Magnetic liquid capable of regulating and controlling volatilization rate of base carrier liquid and preparation method of magnetic liquid

Abstract

The invention discloses a magnetic liquid capable of regulating and controlling the volatilization rate of a base carrier liquid and a preparation method of the magnetic liquid, the magnetic liquid capable of regulating and controlling the volatilization rate of the base carrier liquid comprises nano magnetic particles, a surface modifier, the base carrier liquid and a volatilization assisting agent; wherein the volume ratio of the base carrier liquid to the auxiliary volatilizing agent is (9-1): (1-9). By optimizing the volatility of the magnetic liquid-based carrier liquid and the dispersion stability of the magnetic particles, the problem that the magnetic powder is difficult to seal and fill in the prior art is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic liquid preparation, and in particular, the present invention relates to a magnetic liquid capable of adjusting the volatilization rate of a base carrier liquid and a preparation method thereof. Background Art

[0002] Magnetic liquid is a functional magnetic material formed by uniformly and stably dispersing magnetic nanoparticles coated with surfactants in a base carrier liquid. It has both the fluidity of liquid and the magnetic properties of solid. Due to its excellent magnetic response performance and fluidity, it is widely used in mechanical sealing, vibration reduction and drag reduction, biomedicine, surface lubrication and other fields. The existing magnetic liquid preparation technology usually includes the following steps: surface modification of magnetic particles, dispersion of particles in the base carrier liquid, and optimization of the final liquid performance. Among them, the selection of the base carrier liquid plays a decisive role in the performance of the magnetic liquid. In traditional technology, a single solvent such as kerosene and motor oil is often used as the base carrier liquid, and a surfactant (such as stearic acid, oleic acid, etc.) is used to coat the magnetic particles to achieve stable dispersion of the particles.

[0003] In the field of magnetic powder seals, seals achieve gas or liquid isolation through the filling of magnetic powder (generally magnetic powder coated with surfactant) and the effect of magnetic field. Compared with magnetic liquid seals, magnetic powder seals have the advantages of higher pressure resistance, high and low temperature resistance, and more reliable sealing. However, due to the small particle size and poor fluidity of magnetic powder particles, the process of directly filling the sealing cavity is quite difficult.

[0004] In order to solve this problem, the prior art attempts to mix magnetic powder with a base carrier liquid to prepare a magnetic liquid, use the good fluidity of the magnetic liquid to complete the injection operation, and then volatilize the base carrier liquid to make the magnetic powder evenly distributed, and finally form a high-performance magnetic powder seal. However, current inventions and research are mostly focused on developing magnetic liquids with highly stable base carrier liquids, and have failed to completely overcome the bottleneck of this process. In existing patents, although the magnetic liquid disclosed in Chinese patent CN202410070067.6 can be used for sealing, the volatilization time of its base carrier liquid is relatively long, which makes it difficult to effectively solve the above problems, limiting its efficiency and performance improvement in practical applications. U.S. Patent US4356098 discloses a method for preparing silicone oil-based magnetism, which uses a single silicone oil-based surfactant, has poor coating ability, and is prone to agglomeration.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, the present invention provides a magnetic liquid with adjustable evaporation rate of a base carrier liquid and a preparation method thereof.

[0007] On the one hand, an embodiment of the present invention provides a magnetic liquid with adjustable volatilization rate of a base carrier liquid, comprising nanomagnetic particles, a surface modifier, a base carrier liquid and a volatilizer; wherein the volume ratio of the base carrier liquid to the volatilizer is (9~1):(1~9).

[0008] In some embodiments, the nanomagnetic particles include Fe 3 O 4 ,γ-Fe 2 O 3 Or ferrite magnetic particles MFe 2 O 4 wherein M is selected from at least one of Mn, Co, Ni, Cu, Cd, Pb, Sn, Ca, Sr, Ba or Mg.

[0009] In some embodiments, the surfactant includes at least one of oleic acid, stearic acid, palmitic acid, stearylamine, palmitamine, methyl oleate, isopropyl stearate, isooctyl palmitate, KH-570 silane coupling agent, tetraethoxysilane, and n-octyltrimethoxysilane.

[0010] In some embodiments, the base carrier liquid has a boiling point of 75 to 150°C; Preferably, the base carrier liquid includes at least one of ethanol, n-butanol, cyclohexane, n-heptane, water, gasoline, kerosene, ethyl acetate, cyclohexanone and toluene.

[0011] In some embodiments, the propellant comprises at least one of diethyl ether and dichloromethane.

