A method for rapidly preparing high-strength high-density quartz fiber reinforced quartz-based composite material

Abstract

The application relates to the technical field of high-temperature-resistant wave-transparent quartz fiber reinforced quartz-based composite material preparation, and particularly discloses a method for rapidly preparing high-strength and high-density quartz fiber reinforced quartz-based composite material, which comprises the following steps: immersing a quartz fiber preform which has been subjected to interface pretreatment in a vacuum or inert atmosphere in silica sol, continuously applying low pressure and heating, and performing low-pressure boiling immersion-in-place gel solidification-low-pressure drying; the low-pressure boiling immersion-in-place gel solidification-low-pressure drying process is repeated for several times, and the low-pressure boiling immersion time is sequentially shortened in the repeated immersion process; and finally, sintering is performed to obtain the composite material. The quartz fiber reinforced quartz-based composite material prepared by the application has the advantages of uniform matrix distribution, high density, high strength, strong designability, realized integrated operation of the whole process of immersion-gel-drying, simple production equipment, low-concentration commercially available silica sol used, good stability, long storage period, low raw material cost, process safety, and favorability for large-scale industrialized production.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of preparation of high-temperature-resistant wave-transparent quartz fiber reinforced quartz-based composite materials, in particular to a method for rapidly preparing high-strength high-density quartz fiber reinforced quartz-based composite materials. BACKGROUND

[0002] The quartz fiber reinforced quartz ceramic-based composite material has excellent comprehensive performance of force, heat and electricity, is the most mature ceramic-based wave-transparent composite material at home and abroad, and is the most widely used ceramic-based wave-transparent composite material, and an antenna cover / antenna window product prepared from the material has been widely applied to the field of aerospace wave transmission.

[0003] At present, the methods for preparing the quartz fiber reinforced quartz ceramic-based composite material mainly include a sol-gel method, a liquid phase infiltration method (or liquid phase impregnation method) and a chemical vapor infiltration method (CVI), and the most widely used method is the sol-gel method, and the process of the method is as follows: mainly using silicon sol to impregnate a quartz fiber preform, after multiple impregnation-drying gel-sintering cycles, an initial blank component with a certain density is obtained, and finally the product is obtained after processing, moisture-proof treatment and coating treatment, because the stability of high-concentration silicon sol is not high, low-concentration silicon sol is mainly used in the process, and the low-concentration silicon sol needs to be repeatedly impregnated and dried for multiple times, and with the increase of the impregnation period, there are obvious density gradient differences between the surface layer and the core layer of the product, the high density of the surface layer leads to low impregnation efficiency in the later period, and the product needs to be repeatedly processed and then impregnated, the product preparation process is complex, and the preparation period is long, therefore, people explore new processes and methods through various optimization methods, so as to rapidly prepare the high-density uniform quartz fiber reinforced quartz ceramic-based composite material.

[0004] Silica sol impregnation is the key process for densification of quartz fiber reinforced quartz-based composites. The commonly used impregnation methods are vacuum impregnation and high pressure impregnation. Both methods use pressure difference to penetrate silica sol into the pores of quartz fiber or green body. Chinese patent CN 113896554 A discloses a vacuum impregnation process using silica slurry and silica sol in sequence to prepare high-density fiber reinforced quartz ceramic composite materials. However, the silica slurry used in the process is a high-concentration suspension slurry with low stability, which needs to be prepared and used immediately. The two impregnation processes require repeated impregnation and sintering multiple times, which causes great damage to the fibers. Moreover, the structure of the matrix material with dense outer and sparse inner is not fundamentally solved, resulting in low product consistency and being not conducive to industrial production. Chinese patent CN 113511879 A discloses a gradient impregnation process of silica sol with high, medium and low concentrations for quartz fiber preform. The process uses different concentrations of silica sol in different densification cycles to improve the impregnation efficiency and shorten the preparation period of quartz fiber reinforced quartz-based composites. However, the process requires the use of reduced pressure rotary evaporation to concentrate commercial acidic silica sol before impregnation, which increases the process and cost. Chinese patent CN 103601479 A discloses a preparation method of high-temperature resistant ultra-thin antenna window. The process first uses pressure to pre-determine the pressure of the preform, and then uses 55% to 65% silica sol, 38% to 40% silica sol, 30% silica sol, SAR-9 organic silicon resin and 30% silica sol impregnation-drying gel-sintering process in sequence. The process uses gradient concentration silica sol impregnation process to reduce the number of impregnation and shorten the preparation period. However, the high-concentration silica sol in the process has stability problems, and the process needs to use organic silicon resin for impregnation to improve the rigidity. If the organic silicon resin is not completely sintered, it will affect the wave transmission performance of the composite material.

