A high-efficiency infiltrated ceramic slurry and a preparation method thereof

Abstract

The application discloses a kind of high-efficiency infiltrated ceramic slurry and its preparation method, wherein 300-500nm silicon carbide ceramic powder is used in preparation process, the silicon carbide ceramic powder in slurry, both will not because particle mass is too large and spontaneously sink in system quickly, and will not because specific surface area is too large and quickly agglomerate in system and settle, simultaneously using the surface electrostatic repulsion and the steric hindrance stabilizing effect of dispersant macromolecule when particle disperses in water, so that silicon carbide particles are stably dispersed in water in a long time range, obtain low viscosity high solid content slurry and infiltrate.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite material preparation, and particularly relates to a ceramic slurry for efficient infiltration and a preparation method thereof. BACKGROUND

[0002] As a kind of light-weight, high-strength and high-heat-resistant material, ceramic matrix composite is becoming more and more important in industrial production, especially in the application of aircraft surface. When the surface smoothness of the material is taken as the research object to study the aerodynamic drag and frictional resistance generated in the flight of the aircraft, the ceramic matrix composite which can withstand high temperature while maintaining excellent mechanical properties becomes a good option. However, due to the particularity of the microstructure and forming process of the ceramic matrix composite, it is difficult to achieve densification in the structure and on the surface, and it is also difficult to polish the untreated surface. Therefore, the ceramic matrix composite needs to be infiltrated and sintered to achieve densification of the material surface and interior. In the infiltration process, the weight gain efficiency of the carbon fiber preform is the key factor to determine whether the material in the infiltration process is dense, and the weight gain efficiency is directly determined by the viscosity and solid content of the slurry used for infiltration.

[0003] Low viscosity, high solid content and relatively good stability are important conditions to ensure the weight gain efficiency. However, due to the non-wetting characteristics of the interface between silicon carbide powder and water, it is difficult for them to form a relatively stable mutual interface, so that the silicon carbide powder is difficult to disperse stably and uniformly in water, and is prone to sedimentation, accumulating in the form of mud at the bottom of the suspension, with high viscosity. Therefore, it is difficult to simultaneously achieve low viscosity and high solid content of the silicon carbide suspension. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a ceramic slurry for efficient infiltration and a preparation method thereof, so as to solve the problem that low viscosity and high solid content of the silicon carbide suspension cannot be achieved simultaneously. The method can make the silicon carbide particles disperse stably in water for a long time, reduce the viscosity and increase the solid content. Further, the ceramic matrix composite preform obtained by using the slurry for infiltration has high weight gain efficiency.

[0005] To achieve the above purpose, the following technical solutions are adopted in the present application:

[0006] A ceramic slurry for efficient infiltration, comprising silicon carbide powder, polyethyleneimine aqueous solution, ethanol, hydrogen chloride, sodium silicate and water.

[0007] The particle size of the silicon carbide powder is 300-500 nm.

[0008] The further improvement of the present application is:

[0009] Preferably, the mass ratio of the silicon carbide powder, water and ethanol is (75-125):(75-125):(3-5).

[0010] Preferably, the mass fraction of the polyethyleneimine aqueous solution in the ceramic slurry is 0.25-0.35%.

[0011] Preferably, the mass fraction of the polyethyleneimine aqueous solution is 10%.

[0012] Preferably, the pH value of the ceramic slurry ranges from 7.8 to 8.2.

[0013] A preparation method of a high-efficiency infiltrated ceramic slurry comprises the following steps:

[0014] Step 1: mixing silicon carbide powder with a particle size of 300-500 nm and water, then adding polyethyleneimine aqueous solution, adding hydrochloric acid and sodium silicate to adjust the pH value, and then adding ethanol to prepare a mixed slurry;

[0015] Step 2: dispersing the mixed slurry to obtain a silicon carbide ceramic slurry.

[0016] Preferably, in step 1, the pH value of the added hydrochloric acid is 2, and the pH value of the added sodium silicate is 12.

[0017] Preferably, in step 2, the dispersion process is ultrasonic dispersion followed by ball milling dispersion.

