A perfluoropolyether oil-based cobalt-boron magnetic fluid and preparation method thereof

Abstract

The present application provides a method for preparing a perfluoropolyether oil-based cobalt-boron magnetic fluid, which is applied to the technical field of magnetic fluids. The present application synthesizes cobalt boride Co-B magnetic powder by reacting aqueous bis(2-ethylhexyl) succinate sulfonate, sodium bis(2-ethylhexyl) succinate sulfonate and sodium borohydride in an isooctane solution, and then coats the surface of the cobalt boride powder with silica by hydrolysis of ethyl orthosilicate. Perfluoropolyether acyl fluoride is grafted onto the surface of the silica-coated cobalt boride magnetic powder by an amide reaction to improve the compatibility between the cobalt boride magnetic powder and perfluoropolyether oil, thereby preparing a thermodynamically stable perfluoropolyether oil-based Co-B magnetic fluid.

Description

Technical Field

[0001] The present application relates to the technical field of magnetic fluids, and in particular to a perfluoropolyether oil-based cobalt-boron magnetic fluid and a preparation method thereof. Background Art

[0002] Magnetic fluid is a functional material in which solid magnetic particles are stably and evenly dispersed in a carrier liquid, and has both liquid fluidity and magnetic responsiveness. Because it has both the fluidity of a liquid and can be accurately controlled by an external magnetic field, it is widely used in the fields of machinery, electronics, and biomedicine. Traditional magnetic fluids are composed of magnetic micro-nano particles, surfactants, and a carrier liquid, wherein the surfactant connects the magnetic micro-nano particles and the carrier liquid, so that the magnetic micro-nano particles can be evenly dispersed in the carrier liquid. At present, the magnetic fluids developed at home and abroad mainly use water, kerosene, and silicone oil as carrier liquids. This type of magnetic fluid has poor stability and cannot be used in high temperature, high pressure, and highly corrosive environments. Perfluoropolyether oil, as a typical fluorine-containing polymer, can withstand high and low temperatures, and has excellent properties such as chemical inertness, oxidation resistance, corrosion resistance, and lubricity. Therefore, magnetic fluids using perfluoropolyether oil as a carrier liquid for use in harsh working environments have received widespread attention.

[0003] However, most perfluoropolyether oil-based magnetic fluids are now made by using fluoroether acid as a surfactant to modify ferroferric oxide Fe3O4. This magnetic fluid colloid system dispersed with the assistance of surfactants is a kinetically stable system and is prone to phase separation during use. Therefore, the stability of magnetic fluids has always been a key issue in magnetic fluid research.

[0004] Based on this, a new technical solution is needed. Summary of the invention

[0005] In view of this, the embodiments of this specification provide a perfluoropolyether oil-based cobalt-boron magnetic fluid and a preparation method thereof to improve the thermodynamic stability of the magnetic fluid.

[0006] This specification provides the following technical solution: a method for preparing a perfluoropolyether oil-based cobalt-boron magnetic fluid, comprising:

[0007] S1, dispersing bis(2-ethylhexyl)succinate sulfonic cobalt and bis(2-ethylhexyl)succinate sulfonic sodium in isooctane to obtain liquid A; mixing and reacting the bis(2-ethylhexyl)succinate sulfonic sodium isooctane reduction solution containing water and sodium borohydride with liquid A to obtain colloid B; the molar concentration of water in the colloid B is 5-10 times the sum of the molar concentrations of bis(2-ethylhexyl)succinate sulfonic sodium and bis(2-ethylhexyl)succinate sulfonic cobalt;

[0008] S2, magnetically separating colloid B to remove the supernatant, washing to obtain magnetic powder, dispersing the magnetic powder into a mixed solution of ethanol and water, adding ammonia water and tetraethyl orthosilicate in sequence, adding 3-aminopropyltrimethylsilane after ammonia water catalyzes the hydrolysis of tetraethyl orthosilicate, stirring and mixing to react, washing and drying after the reaction to obtain ammoniated silicon dioxide-SiO2-NH2 coated micro-nano magnetic material C;

[0009] S3, dispersing the micro-nano magnetic material C in a hydrophobic solvent, adding perfluoropolyether acyl fluoride and pyridine, and after the reaction is completed, washing and drying, and then adding perfluoropolyether oil and ultrasonically dispersing to obtain a perfluoropolyether oil-based Co-B magnetic fluid.

[0010] Optionally, in S1, the concentration of sodium bis(2-ethylhexyl) succinate sulfonate in colloid B is 0.1-0.6 mol / L, and the concentration of cobalt bis(2-ethylhexyl) succinate sulfonate is 10 -3 -10 -2 mol / L, the molar concentration of sodium borohydride is Co 2+ 3-6 times the concentration.

