CN110422883B - Method for preparing FeAs powder by mechanical alloying - Google Patents
Method for preparing FeAs powder by mechanical alloying Download PDFInfo
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- CN110422883B CN110422883B CN201910798878.7A CN201910798878A CN110422883B CN 110422883 B CN110422883 B CN 110422883B CN 201910798878 A CN201910798878 A CN 201910798878A CN 110422883 B CN110422883 B CN 110422883B
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Abstract
The invention discloses a method for preparing FeAs powder by mechanical alloying, which comprises the following steps: 1) mixing iron powder and arsenic powder according to the proportion of 1:1, putting the mixture into a vacuum ball milling tank, and performing ball milling under the protection of inert atmosphere to perform mechanical alloying reaction; 2) under the protection of inert gas, heating the sample subjected to the mechanical alloying reaction in the step 1) to 100-200 ℃ and preserving heat for 0.5-2 h; then heating to 750-850 ℃, preserving heat for 6-24 h, and cooling to room temperature along with the furnace; 3) and (3) placing the sample cooled in the step 2) into 0.5-4 mol/L diluted hydrochloric acid for stirring treatment, and then carrying out acid washing, water washing and drying to obtain a black FeAs powder sample with high purity and high crystallinity. The invention provides a method for preparing FeAs powder rapidly, massively and at low cost, and the obtained FeAs powder has high purity and high crystallinity and can be used as a precursor for synthesizing an iron-based high-temperature superconducting material.
Description
Technical Field
The invention belongs to the technical field of iron-based high-temperature superconducting materials, and particularly relates to a method for preparing FeAs powder by mechanical alloying.
Background
The transition temperature of the iron-based high-temperature superconducting material breaks through the limit of the traditional Michelan and is the second big high-temperature superconducting family behind the copper-based superconductor. The iron-based high-temperature superconducting material has rich physical properties and great application value, and is beneficial to realization of room-temperature superconductivity and popularization of superconducting technology.
The physical research institute of the Chinese academy of sciences and the research team of the Chinese science and technology university obtain the first-class prize of the national natural science in 2013 by the discovery of the iron-based high-temperature superconductor with more than 40K and the research of a plurality of basic physical properties. In the following years new iron-based superconducting systems such as iron arsenide and iron selenide have been discovered, typical precursors including LaFeAsO, bafea, LiFeAs, FeSe, etc. Theoretical research shows that in an iron arsenide superconducting system, the FeAs layer plays a key role in realizing high-temperature superconductivity.
The preparation of iron-based superconductors is generally divided into two steps. Firstly, synthesizing precursor LnAs (Ln ═ La, Pr, Fe, etc.): respectively and uniformly mixing high-purity La, Pr and Fe powder with As powder, molding and sintering in a high-vacuum quartz tube; then mixing with other component powder required by ReFeAsO according to the mole number required by the chemical formula, forming and sealing in a quartz tube filled with argon gas, and sintering at about 1150 ℃ to prepare a polycrystalline sample of the iron-based superconductor. Therefore, the preparation of precursors is critical in the preparation of iron-based superconductors, and the synthesis of FeAs precursors becomes important due to the necessity of the formation of FeAs layers.
The synthesis of FeAs usually employs a high temperature solid phase reaction. In the literature, high-purity Fe (5N) and high-purity As (6N) are used As raw materials, the raw materials are ground, mixed and placed in a vacuum quartz profile, the temperature is slowly heated to 1000 ℃ and kept for 24 hours, and finally, the product contains 6 wt.% of impure phase FeAs2(Zaikina J V,Batuk M,Abakumov A M,et al.Facile Synthesis of Ba1–xKxFe2As2 Superconductors via Hydride Route[J]Journal of the American Chemical Society,2014,136(48) 169932). The method has expensive raw materials, the pretreatment processes such as weighing, grinding and the like need to be carried out in a glove box, the heating and heat preservation processes are as long as 70 hours, and the energy consumption is high. CN102000815A discloses a negative pressure solid phase reaction preparation method of FeAs powder, wherein the processes of weighing, mixing, grinding and the like of raw materials are all carried out in a glove box, the raw materials are placed in a quartz tube for high temperature negative pressure solid phase reaction after being pressed into tablets, and an XRD (X-ray diffraction) diagram of the product shows that the product contains more impurity phases.