[0018] Preferably, the ultrasonic dispersion power is 150-220 W, and the ultrasonic dispersion time is 10 min.

[0019] Preferably, the stirring speed of the ball milling dispersion is 200-300 rpm, and the ball milling dispersion time is 5-10 h.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] The present application discloses a high-efficiency infiltrated ceramic slurry, wherein a silicon carbide ceramic powder with a particle size of 300-500 nm is used in the preparation process. The silicon carbide ceramic powder in the slurry neither rapidly and spontaneously sinks in the system due to excessive particle mass, nor rapidly aggregates and precipitates in the system due to excessive specific surface area. Meanwhile, the electrostatic repulsion of the surface of the particles dispersed in water and the steric hindrance stabilization effect of the dispersant macromolecules enable the stable dispersion of the silicon carbide particles in water for a long period of time, so that a slurry with low viscosity and high solid content is obtained for infiltration.

[0022] The application further discloses a preparation method of the high-efficiency infiltrated ceramic slurry. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a flow chart.

[0024] Figure 2 is a SEM image of particles;

[0025] Wherein, (a) is a powder with a particle size of 1-3 microns; (b) is a powder with a particle size of 300-500 nm; (c) is a powder with a particle size of 50-100 nm, and obvious particle agglomeration can be observed.

[0026] Figure 3 is a broken line graph of weight gain efficiency of slurry with different particle sizes; C / SiC and SiC / SiC are two different ceramic matrix composites; (Note: the slurry with a particle size of 50-100 nm is paste-shaped and cannot be infiltrated, so there is no corresponding weight gain data).

[0027] Figure 4 is a surface morphology comparison diagram of the slurry with different particle sizes after infiltration; wherein, (a) is a surface of a preform obtained by infiltrating the slurry with a particle size of 1-3 microns; (b) is a surface of a preform obtained by infiltrating the slurry with a particle size of 300-500 nm; (Note: the slurry with a particle size of 50-100 nm is paste-shaped and cannot be infiltrated, so there is no corresponding surface morphology diagram). DETAILED DESCRIPTION

[0028] The application will be further described in detail below in combination with the drawings and specific examples.

[0029] One of the embodiments of the application discloses a high-efficiency infiltrated ceramic slurry, which is a silicon carbide ceramic slurry, and the silicon carbide ceramic slurry comprises silicon carbide powder, polyethylene imine dispersant, ethanol, hydrogen chloride, sodium silicate and water; wherein the particle size of the silicon carbide powder is 300-500 nm; it is found through verification that the particle size of the silicon carbide powder will neither cause particle agglomeration due to too large specific surface area nor lead to unstable suspension due to too high mass.

[0030] Wherein, the mass ratio of the silicon carbide, water and ethanol is (75-125):(75-125):(3-5); the mass fraction of the polyethylene imine dispersant is (0.25-0.35) % based on 100 % of the mass of the ceramic slurry; and the pH value of the slurry is selected to be 4-10 based on the pH value of deionized water being 7.

[0031] As one of the preferred embodiments, when the pH value of the slurry is 7 and the mass fraction of the polyethyleneimine dispersant is 0.3%, the viscosity performance and stability of the slurry are the best.

[0032] One of the embodiments of the present application discloses a preparation method of a high-efficiency infiltrated ceramic slurry, which comprises the following steps:

[0033] Step 1, pour the silicon carbide powder with a particle size of 300-500 nm into a beaker containing deionized water, add a certain mass fraction of polyethyleneimine aqueous solution, adjust the pH of the suspension using hydrochloric acid and sodium silicate aqueous solution, then add ethanol to obtain a mixed slurry;

[0034] The mass fraction of the polyethyleneimine aqueous solution is 10%, the pH value of the added hydrochloric acid is 2, the pH value of the added sodium silicate aqueous solution is 12, and the pH value of the entire mixed slurry is adjusted to 7.8-8.2 by the hydrochloric acid and the sodium silicate aqueous solution.

