阅读说明：本技术 一种多元稀土硼化物纳米粉体及其制备方法 (Multi-element rare earth boride nano powder and preparation method thereof ) 是由 黄美松 赵瑞山 王志坚 刘华 樊玉川 马小波 文康 郭利平 于 2021-08-25 设计创作，主要内容包括：本发明公开了一种多元稀土硼化物纳米粉体及其制备方法,包括以下步骤：S1、采用La-(2)O-(3)、RE-(2)O-(3)、B-(2)O-(3)和Ca作为原料,混合均匀并预压成块,制得块状坯料；S2、将S1中的块状坯料置于真空或惰性气氛保护条件中加热,预定加热温度为800～1000℃,制备得到多元稀土硼化物反应产物；S3、将S2中多元稀土硼化物反应产物经过酸洗、纯水反复清洗至中性,进行过滤、真空干燥,获得多元稀土硼化物La-(1-x)RE-(x)B-(6)纳米粉体,其中0<x<1。本发明中的钙热还原过程降低了La-(1-)-(x)RE-(x)BO-(3)化合物的形成几率,提高了稀土六硼化物收率,而且简化镁热还原法制备稀土六硼化物中的提纯工序,提高了生产效率。(The invention discloses a multi-element rare earth boride nano powder and a preparation method thereof, comprising the following steps: s1, use La 2 O 3 、RE 2 O 3 、B 2 O 3 And Ca as raw materials, uniformly mixing and prepressing into blocks to prepare block blanks; s2, heating the massive blank in the S1 in a vacuum or inert atmosphere protection condition at a preset heating temperature of 800-1000 ℃ to prepare a multi-element rare earth boride reaction product; s3, repeatedly washing the reaction product of the multicomponent rare earth boride in S2 to be neutral by acid washing and pure water, filtering and drying in vacuum to obtain the multicomponent rare earth boride La 1‑x RE x B 6 Nano-powder of which 0<x<1. The hydrothermal reduction process of the invention reduces La 1‑ x RE x BO 3 The formation probability of the compound improves the yield of the rare earth hexaboride and simplifies the preparation of the rare earth hexaboride by a magnesiothermic reduction methodThe purification process in the rare earth hexaboride improves the production efficiency.)

1. A preparation method of multi-element rare earth boride nano powder is characterized by comprising the following steps:

s1, use La₂O₃、RE₂O₃、B₂O₃And Ca as raw materials, uniformly mixing and prepressing into blocks to prepare block blanks;

s2, heating the massive blank in the S1 in a vacuum or inert atmosphere protection condition at a preset heating temperature of 800-1000 ℃ to prepare a multi-element rare earth boride reaction product;

s3, repeatedly washing the reaction product of the multicomponent rare earth boride in S2 to be neutral by acid washing and pure water, filtering and drying in vacuum to obtain the multicomponent rare earth boride La_1-xRE_xB₆Nano-powder of which 0<x<1。

2. The method of claim 1, wherein: and (S2) introducing argon into the inert atmosphere when the temperature reaches 400-500 ℃.

3. The method of claim 2, wherein: the purity of the argon is more than or equal to 99.99 percent, and the pressure is 0.02-0.1 MPa after the argon is introduced.

4. The production method according to any one of claims 1 to 3, characterized in that: and S3, washing with dilute hydrochloric acid, wherein the concentration of the dilute hydrochloric acid solution is 2-8 mol/L, and the washing temperature is 40-60 ℃.

5. The production method according to any one of claims 1 to 3, characterized in that: s2, heating to a preset heating temperature in a three-stage heating mode, then preserving heat for 1-2 hours, and starting heating when the vacuum degree is lower than 0.01Pa, wherein in the first heating temperature rise stage, the temperature is raised from room temperature to 600-750 ℃, and the temperature rise rate is 6-10 ℃/min; in the second heating temperature rise stage, the temperature is raised from 600-750 ℃ to 750-900 ℃, and the temperature rise rate is 3-5 ℃/min; in the third heating temperature rise stage, the temperature is raised from 750-900 ℃ to a preset heating temperature, and the temperature rise rate is 1-2 ℃/min.