[0011] Optionally, in S2, the concentration of ammonia in the mixed solution of ethanol and water is 10 -3 -10 -2 mol / L, the concentration of magnetic powder is 10 -3 -10 -1 mol / L.

[0012] Optionally, in S2, the concentration of tetraethyl orthosilicate is 10 -3 -10 -1 mol / L, the concentration of 3-aminopropyltrimethylsilane is 10 -3 -10 -1 mol / L.

[0013] Optionally, in S2, the volume ratio of the mixed solution of ethanol and water is anhydrous ethanol: water = 5-10:1.

[0014] Optionally, in S3, the concentration of the micro-nano magnetic material C in the hydrophobic solvent is 0.1-1 mol / L, and the concentration of the perfluoropolyether acyl fluoride and pyridine is 10 -3 -10 -1 mol / L.

[0015] Optionally, in S3, the hydrophobic solvent is dichloromethane, chloroform or isooctane.

[0016] Optionally, in S2 and S3, vacuum drying is adopted at a temperature of 60-100°C.

[0017] Optionally, the preparation method is carried out under the protection of an inert gas.

[0018] This specification also provides a perfluoropolyether oil-based cobalt-boron magnetic fluid, which is prepared using the above-mentioned preparation method.

[0019] Compared with the prior art, the at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects:

[0020] Aqueous cobalt bis(2-ethylhexyl) succinate sulfonate, sodium bis(2-ethylhexyl) succinate sulfonate and sodium borohydride are reacted in an isooctane solution to synthesize cobalt boride Co-B magnetic powder, and silica is coated on the surface of the cobalt boride powder by hydrolysis of ethyl orthosilicate. Perfluoropolyether acyl fluoride is grafted onto the surface of the silica-coated cobalt boride magnetic powder by amide reaction to improve the compatibility between the cobalt boride magnetic powder and perfluoropolyether oil, so as to prepare a thermodynamically stable perfluoropolyether oil-based Co-B magnetic fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a schematic diagram of the method flow of this application. DETAILED DESCRIPTION

[0023] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0024] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0025] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspect described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0026] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the examples can be practiced without these specific details.

[0027] There has been a lot of research on magnetic micro-nano particles Fe3O4, which have been widely used. Cobalt boride Co-B has high magnetic permeability and saturation magnetic induction intensity, and is an important magnetic material that can be used to prepare magnetic materials used in magnets, motors, sensors, etc.

[0028] Micro-nano magnetic particles have a wide range of applications as a functional material, one of the important applications is the synthesis and preparation of various types of magnetic liquids. Because they have both the magnetism of solids and the fluidity of liquids, and the properties of magnetic liquids can be adjusted by external fields, they have special applications in the fields of sealing, damping and vibration reduction, and sensors. Among the magnetic liquids of different base carrier types, the research and development of magnetic liquids with high temperature resistance, good chemical stability, and excellent viscosity-temperature performance has unique applications in the field of national defense science and industry.

[0029] Perfluoropolyethers (PFPE) is a synthetic polymer that is liquid at room temperature and has high thermal stability, oxidation stability, good chemical inertness and insulation. Perfluoropolyethers with larger molecular weight also have low volatility, a wide temperature range of use and excellent viscosity-temperature characteristics. Perfluoropolyether oil is extremely stable chemically, inert, non-toxic, and has high viscosity. It has excellent lubricity even at low temperatures, can keep rotating parts rotating for a long time, can withstand strong corrosive chemicals such as acids, alkalis, and oxidants, and can prevent oil decomposition or deterioration caused by etching materials. It can be used for vacuum pump oil used in gas plasma etching equipment and reactive ion etching equipment, diffusion pump oil for uranium hexafluoride enrichment, lubricating oil for oxygen compressors, pumps, and valves; differential pressure transmission fluid and sealing fluid of differential pressure measuring instruments.

[0030] It can be imagined that the preparation of perfluoropolyether oil-based magnetic fluid has good industrial prospects.

[0031] It is difficult to fuse the micro-nano magnetic particles without surface hydrophobic modification with the perfluoropolyether oil-based carrier liquid to form a stable magnetic liquid, because the surface of the synthesized micro-nano magnetic particles without surface hydrophobic modification is hydrophilic. In order for the two to form a stable dispersed phase, the particle surface must be hydrophobically modified. Covering the polar surface of the micro-nano magnetic particles with low reaction activity compounds, or replacing the polar functional groups on the surface with non-polar functional groups, the surface of the micro-nano magnetic particles exhibits hydrophobic characteristics, and the adsorption properties and reaction characteristics of the surface also change accordingly. This surface modification method can be used to prepare composite materials with new properties.