[0005] The common ways for drying and curing of silica sol include air curing, gel curing and rapid gelation curing. A Chinese patent with publication number CN105272119A discloses in-situ gelation curing of silica sol by adding ammonia gas to avoid overflow and loss of silica sol, and then improving drying efficiency by microwave drying technology. However, irritating gas and microwave drying rotating equipment are needed in the process, and the preparation process is relatively complex. A Chinese patent with publication number CN117700251A discloses repeatedly impregnating a preform with low-density silica sol under vacuum conditions, and then combining with a rotating drying method to prepare an antenna cover product with relatively uniform density. Although the vacuum condition is more conducive to the uniform infiltration of silica sol into the internal pores of the fibers, and the rotating drying method avoids the problem of crust formation on the surface of the blank, and eliminates the rough machining process during product impregnation, the total impregnation period exceeds 10 cycles and each impregnation lasts more than 20 hours, which is a long process cycle. Therefore, it is still a difficult point to be solved at present how to rapidly prepare high-strength and high-density quartz fiber reinforced quartz ceramic matrix composite materials from commercially available low-concentration silica sol under relatively simple equipment conditions, and stably realize industrial production of the product. SUMMARY

[0006] In view of the above problems, the present application provides a method for rapidly preparing high-strength and high-density quartz fiber reinforced quartz matrix composite material, which can significantly shorten the preparation period, simplify the impregnation and drying equipment and process flow, reduce the manufacturing cost, and is beneficial to industrial production. The prepared quartz fiber reinforced quartz matrix composite material has high density, small density gradient and high strength. The specific technical scheme is as follows:

[0007] A method for rapidly preparing high-strength and high-density quartz fiber reinforced quartz matrix composite material, comprising the following steps:

[0008] (1) placing a quartz fiber preform which has been interfacially pretreated in a vacuum or inert atmosphere into a vacuum impregnation tank, adding silica sol to ensure that the preform is completely immersed, and sealing the impregnation tank;

[0009] (2) performing low-pressure heating boiling impregnation on the impregnation tank, so that the silica sol is kept in a state of intense boiling at low pressure and low temperature (the pressure in the tank is reduced, and the boiling point of the aqueous solution is correspondingly reduced), and then performing low-pressure boiling impregnation. After maintaining the impregnation for a period of time, the heating temperature is increased to perform in-situ gelation curing of the silica sol, and the whole process is continuously kept at low pressure to obtain a green body. By continuously keeping low pressure and heating, the air in the preform is completely removed, the silica sol is fully infiltrated into the preform, the silica sol is kept in a state of intense boiling, the volatilized water vapor is removed, and the silica sol is continuously concentrated, so that high-concentration silica sol impregnation is realized;

[0010] (3) taking out the green body and cleaning the surface gel, repeating the low-pressure boiling impregnation-in-situ gelation-drying process of step (2) several times, and successively shortening the low-pressure boiling impregnation time in the repeated impregnation process, so as to concentrate the silica sol in the impregnation process and realize in-situ impregnation of silica sol with different gradient concentrations;

[0011] (4) sintering the green body to obtain a high-strength and high-density quartz fiber reinforced quartz-based composite material.