6. The method of claim 5, wherein: and after the heat preservation is finished, cooling at a cooling rate of 15-25 ℃/min, and cooling the reaction product of the multi-element rare earth boride to room temperature and taking out.

7. The production method according to any one of claims 1 to 3, characterized in that: RE₂O₃Is Eu₂O₃、Sm₂O₃、Yb₂O₃One or two of them.

8. The production method according to any one of claims 1 to 3, characterized in that: (La)₂O₃+RE₂O₃)、B₂O₃The molar ratio of Ca to Ca is 1:6 (21-30).

9. A polynary rare earth boride nanopowder prepared by the method of preparation of a polynary rare earth boride nanopowder as claimed in any one of claims 1 to 8, characterized in that: the purity of the multi-element rare earth boride nano powder is more than or equal to 99.8%, and the particle size of the powder is 20-120 nm.

Technical Field

The invention relates to a multi-element rare earth boride, in particular to a multi-element rare earth boride nano powder and a preparation method thereof.

Background

Rare earth hexaboride (REB)₆) The excellent physical and chemical properties of the material have important and wide application in the technical fields of civil use, military industry, national defense and high-end. When REB₆Exhibit some new physicochemical properties when the grain size of (b) is reduced to the nanoscale range, such as LaB deposited on the surface of a fabric by magnetron sputtering techniques₆The film (the particle size is between 30 and 50 nm) has good ultraviolet protection performance, the binary and multicomponent rare earth hexaboride nano-wire (the diameter is 50 to 120nm, the length is several microns) prepared by adopting a chemical vapor deposition method, the nano-cone (the diameter of the taper shank is 100 to 150nm, and the diameter of the taper tip is 10 to 30nm) has good cold field emission characteristics, and the REB prepared by various methods₆When the particle size of the nano powder is less than 100nm, free electrons enriched on the local surface of the particle oscillate collectively to generate plasmon resonance (LSPRs) effect, and the nano powder shows strong absorption characteristic in a near infrared region and keeps good penetrability in a visible region.

The research finds that REB₆The size, the microscopic appearance and the environment medium of the nano particles have great influence on the local surface plasmon resonance of the nano particles, the smaller the particle size is, the higher the light absorption intensity of the nano particles in a near infrared region is, and the same effective diameter isThe lower nanocubes show higher near-infrared extinction efficiency than the spheres, and the larger the dielectric constant of the environment medium in which the nanoparticles are positioned, the larger the LSPRs absorption peak position moves towards the long-wave direction. Furthermore, REB₆The chemical composition of (2) such as carrier concentration and lattice defects also have influence on plasmon resonance, and theoretical and experimental results prove that the binary LaB₆Sm, Eu, Yb and other elements are doped in crystal lattices, so that the wavelength of transmitted light can generate red shift.

The preparation method of the prior multi-element rare earth boride nano powder comprises a high-temperature solid phase synthesis method (Chengdahei, multi-element rare earth hexaboride Sm_1-xEu_xB₆Preparation of nanopowders, characterization and study of light absorption Properties [ D]University of inner Mongolia, 2020.), evaporative condensation (Pandawn Sword, Baulihong, Ningjun, et al_1-xEu_xB₆Preparation of the powder and light absorption study [ J]Journal of physics, 2020.), low temperature solid phase reaction method (Mattox t.m., Coffman d.k., Roh i., et al₆ from IR to near-IR via Eu-doping[J]Materials,2018,11(2): 226), and the like. Other methods such as mechanochemical synthesis, iodine-assisted magnesium thermal reduction, and stirring ball milling for preparing binary REB₆The tree is built on the aspect. In addition, patent CN 111285380 a discloses a method for preparing multiple rare earth co-doped boride nano powder by a microwave solid phase method. The preparation methods have the disadvantages of high reaction temperature, high energy consumption, high pressure, ball milling and other reaction conditions in the preparation process, complicated preparation process, long period, more introduced impurities, high equipment requirement, high preparation cost and unsuitability for industrial production.

Disclosure of Invention

The invention aims to solve the technical problem that the multi-element rare earth boride nano powder and the preparation method thereof are provided aiming at the defects of the prior art, and the prepared multi-element rare earth boride nano powder has high yield, simplifies the process and improves the production efficiency.

