A method for preparing lanthanum gadolinium ferrite nanoparticles with high saturation magnetization and magnetic liquid thereof

Abstract

The present invention discloses a method for preparing lanthanum gadolinium ferrite nanoparticles with high saturation magnetization intensity and magnetic liquid thereof, and relates to the technical field of nanomaterials and magnetic liquid sealing. The method for preparing the nanoparticles is as follows: LaCl3·7H2O, GdCl3·6H2O, FeCl3·6H2O and FeSO4·7H2O are weighed according to a ratio, and stirred and dissolved in water to obtain a salt solution; a sodium hydroxide solution is poured into the salt solution, and stirred and heated at the same time to cause a chemical precipitation reaction. The method for preparing the magnetic liquid is as follows: firstly chemically coating the prepared nanoparticles, and then dispersing them to obtain a fluoroether oil-based magnetic liquid. The method regulates the rare earth metal ion La 3+ , Gd 3+ The doping ratio was adjusted and a simple and easy-to-operate chemical precipitation method was used to prepare lanthanum-gadolinium ferrite nanomagnetic particles and magnetic liquids with high saturation magnetization intensity.

Description

Technical Field

[0001] The invention relates to the technical field of nano materials and magnetic liquid sealing, and in particular to a method for preparing high saturation magnetization lanthanum gadolinium ferrite nano particles and magnetic liquid thereof. Background Art

[0002] Magnetic liquid is composed of three parts: base liquid, nano magnetic particles and surfactant. The surfactant chemically coats the nano magnetic particles and then disperses them in the base liquid to form a stable black colloidal solution system. Since magnetic liquid has both magnetism and fluidity, it is widely used in the field of sealing in specific environments. However, fluoroether oil-based magnetic liquid currently faces the problems of low saturation magnetization and uncontrollable raw material quality, which directly affects the seal life and seal pressure resistance.

[0003] The patent document with publication number CN107799262A discloses a high saturation magnetization intensity Mn 0 .8 Zn 0 .2 The preparation method of Fe2O4 nanoparticles and magnetic liquid thereof comprises the following steps: firstly 2+ 、Zn 2+ , Fe 3+ The salt is dispersed into ultrapure water, and NaOH solution is quickly added under mechanical stirring; the reaction solution is then placed in an oven and heated at high temperature to promote the growth of grains and complete the second step of precipitation; the reaction solution is then taken out, fluoroether acid is added, and the particles are coated under mechanical stirring to prevent them from agglomerating, and then the particles are washed and dried; finally, the dried particles are ground and dispersed into a fluoroether oil-based carrier liquid under mechanical stirring to prepare a magnetic liquid. This method is achieved by regulating Mn 2+ 、Zn 2+ The saturation magnetization intensity of the prepared magnetic liquid is still low and cannot meet the requirements of the saturation magnetization intensity of the magnetic liquid in practical applications.

[0004] Patent document with publication number CN116864286A discloses a method for preparing a high saturation magnetization strength gadolinium ferrite silicone oil magnetic liquid, the method comprising (1) doping and regulating the rare earth ion Gd 2+ The invention prepares Gd ferrite nanoparticles with high saturation magnetization by adjusting the ion ratio, and then performs double-layer chemical coating on the particles. The coated particles are then dispersed in silicone oil with high viscosity to prepare Gd ferrite / silicone oil-based magnetic liquid with high saturation magnetization. This method is to dope Gd alone. 3+ions, the saturation magnetization of the prepared gadolinium ferrite nanoparticles reached up to 95.5emu / g. Although the saturation magnetization of gadolinium ferrite nanoparticles has been improved to a certain extent, there are still certain defects in actual use.

[0005] It can be seen that the saturation magnetization intensity of the magnetic liquid prepared by the current method still has certain defects in practical application, and the saturation magnetization intensity of the nanomagnetic particles and the magnetic liquid needs to be further improved. Summary of the invention

[0006] Based on the problem that the saturation magnetization intensity of currently prepared nanomagnetic particles and magnetic liquids still has certain defects in practical applications, the purpose of the present invention is to provide a method for preparing lanthanum gadolinium ferrite nanoparticles with high saturation magnetization intensity and magnetic liquids thereof, which method can regulate the saturation magnetization intensity of rare earth metal ions La 3+ , Gd 3+ The doping ratio was adjusted and a simple and easy-to-operate chemical precipitation method was used to prepare lanthanum-gadolinium ferrite nanomagnetic particles and magnetic liquids with high saturation magnetization intensity.