[0012] Another aspect of the present invention is to provide a method for preparing the magnetic liquid with adjustable base carrier liquid volatilization rate, comprising the following steps: S1, preparation of nanomagnetic particles by ultrasound-assisted coprecipitation; S2, adding the nanomagnetic particles into an acid solution, performing activation treatment under ultrasonic conditions, and washing to obtain the activated nanomagnetic particles; S3, dispersing the activated nanomagnetic particles into water, adding a surfactant solution to perform a modification reaction, washing and drying to obtain modified nanomagnetic particles; S4, adding the modified nano-magnetic particles into a base carrier liquid, adding a volatilizer, and stirring by ball milling to obtain an initial magnetic liquid; then placing the initial magnetic liquid in a dynamic magnetic field device, and obtaining the magnetic liquid with adjustable base carrier liquid volatilization rate under the action of an alternating magnetic field.

[0013] In some embodiments, in step S1, the reaction temperature of the co-precipitation method is 30-90° C., and the reaction time is 30-120 min.

[0014] In some embodiments, in step S2, the acid solution includes at least one of a citric acid solution, an oxalic acid solution, and a glutamic acid solution, and the concentration of the acid solution is 0.01-0.1 mol / L, and the pH value is 2-3; And / or, the temperature of the activation treatment is 30-50° C., and the activation time is 15-30 min.

[0015] In some embodiments, in step S3, the molar ratio of the nanomagnetic particles to the surfactant in the surfactant solution is 1:(0.1-1.0); And / or, the reaction temperature of the modification reaction is 20-100° C., the stirring speed is 200-600 r / min, and the reaction time is 60-180 min.

[0016] In some embodiments, in step S4, the ball milling stirring time is 1 to 8 hours; And / or, the conditions set for the dynamic magnetic field device are: magnetic field frequency is 50-200 Hz, magnetic field intensity is 50-200 mT, and action time is 1-60 min.

[0017] The advantages and beneficial effects of the embodiments of the present invention are as follows: (1) The volatile base carrier liquid prepared in the embodiment of the present invention can volatilize the base carrier liquid in the system quickly at room temperature by optimizing the volatility of the base carrier liquid and the dispersion stability of the magnetic particles, thereby forming a uniformly distributed magnetic powder layer, which is particularly suitable for magnetic powder sealing. The magnetic liquid of the present invention can complete the injection operation with good fluidity at room temperature or low temperature, and volatilize quickly to form a uniformly distributed magnetic powder layer, which is particularly suitable for magnetic powder sealing.

[0018] (2) The nano-magnetic particles in the embodiments of the present invention are evenly distributed through surface modification and the action of a particle activator. At the same time, a volatilizer is used to form a gradient volatilization system, and the volatilization rate is controlled by a base carrier liquid with different volatilization rates. This avoids the agglomeration of particles after the base carrier liquid evaporates quickly at one time, resulting in a decrease in sealing stability and pressure resistance, thereby improving the storage stability of the magnetic liquid and the subsequent application effect.

[0019] (3) The method for preparing the magnetic liquid with a volatile base carrier liquid proposed in the embodiment of the present invention is simple, efficient, has a large magnetic saturation intensity, has low requirements on equipment, and uses an environmentally friendly solvent system, which is green and environmentally friendly. DETAILED DESCRIPTION

[0020] Embodiments of the present invention are described in detail below. The embodiments are exemplary and intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0021] Where values ​​are described herein as a range, it should be understood that such disclosure includes disclosure of all possible sub-ranges within that range, as well as specific values ​​falling within that range, regardless of whether a specific value or a specific sub-range is explicitly stated.

[0022] Herein, the words "comprises" and "includes" and variations thereof mean that other elements or integers which are permitted but not specifically described may be included.

[0023] In this article, the term "and / or" is merely a term used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0024] On the one hand, an embodiment of the present invention provides a magnetic liquid with adjustable volatilization rate of a base carrier liquid, comprising nanomagnetic particles, a surface modifier, a base carrier liquid and a volatilizer; wherein the volume ratio of the base carrier liquid to the volatilizer is (9~1):(1~9), non-limiting examples are: 1:1, 2:1, 5:2, 7:3, 8:9, 3:7, 5:8, 9:1, etc.

[0025] The inventors have found through research that if the volume proportion of the base carrier liquid is too high, the overall magnetic liquid base carrier liquid will evaporate slowly, and it will take at least one week to completely evaporate into magnetic powder. The slow volatilization is not suitable for magnetic powder sealing; and if the volume proportion of the propellant is too high, the magnetic liquid base carrier liquid will evaporate too quickly, and it will completely evaporate into magnetic powder during the ball milling process, which cannot meet the requirements of injecting the magnetic liquid into the seal. Therefore, the embodiment of the present invention controls the volume ratio of the base carrier liquid to the propellant within the above range, and the volatilization rate of the base carrier liquid can be controlled by adjusting the volume ratio of the base carrier liquid to the propellant, thereby achieving controllable volatilization of the base carrier liquid.

[0026] In some embodiments, the nanomagnetic particles include Fe 3 O 4 ,γ-Fe 2 O 3 Or ferrite magnetic particles MFe 2 O 4 wherein M is selected from at least one of Mn, Co, Ni, Cu, Cd, Pb, Sn, Ca, Sr, Ba or Mg.

