阅读说明：本技术 一种掺杂低熔点元素诱导合成fct-FePt纳米粒子的方法 (Method for inductively synthesizing fct-FePt nano particles by doping low-melting-point elements ) 是由 裴文利 赵东 吴纯 裴佳澳 于 2019-10-11 设计创作，主要内容包括：本发明涉及一种掺杂低熔点元素诱导合成fct-FePt纳米粒子的方法。主要合成过程：将铂源、铁源、低熔点元素化合物和还原剂加入溶剂中形成混合溶液,除水后向混合溶液中加入表面活性剂,加热到一定温度保温获得黑色混合溶液,冷却至室温,经清洗离心分离,除杂,及二次清洗离心分离,获得黑色粉末,即为fct-FePt纳米粒子。该方法利用低熔点原子与Fe原子之间较大的扩散速率差和先于Fe原子被还原的特点,造成晶格中出现大量空位,从而降低了Fe、Pt原子在晶格中的迁移能垒,诱导Fe、Pt原子组成能量更低的fct结构。可实现在较低温度下直接合成fct-FePt纳米粒子,通过低熔点元素添加量的改变实现有序度的调控,进而获得高质量FePt纳米材料。(the invention relates to a method for synthesizing fct-FePt nano particles by doping low-melting-point elements in an inducing manner. The main synthesis process comprises the following steps: adding a platinum source, an iron source, a low-melting-point element compound and a reducing agent into a solvent to form a mixed solution, adding a surfactant into the mixed solution after dewatering, heating to a certain temperature, preserving the temperature to obtain a black mixed solution, cooling to room temperature, cleaning, centrifugally separating, removing impurities, and secondarily cleaning, centrifugally separating to obtain black powder, namely the fct-FePt nano particles. The method utilizes the characteristics of larger diffusion rate difference between low-melting-point atoms and Fe atoms and reduction of the Fe atoms in advance to cause a large number of vacancies to appear in crystal lattices, thereby reducing the migration energy barrier of the Fe and Pt atoms in the crystal lattices and inducing the Fe and Pt atoms to form an fct structure with lower energy. Can realize direct synthesis of fct-FePt nanoparticles at a lower temperature, and realize regulation of order degree by changing the addition amount of low-melting-point elements, thereby obtaining a high-quality FePt nano material.)

1. A method for inductively synthesizing fct-FePt nano particles by doping low-melting-point elements is characterized by comprising the following steps:

(1) The molar ratio of the raw materials is 1: (0.2-2), weighing metal precursor powder and a reducing agent, wherein the metal precursor powder comprises a platinum source, an iron source and a low-melting-point element compound, and the molar ratio of the platinum source to the iron source to the low-melting-point element compound is (0.2-2): (0.2-2): (0.2-2);

(2) In terms of molar ratio, (metal precursor powder + reducing agent): solvent 1: (5-30), adding metal precursor powder and a reducing agent into a solvent to form a mixed solution, and then performing water removal treatment, wherein the solvent is one of hexadecylamine, oleylamine, octadecylamine or trioctylamine;

(3) In terms of molar ratio, solvent: a surfactant (1-10): 1, adding a surfactant into the dehydrated mixed solution, uniformly mixing, heating to 300-360 ℃ at a heating rate of 1-10 ℃/min, preserving heat for 60-180 min to obtain a black mixed solution, and cooling to room temperature;

(4) And carrying out centrifugal separation, impurity removal and secondary centrifugal separation on the black mixed solution to obtain black powder, namely the fct-FePt nano particles.

2. the method for the induction synthesis of fct-FePt nanoparticles doped with low-melting-point elements as claimed in claim 1, wherein in step (1):

The platinum source is one of platinum acetylacetonate, chloroplatinic acid or potassium chloroplatinate;

The iron source is one of ferrous acetylacetonate, ferric acetylacetonate or ferrous chloride;

The reducing agent is one of potassium borohydride, 1, 2-hexadecanediol or sodium borohydride.