[0007] The present invention is achieved through the following technical solutions:

[0008] In a first aspect, the present application provides a method for preparing lanthanum gadolinium ferrite nanoparticles with high saturation magnetization, comprising the following steps:

[0009] Weigh LaCl3·7H2O, GdCl3·6H2O, FeCl3·6H2O and FeSO4·7H2O according to the ratio, stir and dissolve them in water to obtain a salt solution;

[0010] The sodium hydroxide solution is poured into the salt solution, and the solution is stirred and heated at the same time, so that a chemical precipitation reaction occurs to obtain lanthanum gadolinium ferrite nanoparticles with high saturation magnetization intensity.

[0011] By doping with two rare earth metal ions, La 3+ , Gd 3+ will occupy the A site of the spinel structure, and part of the Fe 3+ will be squeezed into position B. 3+ , Gd 3+ When the doping amount of La is small, the net magnetic moment of the lanthanum gadolinium ferrite nanoparticle molecules becomes larger, thereby increasing the saturation magnetization intensity of the lanthanum gadolinium ferrite nanoparticles. 3+ , Gd 3+ When the doping amount is larger, more La 3+ , Gd 3+ Will occupy the A position, and more Fe 3+The super exchange interaction between metal ions at the BB site is enhanced, so that the arrangement of the magnetic moments of some metal ions at the B site gradually changes from parallel to antiparallel. 3+ , Gd 3+ The increase of doping amount decreases the saturation magnetization intensity, which no longer increases but decreases. 3+ , Gd 3+ The occupancy of ions in the cubic spinel structure makes the prepared lanthanum gadolinium ferrite nanomagnetic particles have a high saturation magnetization intensity, and the lanthanum gadolinium ferrite nanomagnetic particles can be used to prepare a magnetic liquid with a high saturation magnetization intensity.

[0012] As a preferred embodiment of the present application, the mass ratio of LaCl3·7H2O, GdCl3·6H2O, FeCl3·6H2O and FeSO4·7H2O is (0.1~50):(0.1~50):(5~100):(3~100).

[0013] As a preferred embodiment of the present application, the molar ratio of sodium hydroxide solution to FeSO4·7H2O is 8-16.

[0014] As a preferred embodiment of the present application, the reaction temperature during the chemical precipitation reaction is 50° C. to 100° C. The stirring rate is 300 to 1000 rpm, and the stirring time is 20 to 90 minutes.

[0015] In a second aspect, the present application provides a method for preparing a magnetic liquid using lanthanum gadolinium ferrite nanoparticles with high saturation magnetization intensity according to any one of the above embodiments, comprising the following steps:

[0016] A. Preparation of lanthanum gadolinium ferrite nanoparticles with high saturation magnetization intensity: LaCl3·7H2O, GdCl3·6H2O, FeCl3·6H2O and FeSO4·7H2O are weighed according to a ratio, and stirred and dissolved in water to obtain a salt solution; sodium hydroxide solution is poured into the salt solution, and stirred and heated at the same time to cause a chemical precipitation reaction;

[0017] B. Chemical coating of nanomagnetic particles: After the precipitation reaction is completed, the pH value of the reaction solution is adjusted, and perfluoropolyether carboxylic acid is added thereto, followed by stirring and heating. The coated particles are then washed with pure water, placed on a magnet to separate the magnetic particles, and then washed with water until the pH value of the solution is 6.5-7.5, and then washed with anhydrous ethanol to remove the moisture in the particles;

[0018] C. Preparation of fluoroether oil-based magnetic liquid by particle dispersion: The particles after alcohol washing are transferred to a container, perfluoropolyether oil is added thereto, and the particles are dispersed under stirring and heating treatment to obtain a fluoroether oil-based magnetic liquid.

[0019] As a preferred embodiment of the present application, in the chemical coating of the nanomagnetic particles, after the precipitation reaction is completed, the pH value of the reaction solution is adjusted to 6-8.

[0020] As a preferred embodiment of the present application, in the chemical coating of the nano-magnetic particles, the amount of the added perfluoropolyether carboxylic acid accounts for 30 wt % to 80 wt % of the content of the nano-magnetic particles.

