Preparation method of gas-containing film hole ceramic composite material heat insulation screen

Abstract

The present invention discloses a method for preparing a heat shield made of ceramic composite materials containing air film holes. The heat shield is prepared by a net size forming method. On the one hand, the method uses a metal round needle to occupy a position on the surface of a male mold, and directly weaves a fiber fabric on the surface of the male mold to form air film holes in situ, which can avoid fiber damage caused by mechanical processing and drilling, and reduce the influence of stress concentration at the position of the air film holes; on the other hand, the aluminum oxide + silicon oxide binary ceramic matrix is ​​used to solve the problem of insufficient mechanical properties and temperature resistance of a single ceramic matrix. The obtained heat shield made of ceramic composite materials containing air film holes has the advantages of high temperature resistance, high strength and toughness, good heat dissipation, etc., and can be widely used in the field of aviation engines.

Description

Technical Field

[0001] The invention relates to a method for preparing a heat insulation screen, in particular to a method for preparing a heat insulation screen made of a ceramic composite material with air-containing film holes and belonging to the technical field of high-temperature resistant ceramic composite materials. Background Art

[0002] The goal of the new generation of aircraft engines is to continuously improve the thrust-to-weight ratio. As the thrust-to-weight ratio continues to increase, the temperature before the engine turbine will inevitably increase further. The turbine inlet temperature of an engine with a thrust-to-weight ratio of 10 reaches 1527-1727°C, while the turbine inlet temperature of an engine with a thrust-to-weight ratio of 15-20 will reach 1827-2127°C, which far exceeds the melting point of the high-temperature alloy materials in the engine. The current mature engine hot end component materials can only meet the design requirements of engines with a thrust-to-weight ratio of 10. To develop a new generation of advanced equipment with higher thrust, it is necessary to carry out research on the design and preparation technology of new high-temperature resistant materials.

[0003] Alumina, silicon carbide and other ceramic matrix composite materials are the preferred materials for replacing high temperature alloys as the hot end components of engines in the future due to their high temperature resistance and excellent high temperature mechanical properties. At present, the research on alumina ceramic composite materials in China is still in its infancy, mainly focusing on the preparation process and performance testing of flat-plate samples for mechanical properties and temperature resistance of materials. The main problems are concentrated on the damage of alumina fibers caused by high temperature treatment, resulting in low high temperature mechanical properties. In addition, since the preparation process of alumina fiber reinforced ceramic composite structural parts involves very complex fiber preform weaving, fiber preform debonding, matrix sol-gel composite, ceramic heat treatment and subsequent finishing, the fiber orientation design, fiber damage control, interface control, temperature control and other processes have a great influence on the organizational structure of the material; especially in thin-walled parts, hole-forming parts and other locations, if the machining process involves local stress concentration caused by the continuous fiber being cut, the preparation process of this type of structural parts is very difficult. At present, the preparation of structural parts combined with specific application environments is still extremely rare.

[0004] The heat shield in the prior art usually has air film holes with an angle evenly distributed on the surface of the heat shield. The cold air passing through the air film holes can reduce the temperature of the hot surface and improve the temperature uniformity of the heat shield surface to reduce the thermal stress caused by the temperature difference, so as to achieve the purpose of increasing the service life of the heat shield; however, due to the large number of air film holes (hundreds to thousands), drilling holes by mechanical processing will inevitably break the continuous fibers, resulting in a decrease in the mechanical properties of the component, and forming stress concentration at the hole position, resulting in a greater risk of use, thereby affecting the performance of the engine. In order to prevent mechanical drilling from causing fiber damage and resulting in a decrease in the mechanical properties of the component, it is considered a feasible solution to first weave the fabric and then form the air film holes through metal round needles. This method aims to squeeze the continuous fibers at the air film hole position through the metal round needle to maintain the integrity of the fibers. However, in actual operation, it was found that due to the high brittleness of alumina (mullite) fibers, most of the fibers in the fiber fabric with a high volume fraction still broke due to extrusion deformation during the round needle insertion process, and the mechanical properties of the material were greatly affected.

