Test method of magnetic slurry

Abstract

The invention provides a method for testing magnetic slurry. The method comprises the following steps of: adjusting an electron microscope, lofting, applying a magnetic field, measuring and observing a record by using the electron microscope, erecting a model, calculating and the like. Magnetic self-polymerization epoxy resin-based slurry is matched with an external magnetic field to reduce the porosity of the structure, the relationship between the bubble size and the magnetic field intensity is researched, and the theoretical relationship between the bubble size and the magnetic field intensity is established; the influence of the magnetic field on the internal porosity after solidification is explained, so that the research result can be used for guiding the engineering application of the magnetic slurry.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic slurry testing and relates to a magnetic slurry testing method. Background Art

[0002] Under the action of a magnetic field, the basic mechanical properties of a magnetic self-polymerizing epoxy resin-based slurry are greatly improved compared to ordinary slurries. Another reason for the improvement in the performance of the material itself is that the magnetic particles in the slurry are affected by the magnetic field, squeezing the internal bubbles before the slurry solidifies, thereby reducing the internal pores after the slurry solidifies and improving the structural performance. In order to further explore the internal mechanism of the excellent performance of the magnetic self-polymerizing epoxy resin-based slurry material, the present invention establishes a theoretical model between the bubble size and the magnetic field strength, and conducts experiments to predict the required magnetic field strength through the bubble size in the slurry, reduce the bubbles before solidification as much as possible, reduce the porosity of the structure, and optimize the performance of the magnetic self-polymerizing epoxy resin-based slurry material. Summary of the invention

[0003] The purpose of the present invention is to provide a test method for magnetic slurry in view of the defects of the prior art. The method uses magnetic self-polymerizing epoxy resin-based slurry in combination with an external magnetic field to reduce the structural porosity when bubbles are mixed in the grouting process, and establishes a theoretical relationship between bubble size and magnetic field strength.

[0004] The technical purpose of the present invention is achieved through the following technical solutions:

[0005] A method for testing magnetic slurry comprises the following steps:

[0006] Step 1 Adjust the electron microscope:

[0007] Adjust the electron microscope to the magnification that is best for observing the sample and clean the slide;

[0008] Step 2: Lofting:

[0009] Place the magnetic slurry sample on the first glass slide, which is divided into equidistant grids. Gently place the second glass slide obliquely on the droplet and put it down, pressing the center of the cover glass to make the sample spread evenly around.

[0010] Step 3: Apply magnetic field:

[0011] A cylindrical permanent magnet is arranged on the bottom surface of the first glass slide;

[0012] Step 4 Electron microscope measurement and observation:

[0013] The number of grids occupied by bubbles in the slurry and the movement of bubbles are observed under a microscope, the changes in bubble morphology and movement trajectories are recorded, images are extracted frame by frame, and the size of the bubbles in the image and the position information relative to the magnet are converted into data;

[0014] Step 5 Model assumptions and calculations:

[0015] Assuming the magnetic field strength model, the magnetic field strength model is determined through the data collected in Step 4, combined with theoretical analysis and calculation, and the accuracy of the magnetic field strength model is verified.

[0016] Preferably, Step 5 specifically includes the following steps:

[0017] The S1 model assumes that:

[0018] When using magnetic slurry, a magnetic field needs to be applied to obtain the best performance. During the injection process, bubbles are mixed into the magnetic slurry. In order to improve the anchoring density of the magnetic slurry and reduce the structural pores caused by bubbles, the magnetic particles squeeze the bubbles caused by the external magnetic field. The bubbles in the magnetic slurry are assumed as follows:

[0019] 1) The bubble is equivalent to a sphere and is uniformly compressed, and is calculated using the equivalent spherical bubble model;

[0020] 2) The gas in the bubble is an ideal gas and satisfies Boyle's law;

[0021] 3) The magnetic particles have a smooth surface, uniform particle size, and are evenly distributed on the bubble surface, exerting radial pressure on the bubble;

[0022] 4) Liquid is incompressible and interface phase change is not considered;

[0023] 5) The distance between particles is taken as the average distance, and the movement of the bubble in the slurry is regarded as a spring oscillator. The work done by the magnetic slurry to radially compress the bubble is W m Equal to the potential energy increment W of the gas molecules in the bubble b ;