[0021] As a preferred embodiment of the present application, in the chemical coating of the nanomagnetic particles, the temperature of the heating treatment is 50° C. to 100° C., wherein the stirring rate is 300 to 1000 rpm, and the stirring time is 30 to 180 minutes.

[0022] As a better implementation in the present application, in the preparation of fluoroether oil-based magnetic liquid by particle dispersion, the mass ratio of magnetic particles to perfluoropolyether oil is 1 / 4 to 3 / 2.

[0023] As a preferred embodiment of the present application, in the preparation of fluoroether oil-based magnetic liquid by particle dispersion, the heating temperature is 50° C. to 100° C., wherein the stirring rate is 100 to 800 rpm, and the stirring time is 1 to 5 hours.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] (1) The present invention doped two rare earth metal ions and regulated La 3+ , Gd 3+ The ion occupation in the cubic spinel structure makes the prepared lanthanum gadolinium ferrite nano-magnetic particles have a high saturation magnetization intensity, and the lanthanum gadolinium ferrite nano-magnetic particles can be used to prepare a magnetic liquid with a high saturation magnetization intensity;

[0026] (2) The lanthanum gadolinium ferrite fluoroether oil-based magnetic liquid prepared by the present invention has a high saturation magnetization intensity and can be used in a high pressure difference sealing environment;

[0027] (3) The lanthanum gadolinium ferrite fluoroether oil-based magnetic liquid prepared by the present invention has high dispersion stability, and no stratification phenomenon is observed after centrifugation at a speed of 3000 r / min for 3 hours;

[0028] (4) The high saturation magnetization lanthanum gadolinium nanoparticles and magnetic liquid prepared by the present invention have simple preparation process, easy operation, high efficiency, low equipment requirements, and good magnetic properties and stable performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0030] Figure 1 is a VSM image of the lanthanum gadolinium ferrite magnetic particles prepared in Example 1 of the present invention;

[0031] Figure 2 This is a VSM diagram of the lanthanum gadolinium ferrite fluoroether oil-based magnetic liquid prepared in Example 1 of the present invention;

[0032] Figure 3 This is a comparison diagram of the lanthanum gadolinium ferrite fluoroether oil-based magnetic liquid prepared in Example 1 of the present invention before and after centrifugation;

[0033] Figure 4 is a VSM image of the lanthanum gadolinium ferrite magnetic particles prepared in Example 2 of the present invention;

[0034] Figure 5 This is a VSM diagram of the lanthanum gadolinium ferrite fluoroether oil-based magnetic liquid prepared in Example 2 of the present invention;

[0035] Figure 6 is a VSM image of the lanthanum gadolinium ferrite magnetic particles prepared in Example 3 of the present invention;

[0036] Figure 7 This is a VSM diagram of the lanthanum gadolinium ferrite fluoroether oil-based magnetic liquid prepared in Example 3 of the present invention;

[0037] Figure 8 is a VSM image of the lanthanum gadolinium ferrite magnetic particles prepared in Example 4 of the present invention;

[0038] Fig. 9 This is a VSM diagram of the lanthanum gadolinium ferrite fluoroether oil-based magnetic liquid prepared in Example 4 of the present invention;

[0039] Fig.10 is a VSM image of the lanthanum gadolinium ferrite magnetic particles prepared in Example 5 of the present invention;

[0040] Fig.11 This is a VSM diagram of the lanthanum gadolinium ferrite fluoroether oil-based magnetic liquid prepared in Example 5 of the present invention;

[0041] Fig.12 is a VSM image of the lanthanum gadolinium ferrite magnetic particles prepared in Example 6 of the present invention;

[0042] Fig.13 This is a VSM diagram of the lanthanum gadolinium ferrite fluoroether oil-based magnetic liquid prepared in Example 6 of the present invention;

[0043] Fig.14 is the VSM diagram of the ferrite nanoparticles prepared in Comparative Example 1;

[0044] Fig.15 is a VSM image of the gadolinium ferrite nanoparticles prepared in Comparative Example 2;

[0045] Fig.16 This is the VSM diagram of the lanthanum ferrite nanoparticles prepared in Comparative Example 3. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0047] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] Example 1

[0049] This embodiment provides a method for preparing a magnetic liquid, which is carried out according to the following steps:

[0050] S1. Preparation of lanthanum-gadolinium iron oxide nanoparticles with high saturation magnetization

[0051] 0.3 g LaCl3·7H2O, 2.68 g GdCl3·6H2O, 32.87 g FeCl3·6H2O and 22.24 g FeSO4·7H2O were weighed, dissolved in 600 ml ultrapure water with stirring using a glass rod to obtain a salt solution, and then 32 g NaOH was weighed and dissolved in 200 ml ultrapure water to obtain a NaOH solution; then, the NaOH solution was quickly poured into the salt solution while mechanically stirring at a stirring rate of 400 r / min, a stirring time of 40 minutes, and a heating temperature of 70° C. to obtain lanthanum gadolinium ferrite nanoparticles.