3. The method for inductively synthesizing fct-FePt nanoparticles by doping low-melting-point elements as claimed in claim 1, wherein in the step (1), the low-melting-point element compound is one of manganese acetate, lead acetate, tin acetate, antimony acetate or zinc acetate.

4. The method for inductively synthesizing fct-FePt nanoparticles by doping low-melting-point elements according to claim 1, wherein in the step (2), water is removed by a heating mode, the heating temperature is 110-120 ℃, the heat preservation time is 30-60 min, the heating operation is performed under a protective atmosphere, and the flow rate of the protective atmosphere is 20-50 μ l/min.

5. The method for inductively synthesizing fct-FePt nanoparticles by doping low-melting-point elements according to claim 1, wherein in the step (3), the surfactants are oleylamine and oleic acid, and the volume ratio of the oleylamine to the oleic acid is (1-5): (5-1) adding.

6. the method for inductively synthesizing fct-FePt nanoparticles by doping low-melting-point elements according to claim 1, wherein in the step (4), the specific processes of cleaning and centrifugal separation, impurity removal and secondary cleaning and centrifugal separation are as follows:

(1) Dissolving and dispersing the black mixed solution by adopting absolute ethyl alcohol A, centrifuging at the speed of 4000-10000 rpm for 3-10 min, pouring the upper-layer centrifugate, and repeating: adding absolute ethyl alcohol A to dissolve, disperse and centrifugally separate for 3-5 times to obtain a primary product black powder;

(2) Adding nitric acid into the black powder of the primary product, and carrying out acid washing for 10-360 min to remove impurity phases to obtain a product after impurity removal;

(3) And adding absolute ethyl alcohol B with the volume equal to that of the nitric acid into the product after impurity removal, performing centrifugal separation again, pouring out the supernatant centrifugate, dissolving and dispersing the supernatant centrifugate with deionized water with the volume equal to that of the absolute ethyl alcohol B, and performing centrifugal separation for 3-5 times to obtain fct-FePt nano particle black powder, wherein the centrifugal rotation speed is 4000-10000 rpm, and the single centrifugation time is 3-10 min.

7. The method for inductively synthesizing fct-FePt nanoparticles by doping low-melting-point elements according to claim 6, wherein in the step (1), the addition amount of absolute ethyl alcohol A is as follows according to a volume ratio, and the volume ratio of a black mixed solution: anhydrous ethanol a ═ 1: (4-20).

8. The method for inductively synthesizing fct-FePt nanoparticles by doping low-melting-point elements according to claim 6, wherein in the step (2), the concentration of nitric acid is 2-10 wt.%, the addition amount of nitric acid is as follows, and the weight ratio of the initial product black powder: 1 part of nitric acid: (1-20).

The technical field is as follows:

the invention belongs to the technical field of magnetic nano materials, and particularly relates to a method for synthesizing fct-FePt nano particles by doping low-melting-point elements in an induction manner.

Background art:

The fct-FePt nano-particles have high magnetocrystalline anisotropy, good biocompatibility, excellent chemical catalytic performance and high coercive force, and have wide application prospects in the fields of high-density magnetic recording, targeted drug delivery, oxidation-reduction (ORR) catalytic performance and the like. The application properties have higher requirements on the uniform appearance, small size, ordered structure and the like of the particles. The FePt nano particles directly synthesized by the wet chemical reaction are fcc-FePt nano particles with disordered structures, and the FePt nano particles with the disordered structures do not have permanent magnetic characteristics and have low catalytic performance. In order to obtain excellent permanent magnetic performance and excellent catalytic performance, the existing preparation method needs to convert the nanoparticles from a disordered fcc structure to an ordered structure of fct through high-temperature (>550 ℃) ordered annealing. In the high-temperature annealing process, the nanoparticles can be agglomerated and grow abnormally, so that the application characteristics of the nanoparticles are influenced. How to directly synthesize FePt nanoparticles with fct ordered structures and high performance at low temperature is the bottleneck of the field, so that the development of a method for directly synthesizing FePt particles with fct structures at low temperature with good controllability and high order degree is a problem to be solved urgently.

