Composite whisker multi-scale toughened Al2O3 composite ceramic with micron SiC wrapped by nano TiC particle layer
By using nano-TiC particle layer to wrap micro-SiC composite whiskers as toughening phase in Al2O3 ceramics, the problem of low fracture toughness of Al2O3 ceramics is solved, and the multi-dimensional toughening effect and toughness improvement are achieved.
Patent Information
- Application Number
- CN202510213491.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-26
- Publication Date
- 2025-05-13
AI Technical Summary
The fracture toughness of existing Al2O3 ceramic materials is low and difficult to widely use in certain high-demand fields. The effect of single-phase whisker toughening methods has reached its limit and are difficult to further improve.
Complex whiskers wrapped in micro SiC with nano TiC particle layer are used as toughening phase, prepared by molten salt method and combined with Al2O3 matrix, and multi-dimensional toughening effect is generated using multi-scale structure and component differences.
The fracture toughness of Al2O3 composite ceramics is significantly improved, breaking the bottleneck of single whisker toughening, and avoiding the reduction of matrix mechanical properties caused by whisker agglomeration.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of ceramic materials, and in particular to an Al2O3 composite material with a nano-TiC particle layer wrapped with a micron SiC composite whisker for multi-scale toughening. 2 O 3 Composite ceramics and preparation methods thereof. Background Art
[0002] Al 2 O 3 It has a high melting point (2054°C), low density (3.97g / cm 3 ), high hardness, excellent chemical stability, high elastic modulus (380GPa) and good wear resistance, etc., which make it have very broad application prospects in the fields of crucibles, wear-resistant coatings, precision machining tools, impact-resistant armor, aerospace engine parts, etc. However, its low self-diffusion coefficient and strong covalent bond make Al 2 O 3 The fracture toughness of ceramics is extremely low, which seriously limits their wide application in corresponding fields. 2 O 3 The problem of low toughness of ceramics is usually solved by mixing C, B 4 C, TiC, SiC, TiB 2 、Al 2 O 3 Materials such as Al 2 O 3 In the ceramic matrix. Among them, the whisker toughening method is usually to add single-phase whiskers to the matrix material, and toughen it by whisker bridging, pull-out, crack deflection and other methods. However, whiskers of various physical phases have been used. Since these single-phase whiskers have the same toughening structure and a single toughening mechanism, their effects are similar. The toughening effect of single-phase whiskers has reached its limit and it is difficult to improve it. In addition, single-phase whiskers are easy to agglomerate. During the addition process, agglomerates will form in the ceramic matrix, resulting in reduced mechanical properties of the ceramic matrix. Summary of the invention
[0003] The technical problem to be solved by the present invention is to provide a multi-scale toughened Al composite whisker with a nano-TiC particle layer wrapped around a micron SiC layer in order to solve the above-mentioned shortcomings of the prior art. 2 O 3 Composite ceramic and preparation method thereof, by SiC whiskers, TiC nanoparticles, Al 2 O 3 The multiple differences in phase composition, material size and thermal expansion coefficient between the matrix will produce multi-dimensional toughening effects during the toughening process, ultimately achieving Al 2 O 3Further improvement of the toughness of composite ceramics.
[0004] The technical solution adopted by the present invention to solve the above-mentioned problems is:
[0005] A multi-scale toughened Al composite whisker with a nano-TiC particle layer wrapped around a micron SiC 2 O 3 Composite ceramics, with Al 2 O 3 As the matrix phase, the composite whiskers of micron SiC wrapped by nano-TiC particle layer are used as the toughening phase. By mass percentage, Al 2 O 3 80-97%, and the composite whisker of micron SiC wrapped by nano-TiC particle layer is 3-20%.
[0006] The Al2O3 composite whisker multi-scale toughened by nano-TiC particle layer wrapped micron SiC 2 O 3 The preparation method of the composite ceramic comprises the following steps: firstly using SiC whiskers and nano-Ti powder as raw materials, using a molten salt method to prepare a nano-TiC particle layer wrapped with a micron SiC composite whisker, and then the nano-TiC particle layer wrapped with the micron SiC composite whisker and Al 2 O 3 The matrix powder is mixed by magnetic stirring, dried, sieved, and sintered by rapid sintering technology to obtain multi-scale toughened Al 2 O 3 Composite ceramics.