[0052] S2. Chemical coating of lanthanum gadolinium ferrite nanoparticles

[0053] Add dilute hydrochloric acid solution to the result of step S1, adjust the pH of the reaction solution to 7, and uniformly add surfactant perfluoropolyether carboxylic acid thereto, the amount of perfluoropolyether carboxylic acid being 50wt% of the content of the magnetic particles. Mechanically stir the coating, the stirring rate is 400r / min, the reaction temperature is 70°C, and the reaction time is 2 hours. Wash the coated particles with ultrapure water, place them on a magnet to separate the magnetic particles, wash with water until the solution pH is 7, and then wash with anhydrous ethanol several times to remove the moisture in the particles.

[0054] S3. Preparation of Fluoroether Oil-Based Magnetic Liquid by Particle Dispersion

[0055] The alcohol-washed particles were transferred to a suitable beaker, and perfluoropolyether oil was added thereto, wherein the mass ratio of magnetic particles to perfluoropolyether oil was 2:3. Fluoroether oil-based magnetic liquid was obtained by mechanical stirring and dispersion, with a stirring rate of 400 r / min, a reaction temperature of 70°C, and a dispersion time of 4 hours. Among them, anhydrous ethanol will be completely evaporated during the dispersion process.

[0056] The saturation magnetization intensity of the prepared lanthanum gadolinium ferrite nanoparticles was tested using a VSM3107 vibrating magnetometer (test conditions: room temperature, -25000 Oe~25000 Oe). Figure 1 and Figure 2 As shown in the figure, the test result is 125.47emu / g, and the saturation magnetization intensity of the lanthanum gadolinium ferrite fluoroether oil-based magnetic liquid is 64.67emu / g. Figure 3 As shown, the magnetic liquid was placed in a centrifuge tube and centrifuged at 3000 r / min for 3 hours, and no stratification was observed, indicating that the prepared lanthanum gadolinium iron oxide fluoroether oil-based magnetic liquid has a higher saturation magnetization intensity and dispersion stability.

[0057] Example 2

[0058] This embodiment provides a method for preparing a magnetic liquid, which is carried out according to the following steps:

[0059] S1. Preparation of high saturation magnetization lanthanum gadolinium ferrite nanoparticles

[0060] 2.8g LaCl3·7H2O, 1.87g GdCl3·6H2O, 52.71g FeCl3·6H2O and 34.98g FeSO4·7H2O were weighed, stirred with a glass rod and dissolved in 1000ml ultrapure water to obtain a salt solution, and then 50.32g NaOH was weighed and dissolved in 500ml ultrapure water to obtain a NaOH solution. Then, the NaOH solution was quickly poured into the salt solution, and mechanical stirring was performed at the same time, the stirring rate was 300r / min, the stirring time was 50min, and the heating temperature was 70°C to obtain lanthanum gadolinium ferrite nanoparticles.

[0061] S2. Chemical coating of lanthanum gadolinium ferrite nanoparticles

[0062] Add dilute hydrochloric acid solution to the result of step S1 to adjust the pH of the reaction solution to 7, and uniformly add surfactant perfluoropolyether carboxylic acid thereto, the amount of perfluoropolyether carboxylic acid being 40wt% of the content of the magnetic particles. Mechanically stir the coating, the stirring rate is 300r / min, the reaction temperature is 70°C, and the reaction time is 2 hours. Wash the coated particles with ultrapure water, place them on a magnet to separate the magnetic particles, wash with water until the solution pH is 7.5, and then wash with anhydrous ethanol several times to remove the moisture in the particles.

[0063] S3. Preparation of Fluoroether Oil-Based Magnetic Liquid by Particle Dispersion

[0064] The alcohol-washed particles were transferred to a suitable beaker, and perfluoropolyether oil was added thereto, wherein the mass ratio of magnetic particles to perfluoropolyether oil was 3:7. Fluoroether oil-based magnetic liquid was obtained by mechanical stirring and dispersion, with a stirring rate of 300 r / min, a reaction temperature of 80°C, and a dispersion time of 3 hours. Among them, anhydrous ethanol will be completely volatilized during the dispersion process.