[0012] Preferably, in the above method for rapidly preparing a high-strength and high-density quartz fiber reinforced quartz-based composite material, in step (1), the interface pretreatment temperature of the quartz fiber preform is 400-650°C, the heating rate is 1-20°C / min, and the holding time is 60-360 min, and the atmosphere during the pretreatment is vacuum, nitrogen, helium or argon. By cracking the infiltrant resin on the surface of the preform fiber in vacuum or inert atmosphere, an interface layer with a carbon-containing coating is obtained on the surface of the quartz fiber, which reduces the dehydration condensation of the hydroxyl groups on the surface of the quartz fiber and the silica colloidal particles during the silica sol impregnation, weakens the strong interface bonding between the fiber and the matrix, prevents cracks generated by the shrinkage of the matrix from penetrating the fiber due to the strong interface bonding when the material is damaged, and thus prevents the overall brittle fracture of the material, which protects the quartz fiber and is beneficial to the toughening effect of the reinforcing fiber and the improvement of the mechanical properties of the composite material.

[0013] Preferably, in the above method for rapidly preparing a high-strength and high-density quartz fiber reinforced quartz-based composite material, in step (1), the interface pretreatment temperature of the quartz fiber preform is 500-550°C, the heating rate is 5-10°C / min, and the holding time is 90-180 min, and the atmosphere during the pretreatment is vacuum or nitrogen.

[0014] Preferably, in the above method for rapidly preparing a high-strength and high-density quartz fiber reinforced quartz-based composite material, in step (1), the impregnation tank is a profiled impregnation tank designed according to the profile of the fabric to reduce the amount of silica sol, and the liquid level of the silica sol is 10-80 mm higher than the top of the preform after the silica sol is added, so as to ensure that the preform is still immersed in the solution during the continuous heating and low-pressure boiling impregnation process after the volume concentration of the silica sol is reduced.

[0015] Preferably, in the above method for rapidly preparing a high-strength and high-density quartz fiber reinforced quartz-based composite material, in step (1), the liquid level of the silica sol is 30-50 mm higher than the top of the preform after the silica sol is added.

[0016] Preferably, in the method for rapidly preparing high-strength and high-density quartz fiber reinforced quartz-based composite material, the silica sol is a commercially available high-purity stable acidic silica sol, the solid content is 20wt.%-30wt.%, the viscosity is <15mpa·s, the pH is 2-4, and the SiO2 colloid particle size in the silica sol is 5nm-100nm.

[0017] Preferably, in the method for rapidly preparing high-strength and high-density quartz fiber reinforced quartz-based composite material, in the step (2), the whole process maintains the tank air pressure at 500Pa-1500Pa, the low-pressure boiling impregnation temperature is 5℃-35℃, the impregnation time is 0.5h-3h, the in-situ gelation solidification and low-pressure drying process gradually increases the heating temperature, the temperature range is 70℃-250℃, and the gelation solidification time and the low-pressure drying time are both 1h-4h. Under the condition of continuous heating and low pressure, the silica sol temperature is higher than 35℃ and is easy to gel, so the temperature is ensured to be 5℃-35℃ during the impregnation process to prevent the silica sol from gelling too fast and not conducive to the complete infiltration of the preform.

[0018] Further, preferably, in the method for rapidly preparing high-strength and high-density quartz fiber reinforced quartz-based composite material, in the step (2), the whole process maintains the tank air pressure at 500Pa-1000Pa, the low-pressure boiling impregnation temperature is 15℃-35℃, and the in-situ gelation solidification and low-pressure drying process gradually increases the heating temperature, the temperature range is 80℃-200℃.

[0019] Preferably, in the method for rapidly preparing high-strength and high-density quartz fiber reinforced quartz-based composite material, in the step (3), the low-pressure boiling impregnation-in-situ gelation solidification-low-pressure drying cycle is performed 1-6 times, the low-pressure boiling impregnation time is sequentially decreased from the first impregnation time, and the in-situ gelation solidification and drying process system is the same as that in the step (2).

[0020] Preferably, in the method for rapidly preparing high-strength and high-density quartz fiber reinforced quartz-based composite material, in the step (3), the low-pressure boiling impregnation-in-situ gelation solidification-low-pressure drying cycle is performed 2-4 times.

[0021] Preferably, in the method for rapidly preparing high-strength and high-density quartz fiber reinforced quartz-based composite material,

[0022] Preferably, in the method for rapidly preparing high-strength and high-density quartz fiber reinforced quartz-based composite material, the low-pressure boiling impregnation time is sequentially decreased by 0.2-1h.

