Micro-nano magnetic lubricating grease for ultra-clean sealing and preparation method thereof

Abstract

The invention belongs to the technical field of magnetic materials, and particularly relates to micro-nano magnetic lubricating grease for ultra-clean sealing as well as a preparation method and application of the micro-nano magnetic lubricating grease. The micro-nano magnetic lubricating grease for ultra-clean sealing comprises the following raw materials: micro-nano magnetic powder and lubricating grease, the mass ratio of the micro-nano magnetic powder to the lubricating grease is (0.5-1.5): 1. The micro-nano magnetic lubricating grease for ultra-clean sealing has the beneficial effects that the high-viscosity lubricating grease is used as a base carrier, sedimentation and agglomeration of magnetic particles are prevented through the high-viscosity effect of the high-viscosity lubricating grease, the particle size of the used magnetic particles is larger and can reach the micro-nano scale, and meanwhile, the adding amount of magnetic powder is also increased; the micro-nano magnetic lubricating grease for ultra-clean sealing has good stability and extremely low volatilization rate, and can be used in magnetic grease sealing under high temperature and high vacuum.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic materials, and particularly relates to a micro-nano magnetic grease for ultra-clean sealing, a preparation method thereof, and an application thereof. Background Art

[0002] Magnetic grease is a new type of composite nanomaterial. By uniformly dispersing magnetic particles with diameters in the order of dozens or hundreds of nanometers in a grease-based carrier after coating treatment, a paste-like magnetic material that can be attracted by a magnetic field can be formed. Due to its extremely high viscosity, this material can withstand the erosion of liquids when used for sealing and has high stability. At the same time, the internal magnetic particles can enhance the anti-friction and anti-wear effects of the grease, making magnetic grease widely used in fields such as lubrication and magnetic grease sealing.

[0003] Since the specific surface area of nano-magnetic particles is very large and the surface energy is extremely high, they are prone to agglomeration. The used grease-based carrier also has a high viscosity and poor fluidity. Therefore, during the preparation process, the magnetic powder is prone to uneven dispersion in the grease, thereby affecting the performance of the magnetic grease. At the same time, the high dispersion difficulty means that more nano-magnetic powder cannot be added to the grease, which limits the saturation magnetization intensity of the magnetic grease and the pressure resistance when used for magnetic grease sealing.

[0004] In the existing magnetic grease preparation technologies, magnetic nanoparticles are often modified with surfactants first, uniformly dispersed in base oil, and then thickeners are added to make magnetic grease. For example, in the prior art, magnetic nanoparticles are modified with 3-aminopropyltriethoxysilane, added into base oil by ultrasonic dispersion, and then montmorillonite-modified bio-based thickeners are added to the mixture to increase the viscosity and hydrophobic properties of the material, and finally magnetic grease is prepared. Although such methods can make the particles uniformly dispersed in the grease, they are limited by the types of surfactants and the process flow and cannot be used to prepare magnetic grease with high temperature resistance and high vacuum resistance. Because the added surfactants are generally small-molecule substances, they will decompose and volatilize under high-temperature action, affecting the cleanliness and vacuum degree in the sealing cavity. In addition, the added base oil and thickeners can only be used for specific greases, and it is difficult to prepare magnetic grease with high molecular weight, which limits the performance and application range of the corresponding magnetic grease prepared and cannot meet the ultra-clean cavity sealing requirements in fields such as aerospace and nuclear energy. Summary of the Invention

[0005] The present application provides a micro-nano magnetic grease for ultra-clean sealing and a preparation method thereof, aiming to solve the problem that existing magnetic grease needs to be prepared by surface-modifying particles with small-molecule surfactants and then adding thickeners to base oil, and contains volatile small-molecule substances inside and is not resistant to high temperature and high vacuum.

[0006] In the first aspect of the present application, a micro-nano magnetic grease for ultra-clean sealing is provided, which comprises the following raw materials: micro-nano magnetic powder and grease; the mass ratio of the micro-nano magnetic powder to the grease is (0.5 - 1.5):1.