[0032] The present invention first coats SiO2 on the surface of micro-nano magnetic particles, and then aminates them to generate -NH2 functional groups on the surface of SiO2. The -NH2 functional groups are grafted with the acyl fluoride-COF functional groups in the perfluoropolyether acyl fluoride, and the surface of the micro-nano magnetic particles has hydrophobic perfluoropolyether functional groups, which are similarly soluble in perfluoropolyether oil, so that the magnetic particles are stably dispersed in the perfluoropolyether oil and have thermodynamic stability.

[0033] In view of this, the applicant conducted in-depth research and improvement exploration on the synthesis of magnetic particles, surface modification and stability of magnetic fluids, and found that the stability of magnetic fluids depends on the following aspects:

[0034] (1) The -NH2 functional group undergoes a grafting reaction with the acyl fluoride -COF functional group in perfluoropolyether acyl fluoride. Theoretically, the molar ratio of -NH2 to -COF is 1:1. The micro-nanoscale magnetic particles that do not participate in the grafting reaction will be separated and removed in the subsequent magnetic separation and washing process. Considering the steric hindrance effect and ensuring that the micro-nanoscale magnetic particles are fully grafted, the acyl fluoride -COF is in excess, and the molar ratio of -NH2 to -COF is set to 1:1-1.2.

[0035] (2) The magnetic properties and stability of magnetic fluids are mainly determined by the size and surface characteristics of magnetic particles, so the choice of reaction conditions is crucial. Under the condition of a certain ratio of reaction materials, the size of cobalt boride Co-B particles is mainly determined by the ratio of components, reaction temperature, stirring speed, reaction time, etc. Cobalt boride Co-B magnetic particles are obtained by the reduction reaction of NaBH4 with Co(AOT)2 in reverse micelles. In the Co(AOT)2 / Na(AOT) / H2O reverse micelle solution, the size and dispersibility of cobalt boride Co-B magnetic particles are mainly controlled by the water content in the reverse micelles. For example, as the water content increases, the size of cobalt boride Co-B micro-nano particles increases accordingly. Smaller particles are superparamagnetic at room temperature, while larger particles exhibit ferromagnetic behavior. To form dispersed micro-nano cobalt boride particles with magnetic properties, it is necessary to control and optimize the water content in the micelles. In this scheme, Co(AOT)2 is cobalt bis(2-ethylhexyl) succinate sulfonate, and Na(AOT) is sodium bis(2-ethylhexyl) succinate sulfonate.

[0036] Based on this, the present specification proposes a method for preparing a perfluoropolyether oil-based cobalt-boron magnetic fluid: Figure 1 Shown, including

[0037] S1, dispersing bis(2-ethylhexyl)succinate cobalt sulfonate and sodium bis(2-ethylhexyl)succinate sulfonate in isooctane to obtain feed liquid A; mixing and reacting the sodium bis(2-ethylhexyl)succinate sulfonate isooctane reduction solution containing water and sodium borohydride with feed liquid A to obtain colloid B, wherein the molar concentration of water in the colloid B is 5-10 times the sum of the molar concentrations of sodium bis(2-ethylhexyl)succinate sulfonate and cobalt bis(2-ethylhexyl)succinate sulfonate;

[0038] S2, magnetically separating colloid B to remove the supernatant, washing to obtain magnetic powder, dispersing the magnetic powder into a mixed solution of ethanol and water, adding ammonia water and tetraethyl orthosilicate in sequence, adding 3-aminopropyltrimethylsilane after ammonia water catalyzes the hydrolysis of tetraethyl orthosilicate, stirring and mixing to react, washing and drying after the reaction to obtain -SiO2-NH2 coated micro-nano magnetic material C;

[0039] S3, dispersing the micro-nano magnetic material C in a hydrophobic solvent, adding perfluoropolyether acyl fluoride and pyridine, and after the reaction is completed, washing and drying, and then adding perfluoropolyether oil and ultrasonically dispersing to obtain a perfluoropolyether oil-based Co-B magnetic fluid.

[0040] In step S1, the concentration of sodium bis(2-ethylhexyl) succinate sulfonate in colloid B is 0.1-0.6 mol / L, and the concentration of cobalt bis(2-ethylhexyl) succinate sulfonate is 10 -3 -10 -2mol / L, the molar concentration of sodium borohydride is Co 2+ 3-6 times the concentration.

