation are sequentially alternated. Preferably, the grinding balls used for ball milling are zirconia balls, the mass ratio of the zirconia balls to the powder raw material is (2-10):1, and the diameter of the zirconia balls is about 3 mm.
According to the invention, the drying temperature in the steps S2 and S5 is 60-90 ℃, and the drying time is 12-24 hours; the aperture of the screen mesh is 50-200 meshes; the pressure of the pressing block is 5-15 MPa, and the pressing time of the pressing block is 10-20 s.
According to the invention, the temperature of the pre-sintering in the step S3 is 800-1200 ℃, the heat preservation time is 6-24 hours, and the heat preservation time is preferably 8-12 hours. Preferably, the rate of temperature rise is 2 deg.C/min.
According to the invention, in step S3, crushing is carried out by using a high-energy ball mill, wherein the rotating speed of the high-energy ball mill is 800-1100 rpm, and the time is 10 minutes. Preferably, the grinding balls used for the high-energy ball milling are zirconia balls, the diameter of each zirconia ball is about 1cm, and the mass ratio of each zirconia ball to the powder raw material is (2-10): 1.
According to the present invention, the pore-forming agent in step S4 is one or more of cellulose nanofibers, cellulose nanocrystals, and cellulose powder. Preferably, the diameter of the cellulose nanofiber is 4-10 nm, and the length of the cellulose nanofiber is 1-3 mu m; preferably, the diameter is 4 to 8nm and the length is 1.5 to 2 μm. Preferably, the cellulose nanocrystals have a diameter of 5 to 20nm and a length of 50 to 200 nm. Preferably, the cellulose powder has a particle size of 25 μm or less. Preferably, the mass ratio of the tungstic acid-based high-entropy ceramic powder to the pore-forming agent is 1 (0-0.5).
According to the invention, the sintering temperature in the step S5 is 1000-1700 ℃, the heating rate is 2 ℃/min, and the heat preservation time is 6-24 hours.
The technical scheme of the invention is further explained by combining specific examples.
Unless otherwise indicated, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.
Example 1
Preparation of ceric acid rare earth based high entropy ceramics (La) 0.4Gd0.4Er0.4Tm0.4Yb0.4)Ce2O7The flow of steps is shown in fig. 1:
(1) 0.0125mol of La is respectively weighed2O3、Gd2O3、Er2O3、Tm2O3、Yb2O3Powder and 0.0625mol of CeO2Putting the powder into a 500ml zirconia ball milling tank, adding 30ml ethanol, 1.2g PVP and 75g zirconia (diameter of 3mm) balls for high energy ball milling, controlling the rotating speed of a ball mill to be 800rpm, ball milling for 6 hours, wherein after each 4 minutes of work, the interval is 1 minute, and forward rotation and reverse rotation are sequentially alternated.
(2) Placing the mixture after ball millingDrying for 12h at 80 ℃, sieving by a 200-mesh standard sieve after the drying, then briquetting the powder, setting the pressure of a briquetting machine to be 10MPa, and pressing for 10s to obtain a blank A. Placing the blank A into a muffle furnace for presintering, controlling the presintering temperature to be 1200 ℃, the heating speed to be 2 ℃/min and the heat preservation time to be 12h to obtain (La)0.4Gd0.4Er0.4Tm0.4Yb0.4)Ce2O7High entropy ceramics.
(3) Placing the high-entropy ceramic in a zirconia ball milling tank, adding 75g of zirconia balls (the diameter is 1cm), controlling the rotating speed of a ball mill to 800rpm, carrying out ball milling for 10min (without intermission), and crushing the obtained ceric acid rare earth based high-entropy ceramic to obtain ceramic powder; then, the zirconia balls (diameter 1cm) were taken out, and 30ml of ethanol, 1.2g of PVP and 150g of zirconia balls (diameter 3mm) were added to perform high-energy ball milling, and the ball mill speed was controlled at 900rpm for 6 hours (1 minute interval after each 4 minutes of operation).
(4) Drying the mixture at 80 ℃ for 12h, sieving the dried mixture through a 200-mesh standard sieve, briquetting the powder, setting the pressure of a briquetting machine to be 10MPa, pressing for 10s to obtain a green body B, sintering the green body B in a muffle furnace, controlling the sintering temperature to be 1600 ℃, increasing the temperature at 2 ℃/min, and keeping the temperature for 12h to obtain the (La) powder0.4Gd0.4Er0.4Tm0.4Yb0.4)Ce2O7High entropy ceramics.