[0007] According to some embodiments of the micro-nano magnetic grease for ultra-clean sealing described in the present application, the micro-nano magnetic powder is a micro-nano magnetic powder coated with a protective layer.

[0008] According to some embodiments of the micro-nano magnetic grease for ultra-clean sealing described in the present application, the protective layer comprises a silica protective layer and an inert metal protective layer; more preferably, the inert metal comprises one or more of nickel, gold, and silver.

[0009] According to some embodiments of the micro-nano magnetic grease for ultra-clean sealing described in the present application, the particle size of the micro-nano magnetic powder is 10 nm - 1 μm.

[0010] According to some embodiments of the micro-nano magnetic grease for ultra-clean sealing described in the present application, the micro-nano magnetic powder comprises Fe 3 O 4 micro-nano magnetic powder, CoFe 2 O 4 micro-nano magnetic powder, and NiFe 2 O 4 micro-nano magnetic powder, or one or more of them.

[0011] According to some embodiments of the micro-nano magnetic grease for ultra-clean sealing described in the present application, the grease comprises one or more of high-vacuum silicone grease, high-phenyl silicone oil grease, and perfluoropolyether grease.

[0012] In the second aspect of the present application, a preparation method of the micro-nano magnetic grease for ultra-clean sealing described in the first aspect of the present application is provided, which comprises the following steps: heating and mixing the micro-nano magnetic powder and the grease in a magnetic environment to obtain the micro-nano magnetic grease for ultra-clean sealing.

[0013] According to some embodiments of the preparation method of the micro-nano magnetic grease for ultra-clean sealing described in the present application, the micro-nano magnetic powder and the grease are put into a container for stirring and mixing, and a magnet is arranged at the bottom of the outer surface of the container.

[0014] According to some embodiments of the preparation method of the micro-nano magnetic grease for ultra-clean sealing described in the present application, the magnetic energy product of the magnet is ≥35 MGOe.

[0015] According to some embodiments of the preparation method of the micro-nano magnetic grease for ultra-clean sealing described in the present application, the magnet comprises a neodymium iron boron magnet and / or a samarium cobalt magnet.

[0016] According to some embodiments of the preparation method of the micro-nano magnetic grease for ultra-clean sealing described in the present application, the temperature of the heating and mixing is 80-150 °C, and the time of the heating and mixing is 1-3 h.

[0017] According to some embodiments of the preparation method of the micro-nano magnetic grease for ultra-clean sealing described in the present application, the rotation speed of the heating and mixing is 200-500 revolutions per minute.

[0018] The beneficial effects of the present application include: The micro-nano magnetic grease for ultra-clean sealing described in the present application uses a high-viscosity grease as a base carrier, and through its high-viscosity effect, it prevents the settlement and aggregation of magnetic particles. The magnetic particles used have a larger particle size and can reach the micro-nano scale. At the same time, the addition amount of magnetic powder is also increased; the micro-nano magnetic grease for ultra-clean sealing has good stability and an extremely low evaporation rate, and can be used in magnetic grease seals under high temperature and high vacuum.

[0019] During the preparation process of the micro-nano magnetic grease for ultra-clean sealing described in the present application, through the methods of magnetic attraction and high-temperature stirring, the magnetic particles are evenly dispersed in the high-viscosity grease to form a high-temperature and high-pressure magnetic grease for magnetic grease sealing and lubrication, ensuring the cleanliness, vacuum degree and reliability of the sealing system.

[0020] During the preparation process of the micro-nano magnetic grease for ultra-clean sealing described in the present application, the modification with surfactants is avoided, so that the micro-nano magnetic grease for ultra-clean sealing can be used under high temperature and high vacuum, has high thermal stability, low evaporation rate, uniform particle distribution, no aggregation and no settlement. In the preparation process of conventional magnetic grease, the magnetic particles need to be modified with surfactants and then a thickening agent is added, and it is difficult to maintain a low evaporation rate under high temperature and high vacuum conditions. Description of the Drawings

[0021] Figure 1 It is a schematic diagram of the morphology of the magnetic grease described in Example 6 of the present application. Detailed Embodiments

[0022] The embodiments of the present invention are described in detail below. The examples of the embodiments are exemplary and are intended to explain the present invention and should not be construed as a limitation to the present invention.

