Dense ti2alc ceramic and sintering method thereof

Abstract

The application provides a dense Ti2AlC ceramic and a sintering method thereof, and the method is SPS discharge plasma sintering by using pure phase Ti2AlC powder. The application takes pure phase Ti2AlC powder as a sintering raw material, considers that the SPS sintering process parameters have a great influence on the phase, grain size and physical and mechanical properties of the prepared Ti2AlC block material, and the excellent dense Ti2AlC ceramic is prepared by selecting the sintering process parameters. Especially when the pure phase Ti2AlC powder is sintered at a sintering temperature of 1300 DEG C, a sintering pressure of 40 MPa and a holding time of 10 min, the density of the material sintered by the process is 96.8%, the bending strength is 661 MPa, and the fracture toughness is 8.32 MPa.m1 / 2. Compared with the mechanical properties of the Ti2AlC prepared by hot-pressing sintering, the bending strength is increased by about 72%, and the fracture toughness is increased by about 5.85%.

Description

Technical Field

[0001] This invention belongs to the field of ceramic material preparation technology, and more specifically, relates to a dense Ti2AlC ceramic and its sintering method. Background Technology

[0002] Ternary layered ceramics (M n+1 AX n The M-phase (or MAX-phase) is a layered hexagonal structure of carbides or nitrides of pre-transition metals. "M" represents a pre-transition metal element, "A" represents a main group element (mostly Group IIIA and IVA elements), and "X" represents C or N. In the crystal structure of this type of material, near-close-packed M layers are alternated with pure A element layers, and X atoms fill the octahedral positions between the M layers. This structure consists of transition metal carbonitrides M-phases. n+1 X n The MAX phase compounds are composed of alternating stacked nanosheets and group A atomic layers. Due to their unique structural characteristics, these compounds exhibit excellent overall performance, possessing not only the superior thermal, electrical, and mechanical properties of their respective binary metal carbides or nitrides, but also, in some aspects, superior performance. In transition metal carbonitrides (M... n+1 X n In the octahedral structure, the MX bonds are mainly covalent or ionic, thus giving the material the characteristics of traditional ceramics such as low density, high melting point, high elastic modulus, and high yield strength. The octahedral layers are separated by A-atom layers, and the MA bonds exhibit very obvious metallic bonding characteristics, giving the material the electrical and thermal conductivity, good microscopic plasticity, ease of machining, and high damage tolerance of metallic materials. The weak metallic bonds between the layered structures provide the MAX phase compound with self-lubricating properties superior to graphite. Therefore, the MAX phase compound can be used as a bonding material between metals and ceramics, a high-temperature precision structural material, an electrode material, or an anti-corrosion coating, and is thus called a novel type of functional structural ceramic.

[0003] Among the many MAX phase materials discovered in research, Ti2AlC is a typical 211-phase ternary layered MAX phase ceramic and is currently one of the research hotspots in the field of MAX phase materials. Because Ti2AlC materials possess characteristics similar to ceramic materials such as high melting point, low density, high temperature resistance, oxidation resistance, and corrosion resistance, and also have metal-like conductivity and machinability, as well as a unique high-temperature self-healing ability, Ti2AlC materials are expected to find applications in high-tech fields such as aerospace structural materials, armor protection materials, conductive high-speed friction and impact-resistant materials, and marine engineering materials.

[0004] Currently, Ti2AlC bulk materials are mainly prepared by sintering from elemental or compound raw material powders. Different raw material powders require different preparation process conditions, resulting in variations in density and mechanical properties of the Ti2AlC bulk materials obtained through different methods. Furthermore, the preparation process parameters affect the phase purity and grain size, significantly impacting various properties of Ti2AlC and limiting its application in high-end components. Hot pressing sintering is currently the most commonly used method, but research on the impact of SPS sintering on the sintering performance of pure-phase Ti2AlC powder is limited. Therefore, further research is needed on the influence of sintering processes on the sintering performance of pure-phase Ti2AlC powder to provide a reference for determining the sintering process for large-scale MAX phase sintering. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a dense Ti2AlC ceramic and its sintering method, under which a high-performance dense Ti2AlC ceramic is obtained.

[0006] To achieve the above objectives, this invention proposes a sintering method for dense Ti2AlC ceramics, wherein the method involves SPS discharge plasma sintering using pure phase Ti2AlC powder.

[0007] According to one embodiment of the present invention, the sintering temperature of the SPS discharge plasma sintering is 1100℃~1400℃, the pressure is 25~50MPa, and the holding time is 2~15min.