FIG. 2 shows (La)0.4Gd0.4Er0.4Tm0.4Yb0.4)Ce2O7The XRD pattern of the high-entropy ceramic shows that the obtained ceric acid rare earth based high-entropy ceramic is a typical fluorite structural material, and meanwhile, the characteristic peak of the high-entropy ceramic has no impurity peak or burr, which indicates that the obtained product has a complete crystal form. FIG. 3 shows (La)0.4Gd0.4Er0.4Tm0.4Yb0.4)Ce2O7According to the DES element distribution diagram of the high-entropy ceramic, six rare earth ions are uniformly distributed on the ceramic body, so that the rare earth metal is uniformly doped.
The thermal conductivity of the material is tested by a thermal constant analyzer (hotdisk), and the value of the thermal conductivity is 0.8204 W.m-1·K-1。
Example 2
Preparation of ceric acid rare earth based high-entropy porous ceramic (La)0.4Nd0.4Sm0.4Eu0.4Gd0.4)Ce2O7The method comprises the following steps:
(1) respectively weighing 0.0125mol of La2O3、Nd2O3、Sm2O3、Eu2O3、Gd2O3Powder and 0.0625mol of CeO2The powder is placed in a 500ml zirconia ball milling tank, 50ml ethanol, 1.6g PVB and 150g zirconia (diameter 3mm) balls are added for high energy ball milling, the rotation speed of the ball mill is controlled to be 1000rpm, and the ball milling is carried out for 4 hours (the time is 1 minute after 4 minutes of work).
(2) Drying the ball-milled mixture at 90 ℃ for 12h, sieving the ball-milled mixture through a 100-mesh standard sieve, briquetting the powder, setting the pressure of a briquetting machine to be 10MPa, pressing for 20s to obtain a blank A, placing the blank A into a muffle furnace for presintering, controlling the presintering temperature to be 1000 ℃, the heating rate to be 2 ℃/min and the heat preservation time to be 8h to obtain the (La) powder0.4Nd0.4Sm0.4Eu0.4Gd0.4)Ce2O7High entropy ceramics;
(3) placing the obtained high-entropy ceramic in a zirconia ball milling tank, adding 150g of zirconia balls (the diameter is 1cm), controlling the rotating speed of a ball mill to be 1000rpm, carrying out ball milling for 10min (without intermission), and crushing the obtained cerium acid rare earth based high-entropy ceramic; then, the zirconia balls (diameter 1cm) are taken out, 50ml of ethanol, 4g of cellulose nanocrystals (diameter 5-20nm and length 50-200nm), 1.6g of PVB and 150g of zirconia balls (diameter 3mm) are added for high-energy ball milling, the rotation speed of the ball mill is controlled to be 1000rpm, and the ball milling is carried out for 4 hours (the interval is 1 minute after 4 minutes of work).
(4) Drying the mixture at 90 ℃ for 12h, sieving the dried mixture through a 100-mesh standard sieve, briquetting the powder, setting the pressure of a briquetting machine to be 10MPa, pressing for 20s to obtain a green body B, sintering the green body B in a muffle furnace, controlling the sintering temperature to be 1500 ℃, the heating rate to be 2 ℃/min, and keeping the temperature for 8h to obtain the (La) powder 0.4Nd0.4Sm0.4Eu0.4Gd0.4)Ce2O7High entropy porous ceramic materials. The holes are through holes, and the aperture is 0.3 mu m.
The thermal conductivity of the material is measured by a thermal constant analyzer (hotdisk), and the value of the thermal conductivity is 0.6354 W.m-1·K-1
FIG. 4 shows ceric acid rare earth based high entropy porous ceramic (La)0.4Nd0.4Sm0.4Eu0.4Gd0.4)Ce2O7The XRD diagram shows that the obtained ceric acid rare earth based high-entropy ceramic is a typical fluorite structure material, and meanwhile, the characteristic peak of the ceric acid rare earth based high-entropy ceramic has no impurity peak or burr, which indicates that the obtained product has complete crystal form. The DES element distribution diagram is shown in figure 5, and it is seen that six rare earth ions are uniformly distributed on the ceramic body, so that the rare earth metal is uniformly doped.