The invention content is as follows:

The invention aims to provide a method for directly synthesizing fct-FePt nanoparticles at low temperature aiming at the problems in the prior art, which induces FePt to form an fct ordered structure by doping low-melting-point elements (mainly comprising Sn, Pb, Mn, Zn and Sb elements with melting points lower than that of Fe) so as to realize the regulation and control of the ordering degree. Generally, the interatomic bonding energy of the low-melting-point element is low, so that the low-melting-point atom is easy to diffuse and has a high diffusion rate at a relatively low temperature; and these low melting point atoms are easily reduced from their metal precursors, compared to Fe atoms, so in the reaction system of Fe source and Pt source, the low melting point atoms and Pt atoms are reduced earlier than Fe atoms to form crystal nuclei and clusters composed mainly of low melting point atoms and Pt atoms, with the rise of reaction temperature or the extension of holding time, Fe atoms are gradually reduced and deposited on the surface of the previously formed crystal nuclei or clusters, the inside of the particles is enriched by the low melting point atoms, and the outside is enriched by Fe atoms. Due to the driving of different element concentration gradients, Fe atoms diffuse towards the inside of the cluster, low-melting-point atoms diffuse towards the outside, and the low-melting-point atoms have high diffusion rate, so that the low-melting-point atoms diffuse to the surface of the crystal faster than the Fe atoms and can move to the inside of the crystal, and further a large number of vacancies exist in the crystal, and the vacancies enable the Fe atoms and the Pt atoms to be easily rearranged to form an fct-FePt structure with low energy. The fct-FePt synthesized by the method has the characteristics of uniform appearance, high degree of order and controllability. The order degree can be controlled by adjusting the ratio of the raw material precursor, the solvent, the heating rate, the reaction temperature and the reaction time, so that the order degree can be regulated and controlled by changing the addition amount of the low-melting-point element, and further the high-quality FePt nano material can be obtained.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for inducing and synthesizing fct-FePt nano particles by doping low-melting-point elements comprises the following steps:

(1) The molar ratio of the raw materials is 1: (0.2-2), weighing metal precursor powder and a reducing agent, wherein the metal precursor powder comprises a platinum source, an iron source and a low-melting-point element compound, and the molar ratio of the platinum source to the iron source to the low-melting-point element compound is (0.2-2): (0.2-2): (0.2-2);

(2) in terms of molar ratio, (metal precursor powder + reducing agent): solvent 1: (5-30), adding metal precursor powder and a reducing agent into a solvent to form a mixed solution, and then performing water removal treatment, wherein the solvent is one of hexadecylamine, oleylamine, octadecylamine or trioctylamine;

(3) In terms of molar ratio, solvent: a surfactant (1-10): 1, adding a surfactant into the dehydrated mixed solution, uniformly mixing, heating to 300-360 ℃ at a heating rate of 1-10 ℃/min, preserving heat for 60-180 min to obtain a black mixed solution, and cooling to room temperature;

(4) And cleaning and centrifugally separating the black mixed solution, removing impurities, and performing secondary cleaning and centrifugally separating to obtain black powder, namely the fct-FePt nano particles.

in the step (1), the platinum source is acetylacetone platinum Pt (acac)₂Chloroplatinic acid H₂PtCl₆or potassium chloroplatinate K₂PtCl₆One of (1) and (b).

in the step (1), the iron source is ferrous acetylacetonate Fe (acac)₂Fe acetylacetonate (acac)₃or ferrous chloride FeCl₂One of (1) and (b).

in the step (1), the reducing agent is potassium borohydride KBH₄1, 2-hexadecanediol C₁₆H₃₄O₄Or sodium borohydride NaBH₄One of (1) and (b).