[0005] In addition, the use of special molds to press the net size to form a special requirement for multiple rounds of sol-gel combined with high-temperature sintering composite process. Before the composite material thermal insulation screen surface and air film holes are fully formed, the more complex forming mold cannot be removed, which limits the implementation of the early high-temperature sintering process. Targeted design of the sol-gel composite process is required. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing the net size forming of a ceramic composite material heat insulation screen containing air film holes. The ceramic composite material heat insulation screen obtained by this preparation method has regular morphology, air film holes with controllable size and angle, exhibits good heat resistance, and has the advantages of high temperature resistance, high strength and good toughness, and can be widely used in the field of aviation engines.

[0007] In order to achieve the above technical purpose, the present invention provides a method for preparing a gas-containing film hole ceramic composite material heat insulation screen, the method comprising the following steps:

[0008] 1) Designing a male and female mold; the gap between the male and female molds of the male and female molds is consistent with the shape and size of the heat shield, and a plurality of groups of positioning holes are provided at corresponding positions on the surfaces of the male and female molds;

[0009] 2) After inserting a metal round needle into the positioning hole of the male mold, continuous oxide fiber is used to directly perform contour weaving on the surface of the male mold, and during the weaving process, both the warp yarn and the weft yarn bypass the metal round needle to form a fiber fabric on the surface of the male mold;

[0010] 3) After cleaning the fiber fabric on the surface of the male mold, apply alumina sol on the fiber fabric around the metal round needles and allow the alumina sol to penetrate into the fiber fabric, then bake and shape. After shaping is completed, take out all the metal round needles and close the female mold, then insert all the metal round needles through the positioning holes on the outer surface of the female mold and ensure that the metal round needles pass through the round holes of the fiber fabric and the corresponding positioning holes on the surface of the male mold;

[0011] 4) Infiltrating the alumina sol into the fiber fabric in the positive and negative molds by an infiltration method and drying and solidifying I, repeating the process several times until the fiber fabric reaches a desired density, removing the metal round needle and the positive and negative molds, and obtaining a heat shield blank;

[0012] 5) After the heat insulation screen blank is subjected to high temperature sintering I, the silicon oxide sol is infiltrated into the fiber fabric of the heat insulation screen blank by an infiltration method and dried and solidified II, and this is repeated several times until there is no obvious change in the weight gain of the heat insulation screen blank, and then high temperature sintering II is performed to obtain the heat insulation screen blank.

[0013] The heat shield of ceramic composite material containing air film holes prepared by the present invention has the advantages of high temperature resistance, high strength, toughness and good heat dissipation, and can be widely used in the field of aviation engines. The heat shield of the present invention uses continuous alumina (or mullite) fiber as the reinforcing phase, and it is difficult to form air film holes on alumina or mullite fiber fabrics. Since the number of air film holes is particularly large, punching or puncturing after the fiber fabric is formed will affect the mechanical properties of the continuous fiber fabric. The present invention uses metal round needles of designed size to occupy and form during the weaving process of the continuous fiber fabric, which completely eliminates the fiber damage caused by the hole processing in the later stage, thereby reducing the influence of stress concentration at the position of the air film holes, etc. At the same time, except for processing the excess amount around the heat shield, the thickness and hole position of the heat shield are formed by the net size, which improves the overall strength of the heat shield. The heat insulation screen of the present invention uses alumina and silica as a composite matrix. The ceramic material is too soft after alumina or mullite fiber is composited with a single alumina matrix, or the ceramic material has low high-temperature strength after being composited with a single silica matrix. The fiber fabric is first impregnated with an alumina sol matrix for multiple rounds to form the component and reach a certain density, and then impregnated with a silica matrix for multiple rounds to further improve the density and modulus of the component. The composite ceramic material formed not only solves the problem of the pure alumina ceramic composite material being too soft, but also provides good high-temperature mechanical strength.

[0014] As a preferred solution, the size specification of the positioning hole is 1mm to 3mm in diameter, and the angle is 0° to 75° with respect to the normal of the male or female mold surface. The diameter tolerance of the positioning hole is controlled at 0mm to +0.1mm. Based on the special process of forming the air film hole in the heat insulation screen by the metal round needle position forming method of the present invention, the size and angle of the positioning hole can be arbitrarily set as needed without affecting the mechanical properties of the heat insulation screen.