Example 3
Preparation (La)0.4Dy0.4Ho0.4Lu0.4Y0.4)Ce2O7The high-entropy porous ceramic comprises the following steps:
(1) 0.0125mol of La is respectively weighed2O3、Dy2O3、Ho2O3、Lu2O3、Y2O3Powder and 0.0625mol of CeO2Putting the powder into a 500ml zirconia ball milling tank, adding 30ml ethanol, 2g polyethylene glycol and 187g zirconia (diameter 3mm) balls for high-energy ball milling, controlling the rotating speed of a ball mill to be 1100rpm, and carrying out ball milling for 2h (intermittent 1 minute after working for 4 minutes);
(2) drying the ball-milled mixture at 60 ℃ for 24h, sieving the ball-milled mixture through a 50-mesh standard sieve, briquetting the powder, setting the pressure of a briquetting machine to be 10MPa, pressing for 10s to obtain a blank A, placing the blank A into a muffle furnace for presintering, controlling the presintering temperature to be 1100 ℃, the temperature rising speed to be 2 ℃/min and the heat preservation time to be 20h to obtain the (La) powder 0.4Dy0.4Ho0.4Lu0.4Y0.4)Ce2O7High entropy ceramics;
(3) putting the obtained high-entropy ceramic into a zirconia ball milling tank, adding 187g of zirconia balls (diameter of 1cm), controlling the rotating speed of a ball mill to be 1100rpm, carrying out ball milling for 10min (without intermission), and crushing the obtained cerium acid rare earth based high-entropy ceramic; then, taking out the zirconia balls (with the diameter of 1cm), adding 30ml of ethanol, 11.25g of cellulose nano-fiber, 2g of polyethylene glycol and 187g of zirconia balls (with the diameter of 3mm) for high-energy ball milling, controlling the rotating speed of a ball mill to be 1100rpm, and carrying out ball milling for 2h (the interval is 1 minute after 4 minutes of work);
(4) drying the mixture at 60 ℃ for 24h, sieving the dried mixture through a 200-mesh standard sieve, briquetting the powder, setting the pressure of a briquetting machine to be 10MPa, pressing for 10s to obtain a green body B, sintering the green body B in a muffle furnace, controlling the sintering temperature to be 1400 ℃, increasing the temperature at the speed of 2 ℃/min, and keeping the temperature for 24h to obtain the (La) powder0.4Dy0.4Ho0.4Lu0.4Y0.4)Ce2O7High entropy porous ceramics. The holes are through holes, and the aperture is 0.8 mu m.
The thermal conductivity of the material is tested by a thermal constant analyzer (hotdisk), and the value of the thermal conductivity is 0.7658 W.m-1·K-1。
FIG. 6 shows a ceric acid rare earth based high entropy ceramic (La)0.4Dy0.4Ho0.4Lu0.4Y0.4)Ce2O7The XRD diagram shows that the obtained ceric acid rare earth based high-entropy ceramic is a typical fluorite structure material, and meanwhile, the characteristic peak of the ceric acid rare earth based high-entropy ceramic has no impurity peak or burr, which indicates that the obtained product has complete crystal form. The DES element distribution diagram is shown in figure 7, six rare earth ions are uniformly distributed on the ceramic body, and the uniform doping of rare earth metals is realized.
The invention prepares the material with low thermal conductivity coefficient and good infrared absorption performance, and has the characteristics of high melting point, low thermal conductivity, high thermal expansion coefficient, low thermal ratio, high temperature thermal stability and the like.
The above description is only a preferred application of the present invention, and it should be noted that, for those skilled in the art, it is possible to make various improvements and modifications without departing from the technical principle of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention.
Claims (10)
1. A ceric acid rare earth based high-entropy ceramic material is characterized by having the following chemical formula: RE2Ce2O7Wherein RE is at least five rare earth elements selected from La, Nd, Sm, Eu, Gd, Dy, Ho, Yb, Tm, Lu, Sc and Y, and the mole number of each rare earth element is the same.
2. The rare earth cerate-based high-entropy ceramic material as claimed in claim 1, wherein the structural formula of the rare earth cerate-based high-entropy ceramic material is (La)0.4Gd0.4Er0.4Tm0.4Yb0.4)Ce2O7、(La0.4Nd0.4Sm0.4Eu0.4Gd0.4)Ce2O7Or (La)0.4Dy0.4Ho0.4Lu0.4Y0.4)Ce2O7。
3. The rare earth cerate-based high-entropy ceramic material of claim 1, wherein the rare earth cerate-based high-entropy ceramic material is a dense ceramic material or a porous ceramic material.
Preferably, when the ceric acid rare earth based high-entropy ceramic material is a porous ceramic material, the aperture of the through hole is 5 nm-50 μm, and more preferably, the aperture of the through hole is 0.2-50 μm.
