A preparation method of a biomimetic layered C / SiC composite ceramic lubricating material in situ formed by a template method

Abstract

The application provides a preparation method of a biomimetic layered C / SiC composite ceramic lubricating material formed in situ by a template method. h The method sprays Si / Al2O3 / SiO2 and -BN / Al2O3 / SiO2 ceramic suspensions on a given filter paper, uses the filter paper as a template and a carbon source, generates amorphous carbon, SiC and mullite phases in situ through hot-pressing sintering, and prepares the C / SiC ceramic lubricating material with a layered structure. The powder layer with different micron-level layer thicknesses is obtained by adjusting the component ratio and the feeding amount of the suspension. The block material after the laminated sintering has a friction coefficient as low as 0.15-0.38 in the temperature range from room temperature to 1000 DEG C, has a wide temperature range lubricating performance, and is suitable for high-temperature sealing parts in the fields of aviation and spaceflight.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-temperature solid lubricating material, and particularly relates to a preparation method of a biomimetic layered C / SiC composite ceramic lubricating material formed in situ by a template method. BACKGROUND

[0002] In the field of aerospace, lubrication failure is the main cause of friction and wear of key moving parts of aerospace, which further leads to part failure. High-temperature solid lubricating material is an effective way to reduce such friction and wear, and developing high-temperature solid lubricating material with high-temperature resistance, corrosion resistance and wear resistance for seals in the field of aerospace, which has strong adaptability and can be reused, is of great significance to improve the reliability and life of the sealing system of aerospace.

[0003] Ceramic materials have great potential in the field of structural and functional materials due to their high hardness, high strength, high temperature resistance, corrosion resistance and other excellent properties. Among them, SiC ceramic material has high hardness, low density, excellent high-temperature mechanical properties and chemical stability, and has been widely used in hot end parts of aero-engine such as seals. However, single-phase SiC ceramic is usually brittle with high friction coefficient, and its tribological properties need to be further improved to meet the lubrication requirements of harsh working conditions.

[0004] The shell pearl layer is a composite material with a layered structure formed by a certain special layered structure, which has excellent mechanical properties. In recent years, people imitate the structure of shell pearl layer in nature to build biomimetic layered structure ceramic composite material, which overcomes the brittleness problem of ceramic material and can greatly improve the toughness and reliability of the material. SiC ceramic material has high hardness, low density, high temperature resistance and other excellent properties, and is widely used in aero-engine seals. The transfer layer generated by amorphous carbon during friction can effectively enhance the friction reduction and wear resistance, h -BN has a layered structure and is usually used as a high-temperature solid lubricant. Layered structure ceramic material has a structure with strong / weak layers arranged alternately, which can greatly avoid the brittle failure of the material as a structural component and improve the lubrication performance of the material. In the application, filter paper is used as a template and a carbon source, Si, h -BN, Al2O3 and SiO2 ceramic powder is sintered to prepare a layered structure composite ceramic. Amorphous carbon, SiC and mullite phases are generated in situ during sintering. SiC is the main phase, Al2O3 and mullite are strong layers, and amorphous carbon generated in situ by sacrificing the template acts as a weak layer and a high-temperature solid lubricant, and h -BN is introduced as a high-temperature solid lubricant, so as to achieve good tribological performance in a wide temperature range. This lays a solid foundation for preparing composite ceramic lubricating material with micron-level layer thickness structure and high-temperature lubrication. SUMMARY

[0005] The application aims to overcome the deficiencies of the prior art, and provide a preparation method of a biomimetic layered C / SiC composite ceramic lubricating material formed in situ by a template method, which has simple process, low cost, can accurately control layer thickness and endow the material with excellent lubricating performance in a wide temperature range. The method uses cheap and readily available filter paper as a template and carbon source, imitates the layered structure of natural pearl shells, alternately sprays suspensions containing different functional ceramic powders, stacks, dry-presses, removes glue and high-temperature sintering to generate C / SiC composite ceramic lubricating material with strong / weak alternating layered structure in situ. The material has excellent tribological performance in a wide temperature range, and is particularly suitable for high-temperature sealing components in extreme environments such as aerospace.

