CN113772711B - Method for preparing rare earth metal hexaboride through aluminothermic reduction - Google Patents

Method for preparing rare earth metal hexaboride through aluminothermic reduction Download PDF

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CN113772711B
CN113772711B CN202110927326.9A CN202110927326A CN113772711B CN 113772711 B CN113772711 B CN 113772711B CN 202110927326 A CN202110927326 A CN 202110927326A CN 113772711 B CN113772711 B CN 113772711B
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rare earth
earth metal
hexaboride
powder
reduction
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CN113772711A (en
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张国华
汪宇
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University of Science and Technology Beijing USTB
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University of Science and Technology Beijing USTB
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F17/00—Compounds of rare earth metals
    • C01F17/20—Compounds containing only rare earth metals as the metal element
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F17/00—Compounds of rare earth metals
    • C01F17/10—Preparation or treatment, e.g. separation or purification
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Abstract

A method for preparing rare earth metal hexaboride through aluminothermic reduction relates to the technical field of rare earth metal hexaboride preparation, and comprises the following steps: step 1: uniformly mixing rare earth oxide, boron carbide and metal aluminum to obtain a mixed raw material; step 2: heating the mixed raw materials in an inert atmosphere to perform high-temperature reduction reaction; and step 3: sequentially cooling, crushing and finely grinding the product obtained after the high-temperature reduction reaction is finished to obtain reduced product powder; and 4, step 4: and sequentially carrying out alkali washing, filtering, rinsing and drying on the reduction product powder to obtain the rare earth metal hexaboride. The method adopts rare earth oxide, boron carbide and metallic aluminum as raw materials to prepare the rare earth metal hexaboride, solves the problem of strong heat release in the traditional method, greatly reduces the reaction heat effect in the high-temperature process, and comprehensively considers the economy and the practicability of the method.

