A toughening method for ceramic matrix composites

Abstract

The present application relates to the technical field of silicate ceramic composite material preparation, in particular to a toughening preparation method of ceramic matrix composite material, the present application adopts a preform template hot-pressing sintering method to in-situ sinter a mineralized fusion micro-interface laminated staggered microstructure toughening mechanism, realizes the ingenious construction of a shell-like micro-unit structure and the controllable preparation of a high-toughness silicate-based ceramic composite material, develops a new high-toughness ceramic matrix composite material preparation method, and provides a new strategy and method for solving the technical problem of high brittleness and low toughness of ceramic matrix materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicate ceramic composite material preparation, in particular to a toughening preparation method of ceramic matrix composite material. BACKGROUND

[0002] The ceramic matrix composite material mainly based on silicate has unique excellent performances of force, electricity, light, heat and magnetism, etc., and has great application prospect in the high-tech fields of aerospace, military industry, automobile, etc., and is one of the most widely used and largest used ceramic materials in modern engineering materials. However, the inherent defects of the material seriously affect the performance and service life, especially the inherent high brittleness and low toughness, which often leads to disastrous fracture defects in most safety-critical applications, and is a key problem seriously restricting its wide application.

[0003] The current toughening methods are mainly divided into two kinds. One is internal toughening, which acts on the crack tip of nanometer to submicron scale, and inhibits the generation and expansion of ceramic material cracks, including the sliding of toughening phase and the expansion of microcracks. External toughening occurs behind the crack tip in micro and macro scale to hinder the expansion of cracks, such as carbon fiber, graphene sheet bridging, crack deflection and twisting, etc. Related researches also show that the reinforcing phase such as graphene in ceramic matrix composite material can provide excellent toughness, inhibit crack expansion and improve mechanical properties. However, the above methods are difficult to realize the ordered regulation of microstructure of ceramic matrix composite material in a wide range, and cannot fundamentally change the development and expansion mechanism of cracks. Therefore, it is a key scientific problem to constantly invent and optimize new toughening methods to solve the problems of structural disorder and high brittleness and low toughness of the current ceramic matrix composite material. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a toughening preparation method of ceramic matrix composite material, which solves the problems raised in the background art.

[0005] To achieve the above object, the present application provides the following technical scheme:

[0006] A preparation method of high-strength and high-toughness ceramic matrix composite material, characterized in that it comprises the following steps:

[0007] Step 1: Preparation of raw materials

[0008] (1) The main component of the ceramic matrix composite material is silicate mixed powder, the premixed powder is prepared into ultrafine powder raw material with a particle size of 10 nm to 20 um, and polyvinyl alcohol, ethanol and other non-reactive liquid additives are added;

[0009] (2) The content of the graphene oxide GO solution prepared based on Hummer's method is 5-15 mg / ml;

[0010] Step two: preparation of three-dimensional graphene porous framework template and preparation of slurry

[0011] (1) Porous framework template: the GO solution prepared in step one (2) is used for chemical synthesis assembly in a low-pressure polytetrafluoroethylene reaction kettle under certain temperature hydrothermal conditions, and a light and porous three-dimensional graphene aerogel (3D-GA) loose framework template is obtained after low-temperature freezing and vacuum drying;

[0012] (2) Micro-nano ceramic-based slurry: the superfine premixed powder prepared in step one (1) is mixed with liquid additives in a certain proportion, and the slurry is ball-milled and stirred by a high-speed planetary stirrer at a speed of 500-1000 r / min to obtain a micro-nano ceramic-based slurry with good rheological properties;

[0013] Step three: preparation of silicate ceramic-based composite material matrix

[0014] The micro-nano ceramic-based slurry prepared in step two (2) is infiltrated into the 3D-GA porous framework template prepared in step two (1) by self-elongation and self-expansion at normal temperature and pressure; the ceramic-based solid particles are attached to the internal microstructure of the three-dimensional graphene layers in situ; if necessary, this process can be placed in a vacuum device to slowly increase the negative pressure to make the micro-nano ceramic-based slurry infiltrate into the 3D-GA porous framework template again, until no bubbles overflow from the 3D-GA porous framework template at 0.15-0.25 atm, and the pressure is restored to normal pressure; finally, the sample is naturally dried or low-temperature freeze-dried to obtain a silicate ceramic-based composite material matrix with silicate ceramic powder uniformly distributed in the three-dimensional graphene porous structure;

