CN113754422B - Porous high-entropy rare earth ferrite ceramic material and preparation method and application thereof - Google Patents

Porous high-entropy rare earth ferrite ceramic material and preparation method and application thereof Download PDF

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CN113754422B
CN113754422B CN202010485777.7A CN202010485777A CN113754422B CN 113754422 B CN113754422 B CN 113754422B CN 202010485777 A CN202010485777 A CN 202010485777A CN 113754422 B CN113754422 B CN 113754422B
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rare earth
ferrate
porous
ceramic material
powder
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CN113754422A (en
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杨帆
薛丽燕
赵志钢
邵志恒
谢美英
王凯先
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Xiamen Institute of Rare Earth Materials
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Abstract

The invention discloses a porous ferrate rare earth ceramic material, a preparation method and application thereof. The ceramic material is REFeO in chemical formula 3 Representing, RE is selected from at least five of La, nd, sm, eu, gd, ho, er, tm, lu and Y; the porous ferrate rare earth ceramic material contains pores with diameters between 0.1 and 25 mu m. Is prepared by a high-temperature solid phase method or a sol-gel method. The material has a low thermal conductivity.

Description

Porous high-entropy rare earth ferrite ceramic material and preparation method and application thereof
Technical Field
The invention belongs to the technical field of preparation of high-entropy materials, and particularly relates to a porous high-entropy rare earth ferrite ceramic material, and a preparation method and application thereof.
Background
High entropy ceramics generally refer to solid solutions formed from 5 or more ceramic components, which have very excellent high entropy effects and properties. The teaching She Junwei of taiwan in 2004 has proposed the concept of a high-entropy alloy, and the teaching of a rock-salt structured entropy-stable oxide ceramic was reported by cast, maria and Curtarolo et al, university of douglas state, north carolina, us, 2015. The characteristics of the high-entropy ceramic can be summarized as four points: (1) a thermodynamic high entropy effect; (2) lattice distortion effects of the structure; (3) a kinetic hysteresis diffusion effect; (4) a "cocktail" effect on performance.
The main subjects of high entropy ceramics currently include oxides, carbides, borides, silicides, etc., wherein the oxides include perovskite structures, spinel structures, fluorite structures, etc. So far, the synthesis of high-entropy ceramics is mainly high-temperature solid-phase synthesis, and wet chemical and epitaxial growth methods are also adopted. The papers and patent documents published in the prior art about high-entropy ceramics mainly focus on the synthesis method, heat preservation and heat resistance, and other properties have not been paid much attention to, in particular, how to reduce the heat conductivity of materials.
The porous ceramics can be classified into microporous ceramics, mesoporous ceramics and macroporous ceramics, wherein the microporous ceramics refer to porous ceramics with the pore diameter smaller than 2nm, the mesoporous ceramics refer to porous ceramics with the pore diameter between 2nm and 50nm, and the macroporous ceramics refer to porous ceramics with the pore diameter larger than 50nm. At present, the preparation methods of the porous ceramics are mainly four, namely a partial sintering method, a sacrificial template method, a replication template method and a direct foaming method. The porous ceramic has wide application fields, and has very wide application in the fields of catalysis, catalyst carriers, refractory insulating materials and the like.
Rare earth ferrite is used as a typical perovskite structure compound, and has excellent high-temperature resistance and oxidation resistance. ABO (anaerobic-anoxic-oxic) 3 The perovskite structure doped crystal structure can generate distortion, so that two charge compensation mechanisms of oxygen vacancy and element valence change are formed for keeping the structural stability and charge conservation of the material, and the oxygen vacancy is formedThe creation of a site can increase the ability of the material to transfer oxygen and store oxygen, as the elemental valence is such that the carrier transitions from the a site to the B site by changing valence state to effect conduction of holes.
Perovskite type rare earth ferrite REFeO 3 The crystal structure of lanthanum ferrite is ideal and the stability after A, B bit doping is excellent, and the field-induced electron spin direction adjustment, dielectric relaxation, magnetic interaction, magnetism and the like are excellent, so that the crystal structure has rich optical, electrical, magnetic, catalytic and other properties. The method has wide application prospect in the fields of infrared radiation materials, quick magneto-optical switches, spot space position measurement technology, magneto-optical devices such as magneto-optical sensors, photocatalysis, solid oxide fuel cells, chemical sensors, semiconductors and the like. However, how to prepare porous ferrate rare earth ceramics with controllable pore diameter and low heat conductivity coefficient becomes a technical problem to be solved urgently.
Disclosure of Invention
The invention provides a porous ferrate rare earth ceramic material, which is represented by a chemical formula REFeO 3 Representing, RE is selected from at least five of La, nd, sm, eu, gd, ho, er, tm, lu and Y;
the porous ferrate rare earth ceramic material contains pores with diameters between 0.1 and 25 mu m.
According to an embodiment of the invention, the porous high entropy rare earth ferrite ceramic material contains pores with a diameter between 0.3 and 20 μm, exemplary 400nm, 600nm, 800nm, 3 μm, 15 μm, 20 μm.
According to an embodiment of the invention, the pores are uniformly distributed in the porous rare earth ferrate ceramic material. Preferably, the holes may be through holes.
According to an embodiment of the invention, the porous high entropy rare earth ferrite ceramic material has a thermal conductivity of less than 0.6W/mK, preferably less than 0.5W/mK, exemplary 0.45W/mK, 0.46W/mK, 0.47W/mK, 0.48W/mK, 0.49W/mK.
