CN107799262B - A kind of high saturation and magnetic intensity Mn0.8Zn0.2Fe2O4The preparation method of nano particle and its magnetic liquid - Google Patents

Abstract

The invention relates to the field of novel nano-functional materials, specifically a method for preparing Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles with high saturation magnetization and a magnetic liquid thereof. Specifically, Mn ²⁺ , Zn ²⁺ , Fe ³⁺ Disperse the salt into ultrapure water, quickly add NaOH solution under mechanical stirring; then place the reaction solution in an oven and heat it at high temperature to promote the growth of crystal grains and complete the second step of precipitation; then take out the reaction solution and add fluoroether acid, and under the action of mechanical stirring, coat the particles to avoid their agglomeration, and then wash and dry the particles; finally, grind the dry particles, and disperse them into the fluoroether oil-based carrier liquid under mechanical stirring to prepare the magnetic liquid. The Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles prepared by the present invention have the advantages of high saturation magnetization, superparamagnetism, and high oxidation resistance stability. The prepared fluoroether oil-based magnetic liquid can be used in high temperature, corrosion, In the field of rotary shaft seals in oxidizing environments.

Description

A kind of high saturation magnetization Mn0.8Zn0.2Fe2O4 nanoparticles and its magnetic liquid Preparation

technical field

The invention relates to the field of novel nano-functional materials, and relates to a nano-magnetic particle with high saturation magnetization, superparamagnetism and high oxidation resistance stability and its magnetic liquid, specifically a high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ Nanoparticles and their preparation methods for magnetic fluids.

Background technique

Magnetic liquid is a stable colloidal solution system formed by coating nano-scale magnetic particles with surfactants and then dispersing them into the base carrier liquid. It is widely used in new types of sealing and targeting carriers because it has both the magnetism of solid magnets and the fluidity of liquids. Medicine, magnetic heat therapy and other fields. In recent years, the research on Fe ₃ O ₄ nanoparticles has been quite mature. However, due to the presence of Fe ²⁺ ions, the nanoparticles are oxidized during long-term application, and the magnetic properties of magnetic liquids decrease.

In order to improve the anti-oxidation stability and saturation magnetization of the magnetic liquid, Mn ²⁺ and Zn ²⁺ were substituted for Fe ²⁺ to prepare manganese zinc ferrite nano-magnetic particles. Theoretically, when the Zn ²⁺ doping ratio x is 0.2, the saturation magnetization of MnZn ferrite nanoparticles is the highest. Among them, Li Dingguo and others concluded in manganese zinc ferrite nanoparticles and their magnetic liquids that when the zinc doping ratio is 0.2, the saturation magnetization of the particles is the highest. Arulmurugan R. got the same conclusion in Mn-Zn Ferrite Nanoparticles for Ferrofuid Preparation: Study on Thermal-magnetic Properties. Zhang Hongtao also studied the effect of doping ratio on the magnetic properties of particles in the Chinese patent: a preparation method of manganese-zinc ferrite nanopowder (application number: 201410815386.1), and concluded that when the doping ratio of manganese-zinc is 0.2, the preparation The saturation magnetization of MnZn nanoparticles is the highest. However, in the case of a fixed zinc doping ratio of 0.2, the saturation magnetization of the prepared MnZn ferrite nanoparticles is still low, which cannot meet the requirements of high saturation magnetization for magnetic liquids in practical industrial applications.

Contents of the invention

The object of the present invention is to solve the above technical problems and provide a method for preparing Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles with high saturation magnetization and a magnetic liquid thereof. In the method, the nanoparticles are crystallized and grown in two steps through an improved co-precipitation method.

Concrete technical scheme of the present invention is:

A preparation method of high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles, the method adopts chemical co-precipitation method to prepare high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles, and the preparation process is carried out in two steps Precipitation, first according to the conventional method, under strong mechanical stirring, add excess NaOH solution to the salt ion prepared according to a certain molar ratio. Then the obtained solution is improved and placed in a high-temperature oven to keep warm to promote the crystallization and growth of particles. The obtained particles with high saturation magnetization are coated with the surfactant fluoroether acid, and then dispersed into the fluoroether oil to prepare the magnetic liquid.