Disclosure of Invention
In order to solve the problems of high cost, easy generation of impurities and the like in the conventional synthesis method, the invention aims to provide a method for preparing FeAs powder with high purity and high crystallinity by taking non-high-purity metal powder as a raw material and utilizing the synergy of mechanical alloying, heat treatment and acid treatment.
In order to achieve the technical purpose, the invention provides a method for preparing FeAs powder by mechanical alloying, which comprises the following steps:
1) mixing iron powder and arsenic powder according to the proportion of 1:1, putting the mixture into a vacuum ball milling tank, and performing ball milling under the protection of inert atmosphere to perform mechanical alloying reaction;
2) under the protection of inert gas, heating the sample subjected to the mechanical alloying reaction in the step 1) to 100-200 ℃ and preserving heat for 0.5-2 h; then heating to 750-850 ℃, preserving heat for 6-24 h, and cooling to room temperature along with the furnace;
3) and (3) placing the sample cooled in the step 2) into 0.5-4 mol/L diluted hydrochloric acid for stirring treatment, and then carrying out acid washing, water washing and drying to obtain a black FeAs powder sample with high purity and high crystallinity.
The technical scheme of the invention is characterized in that the FeAs powder with low purity and low crystallinity is obtained by mechanical alloying, and then the FeAs powder with high purity and high crystallinity is obtained step by step through the synergistic action among the steps according to the implementation sequence of the process steps strictly by combining heat treatment and acid treatment. The invention establishes a ductile-brittle powder ball-milling system based on the physical properties of elementary substances Fe and As, and synthesizes FeAs through mechanical alloying at room temperature; by appropriate heat treatment, the impurity FeAs is realized2Performing annealing for dearsenification to generate FeAs and FeAs, volatilizing unalloyed simple substance As, and recrystallizing and recovering in a low-temperature area; and finally, removing unreacted Fe and iron oxide by adopting acid washing treatment to obtain black FeAs powder with high purity and high crystallinity.
Preferably, in step 1), the purity of both the iron powder and the arsenic powder is greater than >98.0 wt.%.
Preferably, in the step 1), the ball milling conditions are as follows: the rotating speed is 250-400 r/min, the ball-material ratio is 10-20: 1, the time is 8-48 h; the lining of the vacuum ball milling tank is made of stainless steel, corundum or hard alloy, and preferably the stainless steel; the grinding ball is made of stainless steel, corundum or hard alloy, and is preferably corundum; the grinding balls are 3mm, 6mm, 10mm and 15mm in size, and are preferably 6mm and 10mm grinding balls distributed according to a 1:1 weight ratio. Under the optimal conditions, the invention is beneficial to avoiding the phenomena of local cold welding and bottom agglomeration, improving the powder yield of the product and reducing the proportion of impure phases.
Preferably, in the step 1), the ball milling process is continuously operated for 40-60 min and then is suspended for 5-15 min, and the operation is repeated until the ball milling is finished, so that the local cold welding is prevented.
Preferably, in steps 1) and 2), the inert gas is argon or nitrogen, preferably argon.
Preferably, in the step 2), the first temperature rise rate is 10-20 ℃/min, and the second temperature rise rate is 5-10 ℃/min.
Preferably, in the step 3), the solid-to-liquid ratio of the cooled sample to the dilute hydrochloric acid solution is 1 g/10-20 mL, and the stirring treatment time is 12-24 h. The reasonable solid-liquid ratio and the stirring time can effectively improve the removal rate of impurities Fe and iron oxide in unit time, and simultaneously avoid the loss of target products FeAs compounds.
Preferably, in the step 3), the filtering and washing process after the stirring treatment of the dilute hydrochloric acid is acid washing firstly and then water washing, wherein the acid washing adopts 0.2-1 mol/L dilute hydrochloric acid, and the method can effectively prevent iron ions from hydrolyzing to generate hydroxide colloid and ensure the filtering and washing effect.