[0015] Step four: hot-pressing sintering preparation

[0016] The silicate ceramic-based composite material matrix prepared in step three is placed in a hot-pressing sintering furnace, and a hot-pressing sintering mold shape (such as a cuboid) is designed according to the needs; this process applies vertical pressure to the top surface of the mold, slowly compresses and deforms the silicate ceramic-based composite material matrix, and the three-dimensional graphene and silicate ceramic powder gradually compresses to a shell-like laminated structure under a certain pressure, and the stacking density of the matrix also gradually increases; accompanied by physical and chemical synthesis and changes at a certain temperature, a silicate ceramic body and a graphene laminated ordered interlaced micro-unit structure are formed. Finally, the temperature is lowered and taken out, and the hot-pressing sintering preparation process is completed.

[0017] Further, in step two (1), the hydrothermal temperature is 100-180°C, and the freezing temperature is -20 to -60°C.

[0018] Further, in step two (1), the density of the three-dimensional graphene is 5-20 mg / cm 3 .

[0019] Further, in step two (2), the weight ratio of the micro-nano ceramic-based slurry is 25-50wt% of mixed powder raw materials and 50-75wt% of ethanol.

[0020] Further, in step four, the stress applied to the silicate ceramic matrix composite substrate is 0-60MPa, and the maximum strain loading is more than 90% of the silicate ceramic matrix composite substrate; after the strain or force loading reaches the maximum value, the hot-pressing sintering is maintained for 10-120min; then slowly unloaded to the pressure-free state; the sintering temperature is 500-1900℃, the heating rate is 5-20℃ / min, and the highest temperature holding time is 10-180min.

[0021] Compared with the prior art, the beneficial effects of the present application are:

[0022] The present application adopts the preform template hot-pressing sintering method to in-situ sinter the mineralized fusion micro-interface laminated staggered microstructure toughening mechanism, realizes the ingenious construction of the shell-like micro-unit structure and the controllable preparation of the high-strength and high-toughness silicate-based ceramic composite material, and develops a new type of high-strength and high-toughness ceramic matrix composite material preparation method, which provides a new strategy and method for solving the technical problems of high brittleness and low toughness of ceramic matrix materials.

[0023] The three-dimensional graphene aerogel carbon template involved in the present application has good chemical and physical stability, and the porous and ordered internal structure provides a good three-dimensional skeleton attachment network for the ceramic matrix powder precursor; the compression performance of stable large deformation at high and low temperatures provides a new idea and scheme for the preparation of the shell-like laminated structure of the ceramic matrix composite material, the order of the microstructure and the performance regulation of the high strength and toughness; the preparation method is simple and controllable, and is expected to be applied to the enhancement and toughening performance regulation of other ceramic matrix composites or metal alloys and other brittle engineering materials, and has important guiding significance and application prospect for realizing the wide range of multi-component, microstructure order regulation, high strength and toughness method innovation and expansion, structure-material-function preparation and application of ceramic matrix composites. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a structure diagram of the hot-pressing sintering mold of the present application;

[0025] Figure 2 is a three-dimensional graphene and internal porous morphology diagram in the present application;

[0026] Figure 3 is a morphology diagram of silicate ceramic powder and mineralization in the present application;

[0027] Figure 4is a silicate ceramic composite material prepared in the present application and an internal morphology diagram;

[0028] Figure 5 is a three-point bending performance diagram of the composite material of the present application. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] Embodiment 1

[0031] A preparation method of a high-toughness ceramic matrix composite material, comprising the following steps:

[0032] Step one: raw material preparation

[0033] (1) The main component of the ceramic matrix composite material is silicate mixed powder, and the premixed powder is prepared into ultra-fine powder raw material with a particle size of 10 nm to 20 μm, and is supplemented with liquid phase additives such as polyvinyl alcohol and ethanol which do not react;

[0034] (2) The content of graphene oxide GO solution prepared based on Hummer's method is 5-15 mg / ml;

[0035] Step two: preparation of three-dimensional graphene porous skeleton template and preparation of slurry