A method for preparing Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles with high saturation magnetization and magnetic liquid thereof, specifically comprising the following steps:

A. Weigh MnCl ₂ 4H ₂ O, ZnCl ₂ , FeCl ₃ 4H ₂ O salts in molar ratio (0.8:0.2:2), put them in 500-2000ml ultrapure water at 50-100℃, stir until After completely dissolving, pour it into a reaction kettle with a heat preservation temperature of 50-100°C. Weigh 10-50g of NaOH powder, dissolve it in ultrapure water, and then quickly add it to the reaction kettle. At the same time, carry out strong mechanical stirring on the mixed solution. The stirring speed is 500-1000r/min, and the stirring time is 10-60min.

B. Put the mixture obtained in A into a high-temperature oven for heat preservation at a temperature of 100-500°C and a heat preservation time of 1-5 hours, and use high temperature to promote the crystallization and growth of particles.

C. Wash and lower the temperature of the mixed solution obtained in B to 50-80°C, and adjust its pH value to 6-7, and add a suitable surfactant, fluether acid, to the mixed solution in a uniform dropwise manner, with a mass of 2-8g, and stir 2-10h to coat the nanoparticles, the stirring speed is 500-1000r/min; then, the particles are washed with ultrapure water until the pH value is close to neutral, and the water is removed by magnetic separation, and then the obtained viscous material is dried in a vacuum drying oven , the drying temperature is 50-100° C., and the drying time is 5-10 hours, and Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles with high saturation magnetization can be prepared.

Using the high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles prepared by the above method, the method for further preparing the magnetic liquid comprises the following steps:

D. Grind the particles with a mortar, screen to remove larger particles, and disperse the smaller particles into the fluoroether oil-based carrier liquid at a stirring speed of 500-1000r/min for 2-10 hours to prepare a magnetic liquid. The base carrier liquid is perfluoropolyether oil, and the mass fraction of the dispersed particles in the magnetic liquid is 30-50%.

The positive effects of the present invention are reflected in:

(1) The high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles prepared by the present invention and their magnetic liquid, the saturation magnetization of the particles prepared by coating the two-step precipitation method is as high as 54emu/g, and has extremely low coercivity strength, and higher oxidation stability than Fe ₃ O ₄ nanoparticles.

(2) The high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticle and its magnetic liquid prepared by the present invention can be stably used in an oxidizing environment for a long time.

(3) The high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles and their magnetic liquids prepared by the present invention have simple preparation process and low requirements on equipment.

Description of drawings

FIG. 1 is an XRD pattern of fluether acid-coated high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles prepared in Example 1.

FIG. 2 is an SEM image of fluether acid-coated high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles prepared in Example 1.

FIG. 3 is the FTIR image of the fluether acid-coated high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles prepared in Example 1.

FIG. 4 is a VSM diagram of the high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles prepared in Example 1.

Detailed ways

The present invention is further described below in conjunction with embodiment, but does not limit the scope of the present invention.

Example 1:

A preparation method of high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles, comprising the following steps:

A. Weigh MnCl ₂ 4H ₂ O, ZnCl ₂ , FeCl ₃ 4H ₂ O salts in a molar ratio (0.8:0.2:2), place them in 500ml ultrapure water at 85°C, stir until completely dissolved and pour Put it into a reaction kettle with a heat preservation temperature of 85°C. Weigh 25g of NaOH powder, dissolve it in ultrapure water, then quickly add it into the reaction kettle, and at the same time, carry out strong mechanical stirring on the mixed solution, the stirring speed is 800r/min, and the stirring time is 60min.

B. Put the mixture obtained in A into a high-temperature oven to keep warm at 200°C for 4 hours, and use high temperature to promote the crystallization and growth of particles.

C. Wash and cool the mixed solution obtained in B to 70°C, and adjust its pH value to 6.23. Add a suitable surfactant, fluether acid, to the mixed solution in a uniform dropwise manner, with a mass of 3 g, and stir for 3 hours to coat the nanoparticles. The stirring speed is 500r/min; then, the particles are washed with ultrapure water until the pH value is close to neutral, and the water is removed by magnetic separation, and then the obtained viscous material is dried in a vacuum drying oven at a drying temperature of 80°C and a drying time of After 8 hours, Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles with high saturation magnetization can be prepared.