The invention discloses a preparation method of multi-element rare earth boride nano powder, which comprises the following steps:

s1, use La₂O₃、RE₂O₃、B₂O₃And Ca as raw materials, uniformly mixing and prepressing into blocks to prepare block blanks;

s2, heating the massive blank in the S1 in a vacuum or inert atmosphere protection condition at a preset heating temperature of 800-1000 ℃ to prepare a multi-element rare earth boride reaction product;

s3, repeatedly washing the reaction product of the multicomponent rare earth boride in S2 to be neutral by acid washing and pure water, filtering and drying in vacuum to obtain the multicomponent rare earth boride La_1-xRE_xB₆Nano-powder of which 0<x<1。

The multi-element rare earth boride nano powder prepared by the method has high yield, high purity, simple purification process and high production efficiency.

The synthetic route is as follows:

(1-x)La₂O₃+xRE₂O₃+6B₂O₃+21Ca＝2La_1-xRE_xB₆+21CaO

wherein Ca can be Ca particle or RE₂O₃The rare earth oxide is obtained, and the purity of each raw material is as follows: la₂O₃Purity is more than or equal to 99.99 percent, RE₂O₃Purity not less than 99.99%, B₂O₃The purity is more than or equal to 99.9 percent, and the purity of Ca particles is more than or equal to 99 percent.

Preferably, the inert atmosphere in the S2 is argon, and when the temperature reaches 400-500 ℃, argon is introduced.

Preferably, the purity of the argon is more than or equal to 99.99 percent, and the pressure is 0.02-0.1 MPa after the argon is introduced.

Preferably, dilute hydrochloric acid is adopted for washing in S3, the concentration of the dilute hydrochloric acid solution is 2-8 mol/L, and the washing temperature is 40-60 ℃. According to the amount of reaction products, dilute hydrochloric acid with different concentrations and temperatures is adopted, so that the reaction rate of byproducts is improved, the cleaning time is shortened, and the purity of the rare earth hexaboride nano powder is improved.

Preferably, in S2, a three-stage heating mode is adopted to heat up to a preset heating temperature, then heat preservation is carried out for 1-2 h, heating is started when the vacuum degree is lower than 0.01Pa, wherein in the first heating stage, the temperature is raised from room temperature to 600-750 ℃, and the temperature raising rate is 6-10 ℃/min; in the second heating temperature rise stage, the temperature is raised from 600-750 ℃ to 750-900 ℃, and the temperature rise rate is 3-5 ℃/min; in the third heating temperature rise stage, the temperature is raised from 750-900 ℃ to a preset heating temperature, and the temperature rise rate is 1-2 ℃/min. This application adopts three heating stage respectively, and three heating stage adopts different heating rate respectively, can reduce the energy consumption, appears raw materials when can avoiding high temperature again and sprays, splash etc..

Preferably, after the heat preservation is finished, the temperature is reduced at the cooling rate of 15-25 ℃/min, and the reaction product of the multi-element rare earth boride is cooled to room temperature and taken out. The proper cooling rate is selected, the particle size of the powder particles can be controlled, and the crystallinity of the crystal particles is improved.

Preferably, RE₂O₃Is Eu₂O₃、Sm₂O₃、Yb₂O₃One or two of them.

Preferably, (La)₂O₃+RE₂O₃)、B₂O₃The molar ratio of Ca to Ca is 1:6 (21-30), wherein the molar mass of Ca is slightly excessive, the reaction process is ensured, and the reaction efficiency is improved.

The invention also discloses the polynary rare earth boride nano powder prepared by the preparation method of the polynary rare earth boride nano powder, wherein the purity of the polynary rare earth boride nano powder is more than or equal to 99.8 percent, and the particle size of the powder is 20-120 nm.