According to an embodiment of the invention, the porous high entropy rare earth ferrite ceramic material may be selected from (La 0.2 Sm 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 、(La 0.2 Nd 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 、(La 0.2 Nd 0.2 Eu 0.2 Er 0.2 Lu 0.2 )FeO 3 、(La 0.2 Eu 0.2 Ho 0.2 Er 0.2 Tm 0.2 )FeO 3 Or (La) 0.2 Nd 0.2 Eu 0.2 Ho 0.2 Y 0.2 )FeO 3 。
The invention also provides a preparation method of the porous ferrate rare earth ceramic material, which comprises the following steps:
(A) Mixing the high entropy rare earth ferrite powder with a pore-forming agent A, water and an optional binder which is optionally added or not, ball milling, drying and briquetting the obtained mixture to obtain a compact blank; sintering and preserving heat of the blank to obtain the porous ferrate rare earth ceramic material;
or (B) the colloid formed by the ferrate rare earth powder and the pore-forming agent B is frozen and dried, and then sintered and insulated to obtain the porous ferrate rare earth ceramic material;
the pore-forming agent A is at least one of cellulose nanofiber, cellulose nanocrystalline and cellulose powder, and the pore-forming agent B is melamine-diborate microfibrous sol.
According to an embodiment of the invention, the cellulose nanofibers have a diameter of 4-10nm and a length of 1-3 μm; for example, 4-8nm in diameter and 1.5-2 μm in length.
According to an embodiment of the invention, the cellulose nanocrystals have a diameter of 5-20nm and a length of 50-200nm; for example, 8-16nm in diameter and 80-150nm in length.
According to an embodiment of the invention, the cellulose powder has a particle size of 25 μm or less, for example a particle size of 15 μm or less.
According to an embodiment of the present invention, in the scheme (A), the mass ratio of the ferrate rare earth powder to the pore-forming agent A is 1 (0.1-0.5), for example 1 (0.2-0.4), and is exemplified by 1:0.1, 1:0.2, 1:0.3, and 1:0.4.
According to an embodiment of the present invention, in the embodiment (a), the binder is at least one of PVP, PVB, polyethylene glycol, and the like. Further, the mass ratio of the binder to the high entropy rare earth ferrite powder is (0.03-0.08): 1, for example (0.04-0.07): 1, exemplary 0.03:1,0.04:1,0.05:1,0.06:1,0.07:1,0.08:1.
According to an embodiment of the invention, in scheme (A), the volume to mass ratio (mL/g) of water to the rare earth ferrate powder is (3-10): 3, e.g., (4-7): 3, and exemplary is 5:3.
According to an embodiment of the invention, in scheme (B), the molar ratio of the ferrate rare earth powder to the pore former B is 1 (0.1-0.5), e.g., 1 (0.2-0.4), and is exemplified by 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5.
According to an embodiment of the present invention, in the scheme (B), the rare earth ferrate powder is mixed with the pore-forming agent B, and stirred under heating to form a suspension, and the suspension is naturally cooled to room temperature to form a colloid. Wherein the heating temperature is 85-95deg.C, such as 87-93deg.C, and exemplified by 90deg.C. Wherein the stirring is high-speed stirring.
According to an embodiment of the invention, in scheme (B), the freeze-drying temperature is-90 to-80 ℃, e.g. -88 to-82 ℃, exemplary is-80 ℃ and-90 ℃. Wherein the time of freeze drying is 12-72h, such as 24-60h, and exemplary is 24h, 36h.
According to the embodiment of the invention, the high-entropy rare earth ferrite powder can be prepared by the following scheme (one) or the scheme (two):
scheme (one): (1-1) comprising iron oxide and at least five rare earth oxides RE 2 O 3 The raw materials of the (2) are ball-milled, and the obtained mixture is dried, sieved and pressed into blocks to obtain a compact blank;
(1-2) sintering and preserving heat of the blank to obtain the high-entropy rare earth ferrite ceramic;
(1-3) obtaining the rare earth ferrate powder after the sample crushing treatment of the rare earth ferrate ceramic;
scheme (II): (2-1) at least five rare earth nitrates RE (NO) 3 ) 3 Heating and refluxing the mixture of citric acid and glycol to react to obtainTo rare earth ferrite based sols;
(2-2) evaporating and drying the rare earth ferrite-based sol to obtain rare earth ferrite-based gel;
(2-3) grinding and calcining the rare earth ferrite-based gel to obtain the high entropy rare earth ferrite powder;
wherein RE has the meaning as described above.
According to an embodiment of the invention, the molar amounts of the rare earth elements are the same.
According to an embodiment of the present invention, in step (1-1), fe 3+ With RE 3+ Total (S) The molar ratio of (2) is 1:1.
According to an embodiment of the invention, in step (1-3), the time of the sample crushing treatment is 5-30s, e.g. 10-20s, exemplary 5s, 10s, 15s, 20s, 25s, 30s. Further, the sample crushing treatment can be performed in a tungsten carbide vibration sample grinder.
According to an embodiment of the present invention, in step (2-1), the ME 3+ Total (S) Represents Fe 3+ With RE 3+ Total (S) Sum, ME 3+ Total (S) The molar ratio to citric acid is 1 (1.2-2), for example 1 (1.4-1.8), and is exemplified by 1:1.2, 1:1.4, 1:1.5, 1:1.6, 1:1.8, 1:2.