[0006] I. Preparation of biomimetic layered C / SiC composite ceramic lubricating material formed in situ by a template method:

[0007] The preparation method of the biomimetic layered C / SiC composite ceramic lubricating material formed in situ by a template method comprises the following steps:

[0008] (1) Preparing a ceramic suspension: uniformly dispersing Si, Al2O3 and SiO2 ceramic powders in anhydrous ethanol to prepare suspension I; the mass fraction of Si in suspension I is 2-8%, the mass fraction of Al2O3 is 1-5%, and the mass fraction of SiO2 is 1-3%;

[0009] The h BN, Al2O3 and SiO2 ceramic powders are uniformly dispersed in anhydrous ethanol to prepare suspension II; the mass fraction of BN in suspension II is 2-8%, the mass fraction of Al2O3 is 1-5%, and the mass fraction of SiO2 is 1-3%; h The

[0010] The h The purity of BN is greater than 98.5%, the particle size is 7 μm; the purity of Al2O3 is 99.99%, the particle size is 150 nm; the purity of SiO2 is greater than or equal to 99.8%, the particle size is 7-40 nm; and the purity of Si is 99.99%, the particle size is 500 nm.

[0011] (2) Template spraying and cutting: uniformly spraying suspension I to the front and back sides of the filter paper through a spray gun to form a first ceramic layer, and then spraying suspension II on the first ceramic layer after drying, and cutting to a fixed size after complete drying; the speed of the spray gun is 30-40 mL / min; and the drying temperature is 50-60 ℃;

[0012] The filter paper as a precursor template mainly contains cellulose, and the size after cutting is selected from 50 mm×50 mm, 30 mm×30 mm or 25 mm×25 mm.

[0013] (3) Lamination sintering: the cut filter paper was stacked and placed in a graphite mold, and a green body was prepared by dry pressing at 10-20 MPa (pressure maintaining for 300-600 s);

[0014] The green body was transferred to a hot pressing furnace, and was sequentially subjected to degassing at 500-750℃ (3-5 h), sintering at 1700-1900℃ (35-50 MPa, pressure maintaining for 90-120 min), to in-situ generate a C / SiC composite ceramic lubricating material with a layered structure.

[0015] II. Microstructure characterization of the in-situ formed biomimetic layered C / SiC composite ceramic lubricating material by the template method:

[0016] The present application uses filter paper as a template and a carbon source, imitates the structure of natural pearl shells, and in-situ forms a biomimetic layered C / SiC composite ceramic lubricating material by spraying different ceramic powders on the filter paper to "transform paper into ceramic". The XRD, Raman and SEM characterization results are as follows:

[0017] Figure 1 The XRD pattern of the in-situ formed biomimetic layered C / SiC composite ceramic lubricating material prepared by the present application. The XRD pattern shows that the prepared layered C / SiC composite ceramic lubricating material contains h -BN, Al2O3 and SiO2 three original phases, and new phases of SiC and mullite are detected, and the generation of new phases indicates that Si and carbonized filter paper, Al2O3 and SiO2 have chemical reactions in the sintering process.

[0018] Figure 2 The Raman spectrum of the biomimetic layered C / SiC composite ceramic lubricating material prepared by the present application, which shows a strong D peak and almost no G peak, indicating that the carbon in the material exists in an amorphous form.

[0019] Figure 3 The SEM image of the biomimetic layered C / SiC composite ceramic lubricating material prepared by the present application. It can be observed that the material has a clear layered structure, and the layer thickness is about 25 μm, achieving precise control of the thickness of the layered ceramic layer.

[0020] III. Tribological performance evaluation of the in-situ formed biomimetic layered C / SiC composite ceramic lubricating material by the template method:

[0021] Test method: The sintered sample is processed into a 25 mm x 6.5 mm x 3.5 mm block. Before testing, the sample is polished to a roughness Ra of less than 0.3 μm, and then ultrasonically cleaned with ethanol. The GF-I type high temperature reciprocating friction and wear tester is used to study the tribological properties of the block material at RT~1000 ℃ in an atmospheric environment. The friction experiment uses φ 6 mm x 20 mm alumina bolt as the counter electrode, 56 N (contact pressure is about 2 MPa), 5 Hz and 2 mm as the load, frequency and reciprocating stroke, respectively, and the sliding speed is 0.02 m / s. During the high temperature friction test, the friction coefficient is recorded in real time by the data acquisition software.

[0022] Figure 4 The friction coefficient of the biomimetic layered C / SiC composite ceramic lubricating material formed by the template method at RT~1000 ℃ changes with the reciprocating cycle number curve (a) and the wear rate column chart (b). At 1000 ℃, the friction coefficient of the material gradually stabilizes at about 0.34 after the running-in period, which is lower than the friction coefficient at 900 ℃, and has good lubricating performance at high temperature. It is proved that the in-situ formed biomimetic layered C / SiC ceramic lubricating material prepared by the present application has good tribological properties.