[0015] As a preferred solution, the oxide fiber is alumina fiber and / or mullite fiber. Alumina fiber and mullite fiber are conventionally used as high temperature resistant reinforcement phases in heat insulation shields.

[0016] As a preferred solution, the contoured weaving adopts a 2.5D structure, and the weaving thickness is consistent with the designed heat shield size thickness, and the surrounding dimensions are 5 to 10 mm larger than the designed dimensions of the heat shield. After the component is composite-formed, the surrounding dimensions are cut according to the mold edge and reach the designed dimensions, and the cutting of the heat shield edge will not affect the overall strength of the heat shield.

[0017] As a preferred solution, the volume fraction of the oxide fibers in the fiber fabric is 30% to 45%, and the volume fraction of the oxide fibers is more preferably 35% to 42%.

[0018] As a preferred solution, the cleaning process is: soaking the fiber fabric together with the positive mold in a solvent and then drying, and repeating the soaking and drying 2 to 4 times. After cleaning, the organic impregnating agent such as epoxy resin on the fiber surface can be removed by soaking and cleaning, which is beneficial to the subsequent interface bonding between the ceramic matrix and the fiber.

[0019] As a more preferred solution, the soaking time is 3 to 5 hours.

[0020] As a more preferred solution, the solvent is at least one of water, alcohol, acetone, and 1-3% dilute hydrochloric acid.

[0021] As a more preferred solution, the drying is first blow-drying at 30-50°C for 10-12 hours, and then drying at 100-120°C for 1-3 hours.

[0022] As a preferred solution, the baking and shaping conditions are: keeping warm at 100-150°C for 1-3 hours. The present invention preferably applies alumina sol on the fiber fabric around the metal round needle and allows the alumina sol to penetrate into the fiber fabric, and then bakes and shapes it, mainly to shape the round hole occupied by the metal round needle, so that after the metal round needle is pulled out, the round hole on the fiber fabric can maintain the diameter of the metal round needle, and prevent the fiber fabric from being damaged when the metal round needle is inserted again. Under the preferred baking and shaping conditions, the alumina sol is mainly dehydrated and converted into aluminum oxide to shape the fiber fabric around the metal round needle.

[0023] As a preferred solution, the solid content of the alumina sol is 20wt.% to 40wt.%, and more preferably 25wt.% to 35wt.%. When the solid content of the alumina sol is too high, the sol viscosity is large, the stability of the sol is relatively poor, and multiple impregnation processes are not conducive to the uniformity of the matrix inside the fiber; when the solid content is too low, the amount of matrix obtained in a single sol-gel process is small, and the composite efficiency is low.

[0024] As a preferred solution, the temperature of the drying and curing I is 100°C to 180°C, and the duration is 3 to 10 hours. The temperature of the drying and curing I is more preferably 120°C to 150°C, and the duration of the drying and curing I is more preferably 6 to 8 hours.

[0025] As a preferred embodiment, the number of repeated infiltration of alumina sol and drying and solidification I is 5 to 10 times, more preferably 6 to 8 times.

[0026] As a preferred solution, the temperature of the high temperature sintering I is 600-1200° C., and the duration is 20-120 minutes. The temperature of the high temperature sintering I is more preferably 800-1000° C., and the duration is more preferably 30-60 minutes.

[0027] As a preferred solution, the solid content of the silica sol is 10 wt.% to 25 wt.%, and more preferably 15 wt.% to 20 wt.%.

[0028] As a preferred solution, the temperature of the drying and curing II is 100°C to 180°C, and the duration is 3 to 10 hours. The temperature of the drying and curing II is more preferably 120°C to 150°C, and the duration of the drying and curing II is more preferably 3 to 5 hours.

[0029] As a preferred solution, the temperature of the high temperature sintering II is 600-1200° C., and the duration is 20-120 minutes. The temperature of the high temperature sintering II is more preferably 700-900° C., and the duration is more preferably 30-60 minutes.

[0030] As a preferred embodiment, the number of times of repeating the infiltration of silica sol and drying and solidification II is 2 to 6 times, more preferably 4 to 6 times.

[0031] As a preferred solution, the metal round needle is made of high-hardness stainless steel, and its diameter is determined according to the size of the air film hole.