[0065] The saturation magnetization intensity of the prepared lanthanum gadolinium ferrite nanoparticles was tested using a VSM3107 vibrating magnetometer. Figure 4 and Figure 5 As shown, the test result is 108.19emu / g, and the saturation magnetization of the lanthanum gadolinium ferrite fluoride ether oil-based magnetic liquid is 48.09emu / g. The magnetic liquid was placed in a centrifuge tube and centrifuged at 3000r / min for 3 hours, and no stratification was observed, indicating that the prepared lanthanum gadolinium ferrite fluoride ether oil-based magnetic liquid has a high saturation magnetization and dispersion stability.

[0066] Example 3

[0067] This embodiment provides a method for preparing a magnetic liquid, which is carried out according to the following steps:

[0068] S1. Preparation of high saturation magnetization lanthanum gadolinium ferrite nanoparticles

[0069] 1.83 g LaCl3·7H2O, 1.83 g GdCl3·6H2O, 40.54 g FeCl3·6H2O and 27.44 g FeSO4·7H2O were weighed, stirred with a glass rod and dissolved in 700 ml ultrapure water to obtain a salt solution, and then 31.58 g NaOH was weighed and dissolved in 300 ml ultrapure water to obtain a NaOH solution. Then, the NaOH solution was quickly poured into the salt solution, and mechanical stirring was performed at the same time, the stirring rate was 300 r / min, the stirring time was 60 minutes, and the heating temperature was 70°C to obtain lanthanum gadolinium ferrite nanoparticles.

[0070] S2. Chemical coating of lanthanum gadolinium ferrite nanoparticles

[0071] Add dilute hydrochloric acid solution to the result of step S1 to adjust the pH of the reaction solution to 7.5, and uniformly add surfactant perfluoropolyether carboxylic acid thereto, the amount of perfluoropolyether carboxylic acid used is 35wt% of the content of the magnetic particles. Mechanical stirring coating, stirring rate of 400r / min, reaction temperature of 70°C, reaction time of 1 hour. Wash the coated particles with ultrapure water, place them on a magnet to separate the magnetic particles, wash with water until the solution pH = 7, and then wash with anhydrous ethanol several times to remove the moisture in the particles.

[0072] S3. Preparation of Fluoroether Oil-Based Magnetic Liquid by Particle Dispersion

[0073] The alcohol-washed particles were transferred to a suitable beaker, and perfluoropolyether oil was added thereto, wherein the mass ratio of magnetic particles to perfluoropolyether oil was 1:1. Fluoroether oil-based magnetic liquid was obtained by mechanical stirring and dispersion, with a stirring rate of 200 r / min, a reaction temperature of 70°C, and a dispersion time of 5 h. Among them, anhydrous ethanol will be completely evaporated during the dispersion process.

[0074] The saturation magnetization intensity of the prepared lanthanum gadolinium ferrite nanoparticles was tested using a VSM3107 vibrating magnetometer. Figure 6 and Figure 7 As shown in the figure, the test result is 112.19 emu / g, and the saturation magnetization of the lanthanum gadolinium ferrite fluoride oil-based magnetic liquid is 69.21 emu / g. The magnetic liquid was placed in a centrifuge tube and centrifuged at 3000r / min for 3h, and no stratification was observed, indicating that the prepared lanthanum gadolinium ferrite fluoride oil-based magnetic liquid has a high saturation magnetization and dispersion stability.

[0075] Example 4

[0076] This embodiment provides a method for preparing a magnetic liquid, which is carried out according to the following steps:

[0077] S1. Preparation of high saturation magnetization lanthanum gadolinium ferrite nanoparticles

[0078] Weigh 2g LaCl3·7H2O, 0.22g GdCl3·6H2O, 24.33g FeCl3·6H2O and 16.68g FeSO4·7H2O, stir with a glass rod and dissolve in 600ml ultrapure water to obtain a salt solution, and then weigh 21.6g NaOH and dissolve in 300ml ultrapure water to obtain a NaOH solution. Then, the NaOH solution is quickly poured into the salt solution, and mechanical stirring is performed at the same time, the stirring rate is 400r / min, the stirring time is 40min, and the heating temperature is 80℃ to obtain lanthanum gadolinium ferrite nanoparticles.