[0035] The mass ratio of the silicon carbide, water and ethanol is (75-125):(75-125):(3-5); the mass fraction of the polyethyleneimine aqueous solution in the entire slurry is 0.25-0.35% based on 100% of the mass of the ceramic slurry;

[0036] Preferably, the volume fraction ratio of the anhydrous ethanol and the deionized water is 1:20.

[0037] Step 2, the mixed slurry is sequentially subjected to ultrasonic dispersion and ball milling dispersion treatment to obtain a silicon carbide ceramic slurry;

[0038] The ultrasonic dispersion power is 150-220 W, and preferably, the ultrasonic dispersion power is 195 W; the ultrasonic dispersion time is >10 min.

[0039] Preferably, the stirring speed of the ball milling dispersion is 200-300 rpm; the ball milling dispersion time is 5-10 h.

[0040] Referring to Figure 1 One of the embodiments of the present application discloses a test method for obtaining the above-mentioned silicon carbide ceramic slurry, which comprises the following steps:

[0041] S1, mix a small amount of ceramic powder with deionized water, add different mass fractions of polyethyleneimine (PEI) aqueous solution respectively, adjust the pH to obtain several groups of orthogonal condition parameter dilute solutions.

[0042] The solid phase mass fraction of the suspension in S1 is 0.05% to 0.5%. The suspension with a certain mass fraction is set to make the difference of electrostatic repulsion between the particles in the suspension with different parameters reach the maximum, so that the difference can be measured by the Zeta potential instrument, thereby the optimal pH value and PEI concentration parameters are selected. Preferably, the solid phase mass fraction of the suspension is 0.1%.

[0043] The silicon carbide ceramic particles in S1 have three levels of 1 to 3 microns, 300 to 500 nanometers and 50 to 100 nanometers; the pH parameter range is selected as 4 to 10, and the PEI mass fraction range is selected as 0 to 0.4%. The suitable particle size makes the electrostatic force of the particles in the liquid can offset the gravity, and the particles do not aggregate and settle. The suitable pH value makes the electrostatic repulsion between the particles increase, and the electrostatic steric effect is strong. The suitable dispersant concentration leads to the increase of the distance between the particles, the restriction of the activity space of the particles, and the strengthening of the steric effect. The electrostatic stabilization mechanism and the steric stabilization mechanism generated by the dispersant together make the slurry viscosity low. The two conditions of pH value and PEI concentration are combined into 7 groups of test suspensions by orthogonal test, and the Zeta potential value is measured by Malvern Zeta potential instrument.

[0044] In S2, the zeta potential of the orthogonal solution groups is measured, the group with the maximum absolute value of zeta potential is selected and recorded; according to the orthogonal test results, when the silicon carbide powder particle size is 300 to 500 nanometers, the slurry pH value is 8±0.2, and the dispersant PEI mass fraction is (0.3±0.05)%, the absolute value of zeta potential is the largest

[0045] In S3, the silicon carbide slurry with a mass fraction of 50% is prepared, and the optimal values obtained in S2 are used as the parameters for adjusting the pH value and the PEI concentration.

[0046] In S3, the volume fraction ratio of anhydrous ethanol and deionized water added is 1:10 to 40. The anhydrous ethanol and deionized water are mixed in a certain ratio to improve the infiltration characteristics of the slurry and the carbon fiber preform plate during the infiltration process. The polarity of ethanol molecules is relatively low compared to water molecules, and carbon fiber is non-polar, so the wettability of ethanol to carbon fiber is better than that of water. However, ethanol is volatile, so under the premise of ensuring wettability, the content of ethanol in the whole system should be reduced as much as possible to maintain the good stability of the slurry. Preferably, the volume fraction ratio of anhydrous ethanol and deionized water is 1:20.

[0047] In S4, the mixed slurry is first subjected to ultrasonic dispersion, and then poured into a planetary ball mill for stirring for 4 hours to obtain the required slurry.