[0032] The male and female molds of the present invention are made of stainless steel or aluminum alloy. A plurality of positioning holes corresponding to the positions of the air film holes of the heat insulation screen are provided on the convex surface of the male mold in the male and female molds, and positioning holes corresponding to the positions of the air film holes of the heat insulation screen are provided on the concave surface of the female mold, and the positioning holes on the concave surface of the female mold are set through the concave surface of the female mold. When the angle of the positioning hole is perpendicular to the surface of the male mold or the female mold, the positions of the positioning holes on the male and female molds and the air film holes of the heat insulation screen overlap, and the sizes of the positioning holes and the air film holes are the same as the diameter of the metal round needle; when the angle of the positioning hole is a certain angle with the normal of the male mold or the female mold surface, the positions of the positioning holes on the male and female molds and the air film holes of the heat insulation screen are offset to a certain extent, and the sizes of the positioning holes and the air film holes are the same as the horizontal cross-section size of the metal round needle. The diameter tolerance of the positioning hole is controlled at 0mm to +0.1mm.

[0033] The net size forming preparation method of the gas-containing film hole ceramic composite material heat insulation screen of the present invention specifically comprises the following steps:

[0034] S1. Design and process stainless steel or aluminum alloy male and female molds. The gap (or space) between the male and female molds is consistent with the shape and size of the heat shield to be prepared, and the tolerance of the gap between the male and female molds is controlled at -0.2mm to 0mm; the positioning holes corresponding to the air film holes of the heat shield are processed on the female and male molds of the mold, and the tolerance of the diameter of the positioning holes is controlled at 0mm to +0.1mm;

[0035] S2. Insert a metal round needle with the same diameter as the air film hole into the corresponding hole of the male mold, and use continuous oxide fiber to perform contour weaving according to the outer surface of the male mold. The weaving method adopts a 2.5D structure. During the weaving process, both the warp and weft yarns bypass the metal round needle (the warp continuous oxide fiber bypasses the round needle for hanging yarn, and then the weft oxide fiber is added to weave into the designed size), and a fiber fabric with the same thickness as the designed heat insulation screen is obtained (the thickness size tolerance is controlled at 0mm to 0.2mm), and the surrounding dimensions are 5 to 10mm larger than the designed dimensions of the heat insulation screen, which is convenient for subsequent processing;

[0036] S3. The woven fiber fabric together with the male mold and the metal round needle are immersed in a solvent for 3 to 5 hours, and the solvent is selected from deionized water, alcohol, acetone, and 1 to 3% dilute hydrochloric acid; after immersion, it is placed in a blast drying oven and blown dry at 30 to 50 ° C for 10 to 12 hours, and then dried at 100 to 120 ° C for 1 to 3 hours; the immersion and drying process is repeated 2 to 3 times;

[0037] S4. Brushing alumina sol on the fiber fabric at the periphery of the metal round needle until the fiber fabric at the periphery of the metal round needle is completely penetrated, placing the fiber fabric and the positive mold in an oven at 100 to 150° C. for 1 to 3 hours to initially solidify the fiber fabric at the air film hole position;

[0038] S5. Take out all the metal circular needles and close the female mold. After the mold is assembled in place, insert one end of the metal circular needle tip into the corresponding positioning hole on the female mold, and ensure that the corresponding circular hole on the circular knitted fabric is fully inserted into the positioning hole of the male mold, and the tail end of the metal circular needle is higher than the outer surface of the female mold;

[0039] S6. Install fasteners to secure the mold in place;

[0040] S7. The fiber fabric with the mold is impregnated with alumina sol by a sol-gel process, and dried and cured, and the sol-gel process is repeated 5 to 10 times;

[0041] S8. After the fiber fabric reaches a certain density through the sol-gel process (the weight gain rate of a single sol-gel process is less than 5%), the mold and the metal round needle are removed, and the excess around the heat shield is cut off;

[0042] S9. Sintering the heat shield at high temperature;

[0043] S10. Continue to use the sol-gel process to infiltrate the silica sol, dry and solidify, and repeat the sol-gel process 2 to 6 times until the weight gain rate of a single sol-gel process is less than 1%;

[0044] S11. Sinter the heat insulation screen at high temperature to obtain the product.