[0023] The present application uses filter paper as a template and a carbon source, imitates the structure of natural pearl shells, and prepares a biomimetic layered structure ceramic lubricating material with a micron-level fine structure by spraying different ceramic powder on the filter paper to "transform paper into ceramic". At the same time, the block material prepared by this method has good tribological properties at high temperature, and can be applied to the manufacture of sealing parts in the field of aerospace.

[0024] The present application has the following beneficial effects:

[0025] 1. Process innovation and simplicity: The present application uses inexpensive and readily available qualitative filter paper as a template and a carbon source, and constructs a ceramic coating on the surface of the filter paper through a simple spraying process, and "transforms paper into ceramic" through lamination sintering, realizing the in-situ formation of biomimetic layered C / SiC composite ceramic lubricating material. The whole process is simple and easy to operate, and does not require complex and expensive equipment, which is conducive to reducing production costs and realizing large-scale production.

[0026] 2. Precise controllability of biomimetic layered structure: Using qualitative filter paper as a template and a substrate, combined with the control of spraying rate and suspension concentration, the thickness of the single ceramic layer (20~30 μm) can be precisely controlled. The lamination process can flexibly control the total thickness and the number of layers of the material, thereby realizing the dual control of macro size and micro structure, and solving the problem of preparing micron-level fine layered ceramic by traditional methods.

[0027] 3. Heterogeneous synergy and performance optimization: The present application generates a heterogeneous composite system in-situ during sintering by ingenious raw material design and process control, which is mainly composed of SiC, supplemented by mullite reinforcing phase, and dual lubricating phase of amorphous carbon and h-BN. SiC and mullite constitute the strong phase layer to provide structural strength, and amorphous carbon and h-BN act as the weak phase / lubricating phase layer, which synergistically work together to effectively reduce the friction coefficient through mechanisms such as forming transfer film and interlayer sliding. This "strong-weak-strong-weak" alternating biomimetic layered structure design takes into account the structural load-bearing capacity and lubrication function requirements of the material, and realizes the optimization of comprehensive performance.

[0028] 4. Excellent wide-temperature-range tribological performance: The prepared biomimetic layered C / SiC composite ceramic lubricating material exhibits a low friction coefficient (0.15~0.38) in a wide temperature range from room temperature to 1000℃, especially at high temperatures (such as 1000℃), it can still maintain stable lubrication performance. This is due to the stable lubrication of h-BN at high temperatures, the continuous formation of amorphous carbon transfer film, and the gradual wear mechanism of layered structure during friction, which makes it have great application potential in high-temperature extreme environments such as aerospace.

[0029] In summary, the preparation method of the present application has the advantages of simple process, low cost and good controllability. The prepared biomimetic layered C / SiC composite ceramic lubricating material has unique microstructure and excellent wide-temperature-range tribological performance, which opens up a new way for the design and preparation of high-performance high-temperature lubricating ceramic materials, and has important scientific value and broad application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 XRD pattern of the biomimetic layered C / SiC composite ceramic lubricating material prepared by the present application.

[0031] Figure 2 Raman spectrum of the biomimetic layered C / SiC composite ceramic lubricating material prepared by the present application.

[0032] Figure 3 SEM image of the biomimetic layered C / SiC composite ceramic lubricating material prepared by the present application.

[0033] Figure 4 Friction coefficient curve (a) and wear rate column chart (b) of the biomimetic layered C / SiC composite ceramic lubricating material prepared by the present application in the temperature range from room temperature (RT) to 1000℃. DETAILED DESCRIPTION

[0034] The present application will be further explained and described below in conjunction with specific examples.

[0035] Example 1

[0036] (1) Si, Al2O3, SiO2 ceramic powder, anhydrous ethanol were prepared into suspension I by magnetic stirring and ultrasonic dispersion, the mass fraction of ceramic powder Si, Al2O3, SiO2 was 5%, 3%, 2% respectively; suspension II was prepared by magnetic stirring and ultrasonic dispersion of BN, Al2O3, SiO2 ceramic powder, anhydrous ethanol h , the mass fraction of ceramic powder h BN, Al2O3, SiO2 was 5%, 3%, 2% respectively.

[0037] (2) The ceramic suspension I was uniformly sprayed onto the front and back of the filter paper by a precision flow control spray gun (spray gun rate was 36 ml / min) to form the first layer of ceramic layer, and after drying at 55 ℃, the ceramic suspension II was sprayed on the first layer of ceramic layer in the same way, and after complete drying, it was cut into a fixed size of 50 mm x 50 mm.