[0007] Furthermore, the Al2O3 composite whisker multi-scale toughened with nano-TiC particle layer wrapped micron SiC 2 O 3 The preparation method of the composite ceramic specifically comprises the following steps:
[0008] (1) Removal of impurities from the original SiC whisker: The original SiC whisker is placed in a polytetrafluoroethylene beaker, stirred and pickled with an acid solution, then centrifuged and washed with water until neutral, and then placed in a vacuum drying oven for drying to obtain the SiC whisker after impurities removal;
[0009] (2) Preparation of mixed powder: using the SiC whiskers and nano-Ti powder obtained in step (1) as raw materials, NaCl and KCl as molten salt medium, and anhydrous ethanol as liquid medium, magnetic stirring and mixing are performed on a magnetic stirrer, the solution is evaporated by rotary evaporation, and vacuum drying is performed to obtain mixed powder A;
[0010] (3) Preparation of composite whiskers of micron-SiC coated with nano-TiC particle layer: the mixed powder A obtained in step (2) is placed in a semicircular corundum crucible with a cover, and heated and kept in a high-temperature tube furnace in a flowing argon atmosphere to achieve sintering, and after cooling, a composite whisker powder of micron-SiC coated with nano-TiC particle layer containing impurities is obtained;
[0011] (4) Purification of the composite whiskers of micron-SiC wrapped by nano-TiC particle layer: The composite whisker powder obtained in step (3) is washed with water for multiple times to remove NaCl and KCl molten salts, then washed with hydrofluoric acid to remove impurities, then washed with water to neutrality, and finally dried in a vacuum oven to obtain high-purity composite whiskers of micron-SiC wrapped by nano-TiC particle layer;
[0012] (5)Al 2 O 3 - Preparation of a mixed powder of nano-TiC particle layer wrapped micron SiC composite whiskers: The high-purity nano-TiC particle layer obtained in step (4) is wrapped with a micron SiC composite whisker, Al 2 O 3 The powder is mixed evenly with anhydrous ethanol as a liquid medium, directly evaporated in a water bath, and then vacuum dried and sieved to obtain mixed powder B;
[0013] (6)Al 2 O 3 Preparation of composite ceramics: The mixed powder B obtained in step (5) is sintered at 1400-1600°C for a certain period of time under a certain pressure and heating rate using a rapid sintering device to obtain the multi-scale toughened Al composite whisker with nano-TiC particle layer wrapped in micron SiC. 2 O 3 Composite ceramics.
[0014] According to the above scheme, in step (1), the diameter of the original SiC whisker is 0.1-0.6 μm and the length is 10-50 μm; in step (2), the particle size of the nano-Ti powder is 30-500 nm and the purity is ≥99.8%; in step (5), the Al 2 O 3 The particle size of the powder is less than 1μm and the purity is ≥99.99%.
[0015] According to the above scheme, the acid solution used in step (1) can be an inorganic acid solution such as hydrochloric acid, sulfuric acid, hydrofluoric acid, etc., or an acidic solution prepared by the aforementioned inorganic acid and other solvents, preferably a hydrofluoric acid solution, and the concentration of the hydrofluoric acid solution is 20 to 40wt.%; the stirring time is 30min to 120min.
[0016] According to the above scheme, in step (2), the molar ratio of SiC whiskers to nano-Ti powder is 1:2 to 6:1; the molar ratio of NaCl to KCl is 4:1 to 1:4, preferably 1:1; the mass ratio of molten salt medium to raw material is 2:1 to 8:1; the total mass of SiC whiskers, Ti powder, NaCl and KCl in anhydrous ethanol accounts for 10% to 20%.
[0017] According to the above scheme, in step (3), the flow rate of the flowing argon is 50ml / min~120ml / min, the heating rate of the high-temperature tube furnace is 1~3℃ / min, the sintering temperature is 1100~1400℃, and the insulation time is 1~3h.
[0018] According to the above scheme, in step (4), the concentration of the hydrofluoric acid solution is 35-45wt.%.
[0019] According to the above scheme, in step (5), the mass of the composite whiskers of the nano-TiC particle layer encapsulating the micron SiC is 3-20wt.%, Al 2 O 3 The mass proportion of is 80-97wt.%; the solid content of the mixed powder in anhydrous ethanol is 5%-20%; the particle size of the mixed powder B is not greater than 200 meshes.
[0020] According to the above scheme, in step (6), the pressure used is 30-80 MPa, the heating rate is 50-500°C / min, and the insulation time is 5-10 min.
[0021] The present invention forms a nano-scale TiC particle shell layer by in-situ reaction on the surface of a micron-sized SiC whisker, thereby forming a composite whisker in which a nano-TiC particle layer wraps a micron-sized SiC. The possible mechanism is as follows: in a molten salt environment, nano-Ti gradually decomposes into Ti atoms, which then diffuse into the SiC whisker and react with SiC in-situ to form nano-TiC particles. As the diffusion proceeds, Si atoms in SiC are continuously replaced by Ti atoms, making the shell layer thicker, and the replaced Si atoms diffuse into the molten salt medium, and then are discharged in the form of gas in a high-temperature environment. At the same time, the presence of the molten salt environment and the protective atmosphere ensures that Ti will not be oxidized to form TiO 2 , reducing the influence of impurities on the core-shell structure whiskers. The composite whiskers were then introduced into the Al 2 O 3 The matrix was then sintered using a rapid sintering technique to prepare a multi-scale toughened Al2O3 composite with a nano-TiC particle layer wrapped in a micron SiC composite whisker. 2 O 3 Composite ceramics.