[0048] The present application uses three different particle sizes of silicon carbide powder, which are 1 to 3 microns, 300 to 500 nanometers and 50 to 100 nanometers. Figure 2The morphology of three different particle sizes of SiC powder under scanning electron microscope is shown. It can be seen that the powder with an average particle size of 1 μm and 400 nm is obviously ridge-shaped, and the particles are uniformly arranged. The powder with an average particle size of 50 nm is seriously agglomerated, and is in a cluster shape to reduce the overall surface area and energy. Such characteristics make it extremely difficult for the powder with such a particle size to be stably dispersed in a suspension, resulting in a large viscosity value. The difficulty in the powder dispersion process is that the actual interaction of particles in liquid contact is very complex, in addition to van der Waals force and Coulomb force, there are solvent force, capillary force, hydrophobic force, hydrodynamic force, etc., which are directly related to the liquid medium. All particle surfaces in the liquid medium are charged, so the state of the particles in the liquid medium must also consider the charging condition of the particles. When the particle diameter of the particles dispersed in the liquid is too small, these complex forces will make the powder particles easily form aggregates in the liquid, and settle when the overall volume and mass increase to a certain extent. The finer the powder particles, the larger the specific surface area, and the more obvious this phenomenon is. When the particle diameter of the particles dispersed in the liquid is too large, the influence of these micro-forces in the liquid on the particles is greatly weakened, at this time the particles in the liquid can be basically simplified as only affected by gravity and buoyancy. For silicon carbide particles, when there is no other micro-force to offset the excess gravity, the particles will quickly settle. Therefore, it is particularly important to find a silicon carbide powder with a moderate particle size that can offset the excess gravity to prevent the particles from settling, and can not cause premature aggregation and settling due to the large specific surface area.

[0049] As Figure 3 The weight gain curve of C / SiC composite material using SiC powder with a particle size of 1 μm and 400 nm for vacuum infiltration. It can be seen that the infiltration effect of the two particle sizes of slurry on C / SiC composite material is quite different. The 400 nm particle size slurry with lower viscosity and longer stable time has a weight gain of more than 20%, while the 1 μm particle size slurry can only reach a weight gain of 10% at most. The weight gain efficiency can also be seen from Figure 4 The macroscopic surface of the C / SiC composite material after vacuum infiltration using the above slurry is shown. The macroscopic surface of the material after vacuum infiltration of the 400 nm slurry is basically completely covered with the microscopic structure of the surface relief after drying, providing a good foundation for subsequent surface processing.

[0050] The combined stabilizing mechanism of the steric stabilizing mechanism of the macromolecular dispersant in the liquid and the electrostatic stabilizing mechanism between the particles in the solution can make the particles exist stably in the slurry for a long time. The steric stabilizing mechanism refers to that the macromolecular substance is mixed into the slurry, one end of the long chain of the macromolecule is closely adsorbed to the surface of the particle, and the other end is as far as possible to stretch into the solution, so that the volume effect appears between the particles. To some extent, the particles lose the space for free movement, and the entropy value is reduced accordingly, and the mutual repulsion between the particles is increased, so that the contact between the dispersed particles is hindered, the stability of the dispersion system is maintained, and the steric stabilizing effect is formed. However, when the dispersant concentration is too large, the macromolecule of the dispersant is curled in the liquid, and the macromolecule itself begins to settle, reducing the effect of the steric stabilizing. The principle of the electrostatic stabilizing mechanism is that the attraction and repulsion between the particles in the dispersion system are closely related to the distance. There are first and second minimum values of the potential and a potential barrier. When the distance between the two particles reaches the first minimum value, the attraction becomes the main action, and at this time, the agglomeration of the two is inevitable. The process of electrostatic stabilization is to keep the distance between the two at the second minimum value of the metastable state by increasing the potential barrier. The Zeta potential is a measure of the attraction and repulsion between the particles in the slurry. The larger the absolute value is, the higher the potential barrier is, and the greater the repulsion between the particles in the slurry is, and at this time, the slurry has a lower stable viscosity. Adjusting the pH value is the best way to change the Zeta potential. The combined action of the electrostatic stabilizing mechanism and the steric stabilizing mechanism is the most widely used combined stabilizing mechanism.