In the step (1), the low-melting point element compound is manganese acetate Mn (Ac)₂Lead acetate Pb (Ac)₄Sn (Ac) tin acetate₂antimony acetate Sb (Ac)₂or zinc acetate Zn (Ac)₂one of (1) and (b).

In the step (2), water is removed by a heating mode, the heating temperature is 110-120 ℃, the heat preservation time is 30-60 min, the heating operation is carried out under the protective atmosphere, and the flow rate of the protective atmosphere is 20-50 mu l/min.

In the step (2), the protective atmosphere is 95% Ar + 5% H₂High purity argon Ar or high purity nitrogen N₂One of (1) and (b).

in the step (3), the surfactant is oleylamine and oleic acid, and the volume ratio of the oleylamine to the oleic acid is (1-5): (5-1) adding.

in the step (4), the specific processes of cleaning and centrifugal separation, impurity removal and secondary cleaning and centrifugal separation are as follows:

(1) dissolving and dispersing the black mixed solution by adopting absolute ethyl alcohol A, centrifuging at the speed of 4000-10000 rpm for 3-10 min, pouring the upper-layer centrifugate, and repeating: adding absolute ethyl alcohol A to dissolve, disperse and centrifugally separate for 3-5 times to obtain a primary product black powder;

in the step (1), the addition amount of the absolute ethyl alcohol A is as follows according to the volume ratio, and the black mixed solution: anhydrous ethanol a ═ 1: (4-20).

(2) Adding nitric acid into the black powder of the primary product, and carrying out acid washing for 10-360 min to remove impurity phases to obtain a product after impurity removal;

In the step (2), the concentration of nitric acid is 2 wt.% to 10 wt.%, the addition amount of nitric acid is in mass ratio, and the black powder of the primary product is: 1 part of nitric acid: (1-20).

(3) And adding absolute ethyl alcohol B with the volume equal to that of the nitric acid into the product after impurity removal, performing centrifugal separation again, pouring out the supernatant centrifugate, dissolving and dispersing the supernatant centrifugate with deionized water with the volume equal to that of the absolute ethyl alcohol B, and performing centrifugal separation for 3-5 times to obtain fct-FePt nano particle black powder, wherein the centrifugal rotation speed is 4000-10000 rpm, and the single centrifugation time is 3-10 min.

in the step (4), the fct-FePt nanoparticles are stored in the absolute ethyl alcohol C.

In the step (4), the magnetic property of the black powder is measured by a comprehensive Physical Property Measurement System (PPMS), the morphology and distribution of the nanoparticles are observed by a field emission Transmission Electron Microscope (TEM), and the phase of the nanoparticles is analyzed by X-ray diffraction (XRD) to confirm that the fct-FePt nanoparticles are obtained.

The FePt nano particles with the fct ordered structure can be directly prepared by the steps, the particles have high order degree, the coercive force reaches 4.2-8.9 kOe, subsequent annealing is not needed, and the FePt nano particles can be directly applied.

the invention adopts a method for synthesizing fct-FePt nanoparticles by doping low-melting-point elements in an inducing manner, and fct-FePt nanoparticles with uniform appearance and high degree of order are directly synthesized. Firstly, a third metal precursor low-melting-point element compound, a reducing agent and metal precursor powder (an iron source and a platinum source) are added into a solvent according to a certain proportion, uniformly mixed and fully dissolved. And then heating the mixed solution to a certain temperature, and preserving the temperature for a certain time to ensure that the low-melting-point element is induced to synthesize the high-coercivity fct-FePt nano particle. And then centrifuging the black solution through absolute ethyl alcohol, then washing the black solution with nitric acid for a certain time, and then centrifuging and cleaning the black solution again through absolute ethyl alcohol and deionized water to finally directly synthesize the monodisperse fct-FePt nano particles. The low-melting-point element is used for doping, so that the fcc-to-fct phase transition temperature is reduced, the uniform distribution of the fcc-to-fct phase transition temperature is improved, and the fct-FePt nano-particle with high order degree and high coercivity is synthesized.