[0022] Compared with the prior art, the present invention has the following beneficial effects:
[0023] (1) The present invention does not use a single whisker as the toughening phase, but uses a composite whisker of micron SiC wrapped in a nano-TiC particle layer as the toughening phase. 2 O 3 In the matrix, the composite whiskers and the matrix form a micron-sized SiC whisker-nano-sized TiC particle-micron-sized Al 2 O 3 The transitional change of the material size of the grains triggers a multi-dimensional toughening effect, which can break the toughening bottleneck of a single whisker toughening phase and further improve toughness. The present invention is the first to use a composite whisker of micron SiC wrapped in a nano-TiC particle layer as a toughening phase to enhance Al 2 O 3 The toughness of the composite ceramic. 2 O 3 The improvement of toughness of composite ceramic materials depends on SiC whiskers, TiC nanoparticles and Al 2 O 3 Multiple differences between matrices in terms of phase composition, material size, and thermal expansion coefficients, which are 2 O 3 A complex stress environment and structural changes are formed in the matrix, which leads to a multi-dimensional toughening effect and significantly improves the Al 2 O 3 In addition, the composite whiskers and the matrix together form a micron-sized SiC whisker-nano-sized TiC particles-micron-sized Al 2 O 3 The transition structure of the grains undergoes multi-scale changes in grain size, which will produce a multi-dimensional toughening effect during the toughening process, and finally achieve Al 2 O 3 Improvement of the toughness of composite ceramics.
[0024] (2) The present invention uses a composite whisker of micron SiC wrapped with a TiC nanoparticle layer as a toughening phase, which is beneficial to improving the dispersibility of SiC whiskers. Single-phase whiskers easily form spherical agglomerates, which are difficult to be evenly dispersed in a ceramic matrix. The presence of whisker agglomerates affects the mechanical properties of the matrix. The present invention forms a TiC nanoparticle shell layer on the surface of the SiC whisker through an in-situ reaction, effectively reducing the specific surface area of the SiC whisker and avoiding the reduction of the mechanical properties of the ceramic matrix caused by whisker agglomeration.
[0025] (3) The present invention prepares composite whiskers by in-situ reaction to generate nano-TiC particles, so that the nano-TiC and SiC whiskers have good connectivity, effectively avoiding Al 2 O 3 The nano-TiC particle layer falls off during the mixing process of the composite whisker powder; 2 O3 In the process of composite ceramics, the sintering temperature of SiC and TiC is much higher than that of Al 2 O 3 The sintering temperature of the ceramic makes it difficult for the composite whiskers of micron SiC wrapped by the nano-TiC particle layer to diffuse with the matrix. The above two steps ensure that the composite whiskers can be completely retained in the matrix material; moreover, the use of rapid sintering technology can greatly reduce the holding time, which also ensures that the composite whiskers can be completely present in the matrix phase. The complete composite structure can produce two toughening effects: first, due to the SiC whiskers, TiC nanoparticles and Al that make up the composite whiskers, the composite whiskers can be completely retained in the matrix material. 2 O 3 The thermal expansion coefficients of the substrates differ greatly (3.8×10 -6 / K,7.4×10 -6 / K and 8×10 -6 / K), the large difference in thermal expansion coefficients creates a complex stress concentration zone between the composite whiskers and the matrix, which can effectively deflect cracks, thereby achieving toughening of Al 2 O 3 ceramics; secondly, when the crack passes through the composite whisker, the crack is located between the micron SiC whisker, nano TiC particles, and Al 2 O 3 Between different components of grains, between SiC core and TiC shell, between TiC and Al 2 O 3 Multi-dimensional deflection occurs between the interface layers, achieving an improvement in fracture toughness. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 It is an Al2O3 composite material with nano-TiC particles wrapped in micron SiC composite whiskers as the toughening phase. 2 O 3 Flow chart of preparation of composite ceramics;
[0027] Figure 2 The SEM spectra of the original SiC whisker and the prepared nano-TiC particle layer wrapped micron SiC composite whisker used in Example 3; wherein Figure (a) is the SEM image of the original SiC whisker, (b) is the SEM image of the nano-TiC particle layer wrapped micron SiC composite whisker, and Figures (c)-(d) are SEM images of (b) at different magnifications;
[0028] Figure 3 The XRD spectra of the SiC whiskers used in Example 5 and the composite whiskers of micron-SiC wrapped by the nano-TiC particle layer prepared;
[0029] Figure 4 Al prepared as described in Example 6 2 O3 BSE spectra of composite ceramic polished surface and composite whiskers with nano-TiC particle layer wrapped in micron SiC; Figure (a) is Al 2 O 3 BSE diagram of the polished surface of the composite ceramic. Figure (b) is the BSE diagram of the composite whisker with nano-TiC particle layer wrapped in micron SiC in the polished surface;
[0030] Figure 5 The Al2O3 composite material prepared as described in Example 6 has a nano-TiC particle layer wrapped with a micron SiC composite whisker as a toughening phase. 2 O 3 XRD patterns of composite ceramics. DETAILED DESCRIPTION
[0031] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the present invention is not limited to the following embodiments.