[0023] In the present invention, terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in connection 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 specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0024] An embodiment of the present application provides a micro-nano magnetic grease for ultra-clean sealing, comprising the following raw materials: micro-nano magnetic powder and grease; the mass ratio of the micro-nano magnetic powder to the grease is (0.5 - 1.5):1, such as 0.5:1, 0.6:1, 0.8:1, 1.2:1, 1.5:1.

[0025] The micro-nano magnetic grease for ultra-clean sealing in the present application selects grease as the base carrier for preparing the magnetic grease. Through the viscous action of the grease, the settlement and aggregation of magnetic powder are prevented. The particle size of the magnetic powder that can be used is larger, reaching the micro-nano scale. At the same time, the addition amount of the magnetic powder can also be increased, and the magnetic performance of the obtained magnetic grease is better.

[0026] In some embodiments of the present application, the micro-nano magnetic powder is a micro-nano magnetic powder coated with a protective layer. By coating a protective layer on the surface of the micro-nano magnetic powder, the oxidation of the magnetic powder at high temperature can be prevented and its magnetism can be protected.

[0027] In some embodiments of the present application, the protective layer includes a silica protective layer and an inert metal protective layer; more preferably, the inert metal includes one or more of nickel, gold and silver.

[0028] In some embodiments of the present application, the protective layer is a silica protective layer.

[0029] In some embodiments of the present application, the preparation method of the silica protective layer includes the following steps:

[0030] (1) Add Fe 3 O 4 magnetic powder, absolute ethanol and deionized water into a beaker, and the volume fraction of the magnetic powder in the liquid is 1% - 5%; put the beaker containing the suspension into an ultrasonic cleaner and perform ultrasonic dispersion for not less than 30 min.

[0031] (2) Place the beaker into an electrothermal constant temperature water bath and heat it to 50 - 100 °C. Meanwhile, use a stirrer to perform high-speed stirring to fully mix the magnetic powder and the solution. Then slowly pour the mixture of ammonia water and absolute ethanol into the stirring suspension, and then slowly pour the mixture of tetraethyl orthosilicate and absolute ethanol into the stirred beaker solution. Cover and stir for 3 h. Magnetically precipitate the turbid liquid containing magnetic nanoparticles with a magnet until the upper liquid is clear. After pouring off the clear liquid, add sufficient deionized water for washing, and repeat this step until the pH value of the clear liquid reaches between 7 and 8. Dry the obtained particles into blocks through a vacuum drying oven, and then crush them again through a pulverizer to obtain micro-nano magnetic powder.

[0032] In some embodiments of the present application, the particle size of the micro-nano magnetic powder is 10 nm - 1 μm, such as 10 nm, 20 nm, 100 nm, 300 nm, 500 nm, 800 nm, 1 μm, etc. As the particle size of the magnetic powder increases, the saturation magnetization intensity and magnetic properties of the magnetic powder will also increase, but it is also more likely to settle and agglomerate under the action of a magnetic field. Since the present application uses a high-viscosity grease, once the magnetic powder is evenly distributed inside it, under the action of extremely high viscous force, even without the presence of a surfactant on the surface, it will not settle and agglomerate, and the micro-nano magnetic grease used for ultra-clean sealing can also remain uniform and stable under the action of a strong magnetic field.

[0033] In some embodiments of the present application, the micro-nano magnetic powder includes Fe 3 O 4 micro-nano magnetic powder, CoFe 2 O 4 micro-nano magnetic powder, NiFe 2 O 4 one or more of the micro-nano magnetic powders.

[0034] In some embodiments of the present application, the grease includes one or more of high-vacuum silicone grease, high-phenyl silicone oil grease, and perfluoropolyether grease. The grease of the present application has a relatively high viscosity and an extremely low volatility rate, and can be used for high-temperature and high-vacuum magnetic grease sealing or lubrication working conditions. It does not undergo thermal decomposition and volatilization of components under high-temperature action, and can ensure the vacuum degree requirements in the cavity.