[0051] In the past research on the dispersion state of particles in a liquid dispersant, only one or two of the three important influencing factors of steric hindrance, electrostatic and particle size were often studied. The obtained result is often the optimal solution under the specific data of the other one or two conditions, and the optimal solution obtained by combining the three factors is not obtained. The present application combines the three factors, and studies the comprehensive influence of different pH and dispersant concentration three factors superimposed on the viscosity and stability of the suspension under three different particle sizes. The result is significant, and the finally obtained slurry particles are uniformly dispersed in every corner of the system. Neither is the internal micro force insufficient to offset the gravity of the particles with too large particle diameter, nor is the agglomeration and settlement caused by the too small particle diameter. Under the combined action of the appropriate particle size, dispersant concentration and pH, the action of the steric stabilizing mechanism and the electrostatic stabilizing mechanism is maximized. The gravity, electrostatic force and space resistance received by the particles in the dispersion system are in a relative balance, so that the suspension can exist stably for a long time

[0052] Example 1

[0053] A preparation method of a silicon carbide ceramic slurry, comprising the following steps:

[0054] S1, a small amount of ceramic powder is mixed with deionized water, different mass fractions of polyethyleneimine (PEI) aqueous solution are added respectively, pH is adjusted, and several groups of orthogonal condition parameter dilute solutions are obtained; the particle size of the silicon carbide powder of the silicon carbide ceramic slurry is 300-500 nm; the pH value of the silicon carbide ceramic slurry is 8; and the mass fraction of the polyethyleneimine dispersant added in S1 is 0.3%.

[0055] S2, the zeta potential of the orthogonal solution groups is measured, and the group with the largest absolute value of zeta potential is selected and recorded.

[0056] S3, a silicon carbide slurry with a mass fraction of 50% is prepared, the optimal value obtained in S2 is used as the parameter for adjusting the pH and PEI concentration, and 5% of ethanol is added to the total volume.

[0057] The slurry mass fraction in S3 is 56%; and the mass fraction of anhydrous ethanol is 2% of the total mass fraction.

[0058] S4, the mixed slurry is first subjected to ultrasonic dispersion, and then poured into a planetary ball mill to obtain the required slurry after stirring for 4 h.

[0059] In S4, the ultrasonic dispersion power is 195 W, the working time is set to 2 seconds, the intermittent time is 1 second, the total dispersion time is 10 min, the revolution speed of the planetary ball mill during stirring is 100 RPM, the rotation speed is 200 RPM, the stirring time is 4 h, and the forward and reverse rotation is turned on.

[0060] A preparation method of a silicon carbide ceramic slurry, comprising the following steps:

[0061] S1, the silicon carbide powder with a particle size of 300-500 nm is poured into a beaker containing deionized water, the mass ratio of the silicon carbide powder to the deionized water is 1:1, a polyethyleneimine aqueous solution with a mass fraction of 10% is added, a hydrochloric acid with a pH value of 2 and a sodium silicate aqueous solution with a hydrochloric acid value of 12 are used to adjust the pH of the suspension to 8, and then ethanol is added to obtain a mixed slurry; wherein the mass fraction of the polyethyleneimine aqueous solution in the mixed slurry is 0.3%, the amount of ethanol added is 2% of the mass of the mixed slurry, and the mass ratio of the silicon carbide powder to the deionized water and ethanol is 75:75:2.

[0062] S2, the mixed slurry is subjected to ultrasonic dispersion and ball milling dispersion in sequence to obtain a silicon carbide ceramic slurry; the ultrasonic dispersion power is 195 W, the working time is set to 2 seconds, the intermittent time is 1 second, the total dispersion time is 10 min, the revolution speed of the planetary ball mill during stirring is 100 RPM, the rotation speed is 200 RPM, the stirring time is 5 h, and the forward and reverse rotation is turned on.

[0063] Example 2

[0064] The difference from Example 1 is that:

[0065] The pH value of the silicon carbide ceramic slurry is 4.

[0066] The rest is the same as Example 1, which will not be repeated here.

[0067] Example 3

[0068] The difference from Example 1 is that:

[0069] The pH value of the silicon carbide ceramic slurry is 6.

[0070] The rest is the same as Example 1, which will not be repeated here.