[0032] In the following embodiments, the original SiC whiskers have a diameter of 0.1 to 0.6 μm and a length of 10 to 50 μm and are purchased through commercial channels.
[0033] In the following embodiments, the density of the composite ceramic material is tested by the Archimedes drainage method, the hardness and fracture toughness of the composite ceramic material are measured by a Vickers hardness tester, and the flexural strength of the composite ceramic is measured by a universal testing machine using a three-point bending method.
[0034] Example 1
[0035] A multi-scale toughened Al composite whisker with nano-TiC particle layer wrapped in micron SiC 2 O 3 Composite ceramics, which are based on Al 2 O 3 The matrix phase is the nano-TiC particle layer, and the composite whiskers of micron SiC are used as the toughening phase. By mass percentage, Al 2 O 3 The proportion is 95%, and the composite whiskers of nano-TiC particle layer wrapped in micron-SiC account for 5%.
[0036] The Al2O3 composite whisker multi-scale toughened by nano-TiC particle layer wrapped micron SiC 2 O 3 The preparation method of the composite ceramic comprises the following steps:
[0037] (1) Removal of impurities from the original SiC whiskers: The original SiC whiskers were placed in a polytetrafluoroethylene beaker, and were acid-washed with a 40 wt.% hydrofluoric acid solution by magnetic stirring for 30 min, then centrifuged and washed with water until neutral, and then placed in a vacuum drying oven at 80° C. for 12 h to obtain SiC whiskers with impurities removed;
[0038] (2) Preparation of mixed powder A: SiC whiskers and nano-Ti powder obtained in step (1) are used as raw materials, the molar ratio of SiC whiskers to nano-Ti powder is SiC:Ti=4:1, NaCl and KCl are molten salt media, the molar ratio of NaCl to KCl is 4:1, and the mass ratio of the total mass of the raw material SiC whiskers and nano-Ti powder to the molten salt medium is (SiC+Ti):(NaCl+KCl)=1:2. The SiC whiskers, nano-Ti powder, NaCl and KCl obtained in step (1) are placed in anhydrous ethanol and magnetically stirred for 24 hours to obtain a mixed slurry with a solid phase ratio of 10%, and then the mixed slurry is subjected to rotary evaporation to obtain mixed powder A, which is then placed in a vacuum oven for drying;
[0039] (3) Preparation of nano-TiC particle layer-wrapped micron-SiC composite whiskers: The mixed powder A obtained in step (2) is placed in a semicircular corundum crucible with a cover, and heated to 1100° C. at a heating rate of 1° C. / min in a high-temperature tube furnace in a flowing argon atmosphere (argon flow rate of 120 ml / min), kept warm for 1 h, and cooled to room temperature to obtain a composite whisker powder containing nano-TiC particle layer-wrapped micron-SiC containing impurities;
[0040] (4) Purification of nano-TiC particle layer-wrapped micron-SiC composite whiskers: The composite whisker powder obtained in step (3) is washed with water for multiple times to remove NaCl and KCl molten salts, pickled with 45 wt.% hydrofluoric acid to remove impurities, washed with water until neutral, and then dried in a vacuum oven at 80° C. to obtain high-purity nano-TiC particle layer-wrapped micron-SiC composite whiskers;
[0041] (5)Al 2 O 3 -Preparation of composite whisker mixed powder of nano-TiC particle layer wrapped with micron SiC: Al 2 O 3 The powder and the composite whisker of micron SiC wrapped by the nano-TiC particle layer were mixed with anhydrous ethanol as the liquid medium for 24 hours to obtain a uniform slurry with a solid content of 5%, and then the anhydrous ethanol was directly evaporated in a water bath at 80°C, followed by vacuum drying and passing through a 200-mesh sieve to obtain a mixed powder B;
[0042] (6)Al 2 O 3 Preparation of composite ceramics: Mixed powder B was sintered using spark plasma sintering equipment at a pressure of 30 MPa, at a heating rate of 50 ° C / min, and kept at 1400 ° C for 10 min to obtain a multi-scale toughened Al composite whisker with a nano-TiC particle layer wrapped around a micron SiC. 2 O 3 Composite ceramics.
[0043] After testing, the Al2O3 composite whisker multi-scale toughened with nano-TiC particle layer wrapped micron SiC prepared in this embodiment 2 O 3 The density of the composite ceramic is 3.95g / cm 2 , Vickers hardness is 20.82GPa, fracture toughness is 5.19MPa·m 1 / 2 , the flexural strength is 482MPa.
[0044] Example 2
[0045] A multi-scale toughened Al composite whisker with nano-TiC particle layer wrapped in micron SiC 2 O 3 Composite ceramics, which are based on Al 2 O 3 The matrix phase is the nano-TiC particle layer, and the composite whiskers of micron SiC are used as the toughening phase. By mass percentage, Al 2 O 3 The proportion is 80%, and the composite whiskers of nano-TiC particle layer wrapped in micron-SiC account for 20%.