[0036] (1) Porous skeleton template: the GO solution prepared in step one (2) is chemically synthesized and assembled in a low-pressure polytetrafluoroethylene reaction kettle under certain temperature hydrothermal conditions, and after low-temperature freezing and vacuum drying, a light and porous three-dimensional graphene aerogel (3D-GA) loose skeleton template is obtained;

[0037] (2) Micro-nano ceramic-based slurry: the ultra-fine premixed powder raw material prepared in step one (1) is mixed with liquid phase additives in proportion, and the slurry is ball-milled and stirred by a high-speed planetary stirrer at a speed of 500-1000 r / min, to obtain a micro-nano ceramic-based slurry with good rheological property;

[0038] Step three: preparation of silicate ceramic matrix composite material matrix

[0039] In the normal temperature and pressure, the micro-nano ceramic base slurry prepared in step two (2) is infiltrated into the 3D-GA porous framework template prepared in step two (1) by self-elongation and self-expansion, so that the ceramic base solid particles are attached to the internal microstructure of the three-dimensional graphene sheet in situ; according to the need, the process can be placed in a vacuum pumping device to slowly increase the negative pressure to make the micro-nano ceramic base slurry infiltrate into the 3D-GA porous framework template again, until the 3D-GA porous framework template is free of bubble overflow at 0.15-0.25 atm, and returns to the normal pressure state; finally, the sample is naturally dried or low-temperature freeze-dried to obtain a silicate ceramic powder uniformly distributed in the three-dimensional graphene porous structure, thereby obtaining a silicate ceramic base composite material;

[0040] Step four: hot-pressing sintering preparation

[0041] The silicate ceramic base composite material prepared in step three is placed in a hot-pressing sintering furnace, and a hot-pressing sintering mold shape (such as a cuboid) is designed according to the need; in this process, a vertical pressure is applied to the top surface of the mold to slowly compress and deform the silicate ceramic base composite material, and the three-dimensional graphene and the silicate ceramic powder will be gradually compressed to a shell-like laminated structure under a certain pressure, and the stacking density of the base will also gradually increase; accompanied by physical and chemical synthesis and changes at a certain temperature, a micro-unit structure of the silicate ceramic body and the graphene sheet is formed. Finally, the temperature is lowered and taken out, and the hot-pressing sintering preparation process is completed.

[0042] Further, in step two (1), the hydrothermal temperature is 100-180℃, and the freezing temperature is -20- -60℃.

[0043] Further, in step two (1), the density of the three-dimensional graphene is 5-20 mg / cm 3 .

[0044] Further, in step two (2), the weight ratio of the micro-nano ceramic base slurry is 25-50 wt% of the mixed powder raw material and 50-75 wt% of ethanol.

[0045] Further, in step four, the stress generated by the vertical pressure on the silicate ceramic base composite material is 0-60 MPa, and the strain loading can be up to more than 90% of the silicate ceramic base composite material; when the strain or force loading reaches the maximum value, the hot-pressing sintering is maintained for 10-120 min; then slowly unloaded to the pressure-free state; the sintering temperature is 500-1900℃, the heating rate is 5-20℃ / min, and the highest temperature is maintained for 10-180 min.

[0046] Example 2

[0047] AsFigure 1 As shown, the macroscopic morphology of the hot-press sintered silicate ceramic matrix composite material can be designed according to the size of the mold, and the graphite composite material used in the present application is high-temperature-resistant and in the shape of a cube or a cylinder. During the hot-press sintering process, the pressure rod serves as a vertical force transmission device, and the samples are separated by a gasket. The sleeve can provide equivalent pseudo-triaxial compression to ensure the boundary forming efficiency of the sample. The entire sintering mold is detachable, facilitating the removal of the sample. Figure 2 The macroscopic size and micro-porous morphology of the three-dimensional graphene carbon template with a density of 10 mg / cm 3 The macroscopic size and micro-porous morphology of the three-dimensional graphene carbon template with a density of 10 mg / cm Figure 3 The micro- and macro-morphology of the pure silicate ceramic powder hot-press sintered and the crack propagation generated during the fracture process are shown in