[0008] According to one embodiment of the present invention, the SPS discharge plasma sintering process is as follows: the heating rate before 800°C is 90-110°C / min, the heating rate between 800-1000°C is 45-55°C / min, the heating rate from 1000°C to the sintering temperature of 1100-1400°C is 220-280°C / min, then the temperature is held for 2-15 minutes, followed by cooling, and the pressure during the sintering process is 25-50 MPa.

[0009] According to one embodiment of the present invention, the SPS discharge plasma sintering process is as follows: the heating rate before 800°C is 100-105°C / min, the heating rate between 800-1000°C is 48-52°C / min, and after 1000°C, the temperature is increased at a rate of 240-260°C / min to the sintering temperature of 1300-1400°C, then held for 8-12 minutes, followed by cooling. The pressure during the sintering process is 40-50 MPa.

[0010] According to one embodiment of the present invention, the sintering temperature is 1300℃, the sintering pressure is 40MPa, and the holding time is 10min.

[0011] According to one embodiment of the present invention, a sample preparation step is further included before the SPS discharge plasma sintering:

[0012] 1) Line the inside of the graphite mold with graphite paper to prevent the sample from sticking to the mold at high temperatures;

[0013] 2) Load the weighed Ti2AlC powder into the mold, press the head, blow off the surface powder, and cover it with graphite insulation felt for later use.

[0014] 3) Place the prepared mold into the SPS sintering chamber, set the sintering parameters, and start the sintering process.

[0015] According to one embodiment of the present invention, the pure phase Ti2AlC powder has a particle size of -325 mesh and a particle size D50 of 5-15 μm.

[0016] According to one embodiment of the present invention, after the SPS discharge plasma sintering, the temperature is cooled by water cooling. After cooling, the resulting dense Ti2AlC ceramic is taken out from the mold, the graphite paper adhering to the surface is ground off, and the ceramic is cut into standard samples using wire cutting technology. The surface cutting marks are then removed and the samples are kept for later use.

[0017] According to another aspect of the present invention, a dense Ti2AlC ceramic is also provided, which is obtained by the sintering method of the dense Ti2AlC ceramic described above.

[0018] According to one embodiment of the present invention, the dense Ti2AlC ceramic has a density of 86.5%–96.8%, a flexural strength of 547–661 MPa, and a fracture toughness of 7.55–8.32 MPa·m. 1 / 2 .

[0019] The beneficial effects of this invention are:

[0020] 1) This invention uses pure-phase Ti2AlC powder as the sintering raw material. Considering the significant impact of SPS sintering process parameters on the phase composition, grain size, and physical and mechanical properties of the prepared Ti2AlC bulk material, high-performance dense Ti2AlC ceramics were prepared by selecting appropriate sintering process parameters. Specifically, when pure-phase Ti2AlC powder was sintered at a temperature of 1300℃, a sintering pressure of 40MPa, and a holding time of 10min, the resulting material exhibited a density of 96.8%, a flexural strength of 661MPa, and a fracture toughness of 8.32MPa·m. 1 / 2 Compared with the mechanical properties of Ti2AlC prepared by hot pressing and sintering, the flexural strength is increased by about 72% and the fracture toughness is increased by about 5.85%.

[0021] 2) Sintering temperature is the most important process parameter in sintering. Sintering temperature and sintering pressure have a coupled effect on the material properties. At low temperatures, pressure has a greater impact on the sample properties, and the material density, flexural strength, and fracture toughness all increase with increasing pressure. However, when the sintering temperature is higher, the powder can expel pores through the shrinkage and growth of its own grains, so the pressure has a smaller impact on the material properties. Attached Figure Description

[0022] Figure 1 The diagram shows the bending strength and fracture toughness of the dense Ti2AlC ceramics prepared in Examples 1-1 to 1-12 after being held at different temperatures and pressures for 10 minutes.

[0023] Figure 2 This is a schematic diagram showing the bending strength and fracture toughness of the dense Ti2AlC ceramics prepared in Examples 1-1, 1-13 to 1-17 after being held at 1300℃ for different pressures for different times.

[0024] Figure 3 The images show the backscattered electron morphology of the dense Ti2AlC ceramics prepared in Examples 1-1 to 1-12.

[0025] Figure 4 The images show the fracture morphology of the dense Ti2AlC ceramic materials prepared in Examples 1-1 to 1-12.

[0026] Figure 5 The X-ray diffraction pattern of the dense Ti2AlC ceramic (sample T13-40-10) prepared in Example 1-1 is shown.