[0046] The preparation method of this embodiment is substantially the same as that of embodiment 1, except that: in step (2), the molar ratio of SiC whisker to nano-Ti powder is SiC:Ti=1:2, the molar ratio of NaCl to KCl is NaCl:KCl=1:4, and the mass ratio of the total mass of the raw material SiC whisker and nano-Ti powder to the molten salt medium is (SiC+Ti):(NaCl+KCl)=1:8; the heating rate of step (3) is 3°C / min, the reaction temperature is 1400°C, and the holding time is 3h.
[0047] The Al2O3 composite whisker multi-scale toughened with nano-TiC particle layer wrapped micron SiC prepared in this embodiment 2 O 3 The density of the composite ceramic is 3.87g / cm 2 , Vickers hardness is 20.45GPa, fracture toughness is 5.39MPa·m 1 / 2 , the flexural strength is 493MPa.
[0048] Example 3
[0049] A multi-scale toughened Al composite whisker with nano-TiC particle layer wrapped in micron SiC 2 O 3 Composite ceramics, which are based on Al 2 O 3 The matrix phase is the nano-TiC particle layer, and the composite whiskers of micron SiC are used as the toughening phase. By mass percentage, Al 2 O 3The proportion is 97%, and the composite whiskers of nano-TiC particle layer wrapped in micron-SiC account for 3%.
[0050] The Al2O3 composite whisker multi-scale toughened by nano-TiC particle layer wrapped micron SiC 2 O 3 The preparation method of the composite ceramic comprises the following steps:
[0051] (1) Removal of impurities from the original SiC whiskers: The original SiC whiskers were placed in a polytetrafluoroethylene beaker, and a 20 wt.% hydrofluoric acid solution was added and magnetically stirred for 120 min for acid washing, and then centrifuged and washed with water until neutral, and then placed in a vacuum drying oven at 80° C. for 12 h to obtain SiC whiskers with impurities removed;
[0052] (2) Preparation of mixed powder A: SiC whiskers and nano-Ti powder (60 nm, purity > 99.8%) obtained in step (1) are used as raw materials, the molar ratio of SiC whiskers to nano-Ti powder is SiC:Ti=2:1, NaCl and KCl are molten salt media, the molar ratio of NaCl to KCl is 1:1, and the mass ratio of the total mass of the raw material SiC whiskers and nano-Ti powder to the molten salt medium is (SiC+Ti):(NaCl+KCl)=1:6. The SiC whiskers, nano-Ti powder, NaCl and KCl obtained in step (1) are placed in anhydrous ethanol and magnetically stirred for 24 hours to obtain a mixed slurry with a solid content of 20%, and then the mixed slurry is subjected to rotary evaporation to obtain mixed powder A, which is then placed in a vacuum oven for drying;
[0053] (3) Preparation of composite whiskers of micron-SiC coated with nano-TiC particle layer: The mixed powder A obtained in step (2) is placed in a semicircular corundum crucible with a cover, and heated to 1300° C. at a heating rate of 2° C. / min in a high-temperature tube furnace with a flowing argon atmosphere (50 ml / min), kept warm for 2 h, and cooled to room temperature to obtain composite whisker powders of micron-SiC coated with nano-TiC particle layer containing impurities;
[0054] (4) Purification of composite whiskers with nano-TiC particle layer wrapped micron SiC: The whisker powder obtained in step (3) is washed with water for multiple times to remove NaCl and KCl molten salts, pickled with 40wt.% hydrofluoric acid to remove impurities, washed with water until neutral, and then dried in a vacuum oven at 80°C to obtain high-purity composite whiskers with nano-TiC particle layer wrapped micron SiC;
[0055] (5)Al 2 O 3 -Preparation of composite whisker powder of nano-TiC particle layer wrapped with micron SiC: Al 2 O 3The powder and the composite whisker of micron SiC wrapped by the nano-TiC particle layer were mixed with anhydrous ethanol as the liquid medium for 24 hours to obtain a uniform slurry with a solid content of 15%. The anhydrous ethanol was directly evaporated in a water bath at 80°C, and then vacuum dried and passed through a 200-mesh sieve to obtain a mixed powder B.
[0056] (6)Al 2 O 3 Preparation of composite ceramics: Mixed powder B was sintered using spark plasma sintering equipment at a pressure of 80 MPa, at a heating rate of 500 ° C / min, and kept at 1600 ° C for 8 minutes to obtain a multi-scale toughened Al composite whisker with a nano-TiC particle layer wrapped around a micron SiC. 2 O 3 Composite ceramics.
[0057] The Al2O3 composite whisker multi-scale toughened with nano-TiC particle layer wrapped micron SiC prepared in this embodiment 2 O 3 The density of the composite ceramic is 3.97g / cm 2 , Vickers hardness is 21.23GPa, fracture toughness is 5.53MPa·m 1 / 2 , the flexural strength is 465MPa.
