CN110422883A - A method of FeAs powder is prepared using mechanical alloying - Google Patents

Abstract

The invention discloses a method for preparing FeAs powder by mechanical alloying: 1) mixing iron powder and arsenic powder in a molar ratio of 1:1, putting them into a vacuum ball mill tank, and performing mechanical alloying by ball milling under the protection of an inert atmosphere Reaction; 2) Under the protection of an inert gas, heat the sample after the mechanical alloying reaction in step 1) to 100-200°C for 0.5-2 hours; then heat it to 750-850°C for 6-24 hours, and cool it to room temperature ; 3) Place the cooled sample in step 2) in 0.5-4mol/L dilute hydrochloric acid for stirring treatment, then pickle, wash with water, and dry to obtain a high-purity, high-crystallinity black FeAs powder sample. The invention provides a method for preparing FeAs powder quickly, in large quantities and at low cost. The obtained FeAs powder has high purity and high crystallinity, and can be used as a precursor for the synthesis of iron-based high-temperature superconducting materials.

Description

A method for preparing FeAs powder by mechanical alloying

technical field

The invention belongs to the technical field of iron-based high-temperature superconducting materials, and in particular relates to a method for preparing FeAs powder by mechanical alloying.

Background technique

The transition temperature of iron-based high-temperature superconducting materials breaks through the traditional Macmillan limit, and it is the second largest family of high-temperature superconductors after copper-based superconductors. Iron-based high-temperature superconducting materials have rich physical properties and great application value, which is conducive to the realization of room temperature superconductivity and the promotion of superconducting technology.

The research team of the Institute of Physics of the Chinese Academy of Sciences and the University of Science and Technology of China won the first prize of the 2013 National Natural Science Award for their "discovery of iron-based high-temperature superconductors above 40K and research on some basic physical properties". In the following years, new iron-based superconducting systems such as iron arsenide and iron selenide were continuously discovered, and typical precursors include LaFeAsO, BaFeAs, LiFeAs, and FeSe. Theoretical studies have shown that in the iron arsenide superconducting system, the existence of the FeAs layer plays a key role in the realization of high-temperature superconductivity.

The preparation of iron-based superconductors is generally divided into two steps. The first step is to synthesize the precursor LnAs (Ln=La, Pr, Fe, etc.): mix high-purity La, Pr, and Fe powders with As powder, shape them, and sinter them in a high-vacuum quartz tube; then It is mixed with other component powders required by the chemical formula according to the molar number required by the chemical formula, shaped and sealed in a quartz tube filled with argon, and sintered at about 1150 ° C to form a polycrystalline sample of an iron-based superconductor. Therefore, the preparation of precursors is very critical in the preparation process of iron-based superconductors, and due to the necessity of FeAs layer construction, the synthesis of FeAs precursors becomes very important.

The synthesis of FeAs usually adopts high-temperature solid-state reaction. In the literature, high-purity Fe(5N) and high-purity As(6N) are used as raw materials. After grinding and mixing, they are placed in a vacuum quartz analyte, slowly heated to 1000°C and kept for 24 hours. The final product contains 6wt.% of impurities FeAs ₂ (Zaikina JV, Batuk M, Abakumov AM, et al.Facile Synthesis ofBa _1–x K _x Fe ₂ As ₂ Superconductors via Hydride Route[J].Journal of the American Chemical Society,2014,136(48):16932. ). The raw materials of this method are expensive, and the pretreatment processes such as weighing and grinding need to be carried out in a glove box, and the heating and heat preservation process takes up to 70 hours, and the energy consumption is high. CN102000815A discloses a negative-pressure solid-phase reaction preparation method for FeAs powder. The processes of weighing, mixing and grinding the raw materials are all carried out in a glove box, and after tableting, they are placed in a quartz tube for high-temperature negative-pressure solid-phase reaction , the XRD pattern of the product shows that it contains more impurity phases.

Contents of the invention

In order to solve the problems of high cost and easy generation of impurities in the existing synthesis methods, the purpose of the present invention is to provide a method of using non-high-purity metal powder as raw material to synergistically prepare high-purity, The method of FeAs powder with high crystallinity.

In order to achieve the above technical purpose, the present invention provides a method for preparing FeAs powder by mechanical alloying, comprising the following steps:

1) Mix iron powder and arsenic powder in a molar ratio of 1:1 and put them into a vacuum ball mill tank, and perform mechanical alloying reaction by ball milling under the protection of an inert atmosphere;

2) Under the protection of an inert gas, heat the sample after the mechanical alloying reaction in step 1) to 100-200°C for 0.5-2 hours; then raise the temperature to 750-850°C for 6-24 hours, and cool to room temperature with the furnace;

3) The cooled sample in step 2) is placed in 0.5-4mol/L dilute hydrochloric acid for stirring treatment, and then pickled, washed with water, and dried to obtain a black FeAs powder sample with high purity and high crystallinity.