[0027] Figure 6 Comparison of X-ray diffraction patterns of dense Ti2AlC ceramics (samples T13-40-10 and T14-40-10) prepared in Examples 1-1 and 1-2. Detailed Implementation

[0028] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention. Unless otherwise stated, the raw materials and reagents used in the following embodiments are commercially available products or can be prepared by known methods.

[0029] Example 1-1

[0030] This invention uses Ti2AlC powder provided by Forsmann Technology (Beijing) Co., Ltd. as the raw material for sintering. The powder has a particle size of -325 mesh and a particle size distribution of D10 = 2.874 μm, D50 = 9.533 μm, and D90 = 33.96 μm.

[0031] The SPS equipment used in this experiment is a third-generation SPS discharge plasma sintering furnace manufactured by Shanghai Chenhua Technology Co., Ltd.

[0032] The inner diameter of the graphite mold used in the experiment outer diameter The height is 50mm, and the specific preparation process is as follows:

[0033] (1) Weigh 47.35g of Ti2AlC powder;

[0034] (2) Line the inside of the graphite mold with graphite paper to prevent the sample from sticking to the mold at high temperature;

[0035] (3) Load the weighed Ti2AlC powder into the mold, press the head, blow off the surface powder, and cover it with graphite insulation felt for later use.

[0036] (4) Place the prepared mold into the SPS sintering chamber. The heating rate is 100℃ / min before 800℃, 50℃ / min between 800-1000℃, and 250℃ / min after 1000℃. The cooling method is water cooling. Set the sintering temperature to 1300℃, the sintering pressure to 40MPa, and the holding time to 10min.

[0037] (5) Remove the sample from the mold, grind off the graphite paper adhering to the surface, cut it into a standard sample using wire cutting process, and grind off the surface cutting marks for later use.

[0038] The density of the sample was determined using the Archimedes displacement method, and the specific steps are as follows:

[0039] (1) Grind all the surfaces of the test samples until they are smooth and free of cutting marks. Place them in anhydrous ethanol and ultrasonically clean for 5-10 minutes. Take them out and put them in an oven to dry at 70°C for 30 minutes. Weigh them on a hydrometer balance. After the balance reading stabilizes, record it as m1.

[0040] (2) Take out the sample and immerse it in deionized water for 30 minutes. After taking it out, transfer it to the tray of deionized water in the hydrometer. After it stabilizes, record the mass m2 of the sample when it is completely submerged in deionized water.

[0041] (3) Remove the sample from the deionized water, quickly wipe the deionized water off the sample surface, and weigh its mass m3.

[0042] The density and compactness of the material were measured using Archimedes' method and the immersion medium method, and the calculation formulas are as follows:

[0043]

[0044]

[0045] In the above formula: ρ is the material density, with units of g / cm³. 3 m1, m2, and m3 represent the mass of the sample in air after drying, the mass of the sample submerged in the medium after immersion, and the mass in air after wiping the liquid off the sample surface, respectively; ρ0 is the density of deionized water, approximately 0.997 g / cm³. 3 ; a represents the density of the material.

[0046] According to the national standards GB / T 4711-1999 "Test Method for Bending Strength of Ceramic Materials" and GB / T 6569-2006 "Test Method for Bending Strength of Fine Ceramics", the bending strength of composite materials was measured using the three-point bending method. The test was conducted on a WDW-100 electronic universal testing machine. The three-point bending sample was a cuboid with dimensions of 3mm × 4mm × 30mm, where the sample length s was 30mm, width b was 3mm, thickness h was 4mm, span L was 24mm, and the loading condition was 0.5mm / min. The average value of 5 samples was taken for each test. The formula for calculating the bending strength of the material is shown below:

[0047]

[0048] In the formula, σ represents the bending strength of the material, with units of MPa; F m The maximum load on the sample is in N; L, b, and h are the span, sample width, and sample thickness, respectively, in mm.

[0049] The fracture toughness of the composite material was tested using the single-sided notched beam method (SENB) according to standard ASTM E399-2012e3. The test was conducted on a WDW-100 electronic universal testing machine. The material was cut into specimens with dimensions of 6mm × 3mm × 30mm, and a notch of appropriate depth was cut in the middle of the specimen using a diamond wire cutter with a diameter of approximately 0.2mm. The test was then performed on the electronic universal testing machine. The span L was 24mm, the specimen width b was 6mm, the thickness h was 3mm, the pre-made notch c had a depth of 1.2mm and a width of 0.2mm, and the loading condition was 0.05mm / min. The average value of 5 specimens was taken for each test. The fracture toughness K of the material was determined. ⅠC The calculation formula is as follows:

[0050]

[0051] In the formula K ⅠC The fracture toughness of the material is expressed in MPa·m. 1 / 2 Y is the stress intensity factor; F m The maximum load on the sample is in N; L, b, and h are the span, sample width, and sample thickness, respectively, in mm; c is the slit depth, in mm.