[0041] The basic reaction equation for reducing divalent cobalt ions with sodium borohydride is:

[0042]

[0043] The reaction product is a magnetic cobalt-boron compound Co-B, but in fact some divalent cobalt ions are reduced by sodium borohydride to form Co3B. The magnetic particles are mainly composed of Co2B and Co3B.

[0044] Cobalt boride Co-B magnetic particles are obtained by the reduction reaction of NaBH4 with Co(AOT)2 in reverse micelles. In the Co(AOT)2 / Na(AOT) / H2O reverse micelle solution, the size and dispersibility of cobalt boride Co-B particles are controlled by the water content in the reverse micelles. As the water content increases, the size of cobalt boride Co-B particles increases accordingly.

[0045] Ammonia catalyzes the hydrolysis of tetraethyl orthosilicate (TEOS). The hydrolysis condensation reaction of TEOS is divided into three steps. The first step is the hydrolysis of tetraethyl orthosilicate to form hydroxylated products and corresponding alcohols, and the hydroxylated products are also called silicic acid. The second step is the condensation reaction between silicic acids or between silicic acid and tetraethyl orthosilicate to form a colloidal mixture. The low polymer formed in the third step continues to polymerize to form a three-dimensional silicon network structure. Ethanol is added to adjust the polarity, hydrolysis rate and particle size of the solution.

[0046] Aminopropyltrimethylsilane APTMS is hydrolyzed in an alkaline environment. The -Si-NH2 produced by the hydrolysis can undergo a polycondensation reaction with the -OH on the surface of cobalt boride Co-B to obtain the amidated SiO2-coated micro-nano magnetic material Co-B@SiO2-NH2.

[0047] After being coated with SiO2, the particle size slightly increased, and the SiO2 shell reduced the surface energy of the magnetic nanoparticles, making the particle size distribution more uniform. After being grafted with perfluoropolyether chains, the magnetic micro-nano materials showed a dense stacking phenomenon, which was caused by the mutual attraction and aggregation of the long perfluoropolyether polymer chains grafted on the surface of the material. The micro-nano clusters formed by attraction were of different sizes, resulting in uneven particle size distribution.

[0048] Because Co-B has a large surface energy and is prone to agglomeration, adding TEOS to coat SiO2 can effectively reduce the surface energy of Co-B particles, improve their dispersibility, and thus improve the stability of the magnetic fluid. Not only that, the outer layer of SiO2 can also protect its magnetic core well from erosion. When the concentration of the reactants and the reaction time gradually increase, the saturation magnetization value also gradually decreases. This is because as the amount of TEOS and the reaction time increase, the thickness of the SiO2 coating layer generated by hydrolysis increases, resulting in an increase in the proportion of the non-magnetic part, which ultimately leads to a weakening of the saturation magnetization of the magnetic particles.

[0049] In step S2, the concentration of magnetic powder is 10 -3 -10 -2 mol / L, the concentration of ammonia in the mixed solution of ethanol and water is 10 -3 -10 -1 mol / L, the concentration of ethyl orthosilicate is 10 -3 -10 -1 mol / L, the concentration of 3-aminopropyltrimethylsilane is 10 -3 -10 -1 mol / L; magnetic powder is magnetic micro-nano material.

[0050] The magnetic powder is washed with an ethanol aqueous solution, and the volume ratio of the mixed solution of ethanol and distilled water is anhydrous ethanol: water = 5-10:1.

[0051] In step S3, the concentration of the micro-nano magnetic material C in the hydrophobic solvent is 0.1-1 mol / L, and the concentrations of perfluoropolyether acyl fluoride and pyridine are 10 -3 -10 -1 mol / L.

[0052] In this scheme, the molar concentration of the magnetic powder and the micro-nano magnetic material C is calculated based on the boron-cobalt content.

[0053] The hydrophobic solvent is dichloromethane, chloroform or isooctane.

[0054] In steps S2 and S3, vacuum drying is adopted at a temperature of 60-100°C.

[0055] The preparation method of the perfluoropolyether oil-based cobalt-boron magnetic fluid is carried out under the protection of an inert gas.

[0056] In the present application, unless otherwise specified, all concentrations in the present application are molar concentrations.

[0057] Synthesis of cobalt bis-(2-ethylhexyl)sulfosuccinate (see Petit C., Likon P., Pileni MP., Langmuir 1991, Vol 7, p2620-2625):

[0058] The specific synthesis steps are as follows: In a 50:50 mixture of water and ethanol, 1 mol of sodium bis(2-ethylhexyl) succinate sulfonate was converted into 1 mol of bis(2-ethylhexyl) succinate sulfonic acid by ion exchange through a pre-protonated strong cationic resin (Lewatit SP 500). Subsequently, the acid was reacted with a weakly acidic macroporous cationic Co 2+ Exchange resin (Bio-Rex70) to form 0.5 mol of bis-(2-ethylhexyl) sulfosuccinate cobalt Co(AOT)2.