La of the invention_1-xEu_xB₆In the preparation method of the nano powder, La is treated at different reduction temperatures₂O₃-Eu₂O₃-B₂O₃Phase analysis of the reaction product of the-Ca mixed system, as shown in FIG. 7, revealed that the product LaEuB was produced in addition to the theoretical synthetic route₆And CaO main phase diffraction peak accompanied by Ca (OH)₂、Ca₃(BO₃)₂、CaB₂O₄And CaB₄O₇Diffraction peaks, but lower diffraction intensities, indicate lower levels in the reaction product. The analysis results of the reaction product (FIG. 7) according to the present invention were also not shownNow LaEuBO₃A compound is provided.

In view of Ca₃(BO₃)₂、CaB₂O₄、CaB₄O₇Etc. belonging to salts, La in the target product of the invention_1-xRE_xB₆The nucleation and the growth of the compound are carried out in a liquid molten salt environment medium, the nucleation is mainly carried out in an atom migration mode, and the temperature of the environment medium and the granularity of the raw materials are key influence factors; the heat preservation time and the cooling rate determine the crystallinity and the growth degree of the crystal grains. Increasing the reaction temperature (ambient medium temperature) or increasing the incubation time will cause La to form_1-xRE_xB₆The particles grow rapidly, resulting in an increase in the final particle size. Meanwhile, the over-slow cooling rate easily causes the coarse and conglobation of powder particles, while the over-fast cooling rate causes the fine powder particles but possibly low crystallinity. Therefore, a series of La with different particle size distributions can be prepared by regulating and controlling the reaction temperature (800-1000 ℃), the heat preservation time (1-2 h), the cooling rate (15-25 ℃/min) and the like_1-xRE_xB₆Compared with the nano powder prepared under the vacuum reaction condition, the yield of the nano powder prepared by the reaction under the argon protective atmosphere is obviously improved.

Compared with the prior art, the invention has the following beneficial effects:

1. compared with solid phase reaction (carbothermal reaction and borothermal reaction), the method has the advantages that the reaction temperature is low, the diffusion rate of RE and B atoms is improved due to the existence of a liquid phase environment, the reaction time is shortened, and the energy consumption is reduced.

2. Compared with a magnesiothermic reduction method or a mechanochemical method (magnesium is taken as a reducing agent), the calcium thermal reduction process reduces La_{1- x}RE_xBO₃The compound forming probability improves the yield of the rare earth hexaboride, simplifies the purification process in the preparation of the rare earth hexaboride by the magnesiothermic reduction method, and improves the production efficiency.

3. The invention reduces the additional working procedures in the conventional preparation method of the rare earth hexaboride powder, reduces the introduction of impurities in the intermediate process, improves the purity of the powder and realizes the La_1-xRE_xB₆Controllable preparation of nano powder; la_1-xRE_xB₆The nano powder is in a single-phase structure, the particle size distribution is uniform through SEM analysis, the purity of the nano powder is more than or equal to 99.8% through EDS energy spectrum analysis, the process is simple and easy to control, the cost and the energy consumption are low, and the method is suitable for industrial production. The synthesized high-purity nano powder has small particle size, good dispersibility and high surface activity.

Drawings

FIG. 1 is La prepared in example 1_0.8Eu_0.2B₆XRD spectrogram of the nano powder.

FIG. 2 is La prepared in example 1_0.8Eu_0.2B₆SEM image of the nanopowder.

FIG. 3 is La prepared in example 2_0.6Eu_0.4B₆XRD spectrogram of the nano powder.

FIG. 4 is La prepared in example 3_0.4Eu_0.6B₆XRD spectrogram of the nano powder.

FIG. 5 is La prepared in example 4_0.2Eu_0.8B₆XRD spectrogram of the nano powder.

FIG. 6 shows examples 1 to 4 and comparative example nano La_1-xEu_xB₆Absorption spectra of the powders are compared.

FIG. 7 shows the preparation of La by calcium thermal reduction (800 ℃ C.)_1-xEu_xB₆XRD spectrum of reaction product.

Detailed Description

The invention is further described with reference to the drawings and specific preferred embodiments, but the invention is not limited to the scope of protection. It is to be noted that, for those skilled in the art, changes and modifications of the chemical components of the raw materials and the application range of the present invention can be made without departing from the spirit and scope of the present invention.