The key to the technical solution of the present invention is to use mechanical alloying to obtain FeAs powder with low purity and low crystallinity, and then combine heat treatment and acid treatment, strictly follow the implementation sequence of each process step, and gradually obtain through the synergy between each step FeAs powder with high purity and high crystallinity. Based on the physical properties of elemental Fe and As, the present invention establishes a ductile-brittle powder ball milling system, and synthesizes FeAs through mechanical alloying at room temperature; through appropriate heat treatment, the annealing and unalloying of FeAs and FeAs from the dearsenization of impurity _FeAs2 are realized. The volatilization of the elemental As is recrystallized and recovered in the low temperature area; finally, the unreacted Fe and iron oxides are removed by pickling treatment, and the black FeAs powder with high purity and high crystallinity is obtained.

Preferably, in step 1), the purity of both iron powder and arsenic powder is greater than >98.0wt.%.

Preferably, in step 1), the ball milling conditions are: the rotating speed is 250-400r/min, the ball-to-material ratio is 10-20:1, and the time is 8-48h; the lining material of the vacuum ball milling tank is stainless steel, corundum or hard alloy , preferably stainless steel; the material of the grinding ball is stainless steel, corundum or hard alloy, preferably corundum; the size of the grinding ball is one or more of 3mm, 6mm, 10mm and 15mm, preferably distributed in a weight ratio of 1:1 6mm and 10mm grinding balls. Under optimal conditions, the present invention is beneficial to avoid local cold welding and bottom agglomeration, improve the powder extraction rate of the product and reduce the proportion of impurity phases.

Preferably, in step 1), the ball milling process runs continuously for 40 to 60 minutes, then pauses for 5 to 15 minutes, and repeats until the end of the ball milling, so as to prevent localized cold welding.

Preferably, in steps 1) and 2), the inert gas is argon or nitrogen, preferably argon.

Preferably, in step 2), the heating rate for the first time is 10-20°C/min, and the heating rate for the second time is 5-10°C/min.

Preferably, in 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. Reasonable solid-liquid ratio and stirring time can effectively improve the removal rate of impurities Fe and iron oxides per unit time, while avoiding the loss of the target product FeAs compound.

Preferably, in step 3), the filtration and washing process after the dilute hydrochloric acid stirring treatment is pickling first and then washing with water, and the dilute hydrochloric acid of 0.2-1mol/L is used for pickling, which can effectively prevent the hydrolysis of iron ions to form hydroxides Colloid, to ensure the filtering effect.

Compared with prior art, the beneficial effect of the present invention is:

1. The preparation cost is low, and the requirements for the purity of raw materials are low; the high-temperature treatment process does not need to provide a negative pressure and a closed environment, and a conventional atmosphere furnace is sufficient, and the high-temperature treatment time is short and the temperature is relatively low.

2. Simple and safe operation: there is no need for pretreatment of raw materials in an oxygen-free and water-free environment such as a glove box; 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.

Description of drawings

Fig. 1 is an XRD pattern of a FeAs-MA powder sample prepared in Step 2 of Example 1 of the present invention.

Fig. 2 is the XRD pattern of the FeAs powder sample prepared in Example 1 of the present invention.

FIG. 3 is an XRD pattern of the FeAs powder sample prepared in Comparative Example 1 of the present invention.

FIG. 4 is an XRD pattern of the FeAs powder sample prepared in Comparative Example 2 of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with specific embodiments, and the specific embodiments described here are only used to explain the present invention, and are not intended to limit the present invention.

Example 1

1) Use iron powder and arsenic powder with a purity of 99.5% and 98% respectively, mix them in a molar ratio of 1:1, put them into a vacuum ball mill tank, and then inject high-purity argon gas of about 0.15 MPa;

2) Place the vacuum ball milling tank in step 1) on a high-energy planetary ball mill, the lining material of the vacuum ball milling tank is stainless steel, the material of the grinding balls is stainless steel, and the grinding balls are 6mm and 10mm grinding balls distributed in a weight ratio of 1:1, The ball-to-material ratio is 10:1, and the mechanical alloying reaction is carried out at a rotation speed of 320r/min. During the reaction process, it runs continuously for 40 minutes and then pauses for 5 minutes. The reaction time is 40 hours. After the mechanical alloying reaction is completed, stand still for 2 hours before taking out the sample; As shown in Figure 1, the XRD diffraction peaks of FeAs-MA samples after ball milling are obviously broadened, the crystallinity is low, and there are a lot of impurity phases FeAs ₂ , Fe ₃ O ₄ and As ₂ O ₃ ;