[0027] In some embodiments, the surfactant includes at least one of oleic acid, stearic acid, palmitic acid, stearylamine, palmitamine, methyl oleate, isopropyl stearate, isooctyl palmitate, KH-570 silane coupling agent, tetraethoxysilane, and n-octyltrimethoxysilane.

[0028] In some embodiments, the boiling point of the base carrier liquid is 75-150° C., non-limiting examples include: 75° C., 80° C., 100° C., 120° C., 135° C., 150° C., etc.; Preferably, the base carrier liquid includes at least one of ethanol, n-butanol, cyclohexane, n-heptane, water, gasoline, kerosene, ethyl acetate, cyclohexanone and toluene.

[0029] In some embodiments, the propellant comprises at least one of diethyl ether and dichloromethane.

[0030] Another aspect of the present invention is to provide a method for preparing the magnetic liquid with adjustable base carrier liquid volatilization rate, comprising the following steps: S1, preparation of nanomagnetic particles by ultrasound-assisted coprecipitation; S2, adding the nanomagnetic particles into an acid solution, performing activation treatment under ultrasonic conditions, and washing to obtain the activated nanomagnetic particles; S3, dispersing the activated nanomagnetic particles into water, adding a surfactant solution to perform a modification reaction, washing and drying to obtain modified nanomagnetic particles; S4, adding the modified nano-magnetic particles into a base carrier liquid, adding a volatilizer, and stirring by ball milling to obtain an initial magnetic liquid; then placing the initial magnetic liquid in a dynamic magnetic field device, and obtaining the magnetic liquid with adjustable base carrier liquid volatilization rate under the action of an alternating magnetic field.

[0031] In some embodiments, in step S1, the reaction temperature of the co-precipitation method is 30-90°C (non-limiting examples: 30°C, 50°C, 60°C, 75°C, 80°C, 90°C, etc.), and the reaction time is 30-120min (non-limiting examples: 30min, 50min, 80min, 100min, 120min, etc.).

[0032] In some embodiments, in step S2, the acid solution includes at least one of a citric acid solution, an oxalic acid solution, and a glutamic acid solution, the concentration of the acid solution is 0.01-0.1 mol / L (non-limiting examples: 0.01 mol / L, 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, etc.), and the pH value is 2-3 (non-limiting examples: 2, 2.5, 3, etc.); And / or, the temperature of the activation treatment is 30-50°C (non-limiting examples: 30°C, 40°C, 45°C, 50°C, etc.), and the activation time is 15-30min (non-limiting examples: 15min, 18min, 20min, 25min, 30min, etc.). By using an acid solution to activate the nanomagnetic particles, impurity oxides on the surface can be removed to avoid weakening of magnetism, and surface functional groups can be provided to provide the possibility of binding for the subsequent introduction of surfactants.

[0033] In some embodiments, in step S3, the molar ratio of the nanomagnetic particles to the surfactant in the surfactant solution is 1:(0.1-1.0), non-limiting examples include: 1:0.1, 1:0.2, 1:0.5, 1:0.8, 1:1.0, etc.; And / or, the reaction temperature of the modification reaction is 20-100°C (non-limiting examples: 20°C, 50°C, 60°C, 75°C, 80°C, 100°C, etc.), the stirring speed is 200-600r / min (non-limiting examples: 200r / min, 350r / min, 400r / min, 600r / min, etc.), and the reaction time is 60-180min (non-limiting examples: 60min, 80min, 100min, 120min, 150min, 180min, etc.).

[0034] The surfactant selected in the embodiment of the present invention has the property of one end being hydrophilic and the other end being hydrophobic. By introducing the surfactant for modification, the mutual attraction between particles can be reduced, the agglomeration of the nanomagnetic particles can be prevented, and the oxidation of the nanomagnetic particles can also be prevented.

[0035] In some embodiments, in step S4, the ball milling stirring time is 1 to 8 hours, non-limiting examples include: 1 hour, 2 hours, 4 hours, 5 hours, 8 hours, etc.; And / or, the conditions set by the dynamic magnetic field device are: the magnetic field frequency is 50~200Hz (non-limiting examples: 50Hz, 100Hz, 150Hz, 200Hz, etc.), the magnetic field strength is 50~200mT (non-limiting examples: 50mT, 80mT, 100mT, 120mT, 200mT, etc.), and the action time is 1~60min (1min, 10min, 20min, 45min, 60min, etc.).

[0036] The embodiment of the present invention prepares the magnetic liquid under the action of an alternating magnetic field, which can cause the magnetic particles in the magnetic liquid to rearrange periodically as the magnetic field changes, thereby reducing the impact of agglomeration after volatilization; at the same time, the magnetic loss effect generated by the alternating magnetic field on the magnetic particles will lead to a thermal effect, which can accelerate the volatilization of the base carrier liquid.