[0059] The reagents and testing equipment used in this program are as follows:

[0060] Ammonia (analytical grade), anhydrous ethanol (chemical grade), tetraethyl orthosilicate (TEOS, analytical grade), pyridine (analytical grade), Sinopharm Chemical Reagent Co., Ltd.;

[0061] Sodium bis(2-ethylhexyl) sulfosuccinate, Hubei Hongxin Ruiyu Fine Chemical Co., Ltd., CAS number is CAs#577-11-7;

[0062] 4-Aminopropyltrimethoxysilane (APTMS, analytical grade), Chengdu Kelong Chemical Reagent Factory;

[0063] Perfluoropolyether acyl fluoride (analytical grade), perfluoropolyether oil (analytical grade), Zigong Zhonghao Chenguang Chemical Research Institute Co., Ltd.

[0064] Laser nanoparticle size analyzer (Litesizer TM500; Anton Paar, Austria);

[0065] High-speed centrifuge (TG-19, Sichuan Shuke Instrument Co., Ltd.). Example 1

[0066] S1, 10 -2 mol of bis(2-ethylhexyl) succinate sulfonate cobalt and 0.24 mol of bis(2-ethylhexyl) succinate sulfonate sodium were dispersed in 0.5 L of isooctane to obtain feed solution A; 2.25 mol of water and 4×10 -2 mol of sodium borohydride to form a reducing solution, and the reducing solution is mixed with feed liquid A to react to obtain colloid B;

[0067] In colloid B, the concentration of sodium borohydride is 4×10 -2 mol / L, the concentration of water is 5 times the sum of the concentrations of sodium bis(2-ethylhexyl) sulfosuccinate and cobalt bis(2-ethylhexyl) sulfosuccinate, 2.25 mol / L.

[0068] S2, magnetically separating colloid B to remove the supernatant, washing to obtain magnetic powder, dispersing the magnetic powder into a mixed solution of ethanol and water, adding ammonia water and tetraethyl orthosilicate in sequence, adding 3-aminopropyltrimethylsilane after ammonia water catalyzes the hydrolysis of tetraethyl orthosilicate, stirring and mixing to react, washing and drying after the reaction to obtain ammoniated silicon dioxide-SiO2-NH2 coated micro-nano magnetic material C;

[0069] The concentration of magnetic powder in the mixed solution of ethanol and water is 0.1 mol / L, and the concentration of ammonia water is 0.01 mol / L, the concentration of ethyl orthosilicate is 0.01 mol / L, the concentration of 3-aminopropyltrimethylsilane is 0.01 mol / L, and the volume ratio of ethanol and water in the mixed solution is 7:1.

[0070] S3. Disperse 0.1 mol of micro-nano magnetic material C in 200 ml of dichloromethane to obtain a dichloromethane solution of micro-nano magnetic material C with a concentration of 0.5 mol / L. Add 0.01 mol / L perfluoropolyether acyl fluoride and pyridine respectively. After the reaction is completed, wash and dry. Then add 100 mL of perfluoropolyether oil and ultrasonically disperse to obtain perfluoropolyether oil-based Co-B magnetic fluid.

[0071] In steps S2 and S3, vacuum drying is performed at a temperature of 60° C. The preparation process is carried out under the protection of inert gas nitrogen. Example 2

[0072] S1, 10 -2 mol of bis(2-ethylhexyl) succinate sulfonate cobalt and 0.24 mol of bis(2-ethylhexyl) succinate sulfonate sodium were dispersed in 0.5 L of isooctane to obtain feed solution A; 3.15 mol of water and 4×10 -2 mol of sodium borohydride to form a reducing solution which reacts with liquid A to obtain colloid B;

[0073] The concentration of sodium borohydride is 4×10 -2 mol / L, the concentration of water is 7 times the sum of the concentrations of sodium bis(2-ethylhexyl) sulfosuccinate and cobalt bis(2-ethylhexyl) sulfosuccinate, 3.15 mol / L.

[0074] S2, magnetically separating colloid B to remove the supernatant, washing to obtain magnetic powder, dispersing the magnetic powder into a mixed solution of ethanol and water, adding ammonia water and tetraethyl orthosilicate in sequence, adding 3-aminopropyltrimethylsilane after ammonia water catalyzes the hydrolysis of tetraethyl orthosilicate, stirring and mixing to react, washing and drying after the reaction to obtain ammoniated silicon dioxide-SiO2-NH2 coated micro-nano magnetic material C;

[0075] The concentration of magnetic powder in the mixed solution of ethanol and water is 0.1 mol / L, and the concentration of ammonia water is 10 -2 mol / L, the concentration of ethyl orthosilicate is 10 -2 mol / L, the concentration of 3-aminopropyltrimethylsilane is 10 -2 mol / L, the volume ratio of ethanol and water in the mixed solution is 7:1.