[0079] S2. Chemical coating of lanthanum gadolinium ferrite particles

[0080] Add dilute hydrochloric acid solution to the result of step S1 to adjust the pH of the reaction solution to 7.5, and uniformly add surfactant perfluoropolyether carboxylic acid thereto, the amount of perfluoropolyether carboxylic acid being 45wt% of the content of the magnetic particles. Mechanically stir the coating, the stirring rate is 400r / min, the reaction temperature is 80°C, and the reaction time is 1h. Wash the coated particles with ultrapure water, place them on a magnet to separate the magnetic particles, wash with water until the solution pH is 6.5, and then wash with anhydrous ethanol several times to remove the moisture in the particles.

[0081] S3. Preparation of Fluoroether Oil-Based Magnetic Liquid by Particle Dispersion

[0082] The alcohol-washed particles were transferred to a suitable beaker, and perfluoropolyether oil was added thereto, wherein the mass ratio of magnetic particles to perfluoropolyether oil was 2:3. Fluoroether oil-based magnetic liquid was obtained by mechanical stirring and dispersion, with a stirring rate of 400 r / min, a reaction temperature of 70°C, and a dispersion time of 3 h. Among them, anhydrous ethanol will be completely evaporated during the dispersion process.

[0083] The saturation magnetization intensity of the prepared lanthanum gadolinium ferrite nanoparticles was tested using a VSM3107 vibrating magnetometer. Figure 8 and Fig. 9 As shown in the figure, the test result is 100.31 emu / g, and the saturation magnetization of the lanthanum gadolinium ferrite fluoride ether oil-based magnetic liquid is 60.37 emu / g. The magnetic liquid was placed in a centrifuge tube and centrifuged at 3000r / min for 3h, and no stratification was observed, indicating that the prepared lanthanum gadolinium ferrite fluoride ether oil-based magnetic liquid has a high saturation magnetization and dispersion stability.

[0084] Example 5

[0085] This embodiment provides a method for preparing a magnetic liquid, which is carried out according to the following steps:

[0086] S1. Preparation of high saturation magnetization lanthanum gadolinium ferrite nanoparticles

[0087] Weigh 2.19g LaCl3·7H2O, 0.55g GdCl3·6H2O, 30.27g FeCl3·6H2O and 20.49g FeSO4·7H2O, stir with a glass rod and dissolve in 600ml ultrapure water to obtain a salt solution, and then weigh 26.53g NaOH and dissolve in 200ml ultrapure water to obtain a NaOH solution. Then, quickly pour the NaOH solution into the salt solution, and mechanically stir at the same time, with a stirring rate of 200r / min, a stirring time of 50min, and a heating temperature of 70°C to obtain lanthanum gadolinium ferrite nanoparticles.

[0088] S2. Chemical coating of lanthanum gadolinium ferrite particles

[0089] Add dilute hydrochloric acid solution to the result of step S1 to adjust the pH of the reaction solution to 8, and uniformly add surfactant perfluoropolyether carboxylic acid thereto, the amount of perfluoropolyether carboxylic acid used is 42wt% of the content of the magnetic particles. Mechanical stirring coating, stirring rate of 300r / min, reaction temperature of 70°C, reaction time of 1.5h. Wash the coated particles with ultrapure water, place them on a magnet to separate the magnetic particles, wash with water until the solution pH is 7.5, and then wash with anhydrous ethanol several times to remove the moisture in the particles.

[0090] S3. Preparation of Fluoroether Oil-Based Magnetic Liquid by Particle Dispersion

[0091] The alcohol-washed particles were transferred to a suitable beaker, and perfluoropolyether oil was added thereto, wherein the mass ratio of magnetic particles to perfluoropolyether oil was 1:1. Fluoroether oil-based magnetic liquid was obtained by mechanical stirring and dispersion, with a stirring rate of 200 r / min, a reaction temperature of 80°C, and a dispersion time of 5 h. Among them, anhydrous ethanol will be completely volatilized during the dispersion process.