[0023] Preferably, in the method for rapidly preparing high-strength and high-density quartz fiber reinforced quartz-based composite material, the low-pressure boiling impregnation time is sequentially decreased by 0.5-1h.

[0024] Preferably, in the method for rapidly preparing high-strength and high-density quartz fiber reinforced quartz matrix composite material, the sintering in step (4) is performed in air in a muffle furnace, the sintering temperature is 700-900°C, the heating rate is 1-10°C / min, and the holding time is 30-360 min. The sintering process has the effects of oxidizing and decomposing the carbon coating on the surface of the quartz fiber, and sintering and densifying the preform and the matrix to a certain extent.

[0025] Preferably, in the method for rapidly preparing high-strength and high-density quartz fiber reinforced quartz matrix composite material, the sintering in step (4) is performed in air in a muffle furnace, the sintering temperature is 750-800°C, the heating rate is 1-3°C / min, and the holding time is 90-180 min.

[0026] In another aspect, the application also provides a high-strength and high-density quartz fiber reinforced quartz matrix composite material prepared by the above method.

[0027] Compared with the prior art, the application has the following beneficial effects:

[0028] 1. The method for rapidly preparing high-strength and high-density quartz fiber reinforced quartz matrix composite material of the application, by sintering pretreatment in vacuum or inert atmosphere, the infiltrant on the surface of the quartz fiber is cracked in situ to obtain a carbon-containing interface layer, which prevents the dehydration condensation of the hydroxyl groups on the surface of the quartz fiber and the hydroxyl groups on the surface of the silica sol to form strong interfacial bonding during the impregnation-gel-drying process. Then, by sintering in air in a muffle furnace, the carbon-containing interface layer is oxidized and removed, and a porous gap structure is formed in situ between the fiber and the matrix, which further weakens the strong interfacial bonding between the fiber and the matrix, and prevents the cracks generated by the shrinkage of the matrix from penetrating the fiber due to the strong interfacial bonding when the material is damaged, resulting in brittle fracture of the whole material. The carbon coating obtained by the interface treatment does not affect the dielectric and wave-transparent properties of the composite material, and effectively protects the fiber during high-temperature sintering. The whole composite material preparation process only needs one sintering treatment, which reduces the thermal damage of the quartz fiber caused by multiple sintering treatments, and makes the quartz fiber effectively play a role in toughening and strengthening, thereby improving the mechanical properties of the composite material.

[0029] 2. In the method for rapidly preparing high-strength and high-density quartz fiber reinforced quartz-based composite material of the present application, through continuous heating and low-pressure boiling impregnation, the silica sol can continuously maintain a boiling evaporation state at a low pressure and at a lower temperature (the boiling point of the aqueous solution decreases accordingly as the air pressure decreases), so that the air in the pores of the quartz fiber preform is continuously discharged to be filled with silica sol, while the concentration of the silica sol is continuously concentrated, realizing simultaneous impregnation and concentration of the silica sol, and by controlling the heating temperature of the impregnation to be within 35℃, the influence of the rapid gelation of the silica sol on the impregnation efficiency is prevented. In addition, by shortening the time of low-pressure boiling impregnation in the subsequent cycle impregnation process, and using commercially available silica sol with high stability and low concentration, silica sol with decreasing concentration can be obtained at the end of the impregnation, realizing gradient concentration impregnation in situ again to improve the impregnation efficiency, solving the defect of poor storage stability of high-concentration silica sol, and there is no need to obtain silica sol with different concentrations through pre-decompression process, simplifying the process and being conducive to industrial production.