A method for further preparing a magnetic liquid using the high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles prepared above:

D. Grind the particles with a mortar, then weigh an appropriate amount of particles and fluoroether oil, wherein the solid content of the particles is 42%, with a stirring speed of 500r/min, mechanically stir for 5h to disperse the particles into the fluoroether oil-based carrier liquid to prepare magnetic liquid. The prepared fluoroether oil-based magnetic liquid has a saturation magnetization as high as 13.2 emu/g, has good dispersion stability, and can meet the requirements of the shaft seal.

Example 2:

A preparation method of high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles, comprising the following steps:

A. Weigh MnCl ₂ 4H ₂ O, ZnCl ₂ , FeCl ₃ 4H ₂ O salts in a molar ratio (0.8:0.2:2), place them in 500ml ultrapure water at 85°C, stir until completely dissolved and pour Put it into a reaction kettle with a heat preservation temperature of 85°C. Weigh 28g of NaOH powder, dissolve it in ultrapure water, then quickly add it into the reaction kettle, and at the same time, carry out strong mechanical stirring on the mixed solution, the stirring speed is 800r/min, and the stirring time is 60min.

B. Put the mixture obtained in A into a high-temperature oven to keep warm at 80°C for 4 hours, and use high temperature to promote the crystallization and growth of particles.

C. Wash and cool the mixture obtained in B to 70°C, and adjust its pH value to 5.1. Add a suitable surfactant, fluether acid, to the mixture in a uniform dropwise manner, with a mass of 3 g, and stir for 3 hours to coat the nanoparticles. The stirring speed is 500r/min; then, the particles are washed with ultrapure water until the pH value is close to neutral, and the water is removed by magnetic separation, and then the obtained viscous material is dried in a vacuum drying oven at a drying temperature of 80°C and a drying time of After 8 hours, Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles with high saturation magnetization can be prepared.

A method for further preparing a magnetic liquid using the high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles prepared above:

D. Grind the particles with a mortar, then weigh an appropriate amount of particles and fluoroether oil, wherein the solid content of the particles is 40%, stir the particles mechanically at a stirring speed of 500r/min for 5 hours, and disperse the particles into the fluoroether oil-based carrier liquid to prepare magnetic fluid. The prepared fluoroether oil-based magnetic liquid has a saturation magnetization of 11.5 emu/g and a general dispersion stability, basically meeting the requirements of the shaft seal.

Example 3:

A preparation method of high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles, comprising the following steps:

A. Weigh MnCl ₂ 4H ₂ O, ZnCl ₂ , FeCl ₃ 4H ₂ O salts in a molar ratio (0.8:0.2:2), place them in 500ml ultrapure water at 85°C, stir until completely dissolved and pour Put it into a reaction kettle with a heat preservation temperature of 85°C. Weigh 32g of NaOH powder, dissolve it in ultrapure water, then quickly add it into the reaction kettle, and at the same time vigorously stir the mixed solution with a stirring speed of 800r/min and a stirring time of 60min.

B. Put the mixture obtained in A into a high-temperature oven to keep warm at 250°C for 3 hours, and use high temperature to promote the crystallization and growth of particles.

C. Wash and cool the mixture obtained in B to 70°C, and adjust its pH value to 6.96. Add a suitable surfactant, fluether acid, to the mixture in a uniform dropwise manner, with a mass of 3 g, and stir for 3 hours to coat the nanoparticles. The stirring speed is 500r/min; then, the particles are washed with ultrapure water until the pH value is close to neutral, and the water is removed by magnetic separation, and then the obtained viscous material is dried in a vacuum drying oven at a drying temperature of 80°C and a drying time of After 8 hours, Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles with high saturation magnetization can be prepared.

A method for further preparing a magnetic liquid using the high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles prepared above:

D. Grind the particles with a mortar, then weigh an appropriate amount of particles and fluoroether oil, wherein the solid content of the particles is 50%, stir the particles mechanically at a stirring speed of 500r/min for 5 hours, and disperse the particles into the fluoroether oil-based carrier liquid to prepare magnetic fluid. The prepared fluoroether oil-based magnetic liquid has a saturation magnetization of 13.5 emu/g, good dispersion stability, and basically meets the requirements of the shaft seal.