Example 1

Multi-element rare earth boride La_1-xEu_xB₆Nano powder and its preparing process, La_0.8Eu_0.2B₆For example, the method comprises the following steps:

step 1: raw material La₂O₃、Eu₂O₃、B₂O₃And Ca particles are weighed according to the stoichiometric ratio of 0.8:0.2:6:21, and La is respectively weighed₂O₃16.29g、Eu₂O₃4.4g、B₂O₃26.1g and 68.4g of Ca particles, wherein the excess coefficient of calcium is multiplied by 1.3, the raw materials are uniformly mixed and then pressed into a blocky blank, and the blocky blank is placed in a crucible;

step 2: placing the crucible in a vacuum carbon tube furnace, vacuumizing until the vacuum degree is lower than 0.01Pa, starting heating, and introducing argon into the furnace to 0.05MPa when the temperature reaches 450 ℃; adopt the syllogic heating mode to heat up, include: heating from room temperature to 600 ℃ at a heating rate of 8 ℃/min, heating from 600 ℃ to 750 ℃ at a heating rate of 4 ℃/min, starting heat preservation from 750 ℃ to 800 ℃ at a heating rate of 1 ℃/min, starting cooling after heat preservation for 1h, cooling to room temperature at a cooling rate of 15 ℃/min, and taking out;

and step 3: grinding and acid-washing the synthetic product in the step 2 (2mol/L, dilute hydrochloric acid at 40 ℃), repeatedly washing the synthetic product to be neutral, filtering and drying the product in vacuum to obtain La_0.8Eu_0.2B₆Nano powder;

prepared La_0.8Eu_0.2B₆The sample of the nano powder is in a single-phase structure after being analyzed by X-ray diffraction, and an XRD (X-ray diffraction) spectrum is shown in figure 1; la_0.8Eu_0.2B₆As shown in FIG. 2, the SEM image of the nano-powder shows that the powder particles are cubic, uniformly distributed, and partially agglomerated, and the particle size distribution of the powder particles is 25 nm-88 nm by counting the size distribution of the powder particles. By EDS (electron-dispersive spectroscopy) analysis, the chemical purity of the powder reaches 99.85%, and the yield of the powder is calculated and analyzed to be 91.4%. Determination of La by UV/Vis/NIR Spectrophotometer_0.8Eu_0.2B₆The absorption spectra of the nanopowder samples, as shown in FIG. 6, are due to visible UV instrument lamp change and infrared to visible change detector, respectively, as well as the curve agitation near wavelengths 300nm and 875 nm. Nano La_0.8Eu_0.2B₆In the ultraviolet region around 350nm and around 1000nmShows strong absorption in the near infrared region, and an absorption valley (absorption minimum) occurs at 655nm in the visible region, i.e., a maximum of the transmitted light wavelength.

Example 2

Multi-element rare earth boride La_1-xEu_xB₆Nano powder and its preparing process, La_0.6Eu_0.4B₆For example, the method comprises the following steps:

step 1: raw material La₂O₃、Eu₂O₃、B₂O₃And Ca particles are weighed according to the stoichiometric ratio of 0.6:0.4:6:21, and La is respectively weighed₂O₃12.22g、Eu₂O₃8.8g、B₂O₃26.1g and 68.4g of Ca particles, wherein the excess coefficient of calcium is multiplied by 1.3, the raw materials are uniformly mixed and then pressed into a blocky blank, and the blocky blank is placed in a crucible;

step 2: placing the crucible in a vacuum carbon tube furnace, vacuumizing until the vacuum degree is lower than 0.01Pa, starting heating, and introducing argon into the furnace to 0.05MPa when the temperature reaches 450 ℃; adopt the syllogic heating mode to heat up, include: heating from room temperature to 600 ℃ at a heating rate of 8 ℃/min, heating from 600 ℃ to 750 ℃ at a heating rate of 4 ℃/min, starting heat preservation from 750 ℃ to 800 ℃ at a heating rate of 1 ℃/min, starting cooling after heat preservation for 1h, cooling to room temperature at a cooling rate of 15 ℃/min, and taking out;

and step 3: grinding and acid-washing the synthetic product in the step 2 (2mol/L, dilute hydrochloric acid at 40 ℃), repeatedly washing the synthetic product to be neutral, filtering and drying the product in vacuum to obtain La_0.6Eu_0.4B₆Nano powder;