[0030] 3. In the present application, the process of continuous heating and low-pressure boiling impregnation-in-situ gelation and drying under low pressure is adopted, the continuous heating and low-pressure boiling impregnation can improve the thermal motion and concentration of the silica sol during impregnation, improving the impregnation efficiency: if only continuous low-pressure impregnation is adopted without heating the silica sol, the water evaporation is an endothermic reaction, which leads to lower and slower thermal motion of the silica sol molecules, which is not conducive to impregnation. In-situ gelation maximizes the uniform distribution of silica sol in the preform, avoiding the defect that water molecules drive silica sol molecules to accumulate on the surface of the fabric from the inside to the outside during volatilization, forming an outer dense and inner sparse structure. Continuous heating and vacuum drying are conducive to the formation of open channels for water molecule volatilization, which can not only accelerate water evaporation and speed up the drying process, but also reduce surface closed pores, which is conducive to the next impregnation, reduces the number of impregnation and shortens the impregnation cycle, further improving the impregnation efficiency. At the same time, this process realizes the integration of vacuum impregnation-in-situ gelation and drying, and the continuity and integration of different processes such as vacuum impregnation, in-situ gelation and vacuum drying in the same equipment, greatly simplifying the process equipment, reducing the process operation flow and reducing the production cost.

[0031] 4. The quartz fiber reinforced quartz-based composite material prepared by the present application has uniform matrix distribution, small density gradient, high density, high strength, strong designability, can select the number of cycle impregnation according to needs, the production equipment is simple, the silica sol used is low-concentration commercially available silica sol with good stability and long storage period, the raw material cost is low, the process is safe, and it is conducive to large-scale industrial production and can be applied to the field of aerospace high-temperature wave-transparent materials. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0033] Figure 1 The schematic diagram of the continuous vacuum impregnation-in-situ gelation-drying device structure.

[0034] Legend: 1-impregnation tank, 2-vacuum pump, 3-silica sol, 4-heating body, 5-preform. DETAILED DESCRIPTION

[0035] The specific embodiments of the present application will be described in detail below, but it should be understood that the protection scope of the present application is not limited by the specific embodiments. Unless otherwise defined, all the professional terms used in the following are the same as the meanings commonly understood by those skilled in the art. The professional terms used in this paper are only for the purpose of describing the specific embodiments and are not intended to limit the protection scope of the present application. Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0036] The silica sols of the following examples and comparative examples are aqueous solutions containing SiO2 nanoparticles, purchased from Hebei Jiashihongwei Technology Co., Ltd., and the quartz fiber preforms are purchased from Hubei Feilihua Quartz Glass Co., Ltd.

[0037] Example 1

[0038] A method for rapidly preparing high-strength and high-density quartz fiber reinforced quartz-based composite material, comprising the following steps:

[0039] (1) The hollow cylindrical body quartz fiber preform with an outer diameter of 300 mm, a height of 120 mm and a wall thickness of 12 mm is pre-processed by interfacial in a vacuum furnace at a heating rate of 8℃ / min to 550℃ for 120 min, and then placed in a profiled impregnation tank, and poured into silica sol so that the liquid level is 50 mm higher than the top of the preform, wherein the silica sol has a solid content of 25wt.%, a viscosity of 8mpa·s, and the SiO2 nanoparticles in the silica sol have a particle size distribution of 5nm-60nm, and the impregnation tank is sealed;

[0040] (2) Start the vacuum pump group and the heater, and continuously heat and reduce the pressure to keep the pressure in the tank at about 700 Pa during the low-pressure boiling impregnation, in-situ gelation and drying process. The temperature of the heated silica sol is 25°C during the impregnation. The silica sol is kept in a boiling state during the continuous low-pressure boiling impregnation. After 3 hours of impregnation, the temperature is increased to 80°C, the in-situ gelation is performed for 2 hours, and then the temperature is increased to 200°C for drying for 2 hours.

[0041] (3) After the drying is completed, the preform is taken out and the surface gel is cleaned and polished. After the heating, low-pressure boiling impregnation, in-situ gelation and drying process in step (2) is repeated twice, the impregnation time is sequentially reduced. The second impregnation time is 2.5 hours, and the third impregnation time is 2 hours. A preform blank is obtained. Then, the blank is heated to 800°C at a rate of 2°C / min in a muffle furnace, and is kept at 800°C for 120 minutes for sintering. A quartz fiber reinforced quartz-based composite material is obtained.