[0037] The following are non-limiting examples and comparative examples of the present invention. It should be noted that the schemes of the comparative examples are not prior art and are only provided for comparison with the schemes of the embodiments and are not intended to limit the present invention. Unless otherwise specified, the various raw materials used in the embodiments and comparative examples are conventional commercial products or can be prepared by known methods.

[0038] Example 1 This embodiment provides a method for preparing a magnetic liquid with a controllable evaporation rate of a base carrier liquid, comprising the following steps: S1, weigh 8.1g FeCl 3 and 3.9 g FeCl 2 Dissolved in 250mL of deionized water, and added with 20g of concentrated ammonia water, in an ultrasonic water bath at 200W power, 40Hz frequency, 40℃ water bath, control the stirring speed to 300r / min, stir and mix for 1h, it is found that the color of the solution changes rapidly from red to black, the liquid level first decreases and then increases, and finally stabilizes. After reacting for another 1h, the prepared solution is placed on a permanent magnet to separate the solvent and the nanomagnetic particles, and then the obtained nanomagnetic particles are repeatedly washed five times with deionized water until the buffer capacity of the eluate is ≤0.02mol / L·pH -1 , get nano-Fe 3 O 4 Magnetic particles; S2, prepare 200mL of 0.1mol / L citric acid solution with a pH value of about 3, and then add the nano-Fe 3 O 4 The magnetic particles were placed in a citric acid solution and treated in an ultrasonic water bath at 200 W, 40 Hz, and 40 °C for 15 min. The nano-Fe 3 O 4 Magnetic particles until the eluate buffer capacity ≤ 0.02 mol / L·pH -1 , and the activated nano-Fe 3 O 4 Magnetic particles; S3, the activated nano-Fe 3 O 4 The magnetic particles were dispersed in 250 mL of deionized water, and then a stearic acid solution (prepared by mixing 2 g of stearic acid with 1 g of concentrated ammonia water) was added. The mixture was stirred at 300 r / min in an ultrasonic water bath at 200 W power, 40 Hz frequency, and 80 ° C for 60 min. After the reaction was completed, the reaction product was cooled to room temperature, the black solid was magnetically separated, and washed with water to pH = 7, and then vacuum dried at 60 ° C for 12 h to obtain the modified nano-Fe3 O 4 Magnetic particles; S4, the modified nano-Fe 3 O 4 The magnetic particles were added to 15 mL of n-butanol and 15 mL of ether, and the mixture was ball-milled at a speed of 500 r / min for 6 h to obtain an initial magnetic liquid. The initial magnetic liquid was then placed in a dynamic magnetic field device and dispersed at a magnetic field strength and frequency of 100 mT and 100 Hz for 20 min to obtain a highly dispersed magnetic liquid with a volatile base carrier liquid.

[0039] The saturation magnetization intensity of the magnetic powder of the magnetic liquid obtained above is between 60-150Gs after the base carrier liquid evaporates. The magnetic liquid is placed in a sealed cavity, and the base carrier liquid completely evaporates in about 1-1.5 hours to finally form magnetic powder, which can meet the injection operation by utilizing the good fluidity of the magnetic liquid. Then, the base carrier liquid evaporates to make the magnetic powder evenly distributed, and finally form a high-performance magnetic powder seal.

[0040] Example 2 This embodiment provides a method for preparing a magnetic liquid with a controllable evaporation rate of a base carrier liquid, comprising the following steps: S1, weigh 8.1g FeCl 3 and 3.9 g FeCl 2 Dissolved in 250mL of deionized water, and added with 20g of concentrated ammonia water, in an ultrasonic water bath at 200W power, 40Hz frequency, 40℃ water bath, control the stirring speed to 300r / min, stir and mix for 1h, it is found that the color of the solution changes rapidly from red to black, the liquid level first decreases and then increases, and finally stabilizes. After reacting for another 1h, the prepared solution is placed on a permanent magnet to separate the solvent and the nanomagnetic particles, and then the obtained nanomagnetic particles are repeatedly washed five times with deionized water until the buffer capacity of the eluate is ≤0.02mol / L·pH -1 , get nano-Fe 3 O 4 Magnetic particles, and then nano-Fe 3 O 4 Magnetic particles were suspended in 0.1 mol / L HNO 3 and add 30% H 2 O 2 After 30 minutes of reaction, the oxidized precipitate was washed with deionized water until the buffer capacity of the eluate was ≤ 0.02 mol / L·pH -1 , to obtain nano-γ-Fe 2 O 3 Magnetic particles; S2, prepare 200mL of 0.1mol / L citric acid solution with a pH value of about 3, and then add the nano γ-Fe2 O 3 The magnetic particles were placed in a citric acid solution and treated in an ultrasonic water bath at 200 W, 40 Hz, and 40 °C for 15 min. The nano-γ-Fe 2 O 3 Magnetic particles until the eluate buffer capacity ≤ 0.02 mol / L·pH -1 , and the activated nano-γ-Fe 2 O 3 Magnetic particles; S3, the activated nano-γ-Fe 2 O 3 The magnetic particles were dispersed in 250 mL of deionized water, and then a stearic acid solution (prepared by mixing 2 g of stearic acid with 1 g of concentrated ammonia water) was added. The mixture was stirred at 300 r / min in an ultrasonic water bath at 200 W power, 40 Hz frequency, and 80 ° C for 60 min. After the reaction was completed, the reaction product was cooled to room temperature, the black solid was magnetically separated, and washed with water to pH = 7, and then vacuum dried at 60 ° C for 12 h to obtain the modified nano γ-Fe 2 O 3 Magnetic particles; S4, modified nano-γ-Fe 2 O 3 The magnetic particles were added to 15 mL of n-butanol and 15 mL of ether, and the mixture was ball-milled at a speed of 500 r / min for 6 h to obtain an initial magnetic liquid. The initial magnetic liquid was then placed in a dynamic magnetic field device and dispersed at a magnetic field strength and frequency of 100 mT and 100 Hz for 20 min to obtain a highly dispersed magnetic liquid with a volatile base carrier liquid.