According to an embodiment of the invention, in step (2-1), the mass ratio of citric acid to ethylene glycol is 1 (1.2-1.5), for example 1 (1.3-1.4).
According to an embodiment of the present invention, in step (2-1), the temperature of the heated reflux is 70-90 ℃, e.g. 75-85 ℃, exemplary 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃.
According to an embodiment of the present invention, in the step (2-1), the stirring is maintained under the heating and refluxing conditions at a stirring speed of 300 to 800rpm.
According to an embodiment of the invention, in step (2-1), the reaction time is 2-4h, e.g. 2.5-3.5h, exemplary 2h, 2.5h, 3h, 3.5h, 4h.
According to an embodiment of the invention, in step (2-2), the temperature of the evaporation is 70-90 ℃, e.g. 75-85 ℃, exemplary 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃. Further, the evaporation time is 2-4 hours, for example 2.5-3.5 hours, and exemplary are 2 hours, 2.5 hours, 3 hours, 3.5 hours, and 4 hours.
According to an embodiment of the present invention, in step (2-2), the drying treatment is performed at a temperature of 100-120 ℃, for example 105-115 ℃, and exemplary 100 ℃, 105 ℃, 110 ℃, 115 ℃,120 ℃. Further, the drying treatment is performed for 6 to 12 hours, for example, 7 to 10 hours, and exemplary are 6 hours, 7 hours, 8 hours, 9 hours, and 10 hours.
According to an embodiment of the invention, in step (2-3), the calcination temperature is 600-900 ℃, e.g. 700-800 ℃, exemplary 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃, 900 ℃. Further, the calcination time is 2-3 hours, such as 2 hours, 2.5 hours, 3 hours.
According to an embodiment of the present invention, in the aspect (a) and/or the aspect (one) step (1-1), the ball milling is a high energy ball milling.
For example, the rotational speed of the high energy ball mill is 200-500rpm, such as 300-400rpm, and exemplary are 200rpm, 300rpm, 400rpm, 500rpm.
For example, the high energy ball milling time is 6-24 hours, such as 8-16 hours, and exemplary are 10 hours, 13 hours, 16 hours, 20 hours, 24 hours.
For example, the ball milling mode is 2:4, namely, the ball milling mode is intermittently operated for 4min after 2min, and the forward rotation and the reverse rotation are sequentially rotated.
For example, the milling balls used in ball milling are zirconia balls. For example, the mass ratio of the zirconia balls to the powder raw material is (2-10): 1; such as (3-8): 1, exemplary are 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1.
For example, the mass ratio of large, medium and small spheres in zirconia spheres=1 (1-3): 1, with an exemplary 1:2:1.
According to an embodiment of the present invention, in the embodiment (a) and/or the embodiment (one) step (1-1), the drying temperature is 60 to 90 ℃, for example 70 to 80 ℃, and exemplary 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃. Further, the drying time is 12-24 hours, for example 15-20 hours, and exemplary are 12 hours, 15 hours, 18 hours, 20 hours, 24 hours.
According to an embodiment of the present invention, in the scheme (a) and/or the scheme (one) step (1-1), the pressure of the briquette is 5 to 15MPa, for example 8 to 12MPa, and exemplified by 5MPa, 8MPa, 10MPa, 12MPa, 15MPa. Further, the pressing time of the pressing block is 0.5-1min, such as 0.5min, 0.8min, 1min.
According to an embodiment of the invention, in scheme (a) and/or scheme (one) step (1-1), the sintering temperature is 900-1500 ℃, e.g. 1000-1400 ℃, exemplary 900 ℃, 1000 ℃, 1100 ℃, 1200 ℃, 1300 ℃, 1400 ℃. Further, the incubation time is 6-24 hours, e.g., 8-20 hours, and exemplary are 6 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, 20 hours, 24 hours.
The invention also provides the porous high-entropy rare earth ferrite ceramic prepared by the method.
The invention also provides application of the porous ferrate rare earth ceramic in low heat conduction materials, infrared radiation absorption or magnetic performance.
The invention has the beneficial effects that:
the rare earth ferrite ceramic prepared by the prior art mainly takes lanthanum ferrite, and is temporarily blank in the field of high-entropy rare earth ceramic.
(1) The aperture of the porous ferrate rare earth ceramic provided by the invention is controllable within the range of 0.1-25 mu m.
(2) The invention provides a preparation process of various porous ferrate rare earth, which is simple, and the synthesized powder has small crystal grains and uniform distribution.
(3) According to the invention, the porous ceramic is formed by cellulose pore formation, and the through holes are easily formed by taking cellulose as pore-forming agent, so that the through holes are beneficial to further reducing the heat conductivity coefficient of the material; the carbon content of cellulose is low, so that carbonization of ceramic materials can be effectively prevented; while its cost is relatively low. The melamine-diborate has low carbon content, and can form regular blocks in a cooling gel mode, so that the step of compression molding in subsequent processing is omitted. The increase of the pores increases the specific surface area of the ceramic, and further reduces the heat conductivity coefficient of the material, thereby prolonging the service life of the material. The single rare earth ferrite ceramic has a heat conductivity coefficient of more than 1W/mk, but under the condition of doping of five rare earth ions, the heat conductivity coefficient of the ceramic under the condition of no pore is about 0.72W/mk, and the heat conductivity coefficient of the porous ceramic is less than 0.50W/mk.