[0048] The preparation process of the three-dimensional graphene / silicate-based ceramic composite material (3DG / SCC) is as follows: first, the silicate ceramic premixed powder is prepared into a powder raw material with ultra-fine particle size, and a liquid phase rheological modifier such as ethanol with small surface tension and no reaction with the powder is added. After high-speed shearing by a planetary stirrer, a silicate ceramic slurry with good fluidity is prepared; simultaneously, a graphene oxide GO solution prepared by modification based on the Hummer's method is subjected to hydrothermal treatment and freeze-drying to obtain a three-dimensional graphene aerogel (3D-GA) carbon template with light weight, porosity, and large specific surface area. Then, the adapted micro-nano ceramic-based slurry is infiltrated into the 3D-GA porous skeleton template through vacuum self-elongation and self-expansion, and the excess ethanol and other additives are removed by further natural drying or low-temperature freeze-drying and other physical treatment methods to obtain a silicate ceramic-based composite material substrate with good adhesion of ceramic-based solid particles and three-dimensional graphene layers. Finally, the silicate ceramic-based composite material substrate is reacted under specific temperature and pressure by hot-press sintering to form a three-dimensional graphene / silicate ceramic-based composite material with a two-phase laminated ordered interlaced imitation shell micro-unit structure of silicate ceramic material and graphene carbon material.

[0049] Figure 4The macroscopic crack propagation and microstructure morphology of silicate ceramic matrix composites prepared under different pressures (10 MPa, 50 MPa) in the hot-pressing sintering process are shown. With the increase of the hot-pressing sintering pressure, the macroscopic surface of the silicate ceramic matrix composite is smoother than that of the pure silicate ceramic, the microstructure is more dense, and the ordered arrangement of the silicate mineral bridge is more obvious; the macroscopic crack propagation shows that when the 3DG / SCC breaks, the crack passes through the silicate mineral bridge and the three-dimensional graphene carbon base layer, and obvious dislocation slip and multiple complex deflection occur in the 3DG / SCC, which shows that the existence of the three-dimensional graphene sheet layer inhibits the crack generation and propagation of the 3DG / SCC, so that the crack propagation needs more paths and consumes more energy, thereby improving the mechanical properties of the 3DG / SCC.

[0050] In the present application, the mechanical property test: the size of all samples is polished, polished and the like, and is uniformly cut into a plate structure of 20x10x2.5mm, a three-point bending test method is adopted, a span length of 16mm is set, an equal speed displacement control mode is adopted, and a loading rate is 0.1mm / min.

[0051] As shown in Figure 5 The strain-bending strength curve shows that with the increase of the pressure in the hot-pressing sintering process, the prepared 3DG / SCC has higher bending strength and higher strain. When the pressure is 50MPa, the 3DG / SCC shows a bending strength of 38.9MPa, which is increased by 135.7% compared with the pure silicate ceramic material (16.5MPa), the strain is increased from 5.1% to 7.9%, and the fracture toughness is increased by more than 5 times Figure 5 The right graph). And from the stress drop section in the strain-bending strength curve, it can be seen that the bending strength of the 3DG / SCC does not suddenly drop to zero, which shows that the 3DG / SCC is divided into multiple stages of fracture, which is of great significance for inhibiting the sudden failure of the silicate ceramic structure. The main reason why the 3DG / SCC has high strength and high toughness is that the silicate ceramic particles are pressed in the porous ordered network of three-dimensional graphene to form a more ordered microstructure, and the graphene sheet layer not only has an intrinsic toughening effect of inhibiting crack generation and propagation, but also has an external toughening effect of promoting crack deflection and distortion by bridging the graphene sheet.

[0052] This scheme mainly relies on the doping and mixing of materials, belongs to the two-dimensional graphene sheet mixing process, and has limited effect on the reinforcement and toughening of the material.

[0053] Compared with the silicate composite prepared by two-dimensional graphene mixing, the present scheme has a better carbon-based functional phase network structure, solves the problem of uniform dispersion and agglomeration of graphene in the silicate powder slurry, and can realize the application of ultra-low doping amount, uniform dispersion, dense structure and stable structure of the carbon-based reinforcing phase in the field of ceramic reinforcement, intelligence and functionalization.