[0058] Depend on Figure 2 (a) It can be seen that the purchased original whiskers are severely agglomerated and have a smooth surface. After the composite, the composite whiskers with nano-TiC particles wrapped in micro-SiC have good dispersibility (such as Figure 2 (b) and (c)-(d) Figure 2 (b) is a further enlarged view, from which it can be seen that a nanoscale particle layer is formed on the surface of the composite whisker.
[0059] Example 4
[0060] A multi-scale toughened Al composite whisker with a nano-TiC particle layer wrapped around a micron SiC 2 O 3 Composite ceramics, which are based on Al 2 O 3 The matrix phase is the nano-TiC particle layer, and the composite whiskers of micron SiC are used as the toughening phase. By mass percentage, Al 2 O 3 The proportion is 85%, and the composite whiskers of nano-TiC particle layer wrapped in micron-SiC account for 15%.
[0061] The preparation method of this embodiment is substantially the same as that of embodiment 3, except that: in step (2), the mass ratio of the total mass of the raw material SiC whiskers and nano-Ti powder to the molten salt medium is (SiC+Ti):(NaCl+KCl)=1:4; in step (5), the Al 2 O 3 The mass ratio of the powder to the composite whisker of the nano-TiC particle layer encapsulating the micron-SiC is 85:15.
[0062] The Al2O3 composite whisker multi-scale toughened with nano-TiC particle layer wrapped micron SiC prepared in this embodiment 2 O 3 The density of the composite ceramic is 3.94g / cm 2 , Vickers hardness is 20.48GPa, fracture toughness is 6.89MPa·m 1 / 2 , the flexural strength is 544MPa.
[0063] Example 5
[0064] A multi-scale toughened Al composite whisker with nano-TiC particle layer wrapped in micron SiC 2 O 3 Composite ceramics, which are based on Al 2 O 3 The matrix phase is the nano-TiC particle layer, and the composite whiskers of micron SiC are used as the toughening phase. By mass percentage, Al 2 O 3 The proportion is 92%, and the composite whiskers of nano-TiC particle layer wrapped in micron-SiC account for 8%.
[0065] The Al2O3 composite whisker multi-scale toughened by nano-TiC particle layer wrapped micron SiC 2 O 3 The preparation method of the composite ceramic comprises the following steps:
[0066] (1) Removal of impurities from the original SiC whiskers: The original SiC whiskers were placed in a polytetrafluoroethylene beaker, and acid-washed with a 30 wt.% hydrofluoric acid solution by magnetic stirring for 60 min, then centrifuged and washed with water until neutral, and then placed in a vacuum drying oven at 80° C. for 12 h to obtain SiC whiskers with impurities removed;
[0067] (2) Preparation of mixed powder A: SiC whiskers and nano-Ti powder obtained in step (1) are used as raw materials, the molar ratio of SiC whiskers to nano-Ti powder is SiC:Ti=1:1, NaCl and KCl are molten salt media, the molar ratio of NaCl to KCl is 1:1, and the mass ratio of the total mass of the raw material SiC whiskers and nano-Ti powder to the molten salt medium is (SiC+Ti):(NaCl+KCl)=1:4. SiC whiskers, nano-Ti powder, NaCl and KCl are placed in anhydrous ethanol and magnetically stirred for 24 hours to obtain a mixed slurry with a solid content of 20%, and then the mixed slurry is subjected to rotary evaporation to obtain mixed powder A, which is then placed in a vacuum oven for drying;
[0068] (3) Preparation of composite whiskers of micron-SiC coated with nano-TiC particle layer: The mixed powder A obtained in step (2) is placed in a semicircular corundum crucible with a cover, and heated to 1400° C. at a heating rate of 3° C. / min in a high-temperature tube furnace in a flowing argon atmosphere (100 ml / min), kept warm for 2 h, and cooled to room temperature to obtain composite whisker powder of micron-SiC coated with nano-TiC particle layer containing impurities;
[0069] (4) Purification of composite whiskers with nano-TiC particle layer wrapped micron SiC: The whisker powder obtained in step (3) is washed with water for multiple times to remove NaCl and KCl molten salts, pickled with 35wt.% hydrofluoric acid to remove impurities, washed with water until neutral, and then dried in a vacuum oven at 80°C to obtain high-purity composite whiskers with nano-TiC particle layer wrapped micron SiC;
[0070] (5)Al 2 O 3 -Preparation of composite whisker mixed powder of nano-TiC particle layer wrapped with micron SiC: Al 2 O 3 The powder and the composite whisker of micron SiC wrapped by the nano-TiC particle layer were mixed with anhydrous ethanol as the liquid medium for 24 hours to obtain a uniform slurry with a solid content of 20%, and the anhydrous ethanol was directly evaporated in a water bath at 80°C, followed by vacuum drying and passing through a 200-mesh sieve to obtain a mixed powder B;
[0071] (6)Al 2 O 3 Preparation of composite ceramics: The obtained mixed powder B was placed in a graphite mold, and the graphite mold was wrapped with graphite felt, and then placed in a spark plasma sintering device. Under a pressure of 60 MPa, the temperature was increased at a rate of 100 ° C / min and kept at 1600 ° C for 5 min to obtain a multi-scale toughened Al composite whisker with a nano-TiC particle layer wrapped around a micron SiC. 2 O 3 Composite ceramics.