Example 4:

A preparation method of high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles, comprising the following steps:

A. Weigh MnCl ₂ 4H ₂ O, ZnCl ₂ , FeCl ₃ 4H ₂ O salts in a molar ratio (0.8:0.2:2), place them in 500ml ultrapure water at 85°C, stir until completely dissolved and pour Put it into a reaction kettle with a heat preservation temperature of 85°C. Weigh 55g of NaOH powder, dissolve it in ultrapure water, then quickly add it into the reaction kettle, and at the same time, carry out strong mechanical stirring on the mixed solution, the stirring speed is 800r/min, and the stirring time is 60min.

B. Put the mixture obtained in A into a high-temperature oven for heat preservation at a temperature of 100° C. for 3 hours, and use high temperature to promote the crystallization and growth of particles.

C. Wash and cool the mixture obtained in B to 70°C, and adjust its pH value to 8.3. Add a suitable surfactant, fluether acid, to the mixture in a uniform dropwise manner, with a mass of 3 g, and stir for 3 hours to coat the nanoparticles. The stirring speed is 500r/min; then, the particles are washed with ultrapure water until the pH value is close to neutral, and the water is removed by magnetic separation, and then the obtained viscous material is dried in a vacuum drying oven at a drying temperature of 80°C and a drying time of After 8 hours, Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles with high saturation magnetization can be prepared.

A method for further preparing a magnetic liquid using the high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles prepared above:

D. Grind the particles with a mortar, then weigh an appropriate amount of particles and fluoroether oil, wherein the solid content of the particles is 48%, and disperse the particles into the fluoroether oil-based carrier liquid with a stirring speed of 500r/min and mechanical stirring for 5h Prepare the magnetic liquid. The saturation magnetization of the prepared fluoroether oil-based magnetic liquid is 8.7emu/g, and the dispersion stability is good, which cannot meet the requirements of the shaft seal.

Example 5:

A preparation method of high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles, comprising the following steps:

A. Weigh MnCl ₂ 4H ₂ O, ZnCl ₂ , FeCl ₃ 4H ₂ O salts in a molar ratio (0.8:0.2:2), place them in 500ml ultrapure water at 85°C, stir until completely dissolved and pour Put it into a reaction kettle with a heat preservation temperature of 85°C. Weigh 26g of NaOH powder, dissolve it in ultrapure water, then quickly add it into the reaction kettle, and at the same time, carry out strong mechanical stirring on the mixed solution, the stirring speed is 800r/min, and the stirring time is 60min.

B. Put the mixture obtained in A into a high-temperature oven to keep warm at 400°C for 1 hour, and use high temperature to promote the crystallization and growth of particles.

C. Wash and lower the temperature of the mixed solution obtained in B to 70°C, and adjust its pH value to 6.6. Add a suitable surfactant, fluether acid, to the mixed solution in a uniform dropwise manner, with a mass of 3 g, and stir for 3 hours to coat the nanoparticles. The stirring speed is 500r/min; then, the particles are washed with ultrapure water until the pH value is close to neutral, and the water is removed by magnetic separation, and then the obtained viscous material is dried in a vacuum drying oven at a drying temperature of 80°C and a drying time of After 8 hours, Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles with high saturation magnetization can be prepared.

A method for further preparing a magnetic liquid using the high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles prepared above:

D. Grind the particles with a mortar, then weigh an appropriate amount of particles and fluoroether oil, wherein the solid content of the particles is 52%, stir the particles mechanically at a stirring speed of 500r/min for 5 hours, and disperse the particles into the fluoroether oil-based carrier liquid to prepare magnetic fluid. The prepared fluoroether oil-based magnetic liquid has a saturation magnetization of 11.8 emu/g, good dispersion stability, and basically meets the requirements of the shaft seal.