[0045] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0046] The preparation of the ceramic composite material heat insulation screen containing air film holes provided by the present invention adopts the net size forming technology. The thickness size of the heat insulation screen and the air film holes are directly formed without the need for subsequent mechanical processing to form holes. This solves the fiber and mechanical damage problems caused by the surface dense layer and hole processing during the forming process of the oxide ceramic composite material, and improves the overall strength of the structural parts.

[0047] The method for preparing the gas-containing film hole ceramic composite material heat insulation screen provided by the present invention reduces the multi-pass CNC machining process that may be involved in the forming process of the ceramic composite material structure, simplifies the process flow, and is conducive to large-scale production.

[0048] The preparation method of the air-containing film hole ceramic composite material heat insulation screen provided by the present invention can solve the problems of the ceramic material being too soft after alumina or mullite fiber is composited with a single alumina matrix, or the ceramic material having low high temperature strength after being composited with a single silica matrix, by using an alumina and a silica composite matrix.

[0049] The preparation method of the air-film-hole-containing ceramic composite material heat insulation screen provided by the present invention prefabricates air-film holes during the preparation process of the fiber preform, which not only can controllably prepare the hole morphology, size and angle as needed, but also will not affect the mechanical properties of the fiber fabric. The prepared air-film-hole ceramic composite material exhibits good heat resistance and has the advantages of high temperature resistance, high strength and good toughness, and can be widely used in the field of aviation engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic diagram of the structure of a heat insulation screen with air film holes with a 45° inclination angle.

[0051] Figure 2 Schematic diagram of the air film hole structure with a 45° inclination angle.

[0052] Figure 3 It is a schematic diagram of the heat insulation screen (air-containing film holes) forming mold used in the present invention.

[0053] Figure 4 This is a schematic diagram of mold explosion.

[0054] Figure 5 Schematic diagram of a unit cell using a metal round needle to prefabricate air film holes.

[0055] Figure 6 Schematic diagram of the principle of prefabricating inclined air film holes on fiber fabrics with the assistance of round needles.

[0056] Figure 7 This is a schematic diagram of sampling for tensile breaking load test.

[0057] Among them, 1 is a 45° air film hole, 2 is a press-forming positioning tool, 3 is a forming mold male mold, 4 is a forming mold female mold (containing an air film hole positioning hole), 5 is a metal round needle, 6 is a heat insulation screen with air film holes, 7 is a weft continuous fiber, 8 is a warp continuous fiber, 9 is a forming plate (a single inclined hole), and 10 is a bolt. DETAILED DESCRIPTION

[0058] The following specific examples are intended to further illustrate the present invention rather than to limit the scope of protection of the claims.

[0059] Example 1

[0060] The overall design of the air-containing film hole heat insulation screen is a curved surface structure, such as Figure 1 As shown, the product length is 450mm, the arc length is 700mm, the thickness is 3mm, and the design has There are 960 air film holes in total (the number of air film holes can be increased several times in actual use conditions); the center line of the air film hole is at an angle of 45° to the axial direction of the heat insulation screen surface. Figure 2 shown.

[0061] The preparation process specifically includes the following steps:

[0062] S1. Design and process the stainless steel male and female molds. Process the positioning holes corresponding to the heat shield air film holes on the male and female mold shaping parts of the mold. The hole diameter processing tolerance is required to be 0~+0.1mm. The mold is assembled as follows: Figure 3 As shown in the figure, the gap between the positive and negative molds of the mold is consistent with the shape and size of the heat shield to be prepared. The mold gap is designed to be 3mm, and the gap size tolerance is controlled at -0.2mm to 0mm. Figure 4 Install an explosion diagram for the mold;

[0063] S2. Insert a stainless steel round needle with the same diameter as the air film hole into the corresponding hole position of the male mold, and use continuous alumina fiber to perform 2.5D weaving according to the outer surface of the male mold, so that the warp and weft yarns pass around the metal round needle to obtain a fiber fabric with the same thickness as the designed heat insulation screen size (the thickness size tolerance is controlled at 0mm~0.2mm). After weaving, the dimensions of the four sides are cut to 5mm larger than the mold size; the fiber direction of the round needle position weaving air film hole is as follows Figure 5 As shown, the calculated fiber volume fraction after weaving is about 40% (the calculated total volume includes the hole position);