Compared with the prior art, the invention has the beneficial effects that:
1. the preparation cost is low, and the requirement on the purity of the raw materials is low; the high-temperature treatment process does not need to provide a negative pressure and closed environment, and the high-temperature treatment process can be carried out in a conventional atmosphere furnace, and is short in high-temperature treatment time and relatively low in temperature.
2. The operation is simple and safe: the pretreatment of raw materials in an oxygen-free and water-free environment such as a glove box is not needed; the high temperature treatment process does not involve pressure regulation and the temperature is relatively low.
3. The FeAs product has high crystallinity and high purity.
Drawings
FIG. 1 is an XRD pattern of a sample of FeAs-MA powder obtained in step 2 of example 1 of the present invention.
Fig. 2 is an XRD pattern of a sample of FeAs powder prepared in example 1 of the present invention.
Fig. 3 is an XRD pattern of a sample of the FeAs powder prepared in comparative example 1 of the present invention.
Fig. 4 is an XRD pattern of a sample of the FeAs powder prepared in comparative example 2 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific examples, which are provided for illustration only and are not intended to be limiting.
Example 1
1) Mixing iron powder and arsenic powder with the purity of 99.5 percent and 98 percent respectively according to the molar ratio of 1:1, putting the mixture into a vacuum ball milling tank, and then introducing high-purity argon gas with the pressure of about 0.15 MPa;
2) placing the vacuum ball milling tank in the step 1) on a high-energy planetary ball mill, wherein the lining of the vacuum ball milling tank is made of stainless steel, the grinding balls are 6mm and 10mm grinding balls distributed according to the weight ratio of 1:1, and the ball-material ratio is 10: 1, carrying out mechanical alloying reaction at a rotation speed of 320r/min, continuously operating for 40min in the reaction process, pausing for 5min, reacting for 40h, standing for 2h after the mechanical alloying reaction is finished, and taking out a sample; as shown in figure 1, the XRD diffraction peak of the FeAs-MA sample after ball milling is obviously broadened, the crystallinity is lower, and the FeAs sample contains a large amount of impurity phase2、Fe3O4And As2O3；
3) Taking out the sample in the step 2), placing the sample in a tube furnace purged by argon gas for annealing treatment, raising the temperature from room temperature to 200 ℃ at the speed of 10 ℃/min, and preserving the temperature for 1 h; then heating to 750 ℃ at the speed of 10 ℃/min, preserving heat for 12h, and finally cooling to room temperature along with the furnace;
4) preparing a dilute hydrochloric acid solution with the concentration of 2mol/L, placing the sample in the step 3) into the dilute hydrochloric acid solution according to the solid-to-liquid ratio of 1g:20mL, stirring for 24 hours, washing with the dilute hydrochloric acid solution with the concentration of 0.5mol/L, and finally washing with distilled water for 3 times to obtain a black FeAs powder sample with high purity and high crystallinity. As shown in FIG. 2, the XRD pattern of the sample has no hetero-phase diffraction peak, the peak intensity and the peak position have high matching degree with the standard PDF card of FeAs crystal, no broadening phenomenon exists, and the crystallinity is high.
Example 2
1) Mixing iron powder and arsenic powder with the purity of 99.5 percent and 98 percent respectively according to the molar ratio of 1:1, putting the mixture into a vacuum ball milling tank, and then introducing high-purity nitrogen with the pressure of about 0.15 MPa;
2) placing the vacuum ball milling tank in the step 1) on a high-energy planetary ball mill, wherein the lining of the vacuum ball milling tank is made of corundum, the grinding ball is made of corundum, the size of the grinding ball is 10mm, and the ball-to-material ratio is 15: 1, carrying out mechanical alloying reaction at a rotation speed of 400r/min, continuously operating for 40min in the reaction process, pausing for 10min, reacting for 32h, standing for 2h after the mechanical alloying reaction is finished, and taking out a sample;
3) taking out the sample in the step 2), and placing the sample in a nitrogen-purged tubular furnace for annealing treatment. Heating from room temperature to 200 ℃ at the speed of 10 ℃/min and keeping the temperature for 1 h; then heating to 850 ℃ at the speed of 10 ℃/min, preserving heat for 24 hours, and finally cooling to room temperature along with the furnace;
4) preparing a dilute hydrochloric acid solution with the concentration of 3.5mol/L, placing the sample in the step 3) into the dilute hydrochloric acid solution according to the solid-to-liquid ratio of 1g:15mL, stirring for 12 hours, washing with the dilute hydrochloric acid solution with the concentration of 0.2mol/L, and finally washing with distilled water for 3 times to obtain a black FeAs powder sample with high purity and high crystallinity.