[0024] S2 magnetic particles squeeze bubbles to do work:

[0025] Assume that n magnetic particles are added to the sample and n magnetic particles are uniformly attached to the surface of the bubble. i The magnetic field force on the i-th magnetic particle is:

[0026]

[0027] In the formula, r c is the radius of magnetic particles, χ is the magnetic susceptibility, and H is the strength of the external magnetic field;

[0028] In addition, the i-th magnetic particle is subject to the cohesion force between particles:

[0029]

[0030] The cohesion force between particles is zero along the y-axis, and symmetric about the center of the sphere along the x-axis. The distance between particles Rd Take the average distance By symmetry R is the bubble radius, and the particle magnetization intensity M r =χH;

[0031] The total magnetic force on a single magnetic particle is obtained by adding the magnetic field force on the ith magnetic particle and the cohesion force between particles:

[0032]

[0033] When the bubble shrinks spherically, the magnetic slurry fills the shrinking space of the bubble, n b The magnetic particles act on the bubble wall, and the bubble moves from the radius R0 Changing to R, the work done by squeezing the bubble is:

[0034]

[0035] Due to the external magnetic field, the magnetic particles are subjected to the total magnetic force, and the power of work done on the bubbles is:

[0036]

[0037] Total number of magnetic particles in the sample

[0038] Where: m is the mass of magnetic powder added to the sample, is the magnetic powder density;

[0039] According to the statistical law, using the existing solid particle-bubble collision probability model, the number of magnetic particles on a bubble wall is estimated by the collision probability. c It is expressed as follows:

[0040]

[0041] Where d p is the diameter of magnetic particles; d b is the bubble diameter;

[0042] Therefore, the number of magnetic particles on the bubble surface is n b =P c ×n;

[0043] S3 compresses the gas potential energy increment in the bubble:

[0044] The test was carried out at normal temperature and pressure, and the ideal gas PV = NR 常 T, according to Boyle's law, P0V0=P1V1, the external force compresses the gas in the bubble to do work, causing the potential energy of the gas in the bubble to increase W b :

[0045]

[0046] The work power done by the external force compressing the gas in the bubble is:

[0047]

[0048] S4 The work done by the external force is equal to the increase in potential energy:

[0049] Depend on Arranged in c=3NR 常 T

[0050] S5 Bubbles of any shape are equivalent to spherical bubbles:

[0051] A mixed flow containing multiple bubbles of arbitrary shapes, taking a drum-shaped bubble as an example, assume that the volume of any i-th drum-shaped bubble is V i0 , radius R i0 , opening l, bubble pressure P i0 , equivalent spherical bubble volume V, radius R, pressure P, external pressure P w ;

[0052] Before and after the equivalence, the external squeezing force on the bubble is equal, P w (2πR i0 l+2πR 2 )=P w (4πR 2 ), then the equivalent spherical bubble radius

[0053] From the equivalent before and after, the gas in the bubble satisfies Boyle's law, P i0 V i0 =PV, then the pressure inside the equivalent spherical bubble is

[0054] S6 is substituted into the test data to calculate:

[0055] The initial bubble internal pressure P0 = 1 atm = 101325 Pa, the initial bubble radius R0 = 1 × 10 -4 , initial bubble volume The mass of magnetic powder added is m=20g, the density of magnetic powder Magnetic particle radius r c =4×10 -6 m;

[0056] Repeat the above steps, and by measuring the magnetization intensity at different magnetic powder dosages, the relationship between the magnetic powder dosage and the magnetic susceptibility is obtained.

[0057] Preferably, the magnetic slurry is uniformly mixed with 80-100 parts of fly ash and 80-100 parts of magnetic particles, and then configured with 100 parts of epoxy resin, 50 parts of curing agent, 4-6 parts of active diluent, 1-3 parts of coupling agent, 80-100 parts of magnetic particles and 32-40 parts of water.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] The present invention provides a test method for magnetic slurry. Aiming at the current situation that bubbles are mixed in magnetic slurry during the grouting process, magnetic self-polymerizing epoxy resin-based slurry is used in combination with an external magnetic field to reduce the structural porosity, study the relationship between bubble size and magnetic field strength, and establish a theoretical relationship between bubble size and magnetic field strength.