[0064] S3. The woven fiber fabric together with the male mold and the metal round needle were immersed in an alcohol solvent for 5 hours; after immersion, they were placed in a blast drying oven and dried at 40°C for 10 hours, and then dried at 100°C for 2 hours; the immersion and drying process was repeated 3 times;

[0065] S4. Brush the alumina sol on the air-containing film hole position of the fabric until the hole position is completely penetrated, and place the fabric and the mold in an oven for heat preservation to initially solidify the fabric at the air film hole position;

[0066] S5. Take out all the metal circular needles and close the female mold. After the mold is assembled in place, insert the tip of the metal circular needle into the corresponding positioning hole on the mold, and ensure that the corresponding circular hole on the circular knitted fabric is fully inserted into the positioning hole of the male mold;

[0067] S6. Install fasteners to secure the mold in place;

[0068] S7. The fiber fabric with the mold is impregnated with a 30% solid content of alumina sol by a sol-gel process, and cured and dried, and the sol-gel process is repeated 7 times; wherein the curing and drying temperature is 120°C, and the time is 8h;

[0069] S8. After the fiber fabric reaches a certain density through the sol-gel process (the weight gain rate of a single sol-gel process is less than 5%), the mold and the metal round needle are removed, and the excess around the heat shield is cut off;

[0070] S9. The heat shield components are sintered in a muffle furnace at a temperature of 900°C for 60 minutes;

[0071] S10. Continue to use the sol-gel process to infiltrate a silica sol with a solid content of 15%, and dry and solidify it, repeating the sol-gel process 6 times, wherein the curing and drying temperature is 120°C and the time is 5h; until the weight gain rate of the 6th sol-gel process is about 0.3%;

[0072] S11. The heat insulation shield components are sintered in a muffle furnace at a sintering temperature of 900° C. for 60 minutes.

[0073] Example 2

[0074] The design shape, structure, dimensions and preparation process steps S1 to S6 of the heat insulation shield are the same as those in Example 1.

[0075] The process S7 to S11 is as follows:

[0076] S7. The fiber fabric with the mold is impregnated with a sol-gel process having a solid content of 25% alumina sol, and cured and dried, and the sol-gel process is repeated 8 times; wherein the curing and drying temperature is 150°C, and the time is 6h;

[0077] S8. After the fiber fabric reaches a certain density through the sol-gel process (the weight gain rate of a single sol-gel process is less than 5%), the mold and the metal round needle are removed, and the excess around the heat shield is cut off;

[0078] S9. The heat shield components are sintered in a muffle furnace at a sintering temperature of 1000°C for 30 minutes;

[0079] S10. Continue to use the sol-gel process to infiltrate a silica sol with a solid content of 20%, and dry and solidify it, repeating the sol-gel process 5 times, wherein the curing and drying temperature is 150°C and the time is 3h; until the weight gain rate of the 5th sol-gel process is about 0.45%;

[0080] S11. The heat insulation shield components are sintered in a muffle furnace at a sintering temperature of 800° C. for 60 minutes.

[0081] Comparative performance test pieces:

[0082] In addition, four flat test pieces were prepared with the heat insulation screen in Example 1, and they are as follows:

[0083] Test piece 1 (flat performance sample, alumina & silica binary ceramic matrix, consistent with the heat shield of Example 1):

[0084] The same alumina fiber as the heat shield of Example 1 is used to weave into a 3 mm thick 2.5D structural flat fabric. The weaving parameters such as the warp and weft yarn density are consistent with those of the heat shield, and the fiber volume fraction is designed to be 40%.

[0085] Cut the fabric of about 300mm×150mm×3mm, and use the same alcohol degumming process as the heat shield in Example 1, and then use a stainless steel flat mold to shape it; after molding, it is compounded with the heat shield, and the sol-gel process and sintering process parameters are completely the same as those of the heat shield in Example 1. After the blank is prepared, it is ready for use.

[0086] Test piece 2 (flat performance sample, pure silicon oxide substrate):

[0087] A fabric of about 150 mm × 150 mm × 3 mm was cut from the same fabric as the test piece 1, and after the alcohol degumming process was the same as that of the heat shield in Example 1, a stainless steel flat mold was used for shaping; after molding, it was compounded with the heat shield, and the sol-gel process and sintering process parameters were completely the same as those of the heat shield in Example 1, except that the 30% alumina sol in step S7 was changed to 30% silica sol. After the blank preparation was completed, it was set aside.