[0041] The saturation magnetization intensity of the magnetic powder of the magnetic liquid obtained above is between 60-100Gs after the base carrier liquid evaporates. The magnetic liquid is placed in a sealed cavity, and the base carrier liquid completely evaporates in about 1-1.5 hours to finally form magnetic powder, which can meet the injection operation by utilizing the good fluidity of the magnetic liquid. Then, the base carrier liquid evaporates to make the magnetic powder evenly distributed, and finally form a high-performance magnetic powder seal.

[0042] Example 3 This embodiment provides a method for preparing a magnetic liquid with a controllable evaporation rate of a base carrier liquid, comprising the following steps: S1, weigh 8.1g FeCl 3 and 3.05 g CoCl 2Dissolve in 250mL of deionized water, add 20g of concentrated ammonia water, and place in an ultrasonic water bath at 200W power, 40Hz frequency, and 40℃, control the stirring speed to 300r / min, stir and mix for 1h, and find that the liquid level first decreases, then increases, and finally stabilizes. After reacting for another 1h, place the prepared solution on a permanent magnet to separate the solvent and the nanomagnetic particles, and then wash the obtained nanomagnetic particles repeatedly with deionized water for five times until the buffer capacity of the eluate is ≤0.02mol / L·pH -1 , to obtain nano CoFe 2 O 4 Magnetic particles; S2, prepare 200mL of 0.1mol / L citric acid solution with a pH value of about 3, and then add the nano CoFe 2 O 4 The magnetic particles were placed in a citric acid solution and treated in an ultrasonic water bath at 200 W power, 40 Hz frequency, and 40 ° C for 15 min. The nano-CoFe 2 O 4 Magnetic particles until the eluate buffer capacity ≤ 0.02 mol / L·pH -1 , and the activated nano-CoFe 2 O 4 Magnetic particles; S3, the activated nano-CoFe 2 O 4 The magnetic particles were dispersed in 250 mL of deionized water, and then a stearic acid solution (prepared by mixing 2 g of stearic acid with 1 g of concentrated ammonia water) was added. The mixture was stirred at 300 r / min in an ultrasonic water bath at 200 W power, 40 Hz frequency, and 80 ° C for 60 min. After the reaction was completed, the reaction product was cooled to room temperature, the black solid was magnetically separated, and washed with water to pH = 7, and then vacuum dried at 60 ° C for 12 h to obtain the modified nano CoFe 2 O 4 Magnetic particles; S4, modified nano-CoFe 2 O 4 The magnetic particles were added to 15 mL of n-butanol and 15 mL of ether, and the mixture was ball-milled at a speed of 500 r / min for 6 h to obtain an initial magnetic liquid. The initial magnetic liquid was then placed in a dynamic magnetic field device and dispersed at a magnetic field strength and frequency of 100 mT and 100 Hz for 20 min to obtain a highly dispersed magnetic liquid with a volatile base carrier liquid.

[0043] The saturation magnetization intensity of the magnetic powder of the magnetic liquid obtained above is between 80-150Gs after the base carrier liquid evaporates. The magnetic liquid is placed in a sealed cavity, and the base carrier liquid completely evaporates in about 1-1.5 hours to finally form magnetic powder, which can meet the injection operation by utilizing the good fluidity of the magnetic liquid. Then, the base carrier liquid evaporates to make the magnetic powder evenly distributed, and finally form a high-performance magnetic powder seal.