3) Take out the sample in step 2), place it in an argon-purged tube furnace for annealing treatment, raise it from room temperature to 200°C at a rate of 10°C/min and keep it warm for 1h; then heat it at 10°C/min The temperature was raised to 750°C at a certain rate and kept for 12 hours, and finally cooled to room temperature with the furnace;

4) Configure a dilute hydrochloric acid solution with a concentration of 2mol/L, and place the sample in step 3) in a dilute hydrochloric acid solution for 24 hours according to a solid-to-liquid ratio of 1g:20mL, then wash with a dilute hydrochloric acid solution of 0.5mol/L, and finally Washed 3 times with distilled water to obtain a black FeAs powder sample with high purity and high crystallinity. As shown in Figure 2, there is no impurity phase diffraction peak in the XRD pattern of the sample, and the peak intensity and peak position are highly matched with the standard PDF card of FeAs crystal, without broadening phenomenon, and the crystallinity is high.

Example 2

1) Use iron powder and arsenic powder with a purity of 99.5% and 98% respectively, mix them in a molar ratio of 1:1, put them into a vacuum ball mill tank, and then pass high-purity nitrogen gas of about 0.15 MPa;

2) Place the vacuum ball mill in step 1) on a high-energy planetary ball mill. The lining material of the vacuum ball mill is corundum. The rotation speed of min is used for mechanical alloying reaction. During the reaction process, it runs continuously for 40 minutes and then pauses for 10 minutes. The reaction time is 32 hours. After the mechanical alloying reaction is over, let it stand for 2 hours before taking out the sample;

3) The sample in step 2) is taken out, and placed in a nitrogen-purged tube furnace for annealing treatment. Raise from room temperature to 200°C at a rate of 10°C/min and hold for 1 hour; then raise the temperature to 850°C at a rate of 10°C/min and hold for 24 hours, and finally cool to room temperature with the furnace;

4) Configure a dilute hydrochloric acid solution with a concentration of 3.5mol/L, place the sample in step 3) in a dilute hydrochloric acid solution for 12 hours according to a solid-to-liquid ratio of 1g:15mL, and then wash with a dilute hydrochloric acid solution of 0.2mol/L. Finally, it was washed three times with distilled water to obtain a black FeAs powder sample with high purity and high crystallinity.

Example 3

1) Iron powder and arsenic powder with a purity of 99% are used, mixed according to a molar ratio of 1:1, put into a vacuum ball mill jar, and then high-purity argon gas of about 0.15MPa is introduced.

2) Place the vacuum ball mill in step 1) on a high-energy planetary ball mill. The lining material of the vacuum ball mill is stainless steel, the material of the balls is stainless steel, the size of the balls is 6mm, the ball-to-material ratio is 20:1, and 320r/ The rotation speed of min is used for mechanical alloying reaction. During the reaction process, it runs continuously for 60 minutes and then pauses for 15 minutes. The reaction time is 36 hours. After the mechanical alloying reaction is completed, stand still for 2 hours before taking out the sample;

3) Take out the sample in step 2), place it in an argon-purged tube furnace for annealing treatment, raise it from room temperature to 200°C at a rate of 10°C/min and keep it warm for 1h; then heat it at 10°C/min The temperature was raised to 800°C at a certain rate and kept for 12 hours, and finally cooled to room temperature with the furnace;

4) Configure a dilute hydrochloric acid solution with a concentration of 3.5mol/L, place the sample in step 3) in a dilute hydrochloric acid solution for 24 hours according to the solid-to-liquid ratio of 1g:15mL, and then wash it with a dilute hydrochloric acid solution of 0.8mol/L. Finally, it was washed three times with distilled water to obtain a black FeAs powder sample with high purity and high crystallinity.

Comparative example 1

1) Iron powder and arsenic powder with a purity of 99% are used, mixed according to a molar ratio of 1:1, put into a vacuum ball mill jar, and then high-purity argon gas of about 0.10MPa is introduced.

2) Place the vacuum ball milling tank in step 1) on a high-energy planetary ball mill, the lining material of the vacuum ball milling tank is stainless steel, the material of the grinding balls is stainless steel, and the grinding balls are 6mm and 10mm grinding balls distributed in a weight ratio of 1:1, The ball-to-material ratio is 10:1, and the mechanical alloying reaction is carried out at a rotation speed of 320r/min. During the reaction process, it runs continuously for 60 minutes and then pauses for 15 minutes. The reaction time is 48 hours. After the mechanical alloying reaction is completed, stand still for 2 hours before taking out the sample;

3) Take out the sample in step 2), place it in an argon-purged tube furnace for annealing treatment, raise it from room temperature to 200°C at a rate of 10°C/min and keep it warm for 1h; then heat it at 10°C/min The temperature was raised to 800°C at a certain rate and kept for 12 hours, and finally cooled to room temperature with the furnace;