Meanwhile, the toughness of the ceramic can be increased to a certain extent.
(4) The porous ferrate rare earth ceramic prepared by the invention has excellent infrared radiation absorption and magnetic performance.
(5) The method adopts a high-temperature solid phase method or a sol-gel method, has simple flow and controllable operation conditions, and is easy to industrially popularize and apply.
Drawings
FIG. 1 is a flow chart of a process for preparing porous high entropy rare earth ferrate ceramic by a high temperature solid phase method.
FIG. 2 is a flow chart of a process for preparing porous ferrate rare earth ceramic by a sol-gel method.
FIG. 3 shows the synthesis (La) in example 1 of the present invention 0.2 Sm 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 XRD pattern of porous high entropy ceramic powder.
FIG. 4 shows the synthesis (La) in example 1 of the present invention 0.2 Sm 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 SEM pictures (scale: 5 μm) of porous high entropy ceramic and EDS element distribution plots.
FIG. 5 shows the synthesis (La) in example 2 of the present invention 0.2 Nd 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 SEM pictures (scale: 5 μm) of porous high entropy ceramic and EDS element distribution plots.
FIG. 6 shows the synthesis (La) in example 3 of the present invention 0.2 Nd 0.2 Eu 0.2 Er 0.2 Lu 0.2 )FeO 3 SEM pictures (scale: 5 μm) of porous high entropy ceramic and EDS element distribution plots.
FIG. 7 shows the synthesis (La) in example 4 of the present invention 0.2 Sm 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 SEM pictures (scale: 5 μm) of porous high entropy ceramic and EDS element distribution plots.
FIG. 8 shows the result of synthesis (La) in example 5 of the present invention 0.2 Eu 0.2 Ho 0.2 Er 0.2 Tm 0.2 )FeO 3 SEM pictures (scale: 50 μm) of porous high entropy ceramic and EDS element distribution plots.
FIG. 9 shows the result of synthesis (La) in example 6 of the present invention 0.2 Nd 0.2 Eu 0.2 Ho 0.2 Y 0.2 )FeO 3 SEM pictures (scale: 50 μm) of porous high entropy ceramic and EDS element distribution plots.
Detailed Description
The technical scheme of the invention will be further described in detail below with reference to specific embodiments. It is to be understood that the following examples are illustrative only and are not to be construed as limiting the scope of the invention. All techniques implemented based on the above description of the invention are intended to be included within the scope of the invention.
Unless otherwise indicated, the starting materials and reagents used in the following examples were either commercially available or may be prepared by known methods.
Example 1 a porous ferrate rare earth ceramic material was prepared by the following steps (flow chart shown in figure 1):
(1) La of 0.0125mol was weighed separately 2 O 3 、Sm 2 O 3 、Gd 2 O 3 、Er 2 O 3 、Y 2 O 3 Powder and 0.0625mol of Fe 2 O 3 Placing the powder into a 500ml zirconia ball milling tank, adding 30ml ultra-pure water and 74g zirconia balls (mass ratio of large, medium and small balls=1:2:1) for high-energy ball milling, controlling the rotating speed of the ball mill to 400rpm, and performing ball milling for 24 hours;
(2) Drying the mixture after ball milling for 24 hours at 80 ℃, sieving the mixture by a 200-mesh standard sieve after finishing, then briquetting the powder, setting the pressure of a briquetting machine to be 10MPa, pressing for 1min, putting a green body A into a muffle furnace for sintering after the pressing is finished, controlling the sintering temperature to be 1500 ℃, the heating speed to be 2 ℃/min, the heat preservation time to be 24 hours, putting the green body A into a tungsten carbide vibration sample crusher after the reaction is finished, and reacting for 10s to obtain the high-entropy rare earth ferrite ceramic powder ((La) 0.2 Sm 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 )；
(3) 30g of rare earth ferrate ceramic powder (La) 0.2 Sm 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 6g of cellulose nanofiber (the diameter of the cellulose nanofiber is 4-10nm, the length of the cellulose nanofiber is 1-3 mu m) -pore-forming agent A, placing the cellulose nanofiber into a 500ml zirconia ball milling tank for ball milling, adding 50ml of ultrapure water, performing high-energy ball milling on 72g of zirconia balls (the mass ratio of large ball to medium ball=1:2:1), controlling the rotating speed of the ball milling machine to 400rpm, and performing ball milling for 24 hours;
(4) Drying the mixture after ball milling for 24 hours at 80 ℃, sieving the mixture through a 100-mesh standard sieve after finishing, then briquetting the powder, setting the pressure of a briquetting machine to be 10MPa, pressing for 1min, placing a green body B into a muffle furnace for sintering after the pressing is finished, controlling the sintering temperature to be 1500 ℃, the heating speed to be 2 ℃/min, and the heat preservation time to be 6 hours to obtain the porous high-entropy rare earth ferrite ceramic ((La) 0.2 Sm 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 ) Detecting the heat conductivity coefficient of the material by using a hotisk device, and obtaining the heat conductivity coefficient of the material as follows: 0.4951W/mK.