[0044] Example 4 This embodiment provides a method for preparing a magnetic liquid with a controllable evaporation rate of a base carrier liquid, comprising the following steps: S1, weigh 8.1g FeCl 3 and 3.9 g FeCl 2 Dissolved in 250mL of deionized water, and added with 20g of concentrated ammonia water, in an ultrasonic water bath at 200W power, 40Hz frequency, 40℃ water bath, control the stirring speed to 300r / min, stir and mix for 1h, it is found that the color of the solution changes rapidly from red to black, the liquid level first decreases and then increases, and finally stabilizes. After reacting for another 1h, the prepared solution is placed on a permanent magnet to separate the solvent and the nanomagnetic particles, and then the obtained nanomagnetic particles are repeatedly washed five times with deionized water until the buffer capacity of the eluate is ≤0.02mol / L·pH -1 , get nano-Fe 3 O 4 Magnetic particles; S2, prepare 200mL of 0.1mol / L citric acid solution with a pH value of about 3, and then add the nano-Fe 3 O 4 The magnetic particles were placed in a citric acid solution and treated in an ultrasonic water bath at 200 W, 40 Hz, and 40 °C for 15 min. The nano-Fe 3 O 4 Magnetic particles until the eluate buffer capacity ≤ 0.02 mol / L·pH -1 , and the activated nano-Fe 3 O 4 Magnetic particles; S3, the activated nano-Fe 3 O 4 The magnetic particles were dispersed in 250 mL of deionized water, and then a stearic acid solution (prepared by mixing 2 g of stearic acid with 1 g of concentrated ammonia water) was added. The mixture was stirred at 300 r / min in an ultrasonic water bath at 200 W power, 40 Hz frequency, and 80 ° C for 60 min. After the reaction was completed, the reaction product was cooled to room temperature, the black solid was magnetically separated, and washed with water to pH = 7, and then vacuum dried at 60 ° C for 12 h to obtain the modified nano-Fe 3 O4 Magnetic particles; S4, the modified nano-Fe 3 O 4 The magnetic particles were added to 21 mL of n-butanol and 9 mL of ether, and the mixture was ball-milled at a speed of 500 r / min for 6 h to obtain an initial magnetic liquid. The initial magnetic liquid was then placed in a dynamic magnetic field device and dispersed at a magnetic field strength and frequency of 100 mT and 100 Hz for 20 min to obtain a highly dispersed magnetic liquid with a volatile base carrier liquid.

[0045] The saturation magnetization intensity of the magnetic powder of the magnetic liquid obtained above is between 60-150Gs after the base carrier liquid evaporates. The magnetic liquid is placed in a sealed cavity, and the base carrier liquid completely evaporates in about 3-3.5 hours to finally form magnetic powder, which can meet the injection operation by utilizing the good fluidity of the magnetic liquid. Then, the base carrier liquid evaporates to make the magnetic powder evenly distributed, and finally form a high-performance magnetic powder seal.

[0046] Example 5 This embodiment provides a method for preparing a magnetic liquid with a controllable evaporation rate of a base carrier liquid, comprising the following steps: S1, weigh 8.1g FeCl 3 and 3.9 g FeCl 2 Dissolved in 250mL of deionized water, and added with 20g of concentrated ammonia water, in an ultrasonic water bath at 200W power, 40Hz frequency, 40℃ water bath, control the stirring speed to 300r / min, stir and mix for 1h, it is found that the color of the solution changes rapidly from red to black, the liquid level first decreases and then increases, and finally stabilizes. After reacting for another 1h, the prepared solution is placed on a permanent magnet to separate the solvent and the nanomagnetic particles, and then the obtained nanomagnetic particles are repeatedly washed five times with deionized water until the buffer capacity of the eluate is ≤0.02mol / L·pH -1 , get nano-Fe 3 O 4 Magnetic particles; S2, prepare 200mL of 0.1mol / L citric acid solution with a pH value of about 3, and then add the nano-Fe 3 O 4 The magnetic particles were placed in a citric acid solution and treated in an ultrasonic water bath at 200 W, 40 Hz, and 40 °C for 15 min. The nano-Fe 3 O 4 Magnetic particles until the eluate buffer capacity ≤ 0.02 mol / L·pH -1 , and the activated nano-Fe 3 O 4 Magnetic particles; S3, the activated nano-Fe 3 O 4 The magnetic particles were dispersed in 250 mL of deionized water, and then a stearic acid solution (prepared by mixing 2 g of stearic acid with 1 g of concentrated ammonia water) was added. The mixture was stirred at 300 r / min in an ultrasonic water bath at 200 W power, 40 Hz frequency, and 80 ° C for 60 min. After the reaction was completed, the reaction product was cooled to room temperature, the black solid was magnetically separated, and washed with water to pH = 7, and then vacuum dried at 60 ° C for 12 h to obtain the modified nano-Fe 3 O 4 Magnetic particles; S4, the modified nano-Fe 3 O 4 The magnetic particles were added to 9 mL of n-butanol and 21 mL of ether, and the mixture was ball-milled at a speed of 500 r / min for 6 h to obtain an initial magnetic liquid. The initial magnetic liquid was then placed in a dynamic magnetic field device and dispersed at a magnetic field strength and frequency of 100 mT and 100 Hz for 20 min to obtain a highly dispersed magnetic liquid with a volatile base carrier liquid.