prepared La_0.6Eu_0.4B₆The sample of the nano powder is in a single-phase structure after being analyzed by X-ray diffraction, and an XRD (X-ray diffraction) spectrum is shown in figure 3; the chemical purity of the product can reach 99.89% by EDS energy spectrum analysis, the particle size distribution of the powder is calculated to be 28-90 nm by counting the size distribution of the powder particles, and the yield of the powder analyzed by calculation is 92.1%. Determination of La by UV/Vis/NIR Spectrophotometer_0.6Eu_0.4B₆Absorption spectra of nanopowder samples, e.g.As shown in fig. 6, the transmitted light wavelength (absorption valley) is 720 nm.

Example 3

Multi-element rare earth boride La_1-xEu_xB₆Nano powder and its preparing process, La_0.4Eu_0.6B₆For example, the method comprises the following steps:

step 1: raw material La₂O₃、Eu₂O₃、B₂O₃And Ca particles are weighed according to the stoichiometric ratio of 0.4:0.6:6:21, and La is respectively weighed₂O₃8.14g、Eu₂O₃13.2g、B₂O₃26.1g and 68.4g of Ca particles, wherein the excess coefficient of calcium is multiplied by 1.3, the raw materials are uniformly mixed and then pressed into a blocky blank, and the blocky blank is placed in a crucible;

step 2: placing the crucible in a vacuum carbon tube furnace, vacuumizing until the vacuum degree is lower than 0.01Pa, starting heating, and introducing argon into the furnace to 0.05MPa when the temperature reaches 450 ℃; adopt the syllogic heating mode to heat up, include: heating from room temperature to 600 ℃ at a heating rate of 8 ℃/min, heating from 600 ℃ to 750 ℃ at a heating rate of 4 ℃/min, starting heat preservation from 750 ℃ to 800 ℃ at a heating rate of 1 ℃/min, starting cooling after heat preservation for 1h, cooling to room temperature at a cooling rate of 15 ℃/min, and taking out;

and step 3: grinding and acid-washing the synthetic product in the step 2 (2mol/L, dilute hydrochloric acid at 40 ℃), repeatedly washing the synthetic product to be neutral, filtering and drying the product in vacuum to obtain La_0.4Eu_0.6B₆Nano powder;

prepared La_0.4Eu_0.6B₆The sample of the nano powder is in a single-phase structure after being analyzed by X-ray diffraction, and an XRD (X-ray diffraction) spectrum is shown in figure 4; the chemical purity of the product can reach 99.87% by EDS energy spectrum analysis, the particle size distribution of the powder is 32-95 nm by counting the size distribution of the powder particles, and the yield of the powder is 90.7% by calculation and analysis. Determination of La by UV/Vis/NIR Spectrophotometer_0.4Eu_0.6B₆The absorption spectrum of the nanopowder sample, as shown in FIG. 6, shows the transmitted light wavelength (absorption valley) of 825 nm.

Example 4

Multi-element rare earth boride La_1-xEu_xB₆Nano powder and its preparing process, La_0.2Eu_0.8B₆For example, the method comprises the following steps:

step 1: raw material La₂O₃、Eu₂O₃、B₂O₃And Ca particles are weighed according to the stoichiometric ratio of 0.2:0.8:6:21, and La is respectively weighed₂O₃4.07g、Eu₂O₃17.6g、B₂O₃26.1g and 68.4g of Ca particles, wherein the excess coefficient of calcium is multiplied by 1.3, the raw materials are uniformly mixed and then pressed into a blocky blank, and the blocky blank is placed in a crucible;

step 2: placing the crucible in a vacuum carbon tube furnace, vacuumizing until the vacuum degree is lower than 0.01Pa, starting heating, and introducing argon into the furnace to 0.05MPa when the temperature reaches 450 ℃; adopt the syllogic heating mode to heat up, include: heating from room temperature to 600 ℃ at a heating rate of 8 ℃/min, heating from 600 ℃ to 750 ℃ at a heating rate of 4 ℃/min, starting heat preservation from 750 ℃ to 800 ℃ at a heating rate of 1 ℃/min, starting cooling after heat preservation for 1h, cooling to room temperature at a cooling rate of 15 ℃/min, and taking out;