Porous high entropy rare earth ferrite ceramic (La) 0.2 Sm 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 SEM images and EDS element distribution diagrams of (a) are shown in fig. 4, illustrating: the pore distribution of the ferrate rare earth ceramic prepared by the scheme is uniform, the pore diameter is about 600nm, and the five rare earth elements are uniformly distributed, so that the uniform doping of the five rare earth elements is realized.
The XRD patterns are shown in figure 3, and the XRD patterns are respectively from top to bottom: (La) 0.2 Sm 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 XRD pattern, laFeO 3 (PDF # 75-0439) Standard card, smFeO 3 (PDF#74-1474) Standard card, gdFeO 3 (PDF#74-1476) Standard card, erFeO 3 (PDF#47-0072) Standard card and YFeO 3 (PDF # 73-1345) Standard card. Description: (La) 0.2 Sm 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 Characteristic peaks in the XRD pattern of (2)The rest five kinds of rare earth ferrite are covered, the characteristic peaks of the prepared rare earth ferrate are slightly deviated corresponding to the positions of characteristic peaks of standard cards, and the characteristic peaks are deviated due to the fact that five kinds of rare earth metal ions are doped into the perovskite structure of the ferrite, and the interactions among the ions cause the deviation of the peaks, so that the prepared rare earth ferrate ceramic is shown as (La) 0.2 Sm 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 。
Example 2 a porous ferrate rare earth ceramic material was prepared by the steps of:
(1) La of 0.0125mol was weighed separately 2 O 3 、Nd 2 O 3 、Gd 2 O 3 、Er 2 O 3 、Y 2 O 3 Powder and 0.0625mol of Fe 2 O 3 Placing the powder into a 500ml zirconia ball milling tank, adding 30ml ultra-pure water, performing high-energy ball milling on 370g zirconia balls (mass ratio of large, medium and small balls=1:2:1), controlling the rotating speed of the ball mill to be 200rpm, and performing ball milling for 12 hours;
(2) Drying the mixture after ball milling for 12 hours at 90 ℃, sieving the mixture by a 200-mesh standard sieve after finishing, briquetting the powder, setting the pressure of a briquetting machine to be 15MPa, pressing for 0.5min, placing the block into a muffle furnace for sintering after the pressing is finished, controlling the sintering temperature to be 1500 ℃, the heating speed to be 2 ℃/min, the heat preservation time to be 12 hours, placing the block into a tungsten carbide vibration sample crusher after the reaction is finished, reacting for 20s, and obtaining the high-entropy rare earth ferrite ceramic powder ((La) 0.2 Nd 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 )；
(3) 30g of rare earth ferrate ceramic powder (La) 0.2 Nd 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 3g of cellulose nanocrystalline (the diameter of which is 5-20nm and the length of which is 50-200 nm) -pore-forming agent A, placing the cellulose nanocrystalline into a 500ml zirconia ball milling tank for ball milling, adding 50ml of ultrapure water, performing high-energy ball milling on 360g of zirconia balls (the mass ratio of large ball to medium ball=1:2:1), controlling the rotating speed of the ball milling machine to be 200rpm, and performing ball milling for 12 hours;
(4) Drying the ball-milled mixture at 90 DEG CScreening by a 100-mesh standard sieve after 12h, briquetting the powder, setting the pressure of a briquetting machine to be 10MPa, pressing for 0.5min, placing the block into a muffle furnace for sintering after the pressing, controlling the sintering temperature to be 1500 ℃, and controlling the heating speed to be 2 ℃/min, and keeping the temperature for 6h to obtain the porous high-entropy rare earth ferrite ceramic ((La) 0.2 Nd 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 ) Detecting the heat conductivity coefficient of the material by using a hotisk device, and obtaining the heat conductivity coefficient of the material as follows: 0.4743W/mK.
La 0.2 Nd 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 SEM images and EDS element distribution diagrams of (a) are shown in fig. 5, illustrating: the pore distribution of the ferrate rare earth ceramic prepared by the scheme is uniform, the pore diameter is about 3 mu m, and the distribution of five rare earth elements is uniform, so that the uniform doping of the five rare earth elements is realized.
Example 3 a porous ferrate rare earth ceramic material was prepared by the steps of:
(1) La (NO) of 0.003mol was weighed out separately 3 ) 3 ·6H 2 O、Nd(NO 3 ) 3 ·6H 2 O、Eu(NO 3 ) 3 ·6H 2 O、Er(NO 3 ) 3 ·6H 2 O、Lu(NO 3 ) 3 ·6H 2 O,0.015mol of Fe (NO) 3 ) 3 ·9H 2 O and 0.036mol of citric acid monohydrate are placed in a 200ml round-bottomed flask to prepare the mixture with the total metal ion concentration of 0.3 mol.L -1 9.1213g of ethylene glycol was added as a dispersant;
(2) Heating and refluxing the solution at 70 ℃, controlling the stirring speed to be 500rpm, reacting for 3 hours to form sol, evaporating the sol at 80 ℃ for 4 hours, and drying at 100 ℃ for 12 hours after the sol is completed to obtain rare earth ferrite-based gel; then calcining the gel at 800 ℃ for 2 hours to obtain the rare earth ferrate powder ((La) 0.2 Nd 0.2 Eu 0.2 Er 0.2 Lu 0.2 )FeO 3 )；
(3) 30g of rare earth ferrate ceramic powder (La) 0.2 Nd 0.2 Eu 0.2 Er 0.2 Lu 0.2 )FeO 3 9g of cellulose nanofiber (the diameter of the cellulose nanofiber is 4-10nm, the length of the cellulose nanofiber is 1-3 mu m) -pore-forming agent A, placing the cellulose nanofiber into a 500ml zirconia ball milling tank for ball milling, adding 50ml of ultrapure water, and 120g of zirconia balls (the mass ratio of large ball to medium ball=1:2:1) for high-energy ball milling, controlling the rotating speed of the ball milling machine to be 500rpm, and performing ball milling for 12 hours;
(4) Drying the mixture after ball milling at 80 ℃ for 12 hours, completely drying, briquetting, setting the pressure of a briquetting machine to be 15MPa, pressing for 0.5min, placing the blocks into a muffle furnace for sintering after the pressing is finished, controlling the sintering temperature to be 1500 ℃, and controlling the heating speed to be 2 ℃/min, and preserving the heat for 12 hours to obtain the porous high-entropy rare earth ferrite ceramic ((La) 0.2 Nd 0.2 Eu 0.2 Er 0.2 Lu 0.2 )FeO 3 ) Detecting the heat conductivity coefficient of the material by using a hotisk device, and obtaining the heat conductivity coefficient of the material as follows: 0.4823W/mK.