Description

Method for preparing rare earth metal hexaboride through aluminothermic reduction
Technical Field
The invention relates to the technical field of rare earth metal hexaboride preparation, in particular to a method for preparing rare earth metal hexaboride through aluminothermic reduction.
Background
The rare earth metal boride becomes a high-end electron emission cathode material with extremely wide application at present by virtue of the excellent electron emission characteristic of the rare earth metal boride. Such as LaB6And CeB6Has been largely applied to high-end equipment such as an electron microscope, an electron beam etching system, an X-ray source and the like. In addition, rare earth borides tend to have melting points near 3000 ℃ and are ceramic materials that can be used in extreme conditions. Meanwhile, the rare earth metal boride also has special electromagnetic performance. However, the currently available methods for producing rare earth borides are generally elemental synthesis methods, in which a combination reaction is carried out directly using rare earth metals and amorphous boron powder. As the two raw materials are not easy to obtain, the obtaining cost of the rare earth metal boride is extremely high. In addition, the direct elemental synthesis is accompanied by a strong exotherm, making it difficult to produce the product in large quantities at a time. Both of these limitations limit the large-scale application of this material. The invention aims to design a set of high-temperature reaction process with weak chemical heat effect by using easily-obtained raw materials such as rare earth oxide, boron carbide and metallic aluminum, and realize the purpose of obtaining rare earth metal hexaboride under a mild condition.
Disclosure of Invention
The invention aims to provide a method for preparing rare earth metal hexaboride on a large scale by using cheap raw materials under a milder condition. The invention adopts rare earth oxide, boron carbide and metallic aluminum as raw materials to prepare rare earth metal hexaboride, and the raw materials are common metallurgy, material and chemical products and have lower price. And special conditions are not involved in the transportation and storage processes of the raw materials, so that the production, operation and maintenance costs are further reduced. In the invention, boron carbide is used as a boron source, and compared with the commonly used boron oxide, the thermal effect in the reaction process is lower, thereby being beneficial to realizing the mild and controllable reaction process. In addition, the metal aluminum is used as a raw material, and the aluminum can well perform thorough composite high-temperature reaction with rare earth oxide and boron carbide in consideration of the effect of the aluminum on both a reducing agent and a decarbonizing agent in the high-temperature reaction process. In addition, at high temperature, the vapor pressure of aluminum is far less than that of other metal reducing agents such as potassium, calcium, sodium, magnesium and the like, so that the safety in the actual operation process is higher. Based on the analysis, the method well solves the problems of high raw material cost and strong heat release in the traditional method for preparing the rare earth metal hexaboride, and greatly reduces the raw material cost and the reaction heat effect in the high-temperature process. The invention comprehensively considers the economy and the feasibility of the method and provides favorable conditions for the industrial implementation of the method.
According to a first aspect of the present invention there is provided a process for the aluminothermic production of a rare earth metal hexaboride, the process comprising:
step 1: uniformly mixing rare earth oxide, boron carbide and metal aluminum to obtain a mixed raw material;
step 2: heating the mixed raw materials in an inert atmosphere to perform high-temperature reduction reaction;
and step 3: sequentially cooling, crushing and finely grinding the product obtained after the high-temperature reduction reaction is finished to obtain reduced product powder;
and 4, step 4: and sequentially carrying out alkali washing, filtering, rinsing and drying on the reduction product powder to obtain the rare earth metal hexaboride.
Further, the rare earth oxide has a purity of greater than 99 wt.%;
the boron carbide is a boron-carbon compound with a boron content of 75-90 wt.%;
the metal aluminum is powder or particles.
Further, in the mixed raw materials, the molar ratio of the boron element to the rare earth element is (5.8-8.0): 1;
the molar weight of the aluminum element is not less than 4/3nC+2/3nOAnd not higher than 4nC+2nO(ii) a Wherein n isCIs the molar amount of carbon element; n isOIs the molar amount of the oxygen element.
Further, the temperature of the high-temperature reduction reaction is 1000-1600 ℃, and the time is 2-8 h.
Further, step 4 specifically includes: placing the reduction product powder in alkali liquor, and carrying out alkali washing at the temperature of 30-90 ℃ for 4-12 h; and after the alkaline washing is finished, filtering the leached slurry, washing the filtered solid powder, and drying the washed powder to obtain the rare earth metal hexaboride.
Furthermore, a sodium hydroxide solution with the mass fraction of 25-35 wt.% or a potassium hydroxide solution with the mass fraction of 35-42 wt.% is used in the alkali washing process.
According to a second aspect of the present invention there is provided a rare earth metal hexaboride, which is prepared by the process described above.
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
(1) the invention adopts rare earth oxide (RE)xOy) And boron carbide and metal aluminum as raw materials, wherein the rare earth oxide is a rare earth metal source, the boron carbide is a boron source, and the metal aluminum is a deoxidizer and a decarbonizer. In the high-temperature reduction process, the rare earth oxide is reduced by metallic aluminum, the boronization is completed in the aluminum liquid, and the redundant carbon element is fixed into aluminum carbide by the aluminum. The raw materials are common industrial products in the fields of metallurgy, materials and chemical industry, and are easy to obtain, so that the cost of the raw materials in the implementation process of the invention is low;
(2) compared with the element synthesis method and the magnesiothermic reduction method which are widely used at present, the aluminothermic reaction of the invention has low heat effect and adiabatic temperature (T)ad298) Only 1200-1300 ℃, which is far lower than the traditional method (T)ad2982300 to 2700 ℃ for the rest. Thus, it is an object of the present invention to provide a method for producing a semiconductor deviceThe low reaction heat effect ensures that the conditions in the implementation process of the invention are extremely mild, and the high-temperature reaction process is safe and controllable, thus being suitable for preparing the compounds in large scale.
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The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.
In the drawings:
FIG. 1 is a specific flow chart of the process for preparing rare earth metal hexaboride according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
The method for preparing rare earth metal hexaboride through aluminothermic reduction shown in figure 1 comprises the following specific preparation steps:
(1) rare Earth (RE)xOy) Boron carbide (B)4C) Uniformly mixing with metal aluminum (Al);
(2) heating the mixed raw material obtained in the step (1) in a high-temperature furnace in an inert atmosphere to perform high-temperature reduction reaction;
(3) crushing and finely grinding the cooled product after the reaction is finished to obtain aluminothermic reduction product powder;
(4) and carrying out alkali washing, filtering, rinsing and drying on the obtained aluminothermic reduction product to obtain rare earth metal hexaboride powder.
Further, in the step (1), the rare earth oxide is a rare earth oxide with any valence state, and the content of the rare earth oxide is more than 99 wt.%; the boron carbide is a boron-carbon compound with a boron content of 75-90 wt.%; the metallic aluminum can be powder or granules.
Further, in the step (1), according to the stoichiometric ratio of boron boronized by the target prepared rare earth metal, the molar ratio of boron element to the rare earth metal element(nB/nRE) 5.8 to 8.0; according to the molar quantity of C in the raw materials (n)C) And O moles (n)C) The amount of Al added, the molar amount of aluminum added (n)Al) Should not be less than 4/3nC+2/3nOAnd is not higher than 4nC+2nO。
Further, a sodium hydroxide solution with the mass fraction of 25-35 wt.% or a potassium hydroxide solution with the mass fraction of 35-42 wt.% is used in the alkali washing process. The temperature of the alkaline leaching is 30-90 ℃, and the alkaline leaching time is 4-12 h.
The first embodiment is as follows:
(1) lanthanum oxide (La) with a purity of 99.99 wt.%2O3) Boron carbide (B) with a boron content of 74.4 wt.%4C) And pure metal aluminum powder (Al) are weighed according to the molar ratio of 1:3:9 and uniformly mixed.
(2) And (3) placing the mixed material in the step (1) into a high-temperature furnace filled with argon gas, heating to 1400 ℃, keeping for 6 hours, and taking out the material after the high-temperature furnace is cooled to 20-50 ℃.
(3) Crushing the reduction product obtained in (2) to-50 meshes, placing the product in 30 wt.% sodium hydroxide solution, and performing alkali washing at 90 ℃ for 8 h. And after the alkaline washing is finished, filtering the leached slurry, washing the filtered solid powder, and drying the washed powder. Finally, pure lanthanum boride (LaB) is obtained6) And (3) powder.
Example two:
(1) cerium oxide (CeO) having a purity of 99.5 wt.%2) Boron carbide (B) with a boron content of 85.4 wt.%13C2) And pure metallic aluminum particles (Al) were weighed and mixed uniformly in a molar ratio of 1:0.46: 12.
(2) And (3) placing the mixed material in the step (1) into a high-temperature furnace filled with argon, heating to 1500 ℃, keeping for 4 hours, and taking out the material after the high-temperature furnace is cooled to 20-50 ℃.
(3) Crushing the reduction product obtained in (2) to-50 meshes, placing the product in 25 wt.% sodium hydroxide solution, and carrying out alkali washing at 65 ℃ for 12 h. And after the alkaline washing is finished, filtering the leached slurry, washing the filtered solid powder, and drying the washed powder. Finally, pure boronization is obtainedCerium (CeB)6) And (3) powder.
Example three:
(1) praseodymium oxide (Pr) with the purity of 99 wt.% is added6O11) Boron carbide (B) with a boron content of 77.6 wt.%4C) And pure metal aluminum powder (Al) are weighed according to the molar ratio of 1:9:30 and uniformly mixed.
(2) And (3) placing the mixed material in the step (1) into a high-temperature furnace filled with argon, heating to 1500 ℃, keeping for 4 hours, and taking out the material after the high-temperature furnace is cooled to 20-50 ℃.
(3) Crushing the reduction product obtained in the step (2) to-50 meshes, placing the product in 30 wt.% sodium hydroxide solution, and carrying out alkali washing at 90 ℃ for 8 h. And after the alkaline washing is finished, filtering the leached slurry, washing the filtered solid powder, and drying the washed powder. Finally, pure praseodymium boride (PrB) is obtained6) And (3) powder.
The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments. The present invention is not limited to the above-described embodiments, which are only illustrative and not restrictive, and those skilled in the art can make many modifications without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (4)