[0047] The saturation magnetization intensity of the magnetic powder of the magnetic liquid obtained above is between 60-150Gs after the base carrier liquid evaporates. The magnetic liquid is placed in a sealed cavity, and the base carrier liquid completely evaporates in about 30-50 minutes to finally form magnetic powder, which can meet the injection operation by utilizing the good fluidity of the magnetic liquid. Then, the base carrier liquid evaporates to make the magnetic powder evenly distributed, and finally form a high-performance magnetic powder seal.

[0048] Comparative Example 1 This comparative example provides a method for preparing a magnetic liquid, comprising the following steps: S1, weigh 8.1g FeCl 3 and 3.9 g FeCl 2 Dissolved in 250mL of deionized water, and added with 20g of concentrated ammonia water, in an ultrasonic water bath at 200W power, 40Hz frequency, 40℃ water bath, control the stirring speed to 300r / min, stir and mix for 1h, it is found that the color of the solution changes rapidly from red to black, the liquid level first decreases and then increases, and finally stabilizes. After reacting for another 1h, the prepared solution is placed on a permanent magnet to separate the solvent and the nanomagnetic particles, and then the obtained nanomagnetic particles are repeatedly washed five times with deionized water until the buffer capacity of the eluate is ≤0.02mol / L·pH -1 , get nano-Fe 3 O 4 Magnetic particles; S2, prepare 200mL of 0.1mol / L citric acid solution with a pH value of about 3, and then add the nano-Fe 3 O4 The magnetic particles were placed in a citric acid solution and treated in an ultrasonic water bath at 200 W, 40 Hz, and 40 °C for 15 min. The nano-Fe 3 O 4 Magnetic particles until the eluate buffer capacity ≤ 0.02 mol / L·pH -1 , and the activated nano-Fe 3 O 4 Magnetic particles; S3, the activated nano-Fe 3 O 4 The magnetic particles were dispersed in 250 mL of deionized water, and then a stearic acid solution (prepared by mixing 2 g of stearic acid with 1 g of concentrated ammonia water) was added. The mixture was stirred at 300 r / min in an ultrasonic water bath at 200 W power, 40 Hz frequency, and 80 ° C for 60 min. After the reaction was completed, the reaction product was cooled to room temperature, the black solid was magnetically separated, and washed with water to pH = 7, and then vacuum dried at 60 ° C for 12 h to obtain the modified nano-Fe 3 O 4 Magnetic particles; S4, the modified nano-Fe 3 O 4 The magnetic particles were added to 30 mL of n-butanol and mixed by ball milling at a speed of 500 r / min for 6 hours to obtain an initial magnetic liquid. The initial magnetic liquid was then placed in a dynamic magnetic field device and dispersed at a magnetic field strength and frequency of 100 mT and 100 Hz for 20 minutes to obtain a magnetic liquid.

[0049] The saturation magnetization intensity of the magnetic powder of the magnetic liquid obtained above is between 60-150Gs after the base carrier liquid evaporates. When the magnetic liquid is placed in a sealed cavity, the base carrier liquid takes about 7 days to completely evaporate to form magnetic powder. The evaporation is slow and is not suitable for the injection of magnetic powder in magnetic powder sealing.

[0050] Comparative Example 2 This comparative example provides a method for preparing a magnetic liquid, comprising the following steps: S1, weigh 8.1g FeCl 3 and 3.9 g FeCl 2Dissolved in 250mL of deionized water, and added with 20g of concentrated ammonia water, in an ultrasonic water bath at 200W power, 40Hz frequency, 40℃ water bath, control the stirring speed to 300r / min, stir and mix for 1h, it is found that the color of the solution changes rapidly from red to black, the liquid level first decreases and then increases, and finally stabilizes. After reacting for another 1h, the prepared solution is placed on a permanent magnet to separate the solvent and the nanomagnetic particles, and then the obtained nanomagnetic particles are repeatedly washed five times with deionized water until the buffer capacity of the eluate is ≤0.02mol / L·pH -1 , get nano-Fe 3 O 4 Magnetic particles; S2, prepare 200mL of 0.1mol / L citric acid solution with a pH value of about 3, and then add the nano-Fe 3 O 4 The magnetic particles were placed in a citric acid solution and treated in an ultrasonic water bath at 200 W, 40 Hz, and 40 °C for 15 min. The nano-Fe 3 O 4 Magnetic particles until the eluate buffer capacity ≤ 0.02 mol / L·pH -1 , and the activated nano-Fe 3 O 4 Magnetic particles; S3, the activated nano-Fe 3 O 4 The magnetic particles were dispersed in 250 mL of deionized water, and then a stearic acid solution (prepared by mixing 2 g of stearic acid with 1 g of concentrated ammonia water) was added. The mixture was stirred at 300 r / min in an ultrasonic water bath at 200 W power, 40 Hz frequency, and 80 ° C for 60 min. After the reaction was completed, the reaction product was cooled to room temperature, the black solid was magnetically separated, and washed with water to pH = 7, and then vacuum dried at 60 ° C for 12 h to obtain the modified nano-Fe 3 O 4 Magnetic particles; S4, the modified nano-Fe 3 O 4 The magnetic particles were added to 30 mL of ether and ball-milled at a speed of 500 r / min. During the ball-milling process, the nano-Fe 3 O 4 The magnetic liquid-based carrier liquid formed by mixing magnetic particles and ether is completely evaporated. The evaporation rate is too fast, making the experiment unfeasible and unable to be used for the injection of magnetic powder in magnetic seals.