(La 0.2 Nd 0.2 Eu 0.2 Er 0.2 Lu 0.2 )FeO 3 SEM images and EDS element distribution diagrams of (a) are shown in fig. 6, illustrating: the pore distribution of the ferrate rare earth ceramic prepared by the scheme is uniform, the pore diameter is about 800nm, and the five rare earth elements are uniformly distributed, so that the uniform doping of the five rare earth elements is realized.
Example 4 a porous ferrate rare earth ceramic material was prepared by the steps of:
(1) 0.004mol of La (NO) was weighed out separately 3 ) 3 ·6H 2 O、Sm(NO 3 ) 3 ·6H 2 O、Er(NO 3 ) 3 ·6H 2 O、Gd(NO 3 ) 3 ·6H 2 O、Y(NO 3 ) 3 ·6H 2 O,0.02mol of Fe (NO) 3 ) 3 ·9H 2 O and 0.08mol of citric acid monohydrate are placed in a 200ml round-bottomed flask to prepare the mixture with the total metal ion concentration of 0.4 mol.L -1 25.2168g of ethylene glycol was added as a dispersant;
(2) Heating and refluxing the solution at 80 ℃, controlling the stirring speed to be 500rpm, and reacting for 4 hours to formEvaporating the sol at 90 ℃ for 3 hours, and drying the sol at 120 ℃ for 6 hours after the sol is completed to obtain rare earth ferrite-based gel; then calcining the gel at 900 ℃ for 2 hours to obtain the rare earth ferrate powder ((La) 0.2 Sm 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 )；
(3) 30g of rare earth ferrate ceramic powder (La) 0.2 Sm 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 9g of cellulose powder (the particle size of which is less than or equal to 25 mu m) -pore-forming agent A, placing the cellulose powder into a 500ml zirconia ball milling tank for ball milling, adding 50ml of ultrapure water, performing high-energy ball milling on 300g of zirconia balls (the mass ratio of large ball to medium ball=1:2:1), controlling the rotating speed of the ball milling machine to be 500rpm, and performing ball milling for 6 hours;
(4) Drying the mixture after ball milling for 12 hours at 90 ℃, completely drying, briquetting, setting the pressure of a briquetting machine to be 10MPa, pressing for 0.5min, placing the blocks into a muffle furnace for sintering after the pressing is finished, controlling the sintering temperature to be 1200 ℃, and controlling the heating speed to be 2 ℃/min, and preserving the heat for 24 hours to obtain the porous high-entropy rare earth ferrite ceramic ((La) 0.2 Sm 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 ) Detecting the heat conductivity coefficient of the material by using a hotisk device, and obtaining the heat conductivity coefficient of the material as follows: 0.4933W/mK.
(La 0.2 Sm 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 SEM and EDS diagrams of (a) are shown in fig. 7, illustrating: the pore distribution of the ferrate rare earth ceramic prepared by the scheme is uniform, the pore diameter is about 400nm, and the five rare earth elements are uniformly distributed, so that the uniform doping of the five rare earth elements is realized.