[0060] The present invention uses magnetic slurry to deeply analyze the internal mechanism and explore the relationship between bubble size and magnetic field strength. The bubbles that are not discharged in time become pores after solidification, which explains the influence of the magnetic field on the internal porosity after solidification. The research results of the present invention can be used to guide the engineering application of magnetic slurry.

[0061] The present invention places a magnetic slurry sample on the glass slide, observes and measures the data such as the change of bubble radius and the change of distance between the bubble wall and the magnet under a microscope, and a grid is engraved on the second glass slide to facilitate reading the change of bubble radius with the size of the distance between the bubble wall and the magnet, that is, the size of the magnetic field strength.

[0062] The present invention regards the movement of bubbles in the slurry as a spring oscillator, and the work done by the magnetic slurry to radially compress the bubble is equal to the potential energy increment of the gas molecules in the bubble to establish a balance relationship, and solves the high-order analysis to obtain the relationship R between the magnetic field intensity H and the bubble radius.

[0063] In the theoretical model established by the present invention, the agglomeration force between particles is zero along the y-axis component, and is symmetrical about the center of the sphere along the x-axis component; the distance between particles is taken as an average distance, and the average distance is equal to the bubble radius due to symmetry; the work done by the particles under the action of the magnetic field to squeeze the gas inside the bubble is equal to the area enclosed by the Boyle curve and the coordinate axis; bubbles of any shape are equivalent to equivalent spherical bubbles, and the squeezing force of the bubble by the outside world is equal before and after the equivalence, and the gas inside the bubble satisfies Boyle's law, thereby improving the scientificity and reliability of the test results and having good engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 The figure is a comparison chart of the compressive strength of the magnetic slurry involved in the present invention with and without the effect of a magnetic field.

[0065] Figure 2 This is a glass slide sample diagram involved in the present invention.

[0066] Figure 3It is a schematic diagram of bubbles in the magnetic slurry under the magnetic field involved in the present invention.

[0067] Figure 4 This is a schematic diagram of the particle agglomeration force on the magnetic particles i outside the bubble wall involved in the present invention.

[0068] Figure 5 It is a schematic diagram of the area enclosed by the Boyle curve and the coordinate axis involved in the present invention.

[0069] Figure 6 The figure is a schematic diagram showing that the drum-shaped bubbles involved in the present invention are equivalent to spherical bubbles.

[0070] Figure 7 The present invention relates to a relationship between the amount of magnetic powder added and the magnetization intensity measured by experiments.

[0071] Figure 8 The data measured in the experiment involved in the present invention are substituted into the theoretical model to obtain a curve relationship diagram about the magnetic field intensity H (independent variable) and the bubble radius R (dependent variable).

[0072] Fig. 9 The data of the change of magnetic field intensity H (independent variable) and bubble radius R (dependent variable) obtained by experimental measurement and theoretical model analysis involved in the present invention.

[0073] In the figure: magnetic slurry 1, epoxy resin-based cement slurry 2, magnetic particles 3, bubbles 4, bubble walls 5, gas 6, first glass slide 7, second glass slide 8, magnet 9. DETAILED DESCRIPTION

[0074] In order to enable those skilled in the art to better understand the technical solution of the present invention, the preferred implementation scheme of the present invention is described below in conjunction with specific embodiments. However, it should be understood that the drawings are only used for exemplary descriptions and cannot be understood as limitations on this patent; in order to better illustrate this embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted; the positional relationship described in the drawings is only used for exemplary descriptions and cannot be understood as limitations on this patent.

[0075] As an embodiment of the present invention, see the attached Figure 1-Figure 9 This embodiment provides a method for testing magnetic slurry, comprising the following steps:

[0076] Step 1 Adjust the electron microscope:

[0077] Adjust the electron microscope to the magnification that is best for observing the sample and clean the slide;

[0078] Step 2: Lofting:

[0079] Place the magnetic slurry sample on the first glass slide, which is divided into equidistant grids. Place the second glass slide gently and obliquely on the droplet and slowly lower it, gently press the center of the cover glass to spread the sample evenly around.