[0051] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0052] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A magnetic liquid capable of regulating the evaporation rate of a base carrier liquid, characterized in that: The invention comprises nano magnetic particles, a surface modifier, a base carrier liquid and a volatile promoter; wherein the volume ratio of the base carrier liquid to the volatile promoter is (9-1):(1-9).

2. The magnetic liquid with adjustable base carrier liquid evaporation rate according to claim 1, characterized in that: The nanomagnetic particles include at least one of Fe3O4, γ-Fe2O3 or ferrite magnetic particles MFe2O4; wherein M is selected from at least one of Mn, Co, Ni, Cu, Cd, Pb, Sn, Ca, Sr, Ba or Mg.

3. The magnetic liquid with adjustable base carrier liquid evaporation rate according to claim 1, characterized in that: The surfactant includes at least one of oleic acid, stearic acid, palmitic acid, stearylamine, palmitamine, methyl oleate, isopropyl stearate, isooctyl palmitate, KH-570 silane coupling agent, tetraethoxysilane, and n-octyltrimethoxysilane.

4. The magnetic liquid with adjustable base carrier liquid evaporation rate according to claim 1, characterized in that: The boiling point of the base carrier liquid is 75-150°C; Preferably, the base carrier liquid includes at least one of ethanol, n-butanol, cyclohexane, n-heptane, water, gasoline, kerosene, ethyl acetate, cyclohexanone and toluene.

5. The magnetic liquid with adjustable base carrier liquid evaporation rate according to claim 1, characterized in that: The propellant comprises at least one of ether and dichloromethane.

6. A method for preparing a magnetic liquid with adjustable base carrier liquid volatilization rate as claimed in any one of claims 1 to 5, characterized in that: The steps include: S1, preparation of nanomagnetic particles by ultrasound-assisted coprecipitation; S2, adding the nanomagnetic particles into an acid solution, performing activation treatment under ultrasonic conditions, and washing to obtain the activated nanomagnetic particles; S3, dispersing the activated nanomagnetic particles into water, adding a surfactant solution to perform a modification reaction, washing and drying to obtain modified nanomagnetic particles; S4, adding the modified nano-magnetic particles into a base carrier liquid, adding a volatilizer, and stirring by ball milling to obtain an initial magnetic liquid; then placing the initial magnetic liquid in a dynamic magnetic field device, and obtaining the magnetic liquid with adjustable base carrier liquid volatilization rate under the action of an alternating magnetic field.

7. The method for preparing a magnetic liquid with adjustable base carrier liquid volatilization rate according to claim 6, characterized in that: In the step S1, the reaction temperature of the coprecipitation method is 30-90° C., and the reaction time is 30-120 min.

8. The method for preparing a magnetic liquid with adjustable base carrier liquid volatilization rate according to claim 6, characterized in that: In step S2, the acid solution includes at least one of a citric acid solution, an oxalic acid solution, and a glutamic acid solution, the concentration of the acid solution is 0.01-0.1 mol / L, and the pH value is 2-3; And / or, the temperature of the activation treatment is 30-50° C., and the activation time is 15-30 min.

9. The method for preparing a magnetic liquid with adjustable base carrier liquid volatilization rate according to claim 6, characterized in that: In the step S3, the molar ratio of the nanomagnetic particles to the surfactant in the surfactant solution is 1:(0.1-1.0); And / or, the reaction temperature of the modification reaction is 20-100° C., the stirring speed is 200-600 r / min, and the reaction time is 60-180 min.

10. The method for preparing a magnetic liquid with adjustable base carrier liquid volatilization rate according to claim 6, characterized in that: In step S4, the ball milling stirring time is 1 to 8 hours; And / or, the conditions set for the dynamic magnetic field device are: magnetic field frequency is 50-200 Hz, magnetic field intensity is 50-200 mT, and action time is 1-60 min.