Example 5 a porous ferrate rare earth ceramic material was prepared by the following steps (flow chart shown in figure 2):
(1) 0.004mol of La (NO) was weighed out separately 3 ) 3 ·6H 2 O、Eu(NO 3 ) 3 ·6H 2 O、Ho(NO 3 ) 3 ·6H 2 O、Er(NO 3 ) 3 ·6H 2 O、Tm(NO 3 ) 3 ·6H 2 O，002mol of Fe (NO) 3 ) 3 ·9H 2 O and 0.08mol of citric acid monohydrate are placed in a 200ml round-bottomed flask to prepare the mixture with the total metal ion concentration of 0.4 mol.L -1 25.2168g of ethylene glycol was added as a dispersant;
(2) Heating and refluxing the solution at 80 ℃, controlling the stirring speed to be 500rpm, reacting for 4 hours to form sol, evaporating the sol at 90 ℃ for 3 hours, and drying at 120 ℃ for 6 hours after the sol is completed to obtain rare earth ferrite-based gel; then calcining the gel at 900 ℃ for 2 hours to obtain the rare earth ferrate powder ((La) 0.2 Eu 0.2 Ho 0.2 Er 0.2 Tm 0.2 )FeO 3 )；
(3) 50ml of 0.03 mol.L were measured separately -1 Mixing melamine and boric acid in equal proportion, reacting at 90deg.C for 1 hr to obtain melamine-diborate microfibrous sol, and adding 30g of high entropy rare earth ferrite ceramic powder (La 0.2 Eu 0.2 Ho 0.2 Er 0.2 Tm 0.2 )FeO 3 Stirring at 80 deg.C for 1 hr to form suspension, naturally cooling to room temperature, and freeze drying at-80 deg.C for 36 hr; after the gel is completely dried, the gel is put into a muffle furnace for sintering, the sintering temperature is controlled to be 1200 ℃, the heating speed is 2 ℃/min, and the heat preservation time is 18 hours, thus obtaining the porous ferrate rare earth ceramics ((La) 0.2 Eu 0.2 Ho 0.2 Er 0.2 Tm 0.2 )FeO 3 ) Detecting the heat conductivity coefficient of the material by using a hotisk device, and obtaining the heat conductivity coefficient of the material as follows: 0.4986/mK.
(La 0.2 Eu 0.2 Ho 0.2 Er 0.2 Tm 0.2 )FeO 3 SEM images and EDS element distribution diagrams of (a) are shown in fig. 8, illustrating: the pore distribution of the ferrate rare earth ceramic prepared by the scheme is uniform, the pore diameter is about 20 mu m, and the distribution of five rare earth elements is uniform, so that the uniform doping of the five rare earth elements is realized.
Example 6 preparation of a porous ferrate rare earth ceramic material, comprising the following steps:
(1) Respectively call for0.003mol of La (NO) 3 ) 3 ·6H 2 O、Nd(NO 3 ) 3 ·6H 2 O、Eu(NO 3 ) 3 ·6H 2 O、Ho(NO 3 ) 3 ·6H 2 O、Y(NO 3 ) 3 ·6H 2 O,0.015mol of Fe (NO) 3 ) 3 ·9H 2 O and 0.036mol of citric acid monohydrate are placed in a 200ml round-bottomed flask to prepare the mixture with the total metal ion concentration of 0.3 mol.L -1 9.1213g of ethylene glycol was added as a dispersant;
(2) Heating and refluxing the solution at 90 ℃, controlling the stirring speed to 800rpm, reacting for 3 hours to form sol, evaporating the sol at 90 ℃ for 3 hours, and drying at 100 ℃ for 12 hours after the sol is completely evaporated to obtain rare earth ferrite-based gel; then calcining the gel at 900 ℃ for 2 hours to obtain the rare earth ferrate powder ((La) 0.2 Nd 0.2 Eu 0.2 Ho 0.2 Y 0.2 )FeO 3 )；
(3) 50ml of 0.05 mol.L were measured separately -1 Mixing melamine and boric acid in equal proportion, reacting at 90deg.C for 2 hr to obtain melamine-diborate microfibrous sol, and adding 30g of high entropy rare earth ferrite ceramic powder (La 0.2 Nd 0.2 Eu 0.2 Ho 0.2 Y 0.2 )FeO 3 Stirring at 90 deg.C for 1 hr to form suspension, naturally cooling to room temperature, and freeze drying at-90 deg.C for 24 hr; after the gel is completely dried, the gel is put into a muffle furnace for sintering, the sintering temperature is controlled to 1300 ℃, the heating speed is 2 ℃/min, and the heat preservation time is 6 hours, thus obtaining the porous ferrate rare earth ceramics ((La) 0.2 Nd 0.2 Eu 0.2 Ho 0.2 Y 0.2 )FeO 3 ) Detecting the heat conductivity coefficient of the material by using a hotisk device, and obtaining the heat conductivity coefficient of the material as follows: 0.4925W/mK.
(La 0.2 Nd 0.2 Eu 0.2 Ho 0.2 Y 0.2 )FeO 3 SEM images and EDS element distribution diagrams of (a) are shown in fig. 9, illustrating: the pore of the ferrate rare earth ceramic prepared by the scheme is uniformly distributed, and the pore diameter is about 15 mum, the five rare earth metal elements are uniformly distributed, and the uniform doping of the five rare earth metals is realized.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (15)

1. The preparation method of the porous high-entropy rare earth ferrite ceramic material is characterized by comprising the following steps of:
(A) Mixing the high entropy rare earth ferrite powder with a pore-forming agent A, water and an optional binder which is added or not added, ball milling, drying and briquetting the obtained mixture to obtain a compact blank; sintering and preserving heat of the blank to obtain the porous rare earth ferrate ceramic material, wherein the mass ratio of the rare earth ferrate powder to the pore-forming agent A is 1 (0.1-0.5);
or (B) the gel formed by the high entropy rare earth ferrite powder and the pore-forming agent B is frozen and dried, and then sintered and insulated to obtain the porous high entropy rare earth ferrite ceramic material, wherein the mol ratio of the high entropy rare earth ferrite powder to the pore-forming agent B is 1 (0.1-0.5);
wherein the pore-forming agent A is at least one of cellulose nanofiber, cellulose nanocrystalline or cellulose powder, and the pore-forming agent B is melamine-diborate microfibrous sol;
the high-entropy rare earth ferrite powder is prepared by the following scheme (one) or scheme (two):
scheme (one): (1-1) comprising iron oxide and at least five rare earth oxides RE 2 O 3 The raw materials of the (2) are ball-milled, and the obtained mixture is dried, sieved and pressed into blocks to obtain a compact blank;
(1-2) sintering and preserving heat of the blank to obtain the high-entropy rare earth ferrite ceramic;
(1-3) obtaining the rare earth ferrate powder after the sample crushing treatment of the rare earth ferrate ceramic;
scheme (II): (2-1) Comprises ferric nitrate, at least five rare earth nitrates RE (NO) 3 ) 3 Heating and refluxing a mixture of citric acid and glycol, and reacting to obtain rare earth ferrite-based sol;
(2-2) evaporating and drying the rare earth ferrite-based sol to obtain rare earth ferrite-based gel;
(2-3) grinding and calcining the rare earth ferrite-based gel to obtain the high entropy rare earth ferrite powder;
wherein RE is selected from at least five of La, nd, sm, eu, gd, ho, er, tm, lu and Y;
the porous ferrate rare earth ceramic material is prepared by adopting a chemical formula REFeO 3 A representation;
the porous ferrate rare earth ceramic material contains pores with the diameter of 0.1-25 mu m, the pores are uniformly distributed in the porous ferrate rare earth ceramic material, and the heat conductivity coefficient of the porous ferrate rare earth ceramic material is less than 0.5W/mK.