[0035] The high-vacuum silicone grease of the present application is purchased from DOW CORNING; the high-phenyl silicone oil grease is purchased from Dongguan Ke'erlaimo Grease Co., Ltd.; the perfluoropolyether grease is purchased from KLUBERFOMBLIN.

[0036] The present application also provides a method for preparing the micro-nano magnetic grease for ultra-clean sealing described in the first aspect of the present application, comprising the following steps: heating and mixing the micro-nano magnetic powder and the grease in a magnetic environment to obtain the micro-nano magnetic grease for ultra-clean sealing. Under the action of magnetic force and intense mechanical stirring, the grease and the magnetic powder are continuously mixed, and finally the micro-nano magnetic particles are evenly dispersed in the base carrier to form a stable magnetic grease.

[0037] In some embodiments of the present application, the micro-nano magnetic powder and the grease are placed in a container for stirring and mixing, and a magnet is provided at the bottom of the outer surface of the container. The magnet is placed at the bottom of the stirring container to form a magnetic field gradient in the vertical direction, attracting the magnetic powder to move downward, and the stirring paddle placed inside the container will make the magnetic powder deposited at the bottom move to the top of the container under the action of eddy currents; in this way, the magnetic powder grease inside the grease is continuously mixed with the magnetic powder under the action of magnetic force and violent mechanical stirring, and finally the micro-nano magnetic powder is evenly dispersed in the grease-based carrier to form a stable magnetic grease.

[0038] In some embodiments of the present application, the magnetic energy product of the magnet is ≥35MGOe, such as 35MGOe, 38MGOe, 43MGOe, 47MGOe, 50MGOe, etc. The magnetic field gradient required for dispersing magnetic powder by thermomagnetic convection is provided by an external magnet, which is affected by the geometry, size and material. The magnet used is generally a cylindrical magnet with a diameter comparable to that of the container. The higher the magnetic energy product of the material, the stronger the magnetic properties, the greater the magnetic field gradient provided, the stronger the thermomagnetic convection effect, and the better the dispersion effect. Materials with too low magnetic energy product (such as ferrite permanent magnets) cannot be used for preparation.

[0039] In some embodiments of the present application, the magnet includes a neodymium iron boron magnet and / or a samarium cobalt magnet.

[0040] In some embodiments of the present application, the temperature of the heating and mixing is 80-150°C, such as 80°C, 90°C, 100°C, 120°C, 130°C, 150°C, etc., and the time of the heating and mixing is 1-3h; for example, 1h, 2h, 3h, etc. The higher the mass ratio of the added magnetic powder, the longer the thermal magnetic convection intensity and stirring time required for uniform mixing. The judgment standard is to take a certain amount of magnetic grease at the top and bottom of the container respectively after pausing the stirring, and detect the magnetic powder content through the sensor based on the LC oscillation circuit. If the magnetic powder concentration is the same, it means that the stirring is sufficient and the magnetic grease is prepared. By using the method of magnetic field attraction combined with high-temperature stirring, a large number of micro-nano magnetic particles can be mixed with the base carrier grease, which increases the content of magnetic solid matter and magnetic properties in the obtained magnetic grease, thereby improving the pressure resistance and lubrication effect when used for magnetic grease sealing. The viscosity of the base carrier grease can be reduced by high-temperature heating, so that the viscosity of the base carrier meets the conditions for thermal magnetic convection of the internal magnetic powder. The higher the viscosity of the grease used as the base carrier, the higher the heating temperature. The heating temperature is generally set within a range of 30°C to 50°C below the dropping point of the corresponding grease.

[0041] In some embodiments of the present application, the rotation speed of the heating mixing is 200-500 rpm, for example, 200 rpm, 300 rpm, 320 rpm, 350 rpm, 380 rpm, 430 rpm, 470 rpm, 500 rpm, etc.

[0042] The technical solution of the present application is further described below in conjunction with specific embodiments.