[0080] Step 3: Apply magnetic field:

[0081] A cylindrical permanent magnet is arranged on the bottom surface of the first glass slide;

[0082] Step 4 Electron microscope measurement and observation:

[0083] The number of grids occupied by bubbles in the slurry and the movement of bubbles are observed under a microscope, the changes in bubble morphology and movement trajectories are recorded, images are extracted frame by frame, and the size of the bubbles in the images and the position information relative to the magnet are converted into data; during the test, magnetic particles 3 are gathered outside the bubble wall 5, and the magnetic particles 3 converge toward the magnet 9. As the distance between the magnetic particles 3 and the magnet 9 decreases, the magnetic field strength increases, further squeezing the gas in the bubble;

[0084] Step 5 Model assumptions and calculations:

[0085] Assuming the magnetic field strength model, the magnetic field strength model is determined through the data collected in Step 4, combined with theoretical analysis and calculation, and the accuracy of the magnetic field strength model is verified.

[0086] The magnetic slurry 1 is prepared by using epoxy resin, fly ash, curing agent, magnetic particles, active diluent, coupling agent and water, and the magnetic slurry 1 and epoxy resin-based cement slurry 2 are mixed into one.

[0087] Specifically, the magnetic slurry in the above embodiment is prepared by uniformly mixing 80-100 parts of fly ash and 80-100 parts of magnetic particles, and then configuring with 100 parts of epoxy resin, 50 parts of curing agent, 4-6 parts of active diluent, 1-3 parts of coupling agent, 80-100 parts of magnetic particles and 32-40 parts of water.

[0088] In some embodiments, Step 5 specifically includes the following steps:

[0089] The S1 model assumes that:

[0090] When the magnetic slurry 1 is used, a magnetic field needs to be applied to obtain the best performance. The magnetic slurry is mixed with bubbles during the injection process. In order to improve the anchoring density of the magnetic slurry and reduce the structural pores caused by bubbles, the magnetic particles squeeze the bubbles caused by the external magnetic field. The bubbles in the magnetic slurry are assumed as follows:

[0091] 1) The bubble is equivalent to a sphere and is uniformly compressed, and is calculated using the equivalent spherical bubble model;

[0092] 2) The gas in the bubble is an ideal gas and satisfies Boyle's law;

[0093] 3) The magnetic particles have a smooth surface, uniform particle size, and are evenly distributed on the bubble surface, exerting radial pressure on the bubble;

[0094] 4) Liquid is incompressible and interface phase change is not considered;

[0095] 5) The distance between particles is taken as the average distance, and the movement of the bubble in the slurry is regarded as a spring oscillator. The work done by the magnetic slurry to radially compress the bubble is W m Equal to the potential energy increment W of the gas molecules in the bubble b .

[0096] S2 magnetic particles squeeze bubbles to do work:

[0097] Assume that n magnetic particles are added to the sample and the bubble surface is uniformly attached The magnetic field force on the i-th magnetic particle is:

[0098]

[0099] In the formula, r c is the radius of the magnetic particle, χ is the magnetic susceptibility, H is the strength of the external magnetic field, and in addition, the magnetic particle is subject to the cohesion force between particles:

[0100]

[0101] The cohesion force between particles is zero along the y-axis, and symmetric about the center of the sphere along the x-axis. The distance between particles R d Take the average distance By symmetry R is the bubble radius, such as Figure 4 As shown, the magnetization intensity M of the particles r =χH;

[0102] Add the above formulas together to get the total magnetic force on a single magnetic particle.

[0103]

[0104] When the bubble shrinks spherically, the slurry fills the shrinking space of the bubble, n b The magnetic particles act on the bubble wall, and the bubble moves from the radius R0 Change to R, the work done by squeezing the bubble is

[0105]

[0106] Due to the external magnetic field, the magnetic particles are subjected to the total magnetic force, and the power of work done on the bubbles is

[0107]

[0108] Total number of magnetic particles in the sample

[0109] Where: m is the mass of magnetic powder added to the sample, is the magnetic powder density.

[0110] According to the statistical law, using the existing solid particle-bubble collision probability model, the number of magnetic particles on a bubble wall is estimated by the collision probability. c It is expressed as follows:

[0111]

[0112] Where d p is the diameter of magnetic particles; d b is the bubble diameter,

[0113] Therefore, the number of magnetic particles on the bubble surface n b =P c ×n.