[0054] Compared with the silicate-based ceramic composite prepared by graphene sheet blending, the silicate-based ceramic composite prepared by the hot-pressing sintering template method of the application forms a significant shell-like layered structure, has higher bending strength and fracture toughness than the same component, and the three-dimensional graphene porous ordered network structure plays a key role in reinforcing and toughening

[0055] The embodiments of the application are described above with reference to the drawings, but the application is not limited to the specific embodiments described above, and the specific embodiments described above are only illustrative but not restrictive, and those skilled in the art can make many forms under the inspiration of the application without departing from the purpose of the application and the scope protected by the claims.

Claims

1. A method of producing a high toughness ceramic matrix composite material, characterized by, The method comprises the following steps: Step 1: raw material preparation (1) The main component of the ceramic matrix composite is silicate mixed powder, and the silicate mixed powder is prepared into ultra-fine premixed powder raw material with a particle size of 10 nm to 20 μm, and is supplemented with polyvinyl alcohol, ethanol and other non-reactive liquid additives; (2) The content of the graphene oxide GO solution prepared based on the Hummer's method modification is 5-15 mg / ml; Step 2: preparation of three-dimensional graphene porous skeleton template and preparation of slurry (1) Porous skeleton template: the GO solution prepared in step 1 (2) is chemically synthesized and assembled under the condition of a certain temperature hydrothermal in a low-pressure polytetrafluoroethylene reaction kettle, and then light and porous three-dimensional graphene aerogel 3D-GA loose skeleton template is obtained after low-temperature freezing and vacuum drying; (2) Micro-nano ceramic matrix slurry: the ultra-fine premixed powder raw material prepared in step 1 (1) is mixed with liquid additives in a certain proportion, and the slurry is ball-milled and stirred by a high-speed planetary mixer at a speed of 500-1000 r / min to obtain a micro-nano ceramic matrix slurry with good rheological properties; the weight ratio of the micro-nano ceramic matrix slurry is 25-50 wt% of the mixed powder raw material and 50-75 wt% of ethanol; Step 3: preparation of silicate ceramic matrix composite matrix The micro-nano ceramic matrix slurry prepared in step 2 (2) is infiltrated into the 3D-GA porous skeleton template prepared in step 2 (1) by self-elongation and self-expansion under normal temperature and pressure; the ceramic matrix solid particles are attached to the internal microstructure of the three-dimensional graphene sheet layer in situ; according to the need, the process is placed in a vacuum pumping device to slowly increase the negative pressure to make the micro-nano ceramic matrix slurry infiltrate into the 3D-GA porous skeleton template again, until the 3D-GA porous skeleton template is free of bubble overflow under 0.15-0.25 atm, and then returns to normal pressure state; finally, the sample is naturally dried or low-temperature freeze-dried to obtain a silicate ceramic matrix composite matrix in which silicate ceramic powder is uniformly distributed in the three-dimensional graphene porous structure; Step 4: hot-pressing sintering preparation The silicate ceramic matrix composite matrix prepared in step 3 is placed in a hot-pressing sintering furnace, and a hot-pressing sintering mold shape is designed according to the need; during the process, a vertical pressure is applied to the top surface of the mold, and the silicate ceramic matrix composite matrix is slowly compressed and deformed, wherein the three-dimensional graphene with silicate ceramic powder is gradually compressed to a shell-like laminated structure under pressure, and the stacking density of the matrix is also gradually increased; the stress generated on the silicate ceramic matrix composite matrix by the vertical pressure is 10-60 MPa, and the strain loading is up to more than 90% of the silicate ceramic matrix composite matrix; when the strain or force loading reaches the maximum value, the hot-pressing sintering is maintained for 10-120 min; then it is slowly unloaded to the pressure-free state; a micro-unit structure in which the silicate ceramic body and the graphene sheet layer are stacked and ordered and interlaced is formed; finally, the temperature is lowered and the sample is taken out, and the hot-pressing sintering preparation process is completed.

2. The method of claim 1, wherein the ceramic matrix composite material has a high toughness. In step 2 (1), the hydrothermal temperature is 100-180℃, and the freezing temperature is -20- -60℃.

3. The method of claim 1, wherein the ceramic matrix composite material has a high toughness. In (1) of Step two, the density of the three-dimensional graphene is 5-20 mg / cm 3 .

4. The method of claim 1, wherein the ceramic matrix composite material has a high toughness. In step four, the sintering temperature is 500-1900℃, the temperature rising rate is 5-20℃ / min, and the holding time at the highest temperature is 10-180min.

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