[0076] S3, dispersing 0.1 mol of micro-nano magnetic material C into 200 ml of dichloromethane to obtain a dichloromethane solution of micro-nano magnetic material C with a concentration of 0.5 mol / L, adding 10 -2 mol perfluoropolyether acyl fluoride and pyridine. After the reaction is completed, wash and dry, then add 100 mL of perfluoropolyether oil and ultrasonically disperse to obtain perfluoropolyether oil-based Co-B magnetic fluid.

[0077] In steps S2 and S3, vacuum drying is performed at a temperature of 60° C. The preparation process is carried out under the protection of inert gas nitrogen. Example 3

[0078] S1, 10 -2 mol of bis(2-ethylhexyl) succinate sulfonate cobalt and 0.24 mol of bis(2-ethylhexyl) succinate sulfonate sodium were dispersed in 0.5 L of isooctane to obtain feed solution A; 4.5 mol of water and 4×10 -2 mol of sodium borohydride to form a reducing solution, and the reducing solution is mixed with feed liquid A to react to obtain colloid B;

[0079] The concentration of sodium borohydride is 4×10 -2 mol / L, the concentration of water is 10 times the sum of the concentrations of sodium bis(2-ethylhexyl) sulfosuccinate and cobalt bis(2-ethylhexyl) sulfosuccinate, 4.5 mol / L.

[0080] S2, magnetically separating colloid B to remove the supernatant, washing to obtain magnetic powder, dispersing the magnetic powder into a mixed solution of ethanol and water, adding ammonia water and tetraethyl orthosilicate in sequence, adding 3-aminopropyltrimethylsilane after ammonia water catalyzes the hydrolysis of tetraethyl orthosilicate, stirring and mixing to react, washing and drying after the reaction to obtain ammoniated silicon dioxide-SiO2-NH2 coated micro-nano magnetic material C;

[0081] The concentration of magnetic powder in the mixed solution of ethanol and water is 0.1 mol / L, and the concentration of ammonia water is 10 -2 mol / L, the concentration of ethyl orthosilicate is 10 -2 mol / L, the concentration of 3-aminopropyltrimethylsilane is 10 -2 mol / L, the volume ratio of ethanol and water in the mixed solution is 7:1.

[0082] S3, disperse 0.1 mol of micro-nano magnetic material C in 200 ml of dichloromethane to obtain a dichloromethane solution of micro-nano magnetic material C with a concentration of 0.5 mol / L, and add 10 -2 mol perfluoropolyether acyl fluoride and pyridine. After the reaction is completed, wash and dry, then add 100 mL of perfluoropolyether oil and ultrasonically disperse to obtain perfluoropolyether oil-based Co-B magnetic fluid.

[0083] In steps S2 and S3, vacuum drying is performed at a temperature of 60° C. The preparation process is carried out under the protection of inert gas nitrogen. Example 4

[0084] S1, 2×10 -3 mol of bis(2-ethylhexyl) succinate sulfonate cobalt and 0.1 mol of bis(2-ethylhexyl) succinate sulfonate sodium were dispersed in 0.5 L of isooctane to obtain feed solution A; 1.01 mol of water and 8×10 -3 mol of sodium borohydride to form a reducing solution, and the reducing solution is mixed with feed liquid A to react to obtain colloid B;

[0085] In colloid B, the concentration of sodium borohydride is 8×10 -3 mol / L, the concentration of water is 5 times the sum of the concentrations of sodium bis(2-ethylhexyl) sulfosuccinate and cobalt bis(2-ethylhexyl) sulfosuccinate, 1.01 mol / L.

[0086] S2, magnetically separating colloid B to remove the supernatant, washing to obtain magnetic powder, dispersing the magnetic powder into a mixed solution of ethanol and water, adding ammonia water and tetraethyl orthosilicate in sequence, adding 3-aminopropyltrimethylsilane after ammonia water catalyzes the hydrolysis of tetraethyl orthosilicate, stirring and mixing to react, washing and drying after the reaction to obtain ammoniated silicon dioxide-SiO2-NH2 coated micro-nano magnetic material C;

[0087] The concentration of magnetic powder in the mixed solution of ethanol and water is 0.05 mol / L, and the concentration of ammonia water is 10 -3 mol / L, the concentration of ethyl orthosilicate is 5×10 -3 mol / L, the concentration of 3-aminopropyltrimethylsilane is 5×10 -3 mol / L, the volume ratio of ethanol and water in the mixed solution is 10:1.