Embodiment 6:

A preparation method of high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles, comprising the following steps:

A. Weigh MnCl ₂ 4H ₂ O, ZnCl ₂ , FeCl ₃ 4H ₂ O salts in a molar ratio (0.8:0.2:2), place them in 500ml ultrapure water at 85°C, stir until completely dissolved and pour Put it into a reaction kettle with a heat preservation temperature of 85°C. Weigh an appropriate amount of NaOH powder, dissolve it in ultrapure water, and then quickly add it to the reaction kettle. At the same time, the mixed solution is vigorously stirred mechanically. The stirring speed is 800r/min, and the stirring time is 60min.

B. Put the mixture obtained in A into a high-temperature oven to keep warm at 600°C for 2 hours, and use high temperature to promote the crystallization and growth of particles.

C. Wash and lower the temperature of the mixture obtained in B to 70°C, and adjust its pH to 8.2. Add a suitable surfactant, fluether acid, to the mixture in a uniform dropwise manner, with a mass of 8 g, and stir for 3 hours to coat the nanoparticles. The stirring speed is 500r/min; then, the particles are washed with ultrapure water until the pH value is close to neutral, and the water is removed by magnetic separation, and then the obtained viscous material is dried in a vacuum drying oven at a drying temperature of 80°C and a drying time of After 8 hours, Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles with high saturation magnetization can be prepared.

A method for further preparing a magnetic liquid using the high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles prepared above:

D. Grind the particles with a mortar, then weigh an appropriate amount of particles and fluoroether oil, wherein the solid content of the particles is 25%, stir the particles mechanically at a stirring speed of 500r/min for 5 hours, and disperse the particles into the fluoroether oil-based carrier liquid to prepare magnetic fluid. The saturation magnetization of the prepared fluoroether oil-based magnetic liquid is 3.2emu/g, and the dispersion stability is poor, which cannot meet the requirements of the shaft seal.

The examples are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation. For those of ordinary skill in the company, various changes or changes can be made on the basis of the above description, and the obvious changes or changes derived therefrom are all within the protection scope of the present invention.

Claims (6)

1. A preparation method of high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles, characterized in that, comprising the following steps: A. Weigh MnCl ₂ 4H ₂ O, ZnCl ₂ , FeCl ₃ 6H ₂ O salts in a molar ratio of 0.8:0.2:2, put them in 500-2000ml ultrapure water, stir until completely dissolved, then pour into a water bath to heat In a reaction kettle at 50-100°C; Weigh an appropriate amount of NaOH powder, dissolve it in ultra-pure water, and then quickly add the solution to the salt solution, and at the same time vigorously stir the mixed solution. The speed of strong mechanical stirring is 500 -1000r/min, stirring time is 10-60min; B. Place the mixture obtained in A in a high-temperature oven at 200-500°C for 1-5 hours, and use high temperature to promote the crystallization and growth of particles; C. Wash and cool the mixed solution obtained in B to 50-80°C, and adjust its pH value to 6-7, add an appropriate amount of surfactant to the mixed solution in a uniform dropwise manner, and stir at a speed of 500-1000r/min for 2 -10h to coat the nanoparticles; then, wash the particles with ultrapure water until the pH value is close to neutral, remove the water by magnetic separation, and then dry the obtained viscous material in a vacuum drying oven at 50-100°C for 5-10h, that is Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticles with high saturation magnetization can be prepared. 2. Utilize the high saturation magnetization Mn _0.8 Zn _0.2 Fe ₂ O ₄ nanoparticle prepared in claim 1 to further prepare the method for magnetic liquid, it is characterized in that comprising the following steps: The particles are ground, screened to remove larger particles, and then mechanically stirred and dispersed into a fluoroether oil-based carrier liquid to prepare a magnetic liquid. 3. The preparation method of nanoparticles according to claim 1, characterized in that: in the step A, the amount of NaOH is 10-50g. 4. The method for preparing nanoparticles according to claim 1, characterized in that: in the step C, the added surfactant is perfluoropolyether carboxylic acid, and the dosage is 2-8g. 5. The method for preparing the magnetic liquid according to claim 2, characterized in that: in the step, the speed of mechanical stirring is 500-1000r/min, and the stirring time is 2-10h. 6. The preparation method of the magnetic liquid according to claim 2, characterized in that: in the step, the base carrier liquid is perfluoropolyether oil, and the mass fraction of the dispersed particles in the magnetic liquid is 30-50%.