[0072] The Al2O3 composite whisker multi-scale toughened with nano-TiC particle layer wrapped micron SiC prepared in this embodiment 2 O 3 The density of the composite ceramic is 3.93g / cm 2 , Vickers hardness is 20.23GPa, fracture toughness is 6.78MPa·m 1 / 2 , the flexural strength is 558MPa.
[0073] Figure 3 XRD spectra of the SiC whisker used in this embodiment and the composite whisker of micron SiC wrapped by the prepared nano-TiC particle layer. It can be seen from the figure that the characteristic peaks of the silicon carbide whisker can be clearly observed at 2θ of 35.7°, 41.4°, 60.0°, 71.8° and 75.5°, which can be retrieved by PDF#75-0254 card; the peaks corresponding to TiC in the composite whisker of micron SiC wrapped by the nano-TiC particle layer are clearly observed at 36.1, 41.9, 60.8, 72.8 and 76.6, which can be retrieved by PDF#65-8805, indicating that the TiC layer can be formed on the surface of the SiC whisker by using the present invention.
[0074] Example 6
[0075] A composite whisker of Al2O3 with a nano-TiC particle layer wrapped in a micron SiC as a toughening phase 2 O 3 Composite ceramics, which are based on Al 2 O 3 The matrix phase is the nano-TiC particle layer, and the composite whiskers of micron SiC are used as the toughening phase. By mass percentage, Al 2 O 3 The proportion is 90%, and the composite whisker phase of nano-TiC particle layer wrapped in micron-SiC accounts for 10%.
[0076] The preparation method of this embodiment is substantially the same as that of embodiment 5, except that: in step (2), the mass ratio of the total mass of the raw material SiC whiskers and nano-Ti powder to the mass ratio of the molten salt medium is (SiC+Ti):(NaCl+KCl)=1:6; and the sintering temperature of step (6) is 1500°C.
[0077] The Al2O3 composite whisker multi-scale toughened with nano-TiC particle layer wrapped micron SiC prepared in this embodiment 2 O 3 The density of the composite ceramic is 3.91g / cm 2 , Vickers hardness is 21.38GPa, fracture toughness is 7.61MPa·m 1 / 2 , the flexural strength is 693MPa.
[0078] Depend on Figure 4 (a) It can be seen that in the Al composite whisker containing 10wt.% TiC particles wrapped with micron SiC 2 O 3 In the composite ceramic, the core-shell structure whiskers have good dispersion and basically no large agglomeration occurs. In the further enlarged image ( Figure 4 (b) shows that after sintering in a spark plasma sintering device, the composite whiskers of micron-SiC wrapped by the nano-TiC particle layer can be completely present in the Al 2 O 3 The shell layer is not damaged, indicating that the integrity of the composite whiskers can be guaranteed under this condition.
[0079] Figure 5 The Al2O3 composite whisker with a nano-TiC particle layer wrapped around a micron SiC as a toughening phase is prepared in this embodiment. 2 O 3 XRD spectrum of composite ceramics. From the figure, we can see that the composite ceramic material only contains Al 2 O 3 , SiC and TiC phases, indicating that the composite whiskers of micron SiC and Al 2 O 3 The mixed powder does not undergo chemical reaction after sintering by spark plasma sintering equipment, and Figure 4 Together, they verified that the composition of the composite whiskers did not change after sintering, and the structure could be completely retained in the matrix.
[0080] Comparative Example 1
[0081] This comparison is the blank control group. 2 O 3 The powder was placed in a graphite mold, which was wrapped with graphite felt and placed in a spark plasma sintering device. Under a pressure of 60 MPa, the temperature was increased at a rate of 100 °C / min and kept at 1500 °C for 5 min to obtain Al 2 O 3 ceramics.
[0082] The SiC whisker toughened Al 2 O 3 The density of the composite ceramic is 3.95g / cm 2 , Vickers hardness is 20.58GPa, fracture toughness is 4.67MPa·m 1 / 2 , the flexural strength is 436MPa.
[0083] Comparative Example 2
[0084] This comparative example is a control experiment in which only SiC whiskers are added, and the specific experimental steps are as follows:
[0085] (1) Removal of impurities from the original SiC whiskers: The original SiC whiskers were placed in a polytetrafluoroethylene beaker, and acid-washed with a 30 wt.% hydrofluoric acid solution by magnetic stirring for 60 min, then centrifuged and washed with water until neutral, and then placed in a vacuum drying oven at 80° C. for 12 h to obtain SiC whiskers with impurities removed;
[0086] (2)Al 2 O 3 Preparation of SiC whisker mixed powder: Al 2 O 3 The powder and SiC whiskers were mixed with anhydrous ethanol as a liquid medium for 24 hours to obtain a uniform slurry, and the anhydrous ethanol was directly evaporated in a water bath at 80°C, followed by vacuum drying and passing through a 200-mesh sieve to obtain a mixed powder;
[0087] (3)Al 2 O 3 Preparation of composite ceramics: The obtained mixed powder was placed in a graphite mold, and the graphite mold was wrapped with graphite felt, and then placed in a spark plasma sintering device. Under a pressure of 60 MPa, the temperature was increased at a rate of 100 ° C / min, and the temperature was kept at 1500 ° C for 5 min to obtain Al2O3 toughened with SiC whiskers. 2 O 3 Composite ceramics.