[0114] S3 compresses the gas potential energy increment in the bubble:

[0115] The test was carried out at normal temperature and pressure, and the ideal gas PV = NR 常 T, according to Boyle's law, P0V0=P1V1, the external force compresses the gas in the bubble to do work, causing the potential energy of the gas in the bubble to increase W b ,like Figure 5 The shaded area shows

[0116]

[0117] The work done by the external force compressing the gas in the bubble is

[0118]

[0119] S4 The work done by the external force is equal to the increase in potential energy:

[0120] Depend on Arranged in c=3NR 常 T.

[0121] S5 Bubbles of any shape are equivalent to spherical bubbles:

[0122] A mixed flow containing multiple bubbles of arbitrary shapes, taking a drum-shaped bubble as an example, assume that the volume of any i-th drum-shaped bubble is V i0 , radius R i0 , opening l, bubble pressure P i0 , equivalent spherical bubble volume V, radius R, pressure P, external pressure P w ,like Figure 6 shown.

[0123] From the equivalent before and after, the external squeezing force on the bubble is equal, P w (2πR i0 l+2πR 2 )=P w (4πR 2 ), then the equivalent spherical bubble radius

[0124] From the equivalent before and after, the gas in the bubble satisfies Boyle's law, P i0 V i0 =PV, then the pressure inside the equivalent spherical bubble is

[0125]

[0126] S6 Substitute the test data into:

[0127] The initial bubble internal pressure P0 = 1 atm = 101325 Pa, the initial bubble radius R0 = 1 × 10 -4 , initial bubble volume The mass of magnetic powder added is m=20g, the density of magnetic powder Magnetic particle radius r c =4×10 -6 m.

[0128] Repeat the above steps and measure the magnetization intensity at different magnetic powder dosages to obtain the relationship between magnetic powder dosage and magnetic susceptibility, such as Figure 7 As shown, when the magnetic powder content is 20%, the magnetic susceptibility χ=0.003382,

[0129] Total number of magnetic particles

[0130] Collision Probability

[0131] The number of magnetic particles outside the bubble wall n b =P c ×n=0.0024×1.44×10 10 ;

[0132] a=2.35×10 -5 ,b=1.065×10 -24 ,c=1.273×10 -6 Substituting, we get the curve relationship of R-H, such as Figure 8 shown.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for testing magnetic slurry, characterized in that: The following steps are involved: Step 1 Adjust the electron microscope: Adjust the electron microscope to the magnification that is best for observing the sample and clean the slide; Step 2: Lofting: Place the magnetic slurry sample on the first glass slide, which is divided into equidistant grids. Gently place the second glass slide obliquely on the droplet and put it down flat, pressing the center of the cover glass to spread the sample evenly around. Step 3: Apply magnetic field: A cylindrical permanent magnet is arranged on the bottom surface of the first glass slide; Step 4 Electron microscope measurement and observation: The number of grids occupied by bubbles in the slurry and the movement of bubbles are observed under a microscope, the changes in bubble morphology and movement trajectories are recorded, images are extracted frame by frame, and the size of the bubbles in the image and the position information relative to the magnet are converted into data; Step 5 Model assumptions and calculations: Assuming the magnetic field strength model, the magnetic field strength model is determined through the data collected in Step 4, combined with theoretical analysis and calculation, and the accuracy of the magnetic field strength model is verified.