[0042] The volume density of the prepared quartz fiber reinforced quartz-based composite material member is 1.79 g / cm 3 The density and bending strength of the sample are tested. The sample is taken from 9 different parts of the member in the thickness direction (inside, middle and outside) and the height direction (top, middle and bottom) (sample size: 80*10 mm*5 mm in length, width and thickness). The test results are shown in Table 1. The results show that the average density is 1.79±0.01 g / cm 3 , the average bending strength of the material is 102.0±3.51 MPa, the bending modulus is 21.05±0.89 GPa, the density gradient distribution is small, the density is uniform, and the mechanical properties of the composite material are excellent.

[0043] Table 1. Density and bending strength of the sample obtained by testing the samples taken from different parts in Example 1

[0044]

[0045]

[0046] Comparative Example 1

[0047] The difference between this comparative example and Example 1 is that in step (2), the continuous low-pressure boiling impregnation, in-situ gelation and drying process is not performed. After the pressure in the tank is reduced to 700 Pa and kept for 30 minutes, the vacuum pump group is turned off. The woven part is taken out and dried at normal pressure in a general oven for 3 hours. The other operating conditions are the same. The specific operation steps are as follows:

[0048] (1) Hollow cylinder rotating body quartz fiber preform with outer diameter of 300 mm, height of 120 mm, and wall thickness of 12 mm is preheated in a vacuum furnace at a heating rate of 8 ℃ / min to 550 ℃ for 120 min for interface pretreatment, and then is placed in a profiled impregnation tank, and silicon sol is poured to make the liquid level of the silicon sol 50 mm higher than the preform, wherein the solid content of the silicon sol is 25 wt.%, the viscosity of the silicon sol is 8 mpa·s, the particle size distribution of SiO2 nanoparticles in the silicon sol is 5 nm-60 nm, and the impregnation tank is sealed;

[0049] (2) The vacuum pump set is started, the pressure in the tank is reduced to 700 Pa and maintained for 30 min, then the vacuum pump set is turned off, the preform is taken out after the pressure in the tank is restored to atmospheric pressure after room temperature pressure impregnation for 3 h, and the preform is dried in a general oven at atmospheric pressure, and then the temperature is increased to 200 ℃ for drying for 2 h after drying at 80 ℃ for 2 h.

[0050] (3) After drying is completed, the preform is taken out and the surface gel is cleaned and polished, the above operation is repeated twice to obtain a preform blank, and the impregnation time in the low-pressure boiling impregnation process is sequentially reduced: the second impregnation time is 2.5 h, the third impregnation time is 2 h, and then the blank is sequentially subjected to sintering at 800 ℃ for 120 min in a muffle furnace at a heating rate of 2 ℃ / min to obtain a composite material.

[0051] The composite material member prepared in the comparative example is characterized, and the volume density of the obtained member is 1.56 g / cm 3 The density of the member is tested from different parts of the member, and the results are shown in Table 2, and the average density is 1.56±0.05 g / cm 3 The average bending strength is 56.73±8.40 MPa, and the bending modulus is 12.11±1.52 GPa. Compared with Example 1, the material density of the comparative example is obviously low, the density distribution has a gradient change, and the mechanical properties are relatively poor. Therefore, it is proved that the process of continuous heating, low-pressure boiling impregnation, in-situ gelation and low-pressure drying has a significant effect on improving the overall density and strength of the material.

[0052] Table 2 Density and bending strength of sample strips obtained by testing different parts of Comparative Example 1

[0053]

[0054]

[0055] Comparative Example 2

[0056] The difference between the comparative example and Example 1 is that the preform pretreatment in step (1) is different, and the sintering is directly performed in a muffle furnace without atmosphere protection sintering, and the other operation conditions are the same. The specific operation steps are as follows:

[0057] (1) A cylindrical quartz fiber preform with a diameter of 230 mm, a height of 120 mm, and a wall thickness of 12 mm was heated to 550°C in a muffle furnace at a heating rate of 8°C / min and kept at this temperature for 120 min for interface pretreatment. After the treatment, the preform was placed in a contoured impregnation tank, and silica sol was poured into the preform so that the liquid level was 50 mm higher than the preform. The silica sol had a solid content of 25 wt.%, a viscosity of 8 mPa·s, and a particle size distribution of SiO2 nanoparticles in the silica sol of 5 nm to 60 nm. The impregnation tank was sealed.