[0038] (3) The cut filter paper was placed in a graphite mold and dry pressed at a pressure of 15 MPa for 500 s to form a green body; the green body was transferred to a hot pressing furnace for degassing and sintering to prepare a biomimetic layered C / SiC ceramic lubricating material, the degassing temperature and time were 700 ℃ and 4 h respectively, the sintering temperature was 1800 ℃, the sintering pressure was 50 MPa, and the holding time was 120 min. The XRD pattern (Fig. 1) shows that the prepared layered C / SiC composite ceramic lubricating material contains Figure 1 h BN, Al2O3, SiO2 three original phases, and new phases SiC and mullite phase are detected, the generation of new phase indicates that Si and carbonized filter paper, Al2O3 and SiO2 have chemical reaction in the sintering process. Raman spectrum (Fig. 2) shows that there is a strong D peak and almost no G peak, indicating that the material has amorphous carbon. SEM image (Fig. 3) shows that the material has obvious layered structure, and the layer thickness is about 25 μm, realizing the preparation of fine layer. Figure 2 Figure 3

[0039] (4) The tribological properties of the prepared layered C / SiC composite ceramic lubricating material: at 1000 ℃, the average friction coefficient of the material was 0.35 (Fig. 4), the wear rate was 4.83 x 10 -5 mm 3 / Nm (Fig. 5), which was improved compared with the tribological properties at 900 ℃, and had good lubricating properties at high temperature. Figure 4 Figure 4

[0040] Example 2 ​​​​​

[0041] (1) Si, Al2O3, SiO2 ceramic powder, anhydrous ethanol were prepared into suspension I by magnetic stirring, and the mass fraction of ceramic powder Si, Al2O3, SiO2 was 5%, 3.2%, 1.8% respectively; and h -BN, Al2O3, SiO2 ceramic powder, anhydrous ethanol were prepared into suspension II by magnetic stirring, and the mass fraction of ceramic powder h -BN, Al2O3, SiO2 was 5%, 3.2%, 1.8% respectively.

[0042] (2) The ceramic suspension I was uniformly sprayed onto the front and back sides of the filter paper by a precision flow control spray gun (spray gun rate was 33 ml / min) to form a first layer of ceramic layer, and after drying at 50 ℃, the ceramic suspension II was sprayed on the first layer of ceramic layer in the same way, and after complete drying, it was cut into a fixed size of 25 mm x 25 mm.

[0043] (3) The cut filter paper was placed in a graphite mold and dry-pressed at a pressure of 20 MPa for 600 s to form a green body; the green body was transferred to a hot pressing furnace for degassing and sintering to prepare a biomimetic layered C / SiC ceramic lubricating material, the degassing temperature and time were 750 ℃ and 4 h respectively, the sintering temperature was 1800 ℃, the sintering pressure was 45 MPa, and the holding time was 120 min. The XRD pattern showed that the prepared layered C / SiC composite ceramic lubricating material contained h -BN, Al2O3, SiO2 three original phases, and new phases SiC and mullite phase were detected, the generation of new phases indicated that Si and carbonized filter paper, Al2O3 and SiO2 had chemical reactions during sintering. The Raman spectrum showed a strong D peak and almost no G peak, indicating that the material had amorphous carbon. The SEM image showed that the material had a clear layered structure, and the layer thickness was about 20 μm, realizing the preparation of fine layers.

[0044] (4) The tribological properties of the prepared layered C / SiC composite ceramic lubricating material: at 1000 ℃, the average friction coefficient of the material was 0.36, and the wear rate was 4.98 x 10 -5 mm 3 / Nm, which had good lubricating properties at high temperature.

[0045] Example 3

[0046] (1) Si, Al2O3, SiO2 ceramic powder, anhydrous ethanol were prepared into suspension I by mechanical stirring, and the mass fraction of ceramic powder Si, Al2O3, SiO2 was 6%, 2.5%, 1.5% respectively; and h-BN, Al2O3, SiO2 ceramic powder, anhydrous ethanol were prepared into suspension II by mechanical stirring, and ceramic powder h The mass fraction of BN, Al2O3 and SiO2 was 6%, 2.5% and 1.5% respectively.

[0047] (2) The ceramic suspension I was uniformly sprayed onto both sides of the filter paper through a precision flow control spray gun (spray gun rate was 35 ml / min) to form a first layer of ceramic layer, and after drying at 60 ℃, the ceramic suspension II was sprayed on the first layer of ceramic layer in the same way, and after complete drying, it was cut into a fixed size of 30 mm×30 mm.