[0092] The saturation magnetization intensity of the prepared lanthanum gadolinium ferrite nanoparticles was tested using a VSM3107 vibrating magnetometer. Fig.10 and Fig.11 As shown in the figure, the test result is 104.1 emu / g, and the saturation magnetization of the lanthanum gadolinium ferrite fluoride ether oil-based magnetic liquid is 66.21 emu / g. The magnetic liquid was placed in a centrifuge tube and centrifuged at 3000r / min for 3h, and no stratification was observed, indicating that the prepared lanthanum gadolinium ferrite fluoride ether oil-based magnetic liquid has a high saturation magnetization and dispersion stability.

[0093] Example 6

[0094] This embodiment provides a method for preparing a magnetic liquid, which is carried out according to the following steps:

[0095] S1. Preparation of high saturation magnetization lanthanum gadolinium ferrite nanoparticles

[0096] Weigh 0.91g LaCl3·7H2O, 1.36g GdCl3·6H2O, 25.14g FeCl3·6H2O and 17.01g FeSO4·7H2O, stir with a glass rod and dissolve in 500ml ultrapure water to obtain a salt solution, and then weigh 22.03g NaOH and dissolve in 100ml ultrapure water to obtain a NaOH solution. Then, quickly pour the NaOH solution into the salt solution, and mechanically stir at the same time, with a stirring rate of 300r / min, a stirring time of 40min, and a heating temperature of 60°C to obtain lanthanum gadolinium ferrite nanoparticles.

[0097] S2. Chemical coating of lanthanum gadolinium ferrite particles

[0098] Add dilute hydrochloric acid solution to the result of step S1 to adjust the pH of the reaction solution to 6.5, and uniformly add a surfactant, perfluoropolyether carboxylic acid, to the reaction solution, wherein the amount of perfluoropolyether carboxylic acid is 40wt% of the content of the magnetic particles. Mechanical stirring and coating, the stirring rate is 300r / min, the reaction temperature is 60°C, and the reaction time is 2h. Wash the coated particles with ultrapure water, place them on a magnet to separate the magnetic particles, wash with water until the solution pH is 7, and then wash with anhydrous ethanol several times to remove the moisture in the particles.

[0099] S3. Preparation of Fluoroether Oil-Based Magnetic Liquid by Particle Dispersion

[0100] The alcohol-washed particles were transferred to a suitable beaker, and perfluoropolyether oil was added thereto, wherein the mass ratio of magnetic particles to perfluoropolyether oil was 2:3. Fluoroether oil-based magnetic liquid was obtained by mechanical stirring and dispersion, with a stirring rate of 300 r / min, a reaction temperature of 60°C, and a dispersion time of 4 h. Among them, anhydrous ethanol will be completely volatilized during the dispersion process.

[0101] The saturation magnetization intensity of the prepared lanthanum gadolinium ferrite nanoparticles was tested using a VSM3107 vibrating magnetometer. Fig.12 and Fig.13 As shown in the figure, the test result is 115.82 emu / g, and the saturation magnetization of the lanthanum gadolinium ferrite fluoride ether oil-based magnetic liquid is 63.58 emu / g. The magnetic liquid was placed in a centrifuge tube and centrifuged at 3000r / min for 3h, and no stratification was observed, indicating that the prepared lanthanum gadolinium ferrite fluoride ether oil-based magnetic liquid has a high saturation magnetization and dispersion stability.

[0102] Comparative Example 1

[0103] This comparative example provides a method for preparing a magnetic liquid. The specific method is the same as that of Example 1, except that LaCl3·7H2O and GdCl3·6H2O are not added, and the remaining steps are the same. Fig.14 As shown, the saturation magnetization of the ferrite nanoparticles is 55.28 emu / g. The prepared ferrite magnetic liquid is centrifuged at a rate of 3000 r / min for 3 hours, and no stratification is observed. The saturation magnetization of the prepared magnetic liquid is low.

[0104] It can be seen that doping a certain amount of LaCl3·7H2O and GdCl3·6H2O can increase the saturation magnetization intensity of the magnetic liquid.

[0105] Comparative Example 2

[0106] This comparative example provides a method for preparing a magnetic liquid. The specific method is the same as that of Example 1, except that LaCl3·7H2O is not added, and the remaining steps are the same. Fig.15 As shown, the saturation magnetization of the gadolinium ferrite nanoparticles is 89.2 emu / g. The prepared gadolinium ferrite magnetic liquid is centrifuged at a rate of 3000 r / min for 3 hours, and no stratification is observed. The saturation magnetization of the prepared magnetic liquid is lower than that of the lanthanum gadolinium ferrite magnetic liquid.

