Ceramic material with high-temperature phase stability and high fracture toughness as well as preparation method and application of ceramic material

Abstract

The invention provides a ceramic material with high-temperature phase stability and high fracture toughness as well as a preparation method and application of the ceramic material, and belongs to the technical field of thermal barrier coating materials for hydrogen mixing gas turbines. According to the preparation method, the block material is subjected to heat treatment in a vapor-containing atmosphere, under high-temperature vapor heat treatment, oxygen vacancies are formed due to reduction of oxygen partial pressure and overflow of lattice oxygen, formation of a metastable tetragonal phase (t ') is promoted, and a high-temperature phase of yttria-stabilized zirconia (YSZ) is stabilized; moreover, the phase transformation temperature of YSZ martensite phase transformation is reduced through high-temperature water vapor, martensite laths are refined, and deflection and bridging of cracks are promoted through an increased lath interface; in addition, an extra ferroelastic domain change toughening mechanism is introduced into a t'phase formed under high-temperature water vapor, so that the fracture toughness of the YSZ is greatly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of thermal barrier coating materials for hydrogen hybrid combustion engines, and particularly relates to a ceramic material with high-temperature phase stability and high fracture toughness as well as a preparation method and application thereof. BACKGROUND

[0002] Thermal barrier coatings are key materials for high-temperature components such as aero-engines and gas turbines, mainly used for thermal protection, improving the thrust-to-weight ratio of the engine to improve efficiency, and isolating high-temperature gas to protect the metal substrate.

[0003] Oxide materials such as yttria-stabilized zirconia (YSZ) are widely used as thermal barrier coating materials due to their excellent fracture toughness. However, with the proposal of the "carbon peak" and "carbon neutral" targets, hydrogen energy and hydrogen hybrid combustion engine technology have become a key development direction. Hydrogen combustion is unstable, with local temperatures too high and a large amount of water vapor produced. The traditional thermal barrier coating material YSZ decomposes into tetragonal phase (t') and cubic phase (c) at more than 1200℃, and the t phase transforms into monoclinic phase (m) during the cooling process, resulting in a decrease in the ferroelastic domain toughening effect of the t' phase and the martensitic phase transformation toughening effect of the t phase, and a sharp decrease in the fracture toughness of the material. Under the service environment of thermal barrier coatings, there is a sharp temperature gradient, thermal cycle stress and mechanical load, and high fracture toughness is a key performance indicator to ensure the anti-cracking and anti-peeling of the coating and prolong the service life. In view of the higher service temperature requirement of hydrogen hybrid combustion engines, the deterioration of the fracture toughness of the material is more severe, so higher requirements are placed on the fracture toughness of the material. Therefore, how to further improve the fracture toughness of the ceramic material for ultra-high temperature thermal barrier coatings of hydrogen hybrid combustion engines has become a problem in the prior art. SUMMARY

[0004] The application aims to provide a ceramic material with high-temperature phase stability and high fracture toughness as well as a preparation method and application thereof. The ceramic material prepared by the preparation method provided by the application has better fracture toughness and high-temperature phase stability.

[0005] In order to achieve the above-mentioned application purposes, the application provides the following technical solutions: The application provides a preparation method of a ceramic material, comprising the following steps: (1) sequentially pressing and sintering a metal oxide powder to obtain a bulk material; the metal oxide powder is a mixed powder of yttrium oxide and zirconium oxide; (2) heat-treating the bulk material obtained in step (1) in an atmosphere containing water vapor to obtain a ceramic material.

[0006] Preferably, the mass ratio of yttrium oxide to zirconium oxide in the mixed powder of yttrium oxide and zirconium oxide in step (1) is 1: (10-12).

[0007] Preferably, the metal oxide powder in step (1) has a mesh size ≥ 100 mesh.

[0008] Preferably, the pressing pressure in step (1) is 50~100MPa, and the pressing holding time is 1~10min.

[0009] Preferably, the sintering temperature in step (1) is 1300~1600℃, the sintering holding time is 5~15h, and the rate of heating to the sintering temperature is 1~5℃ / min.

[0010] Preferably, the atmosphere containing water vapor in step (2) includes a water vapor atmosphere or a mixture of water vapor and air.