2. A magnetic slurry testing method according to claim 1, characterized in that: Step 5 specifically includes the following steps: The S1 model assumes that: When using magnetic slurry, a magnetic field needs to be applied to obtain the best performance. During the injection process, bubbles are mixed into the magnetic slurry. In order to improve the anchoring density of the magnetic slurry and reduce the structural pores caused by bubbles, the magnetic particles squeeze the bubbles caused by the external magnetic field. The bubbles in the magnetic slurry are assumed as follows: 1) The bubble is equivalent to a sphere and is uniformly compressed, and is calculated using the equivalent spherical bubble model; 2) The gas in the bubble is an ideal gas and satisfies Boyle's law; 3) The magnetic particles have a smooth surface, uniform particle size, and are evenly distributed on the bubble surface, exerting radial pressure on the bubble; 4) Liquid is incompressible and interface phase change is not considered; 5) The distance between particles is taken as the average distance, and the movement of the bubble in the slurry is regarded as a spring oscillator. The work done by the magnetic slurry to radially compress the bubble is W m Equal to the potential energy increment W of the gas molecules in the bubble b ; S2 magnetic particles squeeze bubbles to do work: Assume that n magnetic particles are added to the sample and n magnetic particles are uniformly attached to the surface of the bubble. b The magnetic field force on the i-th magnetic particle is: In the formula, r c is the radius of magnetic particles, χ is the magnetic susceptibility, and H is the strength of the external magnetic field; In addition, the i-th magnetic particle is subject to the cohesion force between particles: Where μ0 is the vacuum magnetic permeability, R d The distance between particles The cohesion force between particles is zero along the y-axis, and symmetric about the center of the sphere along the x-axis. The distance between particles R d Take the average distance By symmetry R is the bubble radius, and the particle magnetization intensity M r =χH; The total magnetic force on a single magnetic particle is obtained by adding the magnetic field force on the ith magnetic particle and the cohesion force between particles: When the bubble shrinks spherically, the magnetic slurry fills the shrinking space of the bubble, n b The magnetic particles act on the bubble wall, and the bubble moves from the radius R0 Changing to R, the work done by squeezing the bubble is: Due to the external magnetic field, the magnetic particles are subjected to the total magnetic force, and the power of work done on the bubbles is: Total number of magnetic particles in the sample Where: m is the mass of magnetic powder added to the sample, is the magnetic powder density; According to the statistical law, using the existing solid particle-bubble collision probability model, the number of magnetic particles on a bubble wall is estimated by the collision probability. c It is expressed as follows: Where d p is the diameter of magnetic particles; d b is the bubble diameter; Therefore, the number of magnetic particles on the bubble surface is n b =P c ×n; S3 compresses the gas potential energy increment in the bubble: The test was carried out at normal temperature and pressure, and the ideal gas PV = NR 常 T, according to Boyle's law, P0V0=P1V1, the external force compresses the gas in the bubble to do work, causing the potential energy of the gas in the bubble to increase W b , : In the formula, P is the pressure of the gas, V is the volume of the gas, N is the number of moles of the gas, and R 常 =8.314 J / (mol·K) is the gas constant, T is the absolute temperature of the gas, R0 is the bubble radius before compression, and R is the bubble radius after compression. The work power done by the external force compressing the gas in the bubble is: S4 The work done by the external force is equal to the increment of potential energy: Depend on Arranged in S5 Bubbles of any shape are equivalent to spherical bubbles: A mixed flow containing multiple bubbles of arbitrary shapes, taking a drum-shaped bubble as an example, assume that the volume of any i-th drum-shaped bubble is V i0 , radius R i0 , opening l, bubble pressure P i0 , equivalent spherical bubble volume V, radius R, pressure P, external pressure P w ; Before and after the equivalence, the external squeezing force on the bubble is equal, P w (2πR i0 l+2πR 2 )=P w (4πR 2 ), then the equivalent spherical bubble radius From the equivalent before and after, the gas in the bubble satisfies Boyle's law, P i0 V i0 =PV, then the pressure inside the equivalent spherical bubble is S6 is substituted into the test data to calculate: The initial bubble internal pressure P0 = 1 atm = 101325 Pa, the initial bubble radius R0 = 1 × 10 -4 , initial bubble volume The mass of magnetic powder added is m=20g, the density of magnetic powder Magnetic particle radius r c =4×10 -6 m; Repeat the above steps, and by measuring the magnetization intensity at different magnetic powder dosages, the relationship between the magnetic powder dosage and the magnetic susceptibility is obtained.

3. The method for testing magnetic slurry according to claim 1, characterized in that: The magnetic slurry is prepared by uniformly mixing 80-100 parts of fly ash and 80-100 parts of magnetic particles, and then adding 100 parts of epoxy resin, 50 parts of curing agent, 4-6 parts of active diluent, 1-3 parts of coupling agent, 80-100 parts of magnetic particles and 32-40 parts of water.

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