[0071] Example 4

[0072] The difference from Example 1 is that:

[0073] The pH value of the silicon carbide ceramic slurry is 10.

[0074] The rest is the same as Example 1, which will not be repeated here.

[0075] Example 5

[0076] The difference from Example 1 is that:

[0077] The mass fraction of polyethyleneimine dispersant added in the silicon carbide ceramic slurry is 0.

[0078] The rest is the same as Example 1, which will not be repeated here.

[0079] Example 6

[0080] The difference from Example 1 is that:

[0081] The mass fraction of polyethyleneimine dispersant added in the silicon carbide ceramic slurry is 0.2%.

[0082] The rest is the same as Example 1, which will not be repeated here.

[0083] Example 7

[0084] The difference from Example 1 is that:

[0085] The mass fraction of polyethyleneimine dispersant added in the silicon carbide ceramic slurry is 0.4%.

[0086] The rest is the same as Example 1, which will not be repeated here.

[0087] Example 8

[0088] The difference from Example 1 is that:

[0089] The silicon carbide powder of the silicon carbide ceramic slurry has a particle size of 1-3 μm.

[0090] The rest is the same as example 1, which will not be repeated here.

[0091] Example 9

[0092] The difference from example 1 is that:

[0093] The silicon carbide powder of the silicon carbide ceramic slurry has a particle size of 1-3 μm, and the pH value of the silicon carbide ceramic slurry is 4.

[0094] The rest is the same as example 1, which will not be repeated here.

[0095] Example 10

[0096] The difference from example 1 is that:

[0097] The silicon carbide powder of the silicon carbide ceramic slurry has a particle size of 1-3 μm, and the pH value of the silicon carbide ceramic slurry is 6.

[0098] The rest is the same as example 1, which will not be repeated here.

[0099] Example 11

[0100] The difference from example 1 is that:

[0101] The silicon carbide powder of the silicon carbide ceramic slurry has a particle size of 1-3 μm, and the pH value of the silicon carbide ceramic slurry is 10.

[0102] The rest is the same as example 1, which will not be repeated here.

[0103] Example 12

[0104] The difference from example 1 is that:

[0105] The silicon carbide powder of the silicon carbide ceramic slurry has a particle size of 1-3 μm, and the mass fraction of polyethyleneimine dispersant added in the silicon carbide ceramic slurry is 0.

[0106] The rest is the same as example 1, which will not be repeated here.

[0107] Example 13

[0108] The difference from example 1 is that:

[0109] The silicon carbide powder of the silicon carbide ceramic slurry has a particle size of 1-3 μm, and the mass fraction of polyethyleneimine dispersant added in the silicon carbide ceramic slurry is 0.2%.

[0110] The rest is the same as example 1, which will not be repeated here.

[0111] Example 14

[0112] The difference from Example 1 is that:

[0113] The silicon carbide powder particle size of the silicon carbide ceramic slurry is 1-3 μm, and the mass fraction of the polyethyleneimine dispersant added in the silicon carbide ceramic slurry is 0.4%.

[0114] The rest is the same as Example 1, which will not be repeated here.

[0115] Example 15

[0116] The difference from Example 1 is that:

[0117] The silicon carbide powder particle size of the silicon carbide ceramic slurry is 50-100 nm.

[0118] The rest is the same as Example 1, which will not be repeated here.

[0119] Example 16

[0120] The difference from Example 1 is that:

[0121] The silicon carbide powder particle size of the silicon carbide ceramic slurry is 50-100 nm, and the pH value of the silicon carbide ceramic slurry is 4.

[0122] The rest is the same as Example 1, which will not be repeated here.

[0123] Example 17

[0124] The difference from Example 1 is that:

[0125] The silicon carbide powder particle size of the silicon carbide ceramic slurry is 50-100 nm, and the pH value of the silicon carbide ceramic slurry is 6.

[0126] The rest is the same as Example 1, which will not be repeated here.

[0127] Example 18

[0128] The difference from Example 1 is that:

[0129] The silicon carbide powder particle size of the silicon carbide ceramic slurry is 50-100 nm, and the pH value of the silicon carbide ceramic slurry is 10.