[0058] (2) Start the vacuum pump group and the heater, and continue to heat at low pressure so that the pressure in the tank is maintained at about 700 Pa during the heating low-pressure boiling impregnation-in-situ gel curing-low-pressure drying process. The temperature of the heated silica sol during impregnation is 25°C, and the silica sol is kept in a continuous boiling state during the continuous heating low-pressure boiling impregnation process. After impregnation for 3 hours, the heating temperature is increased to 80°C, the in-situ gel is cured for 2 hours, and finally the temperature is increased to 200°C for drying for 2 hours.

[0059] (3) After drying, the preform is taken out and the surface gel is cleaned and polished. After the heating low-pressure boiling impregnation-in-situ gel curing-low-pressure drying process in step (2) is cycled twice, the impregnation time in the impregnation process is reduced successively: the second impregnation time is 2.5 hours, and the third impregnation time is 2 hours, to obtain a preform blank. Subsequently, the blank is placed in a muffle furnace, heated to 800°C at a heating rate of 2°C / min, and sintered for 120 minutes to obtain a quartz fiber reinforced quartz-based composite material.

[0060] The composite material component prepared in this comparative example was calculated using the volume method, and the volume density of the obtained product was 1.78 g / cm 3 The density and bending strength of the steel were tested by sampling from 9 different locations in the thickness direction (inside, middle and outside) and height direction (top, middle and bottom). The test results are shown in Table 3. The results show that the average density is 1.78±0.01g / cm 3 The density gradient distribution is small, which is closer to that of Example 1. However, the average bending strength of the material is only 87.83±3.04MPa, and the bending modulus is 18.05±1.27GPa. The mechanical properties are significantly reduced. This shows that the preform pretreatment forms a cracked carbon coating through inert atmosphere protection, which can effectively protect the quartz fiber during the impregnation-drying-sintering process.

[0061] Table 3 Density and bending strength of strips obtained by sampling and testing at different positions of comparative example 2

[0062]

[0063]

[0064] Example 2

[0065] A method for rapidly preparing high-strength and high-density quartz fiber reinforced quartz-based composite material, comprising the following steps:

[0066] (1) A cylindrical rotary body quartz fiber preform with a diameter of 300 mm, a height of 150 mm, and a wall thickness of 20 mm is pre-processed at an interface in a nitrogen atmosphere furnace at a heating rate of 5℃ / min to 480℃ for 180 min, and then placed in a profiled impregnation tank, and silicon sol is poured to make the liquid level 40 mm higher than the preform, wherein the silicon sol has a solid content of 25wt.%, a viscosity of 8mpa·s, and the particle size distribution of SiO2 nanoparticles in the silicon sol is 5nm-60nm, and the impregnation tank is sealed;

[0067] (2) Start the vacuum pump set and the heater, and continuously heat at low pressure to keep the pressure in the tank at about 700Pa during the impregnation-in-situ gelation-drying process, the heating temperature of the silicon sol is 20℃ during impregnation, and the silicon sol keeps boiling during the continuous heating and low pressure process, after 3h of impregnation, the heating temperature is increased to 100℃, the in-situ gelation-drying is carried out for 2h, and finally the temperature is increased to 180℃ for drying for 2h.

[0068] (3) After drying, the preform is taken out and the surface gel is cleaned and polished, and the above operation is repeated twice to obtain a preform blank, and the impregnation time in the heating and low pressure boiling impregnation process is gradually reduced: the second impregnation time is 2.5h, the third impregnation time is 2h, and then the blank is sintered in a muffle furnace at a heating rate of 2℃ / min to 750℃ for 150min, and a composite material is obtained.

[0069] The quartz fiber reinforced quartz-based composite material member prepared in this embodiment is calculated by volume method, and the volume density of the obtained sample is 1.75g / cm 3 Density blocks are taken from different parts of the member in the thickness direction for density test, and the density fluctuation is ±0.03g / cm 3 After mechanical property test, the bending strength of the material is 106.2MPa, and the bending modulus is 18.92GPa, and the mechanical property is good.