The invention has the beneficial effects that:

(1) The high-coercivity fct-FePt nano particles are synthesized by doping low-melting-point elements and inducing, and are synthesized at a lower temperature by a one-step wet chemical method, so that the experiment is easy to operate, low-carbon and environment-friendly;

(2) By a reasonable experimental process, fct-FePt nanoparticles with high order degree and uniform appearance can be obtained;

(3) The catalytic performance of the fct-FePt nano particles can be improved by doping low-melting-point elements;

(4) Because the fct-FePt nano-particles have important application prospects in the fields of magnetic recording, biomedicine, catalysis and the like, but the complicated operation steps and the high cost limit the range of the fct-FePt nano-particles, the invention promotes the practicability of the technology for synthesizing the fct-FePt nano-particles in one step, simplifies the prior process, further saves the cost and has important theoretical and application values.

description of the drawings:

FIG. 1 is a hysteresis loop of fct-FePt nanoparticles prepared by the method of example 1 of the present invention;

FIG. 2 is an XRD pattern of fct-FePt nanoparticles prepared by the method of example 1 of the present invention;

FIG. 3 is a TEM image of fct-FePt nanoparticles prepared by the method of example 1 of the present invention;

FIG. 4 is a hysteresis loop of fct-FePt nanoparticles prepared by the method of example 2 of the present invention;

FIG. 5 is an XRD pattern of fct-FePt nanoparticles prepared by the method of example 2 of the present invention;

FIG. 6 is a TEM image of fct-FePt nanoparticles prepared by the method of example 2 of the present invention;

FIG. 7 is a hysteresis loop of fct-FePt nanoparticles prepared by the method of example 3 of the present invention;

FIG. 8 is an XRD pattern of fct-FePt nanoparticles prepared by the method of example 3 of the present invention;

FIG. 9 is a TEM image of fct-FePt nanoparticles prepared by the method of example 3 of the present invention.

The specific implementation mode is as follows:

The present invention will be described in further detail with reference to examples.

in the following examples:

The preparation equipment is commercially available and can be purchased in the market, and the preparation equipment comprises: three-neck flask, condenser tube, electronic balance, mechanical stirring heating jacket and centrifuge;

Chloroplatinic acid, potassium chloroplatinate, platinum acetylacetonate, ferrous acetylacetonate, ferric acetylacetonate, ferrous chloride, manganese acetate, tin acetate, lead acetate, zinc acetate, antimony acetate, 1, 2-hexadecanediol, potassium borohydride, sodium borohydride, hexadecylamine, octadecylamine, trioctylamine, oleylamine, oleic acid, 95% Ar + 5% H₂the high-purity argon and the high-purity nitrogen are all commercial products purchased from the market;

The absolute ethyl alcohol A, B and C used for the dispersion for the dissolution dispersion of the black powder are expressed only for the convenience of distinction, the nitric acid pickling function is to remove the heterogeneous phase, and the absolute ethyl alcohol and the nitric acid used are commercial products.

A method for inducing and synthesizing fct-FePt nano particles by doping low-melting-point elements comprises the following steps:

(1) The molar ratio of the raw materials is 1: (0.2-2), weighing metal precursor powder and a reducing agent, wherein the metal precursor powder comprises a platinum source, an iron source and a low-melting-point element compound, and the molar ratio of the platinum source to the iron source to the low-melting-point element compound is (0.2-2): (0.2-2): (0.2-2);

(2) In terms of molar ratio, (metal precursor powder + reducing agent): solvent 1: (5-30), adding metal precursor powder and a reducing agent into a solvent to form a mixed solution, and then performing water removal treatment, wherein the solvent is one of hexadecylamine, oleylamine, octadecylamine or trioctylamine;