[0048] (3) The cut filter paper was placed in a graphite mold and dry pressed at a pressure of 16 MPa for 540 s to form a green body; the green body was transferred to a hot pressing furnace for degassing and sintering to prepare a biomimetic layered C / SiC ceramic lubricating material, the degassing temperature and time were 650 ℃ and 4.5 h respectively, the sintering temperature was 1800 ℃, the sintering pressure was 50 MPa, and the holding time was 100 min. The XRD pattern showed that the prepared layered C / SiC composite ceramic lubricating material contained h -BN, Al2O3, SiO2 three original phases, and new phases SiC and mullite phase were detected, the generation of new phase indicated that Si and carbonized filter paper, Al2O3 and SiO2 occurred chemical reaction in the sintering process. The Raman spectrum showed obvious strong D peak and weak G peak, indicating that the material had amorphous carbon. The SEM image showed that the material had obvious layered structure, and the layer thickness was about 30 μm, realizing the preparation of fine layer.

[0049] (4) The tribological properties of the prepared layered C / SiC composite ceramic lubricating material: at 1000 ℃, the average friction coefficient of the material was 0.38, and the wear rate was 4.57×10 -5 mm 3 / Nm, which had good lubricating performance at high temperature.

[0050] In the above examples, the raw materials used h -BN purity > 98.5%, particle size ~ 7 μm, Al2O3 purity 99.99%, particle size ~ 150 nm, SiO2 purity ≥ 99.8%, particle size 7-40 nm, Si purity 99.99%, particle size ~ 500 nm.

Claims

1. A method for preparing a biomimetic layered C / SiC composite ceramic lubricating material in situ by a template method, characterized in that, The method comprises the following steps: (1) preparing a ceramic suspension: uniformly dispersing Si, Al2O3 and SiO2 ceramic powder in anhydrous ethanol to obtain suspension I; the mass fraction of Si in suspension I is 2-8%, the mass fraction of Al2O3 is 1-5%, and the mass fraction of SiO2 is 1-3%; The h The ceramic powders of BN, Al2O3 and SiO2 are uniformly dispersed in anhydrous ethanol to obtain a suspension II; the mass fraction of BN in the suspension II is 2-8%, the mass fraction of Al2O3 is 1-5%, and the mass fraction of SiO2 is 1-3%. h The ceramic powders of BN, Al2O3 and SiO2 are uniformly dispersed in anhydrous ethanol to obtain a suspension II; the mass fraction of BN in the suspension II is 2-8%, the mass fraction of Al2O3 is 1-5%, and the mass fraction of SiO2 is 1-3%. (2) template spraying and cutting: uniformly spraying suspension I to the front and back sides of filter paper through a spray gun to form a first ceramic layer, and then spraying suspension II on the first ceramic layer through the spray gun after drying, and cutting into a fixed size after complete drying; the speed of the spray gun is 30-40 mL / min; (3) laminated sintering: placing the cut filter paper in a graphite mold in sequence to form a green body by dry pressing; transferring the green body to a hot pressing furnace for degassing and sintering to generate a C / SiC composite ceramic lubricating material with a layered structure in situ; The material has a clear layered structure with a layer thickness of 20-30 μm and contains in situ generated SiC phases, mullite phases and amorphous carbon, while h - BN, Al2O3 and SiO2 primary phases; The degassing process parameters are: temperature 500-750 DEG C, time 3-5 h; the sintering process parameters are: temperature 1700-1900 DEG C, pressure 35-50 MPa, and holding time 90-120 min.

2. The production method according to claim 1, characterized by, In step (1), the ceramic powder h - BN purity > 98.5%, particle size ~ 7 μm; Al2O3 purity 99.99%, particle size ~ 150 nm; SiO2 purity ≥ 99.8%, particle size 7-40 nm; Si purity 99.99%, particle size ~ 500 nm.

3. The preparation method according to claim 1, characterized in that, In step (1), the preparation method of the suspensions I and II comprises at least one of magnetic stirring, mechanical stirring and ultrasonic dispersion.

4. The method of claim 1, wherein, In step (2), the filter paper as a precursor template mainly comprises cellulose; the size of the cut filter paper is 50 mm x 50 mm, 30 mm x 30 mm or 25 mm x 25 mm.

5. The preparation method according to claim 1, characterized in that, In step (3), the dry pressing pressure is 10-20 MPa, and the pressure holding time is 300-600 s.

6. The biomimetic layered C / SiC composite ceramic lubricating material prepared by the method according to any one of claims 1-5, characterized in that, In the temperature range of room temperature to 1000 DEG C, the friction coefficient is 0.15-0.

38.

7. The bionic layered C / SiC composite ceramic lubricating material of claim 6 is used for high-temperature sealing components in the field of aerospace.

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