Example 3
1) Iron powder and arsenic powder with the purity of 99 percent are mixed according to the molar ratio of 1:1 and then are put into a vacuum ball milling tank, and then high-purity argon gas with the pressure of about 0.15MPa is introduced.
2) Placing the vacuum ball milling tank in the step 1) on a high-energy planetary ball mill, wherein the lining of the vacuum ball milling tank is made of stainless steel, the grinding balls are made of stainless steel, the size of the grinding balls is 6mm, and the ball-to-material ratio is 20: 1, carrying out mechanical alloying reaction at a rotation speed of 320r/min, continuously operating for 60min in the reaction process, pausing for 15min, reacting for 36h, standing for 2h after the mechanical alloying reaction is finished, and taking out a sample;
3) taking out the sample in the step 2), placing the sample in a tube furnace purged by argon gas for annealing treatment, raising the temperature from room temperature to 200 ℃ at the speed of 10 ℃/min, and preserving the temperature for 1 h; then heating to 800 ℃ at the speed of 10 ℃/min, preserving heat for 12h, and finally cooling to room temperature along with the furnace;
4) preparing a dilute hydrochloric acid solution with the concentration of 3.5mol/L, placing the sample in the step 3) into the dilute hydrochloric acid solution according to the solid-to-liquid ratio of 1g:15mL, stirring for 24 hours, washing with the dilute hydrochloric acid solution with the concentration of 0.8mol/L, and finally washing with distilled water for 3 times to obtain a black FeAs powder sample with high purity and high crystallinity.
Comparative example 1
1) Iron powder and arsenic powder with the purity of 99 percent are mixed according to the molar ratio of 1:1 and then are put into a vacuum ball milling tank, and then high-purity argon gas with the pressure of about 0.10MPa is introduced.
2) Placing the vacuum ball milling tank in the step 1) on a high-energy planetary ball mill, wherein the lining of the vacuum ball milling tank is made of stainless steel, the grinding balls are 6mm and 10mm grinding balls distributed according to the weight ratio of 1:1, and the ball-material ratio is 10: 1, carrying out mechanical alloying reaction at a rotation speed of 320r/min, continuously operating for 60min in the reaction process, pausing for 15min, reacting for 48h, standing for 2h after the mechanical alloying reaction is finished, and taking out a sample;
3) taking out the sample in the step 2), placing the sample in a tube furnace purged by argon gas for annealing treatment, raising the temperature from room temperature to 200 ℃ at the speed of 10 ℃/min, and preserving the temperature for 1 h; then heating to 800 ℃ at the speed of 10 ℃/min, preserving heat for 12h, and finally cooling to room temperature along with the furnace;
4) preparing a dilute hydrochloric acid solution with the concentration of 0.2mol/L, placing the sample in the step 3) into the dilute hydrochloric acid solution according to the solid-to-liquid ratio of 1g:20mL, stirring for 24 hours, washing with the dilute hydrochloric acid solution with the concentration of 0.2mol/L, and finally washing with distilled water for 3 times to obtain a black FeAs powder sample. As shown in FIG. 3, the crystallinity of the FeAs powder is high, but the impurity Fe is caused by poor impurity removal effect of the low-concentration hydrochloric acid solution3O4The content is also higher.