[0130] The rest is the same as Example 1, which will not be repeated here.

[0131] Example 19

[0132] The difference from Example 1 is that:

[0133] The silicon carbide powder of the silicon carbide ceramic slurry has a particle size of 50-100 nm, and the mass fraction of the polyvinyl imine dispersant added in the silicon carbide ceramic slurry is 0.2%.

[0134] The rest is the same as in Example 1, which will not be repeated here.

[0135] Example 20

[0136] The difference from Example 1 is that:

[0137] The silicon carbide powder of the silicon carbide ceramic slurry has a particle size of 50-100 nm, and the mass fraction of the polyvinyl imine dispersant added in the silicon carbide ceramic slurry is 0.2%.

[0138] The rest is the same as in Example 1, which will not be repeated here.

[0139] Example 21

[0140] The difference from Example 1 is that:

[0141] The silicon carbide powder of the silicon carbide ceramic slurry has a particle size of 50-100 nm, and the mass fraction of the polyvinyl imine dispersant added in the silicon carbide ceramic slurry is 0.4%.

[0142] The rest is the same as in Example 1, which will not be repeated here.

[0143] 1. Viscosity test: at 25°C, 20mL of the prepared slurry was taken at the first time and poured into a NDJ-1S type rotary viscometer standard measuring cylinder. Select No. 0 rotor, and measure the viscosity of the slurry at rotor speeds of 60RPM, 30RPM, 12RPM, 6RPM, and four gradient conditions. Take the measured value at 30%-50% of the corresponding rotor speed range as the viscosity measurement value of the slurry of this example.

[0144] 2. Stability test: the slurry with measured viscosity was poured into a 15mL sample bottle and sealed, and was placed in the same external conditions. The settling and layering of the slurry were recorded every 1 hour. When an obvious liquid-solid interface appeared in the sample bottle, it was recorded as the settling time of the slurry of this example. The performance comparison of each example after viscosity test and stability test is shown in Table 1:

[0145] Table 1 Parameter Performance Table of Each Example

[0146] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Viscosity value / mPa.s 3.34 4.86 6.46 5.28 >100 6.19 5.11 Settling time / h 36 25 20 60 0 20 17 Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 Viscosity value / mPa.s 3.83 7.84 10.39 7.69 >100 5.45 9.55 Settling time / h 1 0.2 0.2 0.1 0 0.5 0.3 Example 15 Example 16 Example 17 Example 18 Example 19 Example 20 Example 21 Viscosity value / mPa.s 94.62 >100 >100 >100 >100 >100 >100 Settling time / h - - - - - - -

[0147] From the above Table 1, it can be seen that the slurry of the present application has lower viscosity and higher stability compared with the existing slurry for infiltration. Comparing Examples 1-7, the viscosity performance of the slurry is basically the same as the change of the absolute value of Zeta potential of the dilute solution prepared in S1. When the mass fraction of polyethylene imine dispersant in the slurry is 0.3% and the pH value of the slurry is 8, the viscosity performance and stability are the best. Because the steric hindrance effect and the electrostatic steric hindrance effect in the slurry are both optimal under this condition, it can be seen from Examples 2-7 that the parameters around this condition cannot achieve the effect. It can be seen from the comparison of Comparative Examples 1-7 and Examples 8-14 that the powder with a particle size of 1-3 μm is more difficult to disperse and stabilize than the powder with a particle size of 300-500 nm. The reason is that the powder with a particle size of 1-3 μm has a relatively large mass, and the micro force acting on a single particle in the slurry is small, which cannot offset the excess gravity, and it is more likely to sink. Therefore, the viscosity and stability are both worse than those of the slurry with a particle size of 300-500 nm under the same condition. It can be seen from the comparison of Comparative Examples 1-7 and Examples 15-21 that the powder with a particle size of 50-100 nm has a too large specific surface area, and the agglomeration between particles is obvious. It is difficult to separate the particles and form a stable interface with water in the powder state, so it is difficult to disperse in water. Even if a small part of it is dissolved in water, it will soon agglomerate with adjacent particles again to form a paste. The viscosity is extremely large, and it is not meaningful to count the sedimentation time. This is because when the silicon carbide powder is in a mesoscale, the energy required to form an interface with adjacent particles is much lower than that required to form an interface with water of the same area. Therefore, the interfacial energy of the SiC-SiC interface is much lower than that of the SiC-H2O interface. When adjacent silicon carbide particles approach, the SiC-SiC interface will spontaneously form to reduce the area of the SiC-H2O interface, thereby reducing the total energy of the system.