[0052] The obtained sample had a density of 96.8%, a flexural strength of 661 MPa, and a fracture toughness of 8.32 MPa·m. 1 / 2 .

[0053] Examples 1-2

[0054] Ti2AlC powder provided by Forsmann Technology (Beijing) Co., Ltd. was selected as the raw material for sintering. The powder particle size was -325 mesh, and the particle size distribution was D10 = 2.874 μm, D50 = 9.533 μm, and D90 = 33.96 μm.

[0055] The SPS equipment used in this experiment is a third-generation SPS discharge plasma sintering furnace manufactured by Shanghai Chenhua Technology Co., Ltd.

[0056] The inner diameter of the graphite mold used in the experiment outer diameter The height is 50mm, and the specific preparation process is as follows:

[0057] (1) Weigh 48.05g of Ti2AlC powder;

[0058] (2) Line the inside of the graphite mold with graphite paper to prevent the sample from sticking to the mold at high temperature;

[0059] (3) Load the weighed Ti2AlC powder into the mold, press the head, blow off the surface powder, and cover it with graphite insulation felt for later use.

[0060] (4) Place the prepared mold into the SPS sintering chamber. The heating rate is 100℃ / min before 800℃, 50℃ / min between 800-1000℃, and 250℃ / min after 1000℃. The cooling method is water cooling. Set the sintering temperature to 1400℃, the sintering pressure to 40MPa, and the holding time to 10min.

[0061] (5) Remove the sample from the mold, grind off the graphite paper adhering to the surface, cut it into a standard sample using wire cutting process, and grind off the surface cutting marks for later use.

[0062] The obtained sample had a density of 86.5%, a flexural strength of 547 MPa, and a fracture toughness of 7.55 MPa·m. 1 / 2 .

[0063] Examples 1-3 to 1-12

[0064] The preparation method is the same as in Example 1-1, except for the sintering temperature and sintering pressure, as shown in Table 1.

[0065] Table 1

[0066] Example 1-1 1300 40 10 Examples 1-2 1400 40 10 Examples 1-3 1200 40 10 Examples 1-4 1100 40 10 Examples 1-5 1300 25 10 Examples 1-6 1100 25 10 Examples 1-7 1200 25 10 Examples 1-8 1400 25 10 Examples 1-9 1300 50 10 Examples 1-10 1100 50 10 Examples 1-11 1200 50 10 Examples 1-12 1400 50 10

[0067] The mechanical properties of the dense Ti2AlC ceramics prepared in Examples 1-1 to 1-12 after holding at different temperatures and pressures for 10 min are as follows: Figure 1 As shown in Figures a and b, it can be seen that the dense Ti2AlC ceramic obtained under the sintering conditions in Example 1-1 exhibits the best flexural strength and fracture toughness.

[0068] Figure 3 These are backscattered electron morphology images of the dense Ti2AlC ceramics prepared in Examples 1-1 to 1-12. Figure 3 As can be seen, at a constant sintering temperature, the internal porosity of the material decreases with increasing pressure, exhibiting a densification trend. Simultaneously, it can be observed that at lower sintering temperatures, higher pressure results in fewer internal pores. This is because before 1300℃, the material relies on pressure to forcibly compress and bond the powder, thus decreasing the internal porosity with increasing pressure. Furthermore, it can be found that higher pressure is not always better. Pores can be observed in Figure i because excessive pressure leads to overlap of the heat-affected zone, increased local temperature, faster mass exchange, increased matrix decomposition, and grain fusion and growth.

[0069] Figure 4 The images show the fracture morphology of the dense Ti2AlC ceramics prepared in Examples 1-1 to 1-12. Figure 4 As can be seen, the fracture morphology of Examples 1-1 to 1-12 contains a large number of uneven grain undulations, and almost all of the fracture surfaces contain layered features. This indicates that the crack path is tortuous during the crack propagation process, and therefore more energy is required for crack propagation, resulting in higher bending strength and fracture toughness of the material.