4) Configure a dilute hydrochloric acid solution with a concentration of 0.2mol/L, place the sample in step 3) in a dilute hydrochloric acid solution for 24 hours according to a solid-to-liquid ratio of 1g:20mL, and then wash with a dilute hydrochloric acid solution of 0.2mol/L. Finally, it was washed three times with distilled water to obtain a black FeAs powder sample. As shown in Figure 3, the crystallinity of the product FeAs powder is relatively high, but the content of impurity Fe ₃ O ₄ is also high due to the poor removal effect of the low-concentration hydrochloric acid solution.

Comparative example 2

1) Iron powder and arsenic powder with a purity of 99% are used, mixed according to a molar ratio of 1:1, put into a vacuum ball mill tank, and then high-purity argon gas of about 0.15MPa is introduced;

2) Place the vacuum ball mill tank in step 1) on a high-energy planetary ball mill, and use the rotation speed of 320r/min to carry out mechanical alloying reaction. During the reaction process, it runs continuously for 60 minutes and then pauses for 15 minutes. The reaction time is 36 hours, and the mechanical alloying reaction After the end, stand still for 2h and then take out the sample;

3) Configure a dilute hydrochloric acid solution with a concentration of 3.5mol/L, place the sample in step 2) in a dilute hydrochloric acid solution for 24 hours according to the solid-to-liquid ratio of 1g:15mL, and then wash with a dilute hydrochloric acid solution of 0.5mol/L. Finally, wash 3 times with distilled water and dry;

4) The sample in step 2) was placed in an argon-purged tube furnace for annealing treatment, and the temperature was raised from room temperature to 200 °C at a rate of 10 °C/min and kept for 1 h; then at a rate of 10 °C/min The temperature was raised to 750°C and kept for 12 hours, and finally cooled to room temperature with the furnace to obtain a black FeAs powder sample. As shown in Figure 4, the crystallinity of the product FeAs powder is relatively high, but the impurities of Fe ₃ O ₄ increase significantly after heat treatment.

Claims (8)

1. a kind of method for preparing FeAs powder using mechanical alloying, which comprises the following steps:

1) it is put into vacuum ball grinder after mixing iron powder and arsenic powder by the molar ratio of 1:1, ball milling carries out under inert atmosphere protection Mechanical alloying reaction；

2) under inert gas shielding, the sample after mechanical alloying reaction in step 1) is first warming up to 100~200 DEG C of heat preservations 0.5~2h；Then heat to 750~850 DEG C heat preservation 6~for 24 hours, cool to room temperature with the furnace；

3) sample after cooling in step 2) is placed in stir process in the dilute hydrochloric acid of 0.5~4mol/L, then through pickling, washing, The black FeAs powder sample of high-purity, high-crystallinity is obtained after drying.

2. a kind of method for preparing FeAs powder using mechanical alloying according to claim 1, it is characterised in that: step 1) in, the purity of iron powder and arsenic powder is all larger than > 98.0wt.%.

3. a kind of method for preparing FeAs powder using mechanical alloying according to claim 1, it is characterised in that: step 1) in, ball milling condition are as follows: revolving speed is 250~400r/min, and ratio of grinding media to material is 10~20:1, and the time is 8~48h；Vacuum ball grinder Liner material is stainless steel, corundum or hard alloy；Material quality of grinding balls is stainless steel, corundum or hard alloy；Abrading-ball size is One or more of 3mm, 6mm, 10mm and 15mm.

4. a kind of method for preparing FeAs powder using mechanical alloying according to claim 1, it is characterised in that: step 1) in, suspend 5~15min in mechanical milling process after 40~60min of continuous operation, being repeated up to ball milling terminates.

5. a kind of method for preparing FeAs powder using mechanical alloying according to claim 1, it is characterised in that: step And 2) 1) in, the inert gas is argon gas or nitrogen.

6. a kind of method for preparing FeAs powder using mechanical alloying according to claim 1, it is characterised in that: step 2) in, first time heating rate is 10~20 DEG C/min, and second of heating rate is 5~10 DEG C/min.

7. a kind of method for preparing FeAs powder using mechanical alloying according to claim 1, it is characterised in that: step 3) in, the solid-to-liquid ratio of sample and dilute hydrochloric acid solution after cooling is 1g:10~20mL, the stir process time is 12~for 24 hours.

8. a kind of method for preparing FeAs powder using mechanical alloying according to claim 1, it is characterised in that: step 3) in, the diafiltration process after dilute hydrochloric acid stir process is first pickling, rear washing, and pickling uses dilute salt of 0.2~1mol/L Acid.