[0107] It can be seen that doping a certain amount of LaCl3·7H2O and GdCl3·6H2O can synergistically improve the saturation magnetization intensity of the magnetic liquid.

[0108] Comparative Example 3

[0109] This comparative example provides a method for preparing a magnetic liquid. The specific method is the same as that of Example 1, except that GdCl3·6H2O is not added, and the remaining steps are the same. Fig.16 As shown, the saturation magnetization of lanthanum ferrite nanoparticles is 76.87 emu / g. The prepared lanthanum ferrite magnetic liquid is centrifuged at 3000r / min for 3h without stratification. The saturation magnetization of the prepared magnetic liquid is lower than that of the lanthanum gadolinium ferrite magnetic liquid.

[0110] It can be seen that doping a certain amount of LaCl3·7H2O and GdCl3·6H2O can synergistically improve the saturation magnetization intensity of the magnetic liquid.

[0111] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing lanthanum gadolinium ferrite nanoparticles with high saturation magnetization, characterized in that: Weigh LaCl3·7H2O, GdCl3·6H2O, FeCl3·6H2O and FeSO4·7H2O according to the ratio, stir and dissolve them in water to obtain a salt solution; Pouring sodium hydroxide solution into the salt solution, stirring and heating the solution, so that a chemical precipitation reaction occurs to obtain lanthanum gadolinium ferrite nanoparticles with high saturation magnetization intensity; The mass ratio of LaCl3·7H2O, GdCl3·6H2O, FeCl3·6H2O and FeSO4·7H2O is (0.1~50):(0.1~50):(5~100):(3~100).

2. The method for preparing lanthanum gadolinium ferrite nanoparticles with high saturation magnetization according to claim 1, characterized in that: The molar ratio of sodium hydroxide solution to FeSO4·7H2O is 8-16.

3. The method for preparing lanthanum gadolinium ferrite nanoparticles with high saturation magnetization according to claim 1, characterized in that: The reaction temperature during the chemical precipitation reaction is 50°C to 100°C.

4. A method for preparing a magnetic liquid using lanthanum gadolinium ferrite nanoparticles with high saturation magnetization prepared by the method described in any one of claims 1 to 3, characterized in that: The following steps are involved: Preparation of lanthanum gadolinium ferrite nanoparticles with high saturation magnetization intensity: LaCl3·7H2O, GdCl3·6H2O, FeCl3·6H2O and FeSO4·7H2O are weighed according to a ratio, and stirred and dissolved in water to obtain a salt solution; sodium hydroxide solution is poured into the salt solution, and stirred and heated at the same time to cause a chemical precipitation reaction; Chemical coating of nanomagnetic particles: After the precipitation reaction is completed, the pH value of the reaction solution is adjusted, and perfluoropolyether carboxylic acid is added thereto, followed by stirring and heating. The coated particles are then washed with pure water, and the magnetic particles are separated by placing them on a magnet. The particles are then washed with water until the pH value of the solution is 6.5 to 7.5, and then washed with anhydrous ethanol to remove the water from the particles. Preparation of fluoroether oil-based magnetic liquid by particle dispersion: the particles after alcohol washing are transferred to a container, perfluoropolyether oil is added thereto, and the particles are dispersed under stirring and heating treatment to obtain a fluoroether oil-based magnetic liquid.

5. The method for preparing a magnetic liquid according to claim 4, characterized in that: In the chemical coating of the nanomagnetic particles, after the precipitation reaction is completed, the pH value of the reaction solution is adjusted to 6-8.

6. The method for preparing a magnetic liquid according to claim 4, characterized in that: In the chemical coating of the nano-magnetic particles, the amount of the added perfluoropolyether carboxylic acid accounts for 30wt% to 80wt% of the content of the nano-magnetic particles.

7. The method for preparing a magnetic liquid according to claim 4, characterized in that: In the chemical coating of the nanomagnetic particles, the temperature of the heating treatment is 50°C to 100°C.

8. The method for preparing a magnetic liquid according to claim 4, characterized in that: In the preparation of fluoroether oil-based magnetic liquid by particle dispersion, the mass ratio of magnetic particles to perfluoropolyether oil is 1 / 4 to 3 / 2.

9. The method for preparing a magnetic liquid according to claim 4, characterized in that: In the preparation of fluoroether oil-based magnetic liquid by particle dispersion, the temperature of heating treatment is 50°C to 100°C.

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