1. A method for preparing rare earth metal hexaboride through aluminothermic reduction, which is characterized by comprising the following steps:
step 1: uniformly mixing rare earth oxide, boron carbide and metal aluminum to obtain a mixed raw material; the molar ratio of the boron element to the rare earth element is (5.8-8.0): 1; the molar weight of the aluminum element is not less than 4/3nC+2/3nOAnd not higher than 4nC+2nO(ii) a Wherein n isCIs the molar amount of carbon element; n isOIs the molar amount of oxygen element;
step 2: heating the mixed raw materials in an inert atmosphere to perform a high-temperature reduction reaction, wherein the temperature of the high-temperature reduction reaction is 1000-1500 ℃, and the time is 2-8 hours;
and step 3: sequentially cooling, crushing and finely grinding the product obtained after the high-temperature reduction reaction is finished to obtain reduced product powder;
and 4, step 4: and sequentially carrying out alkali washing, filtering, rinsing and drying on the reduction product powder to obtain the rare earth metal hexaboride.
2. The process for the preparation of rare earth hexaboride by aluminothermic reduction according to claim 1, wherein the rare earth oxide has a purity of greater than 99 wt.%;
the boron carbide is a boron-carbon compound with a boron content of 75-90 wt.%;
the metal aluminum is powder or particles.
3. The method for preparing rare earth metal hexaboride through aluminothermic reduction according to claim 1, wherein the step 4 specifically comprises: placing the reduction product powder in alkali liquor, and carrying out alkali washing at the temperature of 30-90 ℃ for 4-12 h; and after the alkaline washing is finished, filtering the leached slurry, washing the filtered solid powder, and drying the washed powder to obtain the rare earth metal hexaboride.
4. The method for preparing rare earth metal hexaboride through thermite reduction according to claim 3, wherein a sodium hydroxide solution with a mass fraction of 25-35 wt.% or a potassium hydroxide solution with a mass fraction of 35-42 wt.% is used in the alkali washing process.
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