[0088] S3, disperse 0.1 mol of micro-nano magnetic material C in 500 ml of dichloromethane to obtain a dichloromethane solution of micro-nano magnetic material C with a concentration of 0.2 mol / L, and add 10 -3 mol perfluoropolyether acyl fluoride and pyridine. After the reaction is completed, wash and dry, then add 100 mL of perfluoropolyether oil and ultrasonically disperse to obtain perfluoropolyether oil-based Co-B magnetic fluid.

[0089] In steps S2 and S3, vacuum drying is performed at a temperature of 60° C. The preparation process is carried out under the protection of inert gas nitrogen. Example 5

[0090] S1, 5×10 -3 mol of bis(2-ethylhexyl) succinate sulfonate cobalt and 0.3 mol of bis(2-ethylhexyl) succinate sulfonate sodium were dispersed in 0.5 L of isooctane to obtain feed solution A; 3.025 mol of water and 2.5×10 -2 mol of sodium borohydride to form a reducing solution, and the reducing solution is mixed with feed liquid A to react to obtain colloid B;

[0091] In colloid B, the concentration of sodium borohydride is 2.5×10 -2 mol / L, the concentration of water is 5 times the sum of the concentrations of sodium bis(2-ethylhexyl) sulfosuccinate and cobalt bis(2-ethylhexyl) sulfosuccinate, 3.025 mol / L.

[0092] S2, magnetically separating colloid B to remove the supernatant, washing to obtain magnetic powder, dispersing the magnetic powder into a mixed solution of ethanol and water, adding ammonia water and tetraethyl orthosilicate in sequence, adding 3-aminopropyltrimethylsilane after ammonia water catalyzes the hydrolysis of tetraethyl orthosilicate, stirring and mixing to react, washing and drying after the reaction to obtain ammoniated silicon dioxide-SiO2-NH2 coated micro-nano magnetic material C;

[0093] The concentration of magnetic powder in the mixed solution of ethanol and water is 0.1 mol / L, and the concentration of ammonia water is 0.01 mol / L, the concentration of ethyl orthosilicate is 0.01 mol / L, the concentration of 3-aminopropyltrimethylsilane is 0.01 mol / L, and the volume ratio of ethanol and water in the mixed solution is 5:1.

[0094] S3. Disperse 0.2 mol of micro-nano magnetic material C in 200 ml of dichloromethane to obtain a dichloromethane solution of micro-nano magnetic material C with a concentration of 1 mol / L. Add 0.02 mol of perfluoropolyether acyl fluoride and pyridine respectively. After the reaction is completed, wash and dry. Then add 100 mL of perfluoropolyether oil and ultrasonically disperse to obtain a perfluoropolyether oil-based Co-B magnetic fluid.

[0095] In steps S2 and S3, vacuum drying is performed at a temperature of 60° C. The preparation process is carried out under the protection of inert gas nitrogen.

[0096] Comparative Example 1

[0097] The difference between this comparative example and Example 1 is that in step S1, the concentration of water is 3 times the sum of the concentrations of sodium bis(2-ethylhexyl) succinate sulfonate and cobalt bis(2-ethylhexyl) succinate sulfonate, 1.32 mol / L.

[0098] Comparative Example 2

[0099] The difference between this comparative example and Example 1 is that in step S1, the concentration of water is 20 times the sum of the concentrations of sodium bis(2-ethylhexyl) succinate sulfonate and cobalt bis(2-ethylhexyl) succinate sulfonate, 8.8 mol / L.

[0100] Comparative Example 3

[0101] The difference between this comparative example and Example 1 is that in step S2, no 3-aminopropyltrimethylsilane is added.

[0102] Comparative Example 4

[0103] The difference between this comparative example and Example 1 is that in step S3, no perfluoropolyether acyl fluoride is added.

[0104] Test Method

[0105] Magnetic fluid stability test: Pour 5 mL of perfluoropolyether magnetic fluid into a test tube, place the test tube in a centrifuge at 4500 r / min for 10 min, and observe the stability;

[0106] Magnetic fluid average particle size test: JEOL Ltd., JEM-2100F;

[0107] Magnetic fluid saturation magnetization intensity test: Changzhou Dedu Precision Instrument Co., Ltd., LZ-820 fluxmeter.