4. The ceric acid rare earth based high-entropy ceramic material of claim 1, wherein the thermal conductivity of the ceric acid rare earth based high-entropy ceramic material is 0.6W/mK to 0.9W/mK.
5. A preparation method of a ceric acid rare earth based high-entropy ceramic material is characterized by comprising the following steps:
s1, mixing cerium oxide and at least five rare earth oxides RE2O3Mixing, adding absolute ethyl alcohol and a binder, and performing high-energy ball milling; wherein the rare earth oxide RE2O3Rare earth in (1)The elements are selected from at least five of La, Nd, Sm, Eu, Gd, Dy, Ho, Yb, Tm, Lu, Sc and Y;
s2, drying, sieving and tabletting the mixture obtained in the step S1 to obtain a compact blank A;
s3, pre-sintering the compact blank A, preserving heat, and crushing to obtain ceric acid rare earth based high-entropy ceramic powder;
s4, carrying out high-energy ball milling on the ceric acid rare earth based high-entropy ceramic powder obtained in the step S3, absolute ethyl alcohol and a binder; or mixing the ceric acid rare earth based high-entropy ceramic powder with a pore-forming agent, absolute ethyl alcohol and a binder, and then carrying out high-energy ball milling to obtain a mixture;
s5, drying, sieving and briquetting the mixture obtained in the step S4 to obtain a compact blank B, and sintering and insulating the blank B to obtain the ceric acid rare earth based high-entropy compact or porous ceramic.
6. The method of claim 5, wherein the cerium oxide and the metal ions in the five rare earth oxides in step S1 satisfy Ce4+To the total RE3+The molar ratio is 1: 1.
Preferably, the molar ratio of the rare earth elements in the five rare earth oxides is 1:1:1:1: 1.
7. The method of claim 5, wherein the binder is PVP, PVB, or polyethylene glycol.
Preferably, the mass ratio of the adhesive to the mixture powder/the ceric acid rare earth-based high-entropy ceramic powder is (0.03-0.08):1, and the volume mass ratio of the ethanol and mixture powder/the ceric acid rare earth-based high-entropy ceramic powder is (1-10): 3.
8. The preparation method according to claim 5, characterized in that the rotation speed of the high-energy ball mill in the step S1 is 800-1100 rpm, and the time is 2-6 hours; the high-energy ball milling mode is that the interval is 1 minute every 4 minutes of work, and the positive rotation and the negative rotation are sequentially alternated.
Preferably, the grinding balls in the high-energy ball milling in the step S1 are zirconia balls, and the mass ratio of the zirconia balls to the powder raw material is (2-10): 1; the diameter of the zirconia ball is 3 mm.
9. The method according to claim 5, wherein the drying temperature in the steps S2 and S5 is 60 to 90 ℃, and the drying time is 12 to 24 hours;
Preferably, the aperture of the sieved screen mesh is 50-200 meshes.
Preferably, the pressure of the briquetting during tabletting is 5-15 MPa, and the pressing time of the briquetting is 10-20 s.
Preferably, the pre-sintering temperature in the step S3 is 800-1200 ℃, the heating rate is 2 ℃/min, the heat preservation time is 6-24 hours, and the heat preservation time is preferably 8-12 hours.
10. The preparation method according to claim 5, wherein the step S3 is implemented by high energy ball mill crushing treatment at a rotation speed of 800-1100 rpm for 10 minutes.
Preferably, in the step S4, zirconia balls are used for the high-energy ball milling, the mass ratio of the zirconia balls to the cerium acid rare earth based high-entropy ceramic powder is (2-10):1, and the diameter of the zirconia balls is about 1 cm.
Preferably, the pore-forming agent in step S4 is one or more of cellulose nanofiber, cellulose nanocrystal and cellulose powder.
Preferably, the cellulose nanofibers have a diameter of 4-10 nm and a length of 1-3 μm; preferably, the diameter is 4 to 8nm and the length is 1.5 to 2 μm.
Preferably, the cellulose nanocrystal has a diameter of 5-20 nm and a length of 50-200 nm.
Preferably, the cellulose powder has a particle size of 25 μm or less.
Preferably, the mass ratio of the pore-forming agent to the tungstic acid-based high-entropy ceramic powder is (0-0.5): 1.
Preferably, the sintering temperature in the step S5 is 1000-1700 ℃, preferably 1400-1600 ℃, the heating rate is 2 ℃/min, and the heat preservation time is 6-24 hours.
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