(3) In terms of molar ratio, solvent: a surfactant (1-10): 1, adding a surfactant into the dehydrated mixed solution, uniformly mixing, heating to 300-360 ℃ at a heating rate of 1-10 ℃/min, preserving heat for 60-180 min to obtain a black mixed solution, and cooling to room temperature;

(4) and cleaning and centrifugally separating the black mixed solution, removing impurities, and performing secondary cleaning and centrifugally separating to obtain black powder, namely the fct-FePt nano particles.

in the step (1), the platinum source is acetylacetone platinum Pt (acac)₂Chloroplatinic acid H₂PtCl₆Or potassium chloroplatinate K₂PtCl₆one of (1) and (b).

SaidIn the step (1), the iron source is ferrous acetylacetonate Fe (acac)₂Fe acetylacetonate (acac)₃Or ferrous chloride FeCl₂one of (1) and (b).

in the step (1), the reducing agent is potassium borohydride KBH₄1, 2-hexadecanediol C₁₆H₃₄O₄Or sodium borohydride NaBH₄One of (1) and (b).

In the step (1), the low-melting point element compound is manganese acetate Mn (Ac)₂Lead acetate Pb (Ac)₄Sn (Ac) tin acetate₂antimony acetate Sb (Ac)₂Or zinc acetate Zn (Ac)₂One of (1) and (b).

In the step (2), water is removed by a heating mode, the heating temperature is 110-120 ℃, the heat preservation time is 30-60 min, the heating operation is carried out under the protective atmosphere, and the flow rate of the protective atmosphere is 20-50 mu l/min.

In the step (2), the protective atmosphere is 95% Ar + 5% H₂High purity argon Ar or high purity nitrogen N₂One of (1) and (b).

In the step (3), the surfactant is oleylamine and oleic acid, and the volume ratio of the oleylamine to the oleic acid is (1-5): (5-1) adding.

In the step (4), the specific processes of cleaning and centrifugal separation, impurity removal and secondary cleaning and centrifugal separation are as follows:

(1) dissolving and dispersing the black mixed solution by adopting absolute ethyl alcohol A, centrifuging at the speed of 4000-10000 rpm for 3-10 min, pouring the upper-layer centrifugate, and repeating: adding absolute ethyl alcohol A to dissolve, disperse and centrifugally separate for 3-5 times to obtain a primary product black powder;

In the step (1), the addition amount of the absolute ethyl alcohol A is as follows according to the volume ratio, and the black mixed solution: anhydrous ethanol a ═ 1: (4-20).

(2) Adding nitric acid into the black powder of the primary product, and carrying out acid washing for 10-360 min to remove impurity phases to obtain a product after impurity removal;

In the step (2), the concentration of nitric acid is 2 wt.% to 10 wt.%, the addition amount of nitric acid is proportioned, and the primary product is black powder: 1 part of nitric acid: (1-20).

(3) and adding absolute ethyl alcohol B with the volume equal to that of the nitric acid into the product after impurity removal, performing centrifugal separation again, pouring out the supernatant centrifugate, dissolving and dispersing the supernatant centrifugate with deionized water with the volume equal to that of the absolute ethyl alcohol B, and performing centrifugal separation for 3-5 times to obtain fct-FePt nano particle black powder, wherein the centrifugal rotation speed is 4000-10000 rpm, and the single centrifugation time is 3-10 min.

In the step (4), the fct-FePt nanoparticles are stored in the absolute ethyl alcohol C.

In the step (4), the magnetic property of the black powder is measured by a comprehensive Physical Property Measurement System (PPMS), the morphology and distribution of the nanoparticles are observed by a field emission Transmission Electron Microscope (TEM), and the phase of the nanoparticles is analyzed by X-ray diffraction (XRD) to confirm that the fct-FePt nanoparticles are obtained.

The FePt nano particles with the fct ordered structure can be directly prepared by the steps, and the particles have high order degree, do not need subsequent annealing and can be directly applied.