[0043] Example 1

[0044] A method for preparing micro-nano magnetic grease for ultra-clean sealing comprises the following steps:

[0045] (1) Take 60g of Fe with a particle size of 200nm 3 O 4 The magnetic powder was added to a mixture of 50 ml of alcohol and 300 ml of deionized water to form a suspension, and then ultrasonically dispersed for 30 min.

[0046] (2) The suspension is heated to 60°C and stirred with a stirrer at a stirring speed of 400 rpm for 10 min. Then, 20 ml of ammonia water and 20 ml of alcohol are measured and mixed and then slowly poured into the stirring suspension. After stirring for 5 min, 10 ml of ethyl orthosilicate and 10 ml of alcohol are measured and mixed thoroughly. Then, the mixture is slowly poured into the suspension. After the addition is completed, the mixture is capped and stirred for 3 h to obtain a turbid solution containing magnetic nanoparticles.

[0047] (3) using a magnet to precipitate the turbid liquid containing the magnetic nanoparticles until the upper liquid is clear, pouring out the clear liquid and adding sufficient deionized water for washing, repeating this step until the pH value of the clear liquid reaches between 7 and 8;

[0048] (4) placing the washed magnetic nanoparticles in a drying oven at 60° C. for 48 h, and then crushing the dried magnetic particles into powder using a crusher to obtain micro-nano magnetic particles with a particle size of 200 nm and a surface coated with a silicon dioxide protective layer;

[0049] (5) The above-mentioned micro-nano magnetic powder and high-phenyl silicone oil grease are mixed in a container at a mass ratio of 1.2:1, pre-stirred for 5 minutes, and then heated to 80°C. At the same time, a neodymium iron boron magnet with a magnetic energy product of 35MGOe is placed at the bottom of the outer surface of the container, and stirred at 200 rpm for 1 hour to obtain a high-phenyl silicone oil-based micro-nano magnetic grease.

[0050] Example 2

[0051] The only difference between Example 2 and Example 1 is that in the preparation process of the micro-nano magnetic grease for ultra-clean sealing described in Example 2, micro-nano magnetic powder with a particle size of 1 μm and a surface coated with a silica protective layer is used instead of micro-nano magnetic powder with a particle size of 200 nm and a surface coated with a silica protective layer, and the remaining operating steps are the same as in Example 1.

[0052] Example 3

[0053] The only difference between Example 3 and Example 1 is that in the preparation process of the micro-nano magnetic grease for ultra-clean sealing described in Example 3, perfluoropolyether grease is used instead of high-phenyl silicone oil grease, and the remaining operating steps are the same as those in Example 1.

[0054] Example 4

[0055] The only difference between Example 4 and Example 1 is that in the preparation process of the micro-nano magnetic grease for ultra-clean sealing described in Example 4, high vacuum silicone grease is used instead of high-phenyl silicone oil grease, and the remaining operating steps are the same as those in Example 1.

[0056] Example 5

[0057] The only difference between Example 5 and Example 1 is that in the preparation process of the micro-nano magnetic grease for ultra-clean sealing described in Example 5, a neodymium iron boron magnet with a magnetic energy product of 40 MGOe is used instead of a neodymium iron boron magnet with a magnetic energy product of 35 MGOe, and the remaining operating steps are the same as those in Example 1.

[0058] Example 6

[0059] The only difference between Example 6 and Example 1 is that in the preparation process of the magnetic grease described in Example 6, a samarium cobalt magnet with a magnetic energy product of 20 MGOe is used instead of a neodymium iron boron magnet with a magnetic energy product of 35 MGOe, and the remaining operating steps are the same as those in Example 1.

[0060] Example 7

[0061] The only difference between Example 7 and Example 1 is that during the preparation of the magnetic grease described in Example 7, the micro-nano magnetic powder and high-phenyl silicone oil grease are heated to 65° C. and stirred, and the remaining operating steps are the same as those in Example 1.

[0062] Example 8

[0063] The only difference between Example 8 and Example 1 is that in the preparation process of the micro-nano magnetic grease described in Example 8, the micro-nano magnetic powder and high-phenyl silicone oil grease are heated to 100° C. and stirred, and the remaining operating steps are the same as those in Example 1.