[0088] The SiC whisker toughened Al 2 O 3 The density of the composite ceramic is 3.78g / cm 2 , Vickers hardness is 21.02GPa, fracture toughness is 6.18MPa·m 1 / 2 , the flexural strength is 479MPa.
[0089] The above is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and changes without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.
Claims
1. An Al2O3 composite ceramic with multi-scale toughening of composite whiskers of micron SiC wrapped with a nano-TiC particle layer, characterized in that: The Al2O3 composite ceramic uses Al2O3 as the matrix phase and composite whiskers of micron SiC wrapped by nano TiC particle layer as the toughening phase. By mass percentage, Al2O3 accounts for 80-97% and composite whiskers of micron SiC wrapped by nano TiC particle layer accounts for 3-20%.
2. The Al2O3 composite ceramic with multi-scale toughening of composite whiskers of micron SiC wrapped with nano-TiC particle layer according to claim 1, characterized in that: The density of the Al2O3 composite ceramic is 3.87-3.97 g / cm 3 , Vickers hardness is 20.23~21.38GPa, fracture toughness is 5.19~7.61MPa·m 1 / 2 , the flexural strength is 465~693MPa.
3. The method for preparing the Al2O3 composite ceramic according to claim 1, characterized in that: First, SiC whiskers and nano-Ti powder are used as raw materials, and a molten salt method is used to prepare composite whiskers of micron SiC wrapped by a nano-TiC particle layer; the composite whiskers of micron SiC wrapped by a nano-TiC particle layer are mixed and sintered with Al2O3 powder to obtain Al2O3 composite ceramics.
4. The method for preparing Al2O3 composite ceramics according to claim 3, characterized in that: The following steps are involved: (1) SiC whiskers and nano-Ti powder are used as raw materials, NaCl and KCl are used as molten salt media, and mixed evenly in a liquid medium, and dried to obtain a mixed powder A; (2) calcining the mixed powder A obtained in step (1) in a high-temperature tube furnace in a protective atmosphere to obtain a composite whisker containing a nano-TiC particle layer wrapped in micron-SiC containing impurities, and after acid washing and water washing to remove impurities, drying to obtain a composite whisker containing a nano-TiC particle layer wrapped in micron-SiC; (3) mixing the composite whiskers of micron-SiC wrapped by the nano-TiC particle layer obtained in step (2) and Al2O3 powder in a liquid medium, and drying to obtain a mixed powder B; (4) Pressurizing the mixed powder B and heating it to 1400-1600° C. for sintering to obtain a multi-scale toughened Al 2 O 3 composite ceramic with a composite whisker of nano-TiC particles wrapped around micro-SiC.
5. The Al2O3 composite ceramic and the preparation method thereof according to claim 4, characterized in that: The diameter of the SiC whisker is 0.1-0.6 μm, and the length is 10-50 μm. The SiC whisker is pickled to remove impurities before use, then washed with water to neutrality, and dried for later use.
6. The Al2O3 composite ceramic and the preparation method thereof according to claim 4, characterized in that: The particle size of nano-Ti powder is 30-500nm, and the purity is ≥99.8%; the particle size of Al2O3 powder is less than 1μm, and the purity is ≥99.99%.
7. The Al2O3 composite ceramic and the preparation method thereof according to claim 4, characterized in that: In step (1), the molar ratio of SiC whisker to nano-Ti powder is 1:2-6:1, the molar ratio of NaCl to KCl is 4:1-1:4, and the mass ratio of molten salt medium to raw material is 2:1-8:
1.
8. The Al2O3 composite ceramic and the preparation method thereof according to claim 4, characterized in that: In step (2), the protective atmosphere is flowing argon, the gas flow rate is 50-120 ml / min, the heating rate of the high-temperature tube furnace is 1-3° C. / min, the calcination temperature is 1100-1400° C., and the insulation time is 1-3 h.
9. The Al2O3 composite ceramic with multi-scale toughening by wrapping micron SiC composite whiskers with nano-TiC particle layer and the preparation method thereof according to claim 4, characterized in that: In step (3), the mass proportion of the nano-TiC particle layer encapsulating the micron SiC composite whisker is 3-20wt.%, and the mass proportion of Al2O3 is 80-97wt.%.
10. The Al2O3 composite ceramic with multi-scale toughening by wrapping micron SiC composite whiskers with nano-TiC particle layer and the preparation method thereof according to claim 4, characterized in that: In step (4), the pressure used is 30-80 MPa, the heating rate is 50-500° C. / min, and the insulation time is 5-10 min.