[0070] Figure 5The XRD pattern of the dense Ti2AlC ceramic (sample T13-40-10) prepared in Example 1-1 shows that the peak positions of the XRD diffraction in Example 1-1 are largely consistent with those in the standard Ti2AlC spectrum, but the peak intensities differ somewhat. Strong peaks appear at 39.5° (006 crystal plane) and 71.5° (109 crystal plane), while the peak intensities at the main peak at 39.2° (103 crystal plane) and 60.4° (110 crystal plane) decrease, indicating that the grains inside the material exhibit preferred orientation during growth.

[0071] Figure 6 The XRD patterns of the dense Ti2AlC ceramics (samples T13-40-10 and T14-40-10) prepared in Examples 1-1 and 1-2 are compared. It can be seen that the XRD patterns of Examples 1-2 fit well with the standard Ti2AlC pattern, but there is a Ti3AlC2 main peak at the 39° peak position that is significantly different from the Ti2AlC peak. In addition, the TiC peak at the 34° peak position disappears and the peak intensity at the 59° peak position decreases significantly, indicating that the sintering temperature has a significant impact on the phase composition of the material.

[0072] Examples 1-13 to 1-17

[0073] The preparation method is the same as in Example 1-1, except for the sintering pressure and holding time, as shown in Table 2.

[0074] Table 2

[0075] Example 1-1 1300 40 10 Examples 1-13 1300 40 2 Examples 1-14 1300 40 5 Examples 1-15 1300 50 10 Examples 1-16 1300 50 2 Examples 1-17 1300 50 5

[0076] The flexural strength and fracture toughness of the dense Ti2AlC ceramics prepared in Examples 1-13 to 1-17 after holding at 1300℃ under different pressures for different times are as follows: Figure 2 As shown in a and 2b, it can be seen that the sample prepared in Example 1-1 has the best performance.

[0077] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A sintering method for dense Ti2AlC ceramics, characterized in that, The method involves SPS (spark plasma sintering) using pure-phase Ti2AlC powder; the pure-phase Ti2AlC powder has a particle size of -325 mesh and a particle size distribution of D10 = 2.874 µm, D50 = 9.533 µm, and D90 = 33.96 µm. The SPS discharge plasma sintering process is as follows: the heating rate is 90~110℃ / min before 800℃, the heating rate is 45~55℃ / min between 800-1000℃, the heating rate is 220-280℃ / min after 1000℃ to the sintering temperature of 1100-1400℃, then the temperature is held for 2~15min, followed by cooling. The pressure during the sintering process is 25~50MPa.

2. The sintering method according to claim 1, characterized in that, The sintering temperature of the SPS discharge plasma sintering is 1100℃~1400℃, the pressure is 25~50Mpa, and the holding time is 2~15min.

3. The sintering method according to claim 1, characterized in that, The SPS discharge plasma sintering process is as follows: the heating rate is 100~105℃ / min before 800℃, the heating rate is 48~52℃ / min between 800-1000℃, and after 1000℃, the temperature is increased to the sintering temperature of 1300-1400℃ at a rate of 240~260℃ / min, then held for 8~12min, followed by cooling. The pressure during the sintering process is 40-50MPa.

4. The sintering method according to claim 3, characterized in that, The sintering temperature is 1300℃, the sintering pressure is 40MPa, and the holding time is 10min.

5. The sintering method according to claim 1, characterized in that, The process prior to SPS discharge plasma sintering also includes a sample preparation step: 1) Line the inside of the graphite mold with graphite paper to prevent the sample from sticking to the mold at high temperatures; 2) Load the weighed Ti2AlC powder into the mold, press the head, blow off the surface powder, and cover it with graphite insulation felt for later use. 3) Place the prepared mold into the SPS sintering chamber, set the sintering parameters, and start the sintering process.

6. The sintering method according to claim 1, characterized in that, After the SPS discharge plasma sintering, the temperature is cooled by water cooling. After cooling, the resulting dense Ti2AlC ceramic is taken out of the mold, the graphite paper adhering to the surface is ground off, and it is cut into standard samples using wire cutting technology. The surface cutting marks are then polished off for later use.

7. A dense Ti2AlC ceramic, characterized in that, It is obtained by sintering the dense Ti2AlC ceramic according to any one of claims 1 to 6.

8. The dense Ti2AlC ceramic according to claim 7, characterized in that, The density is 86.5%–96.8%, the flexural strength is 547–661 MPa, and the fracture toughness is 7.55–8.32 MPa·m. 1 / 2 .

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