[0064] Example 9

[0065] The only difference between Example 9 and Example 1 is that in the preparation process of the micro-nano magnetic grease for ultra-clean sealing described in Example 9, the mass ratio of micro-nano magnetic powder to high-phenyl silicone oil grease is 1.5:1.

[0066] Comparative Example 1

[0067] The difference between Comparative Example 1 and Example 1 is that during the preparation of the magnetic grease in Comparative Example 1, stirring is not performed in a magnetic environment, and the specific operation method includes the following steps:

[0068] (1) Take 60g of Fe with a particle size of 200nm 3 O 4 The magnetic powder was added to a mixture of 50 ml of alcohol and 300 ml of deionized water to form a suspension, and then ultrasonically dispersed for 30 min.

[0069] (2) The suspension is heated to 60°C and stirred with a stirrer at a stirring speed of 400 rpm for 10 min. Then, 20 ml of ammonia water and 20 ml of alcohol are measured and mixed and then slowly poured into the stirring suspension. After stirring for 5 min, 10 ml of ethyl orthosilicate and 10 ml of alcohol are measured and mixed thoroughly. Then, the mixture is slowly poured into the suspension. After the addition is completed, the mixture is capped and stirred for 3 h to obtain a turbid solution containing magnetic nanoparticles.

[0070] (3) using a magnet to precipitate the turbid liquid containing the magnetic nanoparticles until the upper liquid is clear, pouring out the clear liquid and adding sufficient deionized water for washing, repeating this step until the pH value of the clear liquid reaches between 7 and 8;

[0071] (4) placing the washed magnetic nanoparticles in a drying oven at 60° C. for 48 h, and then crushing the dried magnetic particles into powder using a crusher to obtain micro-nano magnetic particles with a particle size of 200 nm and a surface coated with a silicon dioxide protective layer;

[0072] (5) The above-mentioned micro-nano magnetic powder and high-phenyl silicone oil grease were mixed in a container at a mass ratio of 1.2:1, pre-stirred for 5 minutes, heated to 80° C., and stirred at 200 rpm for 1 hour to obtain high-phenyl silicone oil-based magnetic grease.

[0073] Comparative Example 2

[0074] The difference between Comparative Example 2 and Example 1 is that during the preparation of the magnetic grease in Comparative Example 2, no silicon dioxide protective layer is formed on the surface of the magnetic powder. The specific operation method includes the following steps:

[0075] The mass ratio of Fe is 1.2:1. 3 O 4 Magnetic powder (particle size of 200nm) and high-phenyl silicone oil grease are mixed in a container, pre-stirred for 5 minutes, and then heated to 80°C. At the same time, a neodymium iron boron magnet with a magnetic energy product of 35MGOe is placed at the bottom of the outer surface of the container. The mixture is stirred for 1 hour under mechanical stirring conditions of 200rpm to obtain high-phenyl silicone oil-based magnetic grease.

[0076] Performance study of the magnetic grease described in Examples 1-8 and Comparative Examples 1-2 of the present application:

[0077] Test method:

[0078] Saturation magnetization intensity: Take a certain mass of magnetic grease sample, place it in a plastic container with a volume of 0.07mL, use a vibrating sample magnetometer to test the magnetization curve, and obtain the saturation magnetization intensity;

[0079] Vacuum volatility: Take a certain mass of magnetic grease sample, place it in a glass culture dish, put it into a high and low temperature box, adjust the temperature to 90°C, take out the sample after 80 hours, cool it to room temperature, and use a precision balance with a resolution of 0.0001g to measure the mass to obtain the vacuum volatility;

[0080] Viscosity: Take the sample and spread it evenly on the sample table of the rotary viscometer. After lowering the rotor to the specified gap, remove the excess sample and test the shear stress at different shear rates to obtain the viscosity value.

[0081] The results are shown in Table 1:

[0082] Table 1

[0083]

[0084]

[0085] Note: “-” in the table means the relevant test data have not been tested.