[0108] Table 1 Main test results of Examples 1-3 and Comparative Examples 1-4

[0109]

[0110] By comparing Comparative Examples 1 and 2 with Example 1, it can be seen that when the water content is low (Comparative Example 1, 3 times), the reduction reaction is incomplete and cannot be carried out effectively; when the water content is high (Comparative Example 2, 20 times), the formed particles are unstable and precipitation occurs.

[0111] Examples 1-5 show that when the water content is moderate, between 5 and 10, a stable emulsion is formed, effective surface hydrophobic modification can be performed, and a stable magnetic fluid is formed. The average particle size of the magnetic particles increases with the increase of the water content in the emulsion.

[0112] By comparing Comparative Example 3 with Example 1, it can be seen that without adding aminopropyltrimethylsilane, -Si-NH2 is not produced, so that the -OH on the surface of cobalt boride Co-B cannot react with SiO2 produced by hydrolysis, and the amidated SiO2-coated micro-nano magnetic material Co-B@SiO2-NH2 cannot be obtained. Since the surface energy of Co-B is large, agglomeration occurs, resulting in emulsion precipitation.

[0113] By comparing Comparative Example 4 with Example 1, it can be seen that without adding perfluoropolyether acyl fluoride, the ability of the micro-nano magnetic particles to bind to the perfluoropolyether oil is reduced, resulting in precipitation.

[0114] In this specification, the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the embodiments described later, the description is relatively simple, and the relevant parts can be referred to the partial description of the previous embodiments.

[0115] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for preparing a perfluoropolyether oil-based cobalt-boron magnetic fluid, characterized in that: include S1. Dispersing bis(2-ethylhexyl)succinate sulfonic cobalt and sodium bis(2-ethylhexyl)succinate sulfonate in isooctane to obtain feed liquid A; mixing a sodium bis(2-ethylhexyl)succinate sulfonate isooctane reduction solution containing water and sodium borohydride with feed liquid A to obtain colloid B, wherein the molar concentration of water in the colloid B is 5-10 times the sum of the molar concentrations of sodium bis(2-ethylhexyl)succinate sulfonate and cobalt bis(2-ethylhexyl)succinate sulfonate, the concentration of sodium bis(2-ethylhexyl)succinate sulfonate in the colloid B is 0.1-0.6 mol / L, and the concentration of cobalt bis(2-ethylhexyl)succinate sulfonate is 10 -3 -10 -2 mol / L, the molar concentration of sodium borohydride is Co 2+ 3-6 times the concentration; S2, magnetically separating colloid B to remove the supernatant, washing to obtain magnetic powder, dispersing the magnetic powder into a mixed solution of ethanol and water, adding ammonia water and tetraethyl orthosilicate in sequence, adding 3-aminopropyltrimethylsilane after ammonia water catalyzes the hydrolysis of tetraethyl orthosilicate, stirring and mixing to react, washing and drying after the reaction to obtain -SiO2-NH2 coated micro-nano magnetic material C, the concentration of ammonia water in the mixed solution of ethanol and water is 10 -3 -10 -2 mol / L, the concentration of magnetic powder is 10 -3 -10 -1 mol / L, the concentration of ethyl orthosilicate is 10 -3 -10 -1 mol / L, the concentration of 3-aminopropyltrimethylsilane is 10 -3 -10 -1 mol / L; S3, dispersing the micro-nano magnetic material C in a hydrophobic solvent, adding perfluoropolyether acyl fluoride and pyridine, after the reaction is completed, washing and drying, and then adding perfluoropolyether oil, ultrasonic dispersion to obtain a perfluoropolyether oil-based Co-B magnetic fluid, wherein the concentration of the micro-nano magnetic material C in the hydrophobic solvent is 0.1-1 mol / L, and the concentration of the perfluoropolyether acyl fluoride and pyridine is 10 -3 -10 -1 mol / L.

2. The method for preparing the perfluoropolyether oil-based cobalt-boron magnetic fluid according to claim 1, characterized in that: In S2, the volume ratio of the mixed solution of ethanol and water is anhydrous ethanol: water = 5-10:

1.

3. The method for preparing the perfluoropolyether oil-based cobalt-boron magnetic fluid according to claim 1, characterized in that: In S3, the hydrophobic solvent is dichloromethane, chloroform or isooctane.

4. The method for preparing the perfluoropolyether oil-based cobalt-boron magnetic fluid according to claim 1, characterized in that: In S2 and S3, vacuum drying is adopted at a temperature of 60-100°C.

5. The method for preparing the perfluoropolyether oil-based cobalt-boron magnetic fluid according to claim 1, characterized in that: The preparation method is carried out under the protection of inert gas.

6. A perfluoropolyether oil-based cobalt-boron magnetic fluid, characterized in that: The method is prepared by the method according to any one of claims 1 to 5.

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