[0088] Test piece 3 (flat performance sample, pure alumina matrix):

[0089] Cut a fabric of about 150 mm × 150 mm × 3 mm from the same fabric as the test piece 1, and use the same alcohol degumming process as the heat shield of Example 1, and then use a stainless steel flat mold to shape it; after molding, compound it with the heat shield, and the sol-gel process and sintering process parameters are completely the same as those of the heat shield of Example 1, except that the 15% silica sol in step S10 is changed to 15% alumina sol. After the blank is prepared, it is ready for use.

[0090] Test piece 4 (air film holes are reserved by inserting needles after fiber weaving):

[0091] A fabric of about 150 mm × 150 mm × 3 mm was cut from the same fabric as the test piece 1, and after the alcohol degumming process was the same as that of the heat shield in Example 1, a stainless steel flat mold was used to shape the fabric. The stainless steel flat mold was used to process positioning holes with the same spacing position size, hole diameter, and angle as the heat shield, and a high-hardness stainless steel round needle (needle head taper of about 20°) was inserted through the positioning hole to pre-occupy the air film hole position. The occupying principle is as follows: Figure 6 As shown; after molding, it is compounded with the heat insulation screen, and the sol-gel process and sintering process parameters are completely consistent with the heat insulation screen of Example 1.

[0092] A flat test piece was prepared with the heat insulation screen in Example 2 as follows:

[0093] Test piece 5 (flat performance sample, alumina & silicon oxide binary ceramic matrix, consistent with the heat shield of Example 2):

[0094] A fabric of about 150 mm × 150 mm × 3 mm was cut from the same fabric as the test piece 1, and after the alcohol degumming process was the same as that of the heat shield in Example 2, a stainless steel flat mold was used for shaping; after molding, it was compounded with the heat shield, and the sol-gel process and sintering process parameters were completely the same as those of the heat shield in Example 2. After the blank preparation was completed, it was set aside.

[0095] Comparative test of bending properties of alumina ceramic composite materials:

[0096] 50×4×3mm (length×width×thickness) test samples were cut from the test pieces 1, 2, 3, and 5 respectively, and the room temperature flexural strength and modulus of the materials were tested (the test method was in accordance with GB / T6569-2006).

[0097] 50×4×3mm (length×width×thickness) test samples were cut from the test pieces 1, 2, 3, and 5 respectively. After being kept at 1500℃ for 1 hour, the flexural strength and modulus of the materials were tested at room temperature (the test method was in accordance with GB / T6569-2006).

[0098] The test results are shown in Table 1. Test piece 1 is a binary matrix produced by the same process as the heat shield of Example 1, test piece 2 is a pure silicon oxide matrix, test piece 3 is a pure aluminum oxide matrix, and test piece 5 is a binary matrix produced by the same process as the heat shield of Example 2.

[0099] Table 1 Bending properties of composite materials obtained by examples

[0100]

[0101] Comparative test of tensile breaking load of samples with holes:

[0102] Heat insulation screen Example 1 Sample: Take samples from the heat insulation screen Example 1 component body, and take 5 samples along the airflow direction of the heat insulation screen component. The sample size is 120mm×20mm×3mm (similar to a flat plate). Each sample has the same hole position, such as Figure 7 As shown, the average tensile breaking load tested by a universal tensile testing machine is 11552N.

[0103] Heat insulation shield Example 2 Sample: Samples were taken from the heat insulation shield Example 2 component body, and 5 samples were taken along the airflow direction of the heat insulation shield component. The sample size was 120 mm × 20 mm × 3 mm (similar to a flat plate). Each sample had the same hole position, such as Figure 7 As shown, the average tensile breaking load tested by a universal tensile testing machine is 10943N.

[0104] Test piece 1 specimen (machined with holes): Samples were taken from test piece 1, the specimen size was 120mm×20mm×3mm, and holes were drilled at the same hole position, size, and angle as the heat shield. The average tensile breaking load tested by a universal tensile testing machine was 8443N.