Comparative example 2
1) Mixing iron powder and arsenic powder with the purity of 99% according to a molar ratio of 1:1, putting the mixture into a vacuum ball milling tank, and then introducing high-purity argon gas with the pressure of about 0.15 MPa;
2) placing the vacuum ball milling tank in the step 1) on a high-energy planetary ball mill, performing mechanical alloying reaction at a rotation speed of 320r/min, continuously operating for 60min in the reaction process, pausing for 15min, reacting for 36h, standing for 2h after the mechanical alloying reaction is finished, and taking out a sample;
3) preparing a dilute hydrochloric acid solution with the concentration of 3.5mol/L, placing the sample in the step 2) into the dilute hydrochloric acid solution according to the solid-to-liquid ratio of 1g:15mL, stirring for 24 hours, washing by using the dilute hydrochloric acid solution with the concentration of 0.5mol/L, washing for 3 times by using distilled water, and drying;
4) placing the sample in the step 2) into argonAnnealing treatment is carried out in the blown tube furnace, the temperature is increased from room temperature to 200 ℃ at the speed of 10 ℃/min, and the temperature is kept for 1 h; and then heating to 750 ℃ at the speed of 10 ℃/min, preserving the heat for 12 hours, and finally cooling to room temperature along with the furnace to obtain a black FeAs powder sample. As shown in FIG. 4, the FeAs powder product has high crystallinity, but the heat-treated Fe3O4The impurities are increased significantly.
Claims (8)
1. A method for preparing FeAs powder by mechanical alloying is characterized by comprising the following steps:
1) mixing iron powder and arsenic powder according to the proportion of 1:1, putting the mixture into a vacuum ball milling tank, and carrying out ball milling under the protection of nitrogen or inert gas to carry out mechanical alloying reaction;
2) under the protection of nitrogen or inert gas, firstly heating the sample subjected to the mechanical alloying reaction in the step 1) to 100-200 DEG CoC, preserving the heat for 0.5-2 h; then heating to 750-850 deg.CoC, preserving heat for 6-24 hours, and cooling to room temperature along with the furnace;
3) and (3) placing the sample cooled in the step 2) into 0.5-4 mol/L diluted hydrochloric acid for stirring treatment, and then carrying out acid washing, water washing and drying to obtain a black FeAs powder sample with high purity and high crystallinity.
2. The method for preparing FeAs powder by mechanical alloying according to claim 1, wherein: in step 1), the purity of both the iron powder and the arsenic powder is greater than >98.0 wt.%.
3. The method for preparing FeAs powder by mechanical alloying according to claim 1, wherein: in the step 1), the ball milling conditions are as follows: the rotating speed is 250-400 r/min, the ball-material ratio is 10-20: 1, the time is 8-48 h; the lining of the vacuum ball milling tank is made of stainless steel, corundum or hard alloy; the grinding ball is made of stainless steel, corundum or hard alloy; the size of the grinding ball is one or more of 3mm, 6mm, 10mm and 15 mm.
4. The method for preparing FeAs powder by mechanical alloying according to claim 1, wherein: in the step 1), the ball milling process is continuously operated for 40-60 min, then is suspended for 5-15 min, and is repeated until the ball milling is finished.
5. The method for preparing FeAs powder by mechanical alloying according to claim 1, wherein: in the steps 1) and 2), the inert gas is argon.
6. The method for preparing FeAs powder by mechanical alloying according to claim 1, wherein: in the step 2), the first temperature rise rate is 10-20oC/min, the second heating rate is 5-10oC/min。
7. The method for preparing FeAs powder by mechanical alloying according to claim 1, wherein: in the step 3), the solid-to-liquid ratio of the cooled sample to the dilute hydrochloric acid solution is 1g: 10-20 mL, and the stirring treatment time is 12-24 h.
8. The method for preparing FeAs powder by mechanical alloying according to claim 1, wherein: in the step 3), the filtering and washing process after the stirring treatment of the dilute hydrochloric acid is acid washing and then water washing, wherein the acid washing adopts 0.2-1 mol/L dilute hydrochloric acid.
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