[0070] The foregoing description of specific exemplary embodiments of the application is intended for purposes of illustration and example only. These descriptions are not intended to limit the application to the precise form disclosed, and it is obvious that many modifications and variations are possible in light of the above teachings. The specific exemplary embodiments were chosen and described in order to explain the principles of the application and its practical application to thereby enable others skilled in the art to best utilize the application and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the application be defined by the claims and their equivalents.

Claims

1. A method for rapidly preparing a high-strength and high-density quartz fiber reinforced quartz-based composite material, characterized in that: The following steps are involved: (1) placing a quartz fiber preform with interface pretreatment in a vacuum or inert atmosphere into a vacuum impregnation tank, adding silica sol to ensure that the preform is completely immersed, and sealing the impregnation tank; (2) Continuously heating the impregnation pot at low pressure to keep the silica sol in a vigorous boiling state at low pressure and low temperature, and performing low-pressure boiling impregnation. After impregnation for a period of time, the heating temperature is increased to perform in-situ gel curing of the silica sol, and low-pressure drying is performed. The low pressure state is maintained throughout the entire process to obtain a preform; (3) taking out the preform and cleaning the surface gel, and cyclically performing the low-pressure boiling impregnation-in-situ gel curing-low-pressure drying process of step (2) for several times, successively shortening the low-pressure boiling impregnation time during the cyclic impregnation process to obtain a preform; (4) Sintering the blank to obtain a high-strength and high-density quartz fiber reinforced quartz-based composite material.

2. The method for rapidly preparing a high-strength and high-density quartz fiber reinforced quartz-based composite material according to claim 1, characterized in that: In the step (1), the interface pretreatment temperature of the quartz fiber preform is 400°C to 650°C, the heating rate is 1°C / min to 20°C / min, the holding time is 60min to 360min, and the atmosphere during the pretreatment process is vacuum, nitrogen, helium or argon.

3. The method for rapidly preparing a high-strength and high-density quartz fiber reinforced quartz-based composite material according to claim 1, characterized in that: In the step (1), the dipping tank is a contoured dipping tank, which is contoured according to the outer dimensions of the fabric. After the silica sol is added, the silica sol liquid level is 10 mm to 80 mm higher than the top of the preform.

4. The method for rapidly preparing a high-strength and high-density quartz fiber reinforced quartz-based composite material according to claim 1, characterized in that: The silica sol is a high-purity stable acidic silica sol with a solid content of 20wt.% to 30wt.%, a viscosity of less than 15mPa·s, a pH of 2 to 4, and a SiO2 micelle particle size of 5nm to 100nm.

5. The method for rapidly preparing a high-strength and high-density quartz fiber reinforced quartz-based composite material according to claim 1, characterized in that: In the step (2), the air pressure in the tank is maintained at 500Pa to 1500Pa throughout the entire process, the low-pressure boiling immersion temperature is 5°C to 35°C, the immersion time is 0.5h to 3h, and the heating temperature is gradually increased during the in-situ gel curing and low-pressure drying process, the temperature range is 70°C to 250°C, and the gel curing time and low-pressure drying time are both 1h to 4h.

6. The method for rapidly preparing a high-strength and high-density quartz fiber reinforced quartz-based composite material according to claim 1, characterized in that: In the step (3), the low-pressure boiling impregnation-in-situ gel curing-low-pressure drying cycle is repeated 1 to 6 times, the low-pressure boiling impregnation time decreases from the first vacuum impregnation time, and the in-situ gel curing and drying process is the same as that of step (2).

7. The method for rapidly preparing a high-strength and high-density quartz fiber reinforced quartz-based composite material according to claim 6, characterized in that: The circulating low-pressure boiling immersion time is reduced by 0.2 to 1 hour.

8. The method for rapidly preparing a high-strength and high-density quartz fiber reinforced quartz-based composite material according to claim 1, characterized in that: In the step (4), sintering is carried out in the air of a muffle furnace, the sintering temperature is 700° C. to 900° C., the heating rate is 1° C. / min to 10° C. / min, and the holding time is 30 min to 360 min.

9. A high-strength and high-density quartz fiber reinforced quartz-based composite material, characterized in that: The composite material is prepared by the method according to any one of claims 1 to 8.

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