[0105] Specimen of test piece 4 (punched with needles after weaving): 5 specimens were taken from test piece 4 at the same hole positions as the heat shield specimens. The specimen size was 120 mm × 20 mm × 3 mm. The average tensile breaking load tested by a universal tensile testing machine was 9072 N.

[0106] Table 2 Tensile fracture load of composite materials obtained by the examples

[0107]

Claims

1. A method for preparing a gas-containing film hole ceramic composite material heat insulation screen, characterized in that: The following steps are involved: 1) Designing a male and female mold; the gap between the male and female molds of the male and female molds is consistent with the shape and size of the heat shield, and a plurality of positioning holes are provided at corresponding positions on the surfaces of the male and female molds; 2) After inserting a metal round needle into the positioning hole of the male mold, continuous oxide fiber is used to directly perform contour weaving on the surface of the male mold, and during the weaving process, both the warp yarn and the weft yarn bypass the metal round needle to form a fiber fabric on the surface of the male mold; the oxide fiber is alumina fiber and / or mullite fiber; 3) After cleaning the fiber fabric on the surface of the male mold, apply alumina sol on the fiber fabric around the metal round needles and allow the alumina sol to penetrate into the fiber fabric, then bake and shape. After shaping is completed, take out all the metal round needles and close the female mold, then insert all the metal round needles from the positioning holes on the outer surface of the female mold and ensure that the metal round needles pass through the round holes of the fiber fabric and the corresponding positioning holes on the surface of the male mold; 4) Infiltrating the alumina sol into the fiber fabric in the positive and negative molds by an infiltration method and drying and solidifying I, repeating the process several times until the fiber fabric reaches the desired density, removing the metal round needle and the positive and negative molds, and obtaining a heat shield blank; 5) After the heat insulation screen blank is subjected to high temperature sintering I, the silicon oxide sol is infiltrated into the fiber fabric of the heat insulation screen blank by an infiltration method and dried and solidified II, and this is repeated several times until there is no significant change in the weight gain of the heat insulation screen blank, and then high temperature sintering II is performed to obtain the heat insulation screen blank.

2. The method for preparing a gas-containing film-pored ceramic composite material heat insulation screen according to claim 1, characterized in that: The size specification of the positioning hole is 1mm~3mm in diameter, and the angle is 0°~75° to the normal of the male mold or female mold surface.

3. The method for preparing a gas-containing film-pored ceramic composite material heat insulation screen according to claim 1, characterized in that: The contoured weaving adopts a 2.5D structure, and the weaving thickness is consistent with the designed thickness of the heat insulation screen, and the surrounding dimensions are 5-10 mm larger than the designed dimensions of the heat insulation screen.

4. The method for preparing a gas-containing film-pored ceramic composite material heat insulation screen according to claim 1, characterized in that: The cleaning process is as follows: soaking the fiber fabric together with the positive mold in a solvent and then drying, and repeating the soaking and drying 2 to 4 times; The soaking time is 3 to 5 hours; The solvent is at least one of water, alcohol, acetone, and 1-3% dilute hydrochloric acid; The drying step is first drying at 30-50° C. for 10-12 hours, and then drying at 100-120° C. for 1-3 hours.

5. The method for preparing a gas-containing film-pored ceramic composite material heat insulation screen according to claim 1, characterized in that: The baking and shaping conditions are: keeping warm at 100-150° C. for 1-3 hours.

6. The method for preparing a gas-containing film-pored ceramic composite material heat insulation screen according to claim 1, characterized in that: The solid content of the alumina sol is 20wt.%~40wt.%.

7. The method for preparing a gas-containing film-pored ceramic composite material heat insulation screen according to claim 1 or 6, characterized in that: The drying and curing process I is performed at a temperature of 100°C to 180°C for a period of 3 to 10 hours; The temperature of the high temperature sintering I is 600-1200° C., and the duration is 20-120 min.

8. The method for preparing a gas-containing film-pored ceramic composite material heat insulation shield according to claim 1, characterized in that: The solid content of the silica sol is 10wt.%~25 wt.%.

9. The method for preparing a gas-containing film-pored ceramic composite material heat insulation screen according to claim 1 or 8, characterized in that: The drying and curing II is performed at a temperature of 100°C to 180°C for 3 to 10 hours; The temperature of the high temperature sintering II is 600-1200° C., and the duration is 20-120 min.

Images