[0086] It can be seen from Table 1 that the present method can be used to prepare magnetic grease with a particle size of micrometers, thereby significantly improving the saturation magnetization of the sample, so that the magnetic grease has better performance. And from the comparison between Example 1 and Example 9, it can be seen that increasing the added mass ratio of magnetic powder can also improve the saturation magnetization.

[0087] By comparing Example 1 with Examples 3-4, it can be seen that the full-service polyether silicone grease and high vacuum silicone grease have a lower volatility rate and a higher viscosity than high-phenyl silicone oil grease due to their high polymer macromolecule content, and can be selected according to specific working conditions.

[0088] By comparing Example 1 with Example 5 and Example 8, it can be seen that the magnetic strength and stirring temperature of the magnet given in Example 1 have satisfied the conditions for forming thermomagnetic convection, and further increasing the magnetic energy product of the permanent magnet or increasing the stirring temperature has no significant effect on the sample, and a uniform magnetic grease can be made. It can be seen from Example 6 that once the magnetic energy product is reduced, the uniformity of dispersion will be affected, and the magnetic grease cannot be successfully prepared. It can be seen from Example 7 that the same problem exists when reducing the stirring temperature, and the particles cannot be evenly dispersed in a high viscosity environment.

[0089] In Comparative Example 1, no magnet was used to provide a magnetic field gradient. Based on the same principle as in Example 6, the particles could not be evenly dispersed and the preparation failed. In Comparative Example 2, the micro-nano magnetic powder was not protected by pre-coating with silica. During the high-temperature stirring process, the magnetic material Fe 3 O 4 Oxidation to generate Fe 2 O 3 , the magnetic properties are significantly reduced.

[0090] The schematic diagram of the magnetic grease described in Example 6 of the present application is as follows Figure 1 shown.

[0091] from Figure 1 It can be seen that lamellar non-uniform substances appear in the grease matrix and cannot be eliminated by extending the stirring time.

[0092] Although the above embodiments have been shown and described, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those of ordinary skill in the art are all within the scope of protection of the present invention.

Claims

1. A micro-nano magnetic grease for ultra-clean sealing, characterized in that: The invention comprises the following raw materials: micro-nano magnetic powder and lubricating grease; the mass ratio of the micro-nano magnetic powder to the lubricating grease is (0.5-1.5):

1.

2. The micro-nano magnetic grease for ultra-clean sealing according to claim 1, characterized in that: The micro-nano magnetic powder is micro-nano magnetic powder coated with a protective layer.

3. The micro-nano magnetic grease for ultra-clean sealing according to claim 2, characterized in that: The protective layer includes a silicon dioxide protective layer and an inert metal protective layer; And / or, the particle size of the micro-nano magnetic powder is 10nm-1μm.

4. The micro-nano magnetic grease for ultra-clean sealing according to claim 1, characterized in that: The micro-nano magnetic powder includes one or more of Fe3O4 micro-nano magnetic powder, CoFe2O4 micro-nano magnetic powder and NiFe2O4 micro-nano magnetic powder.

5. The micro-nano magnetic grease for ultra-clean sealing according to claim 1, characterized in that: The lubricating grease includes one or more of high vacuum silicone grease, high phenyl silicone oil lubricating grease and perfluoropolyether lubricating grease.

6. The method for preparing the micro-nano magnetic grease for ultra-clean sealing according to any one of claims 1 to 5, characterized in that: The following steps are involved: The micro-nano magnetic powder and the lubricating grease are heated and mixed in a magnetic environment to obtain the micro-nano magnetic lubricating grease for ultra-clean sealing.

7. The preparation method according to claim 6, characterized in that: The micro-nano magnetic powder and the lubricating grease are placed in a container for stirring and mixing, and a magnet is arranged at the bottom of the outer surface of the container.

8. The preparation method according to claim 7, characterized in that: The magnetic energy product of the magnet is ≥35 MGOe.

9. The preparation method according to claim 7, characterized in that: The magnets include neodymium iron boron magnets and / or samarium cobalt magnets.

10. The preparation method according to claim 6, characterized in that: The heating and mixing temperature is 80-150° C., and the heating and mixing time is 1-3 hours; And / or, the rotation speed of the heating mixing is 200-500 rpm.

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