[0148] Comparing the 21 different examples in Comparative Example 3 with different particle sizes, it can be easily seen that when the SiC particle size is 300-500 nm, the viscosity and stability time of the slurry are optimal. Under this particle size condition, neither the specific surface area is too large to cause particle agglomeration, nor the mass is too high to cause the particles to be unable to be stably suspended. The slurry described in Example 1 is used to infiltrate the carbon fiber preform, and the weight gain percentage can reach about 25%. The porosity of the preform can be reduced from 26% before infiltration to 12% after infiltration. The preform plate infiltrated by the slurry has basically no fiber exposed on the surface, which provides a strong guarantee for further obtaining a dense high-quality surface.

[0149] Example 22

[0150] In this example, the mass ratio of silicon carbide powder, water and ethanol is 75:75:4, and the rest is the same as in Example 1.

[0151] Example 23

[0152] In this example, the mass ratio of silicon carbide powder, water and ethanol is 125:125:5, and the rest of the parts not involved are the same as example 1.

[0153] Example 24

[0154] In this example, the ultrasonic dispersion power is 150W, the ultrasonic dispersion time is 10min, and the rest of the parts not involved are the same as example 1.

[0155] Example 25

[0156] In this example, the ultrasonic dispersion power is 220W, the ultrasonic dispersion time is 10min, and the rest of the parts not involved are the same as example 1.

[0157] Example 26

[0158] In this example, the stirring power of ball milling dispersion is 220W, the ball milling dispersion time is 10h, and the rest of the parts not involved are the same as example 1.

[0159] Example 27

[0160] In this example, the stirring power of ball milling dispersion is 300W, the ball milling dispersion time is 5h, and the rest of the parts not involved are the same as example 1.

[0161] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A highly efficient impregnation ceramic slurry, characterized in that, Including silicon carbide powder, aqueous solution of polyethyleneimine, ethanol, hydrochloric acid, sodium silicate, and water; The silicon carbide powder has a particle size of 300~500nm, and the polyethyleneimine aqueous solution in the ceramic slurry has a mass fraction of 0.25~0.35%; the pH value of the ceramic slurry is in the range of 7.8~8.

2. The mass fraction of the polyethyleneimine aqueous solution is 10%. The ceramic slurry is dispersed by ball milling; The mass ratio of silicon carbide powder, water and ethanol is (75~125):(75~125):(3~5).

2. A method for preparing a highly efficient impregnating ceramic slurry as described in claim 1, characterized in that, Includes the following steps: Step 1: Mix silicon carbide powder with a particle size of 300~500 nm with water, then add polyethyleneimine aqueous solution, add hydrochloric acid and sodium silicate to adjust the pH value, and then add ethanol to obtain a mixed slurry; Step 2: After dispersing the mixed slurry, a silicon carbide ceramic slurry is obtained.

3. The method for preparing a highly efficient impregnating ceramic slurry according to claim 2, characterized in that, In step 1, the added hydrochloric acid has a pH of 2, and the sodium silicate has a pH of 12.

4. The method for preparing a highly efficient impregnating ceramic slurry according to claim 2, characterized in that, In step 2, the dispersion process involves ultrasonic dispersion followed by ball milling dispersion.

5. The method for preparing a highly efficient impregnating ceramic slurry according to claim 4, characterized in that, The ultrasonic dispersion power is 150~220W, and the ultrasonic dispersion time is 10min.

6. The method for preparing a highly efficient impregnating ceramic slurry according to claim 4, characterized in that, The stirring speed for ball milling dispersion is 200~300 rpm, and the ball milling dispersion time is 5~10 h.

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