and step 3: grinding and acid-washing the synthetic product in the step 2 (2mol/L, dilute hydrochloric acid at 40 ℃), repeatedly washing the synthetic product to be neutral, filtering and drying the product in vacuum to obtain La_0.2Eu_0.8B₆Nano powder;

prepared La_0.2Eu_0.8B₆The sample of the nano powder is in a single-phase structure after being analyzed by X-ray diffraction, and an XRD (X-ray diffraction) spectrum is shown in figure 5; the chemical purity of the product can reach 99.82% by EDS energy spectrum analysis, the particle size distribution of the powder is 30-90 nm by counting the size distribution of the powder particles, and the yield of the powder is 90.5% by calculation and analysis. Determination of La by UV/Vis/NIR Spectrophotometer_0.2Eu_0.8B₆The absorption spectrum of the nanopowder sample, as shown in FIG. 6, shows the transmitted light wavelength (absorption valley) of 1060 nm.

Example 5

Multi-element rare earth boride La_1-xEu_xB₆Nano powder and its preparing process, La_0.6Eu_0.4B₆For example, the method comprises the following steps:

step 1: raw material La₂O₃、Eu₂O₃、B₂O₃And Ca particles are weighed according to the stoichiometric ratio of 0.6:0.4:6:21, and La is respectively weighed₂O₃36.65g、Eu₂O₃26.4g、B₂O₃78.3g and 205.2g of Ca particles, wherein the excess coefficient of calcium is multiplied by 1.3, the raw materials are uniformly mixed and then pressed into a blocky blank, and the blocky blank is placed in a crucible;

step 2: placing the crucible in a vacuum carbon tube furnace, vacuumizing until the vacuum degree is lower than 0.01Pa, starting heating, and introducing argon into the furnace to 0.06MPa when the temperature reaches 450 ℃; adopt the syllogic heating mode to heat up, include: heating from room temperature to 650 ℃ at a heating rate of 8 ℃/min, heating from 650 ℃ to 800 ℃ at a heating rate of 5 ℃/min, starting heat preservation from 800 ℃ to 900 ℃ at a heating rate of 2 ℃/min, starting cooling after heat preservation for 1.5h, cooling to room temperature at a cooling rate of 20 ℃/min, and taking out;

and step 3: grinding and acid-washing the synthetic product in the step 2 (5mol/L, 50 ℃ dilute hydrochloric acid), repeatedly washing with water to neutrality, filtering and vacuum-drying to obtain La_0.6Eu_0.4B₆Nano powder;

prepared La_0.6Eu_0.4B₆The nano powder is analyzed to be of a single-phase structure through X-ray diffraction, the chemical purity of the nano powder reaches 99.83% through EDS (electron-dispersive spectroscopy) energy spectrum analysis, the particle size distribution of the powder is between 35nm and 105nm through statistics on the size distribution of powder particles, and the yield of the powder is 88.2% through calculation and analysis.

Example 6

Multi-element rare earth boride La_1-xEu_xB₆Preparation method of nano powder with La_0.6Eu_0.4B₆For example, the method comprises the following steps:

step 1: raw material La₂O₃、Eu₂O₃、B₂O₃And Ca particles are calculated according to the chemicalThe weight ratio was 0.6:0.4:6:21 (molar ratio), and La was weighed separately₂O₃73.31g、Eu₂O₃52.8g、B₂O₃156.6g and 615.6g of Ca particles, wherein the excess coefficient of calcium is multiplied by 1.3, the raw materials are uniformly mixed and then pressed into a blocky blank which is placed in a crucible;

step 2: placing the crucible in a vacuum carbon tube furnace, vacuumizing until the vacuum degree is lower than 0.01Pa, starting heating, and introducing argon into the furnace to 0.08MPa when the temperature reaches 450 ℃; adopt the syllogic heating mode to heat up, include: heating from room temperature to 750 ℃ at a heating rate of 10 ℃/min, heating from 750 ℃ to 900 ℃ at a heating rate of 5 ℃/min, heating from 900 ℃ to 1000 ℃ at a heating rate of 2 ℃/min, preserving heat, cooling after preserving heat for 2h, cooling to room temperature at a cooling rate of 25 ℃/min, and taking out;