2. The method according to claim 1, wherein the cellulose nanofibers have a diameter of 4 to 10nm and a length of 1 to 3 μm; the diameter of the cellulose nanocrystalline is 5-20nm, and the length is 50-200nm; the particle size of the cellulose powder is less than or equal to 25 mu m.
3. The method according to claim 1, wherein the mass ratio of the binder to the rare earth ferrate powder is (0.03-0.08): 1.
4. The method according to claim 1, wherein in the scheme (A), the volume/mass ratio (mL/g) of the water to the rare earth ferrate powder is (3-10): 3.
5. The process of any one of claims 1 to 4, wherein in scheme (B), the rare earth ferrate powder is mixed with a pore-forming agent B and stirred at a temperature of 85-95 ℃ to form a suspension, and the suspension is naturally cooled to room temperature to form a colloid.
6. The method according to any one of claims 1 to 4, wherein in the step (B), the temperature of the freeze-drying is-90 to-80 ℃, and the time of the freeze-drying is 12 to 72 h.
7. The process according to any one of claims 1 to 4, wherein the molar amounts of the rare earth elements are the same, fe in step (1-1) 3+ With RE 3+ Total (S) In a molar ratio of 1:1, in step (2-1), ME 3+ Total (S) Represents Fe 3+ With RE 3+ Total (S) Sum, ME 3+ Total (S) The molar ratio of the citric acid to the citric acid is 1 (1.2-2).
8. The method according to any one of claims 1 to 4, wherein in the step (2-1), the mass ratio of the citric acid to the ethylene glycol is 1 (1.2-1.5), the temperature of the heating reflux is 70-90 ℃, and the reaction time is 2-4 hours.
9. The method according to any one of claims 1 to 4, wherein in the step (2-2), the temperature of the evaporation is 70 to 90 ℃ and the temperature of the drying treatment is 100 to 120 ℃;
in the step (2-3), the calcining temperature is 600-900 ℃.
10. The method according to any one of claims 1 to 4, wherein in the step (a) and/or the step (1-1), the ball milling is high-energy ball milling.
11. The method according to any one of claims 1 to 4, wherein in the step (1-1) of the scheme (a) and/or the scheme (one), the drying temperature is 60 to 90 ℃, the drying time is 12 to 24 hours, the pressure of the briquette is 5 to 15MPa, the sintering temperature in the step (1-2) of the scheme (a) and/or the scheme (one) is 900 to 1500 ℃, and the heat-retaining time is 6 to 24 hours.
12. A porous rare earth ferrate ceramic material prepared by the method of any one of claims 1-11, wherein the ceramic material is of the formula REFeO 3 Representing, RE is selected from at least five of La, nd, sm, eu, gd, ho, er, tm, lu and Y;
the porous ferrate rare earth ceramic material contains pores with the diameter of 0.1-25 mu m, the pores are uniformly distributed in the porous ferrate rare earth ceramic material, and the heat conductivity coefficient of the porous ferrate rare earth ceramic material is less than 0.5W/mK.
13. The ceramic material of claim 12, wherein the porous rare earth ferrate ceramic material comprises pores having a diameter between 0.3-20 μm.
14. The ceramic material of claim 13, wherein the porous rare earth ferrate ceramic material is selected from the group consisting of (La 0.2 Sm 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 、(La 0.2 Nd 0.2 Gd 0.2 Er 0.2 Y 0.2 )FeO 3 、(La 0.2 Nd 0.2 Eu 0.2 Er 0.2 Lu 0.2 )FeO 3 、(La 0.2 Eu 0.2 Ho 0.2 Er 0.2 Tm 0.2 )FeO 3 Or (La) 0.2 Nd 0.2 Eu 0.2 Ho 0.2 Y 0.2 )FeO 3 。
15. Use of the porous rare earth ferrate ceramic prepared by the method of any one of claims 1-11 in low thermal conductivity materials, infrared radiation absorption or magnetic properties.
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