and step 3: grinding and acid-washing the synthetic product in the step 2 (8mol/L, 60 ℃ dilute hydrochloric acid), repeatedly washing with water to neutrality, filtering and vacuum-drying to obtain La_0.6Eu_0.4B₆Nano powder;

prepared La_0.6Eu_0.4B₆The nano powder is analyzed to be of a single-phase structure through X-ray diffraction, the chemical purity of the nano powder reaches 99.81 percent through EDS (electron-dispersive spectroscopy) energy spectrum analysis, the particle size distribution of the powder is between 40 and 120nm through statistics on the size distribution of powder particles, and the yield of the powder is 87.3 percent through calculation and analysis.

Comparative example 1

Rare earth boride LaB₆The preparation method of the nano powder comprises the following steps:

step 1: raw material La₂O₃、B₂O₃And Ca particles are weighed according to the stoichiometric ratio of 0.8:0.2:6:21, and La is respectively weighed₂O₃20.37g、B₂O₃26.1g and 68.4g of Ca particles, wherein the excess coefficient of calcium is multiplied by 1.3, the raw materials are uniformly mixed and then pressed into a blocky blank, and the blocky blank is placed in a crucible;

step 2: placing the crucible in a vacuum carbon tube furnace, vacuumizing until the vacuum degree is lower than 0.01Pa, starting heating, and introducing argon into the furnace to 0.05MPa when the temperature reaches 450 ℃; adopt the syllogic heating mode to heat up, include: heating from room temperature to 600 ℃ at a heating rate of 8 ℃/min, heating from 600 ℃ to 750 ℃ at a heating rate of 4 ℃/min, starting heat preservation from 750 ℃ to 800 ℃ at a heating rate of 1 ℃/min, starting cooling after heat preservation for 1h, cooling to room temperature at a cooling rate of 15 ℃/min, and taking out;

and step 3: grinding and acid-washing the synthetic product in the step 2 (2mol/L, dilute hydrochloric acid at 40 ℃), repeatedly washing the synthetic product to be neutral, filtering and drying the product in vacuum to obtain LaB₆Nano powder;

prepared LaB₆The nano powder is analyzed to be of a single-phase structure through X-ray diffraction, the chemical purity of the nano powder reaches 99.89% through EDS (electron-dispersive spectroscopy) energy spectrum analysis, the particle size distribution of the powder is 20-80 nm through statistics of the size distribution of powder particles, and the yield of the powder is calculated and analyzed to be 92.5%. LaB determination by UV/Vis/NIR Spectrophotometer₆The absorption spectrum of the nano-powder sample, as shown in FIG. 6, shows a wavelength of 595nm in transmitted light (absorption valley).

Comparative example 2

The preparation is analogous to example 6, with the difference that: and 2, in the heating process of the step 2, argon is not introduced into the vacuum carbon tube furnace.

Prepared La_0.6Eu_0.4B₆The sample of the nano powder is in a single-phase structure after being analyzed by X-ray diffraction, the chemical purity of the nano powder reaches 99.8 percent through EDS (electron-dispersive spectroscopy) energy spectrum analysis, the particle size distribution of the powder is between 40 and 115nm, and the yield of the powder is calculated and analyzed to be 68.5 percent.

As can be seen from the above examples, La prepared according to the present invention_1-xEu_xB₆The nano powder is in a single-phase structure, the purity of the nano powder is more than or equal to 99.8%, the powder particles are cubic and are uniformly distributed, and the particle size is 20-120 nm. FIG. 6 shows the comparison of the absorption spectrum with that of LaB₆In contrast, Eu-doped LaB₆La formed_1-xEu_xB₆The transmitted light wavelength generates red shift, and the transmitted light wavelength continuously increases along with the increase of Eu doping amount, thereby enhancing the near infrared light absorption capability of the Eu infrared absorption electric heater. At the same time, La_1-xEu_xB₆Preparation of nano powderThe yield of the product is obviously improved under the protection of argon atmosphere in the process.