[0011] Preferably, the volume content of water vapor in the atmosphere containing water vapor in step (2) is 10~100%.

[0012] Preferably, in step (2), the heat treatment temperature is 1000~1600℃, the heat treatment holding time is 1~500h, and the rate of heating to the heat treatment temperature is 1~5℃ / min.

[0013] The present invention also provides ceramic materials prepared by the preparation method described in the above technical solution.

[0014] The present invention also provides the application of the ceramic material described in the above technical solution in the thermal barrier coating for hydrogen co-fueling engines.

[0015] This invention provides a method for preparing a ceramic material, comprising the following steps: (1) pressing and sintering metal oxide powder sequentially to obtain a bulk material; wherein the metal oxide powder is a mixture of yttrium oxide and zirconium oxide powder; (2) heat-treating the bulk material obtained in step (1) in an atmosphere containing water vapor to obtain a ceramic material. In this invention, the bulk material is heat-treated in an atmosphere containing water vapor. Under high-temperature water vapor heat treatment, due to the decrease in oxygen partial pressure, lattice oxygen overflows to form oxygen vacancies, which promotes the formation of a metastable tetragonal phase (t'), stabilizing the high-temperature phase of yttrium oxide-stabilized zirconium oxide (YSZ); furthermore, the high-temperature water vapor lowers the phase transformation temperature of the martensitic phase transformation (tm) of YSZ, refines the martensitic laths, and the increased lath interfaces promote crack deflection and bridging; in addition, the t' phase formed under high-temperature water vapor introduces an additional ferroelastic domain transformation toughening mechanism, thereby significantly improving the fracture toughness of YSZ. Attached Figure Description

[0016] Figure 1 Images of the apparatus provided by the present invention; Figure 2XRD patterns of the bulk material prepared in Example 1, and the ceramic materials prepared in Examples 1-3 and Comparative Examples 1-3; Figure 3 Raman diagrams of the bulk material prepared in Example 1, and the ceramic materials prepared in Examples 1-3 and Comparative Examples 1-3; Figure 4 The phase content diagrams are obtained from XRD and Raman plot fitting for the bulk material prepared in Example 1, and the ceramic materials prepared in Examples 1-3 and Comparative Examples 1-3. Figure 5 SEM images of the bulk material prepared in Example 1, and the ceramic materials prepared in Examples 1-3 and Comparative Examples 1-3; Figure 6 A comparison diagram of the fracture toughness of the bulk material prepared in Example 1, and the ceramic materials prepared in Examples 1-3 and Comparative Examples 1-3. Detailed Implementation

[0017] This invention provides a method for preparing a ceramic material, comprising the following steps: (1) The metal oxide powder is pressed and sintered in sequence to obtain a bulk material; (2) The bulk material obtained in step (1) is heat-treated in an atmosphere containing water vapor to obtain ceramic material.

[0018] This invention involves sequentially pressing and sintering metal oxide powders to obtain bulk materials.

[0019] In this invention, the metal oxide powder is preferably subjected to calcination, cooling, ball milling, drying, grinding and sieving in sequence before use.

[0020] In this invention, the calcination temperature is preferably 750~850℃, more preferably 800℃; the calcination time is preferably 2~4h, more preferably 3h; and the rate of heating to the calcination temperature is preferably 4~6℃ / min, more preferably 5℃ / min. This invention calcines metal oxide powder and controls the calcination temperature and time, which can effectively remove moisture and organic impurities from the powder.

[0021] The present invention does not impose any special limitations on the cooling operation; any cooling technique known to those skilled in the art can be used to cool the material to room temperature.

[0022] In this invention, the ball milling is preferably wet ball milling; the milling medium is preferably at least one selected from deionized water, anhydrous ethanol, and isopropanol; the milling balls are preferably 4-6 mm zirconia milling balls and 1-3 mm zirconia milling balls; the mass ratio of the metal oxide powder to the 4-6 mm and 1-3 mm zirconia milling balls is preferably (1-2):(2-4):(4-6); the milling speed is preferably 300-600 r / min; and the milling time is preferably 12-24 h. By controlling the milling parameters within the above ranges, this invention enables a more uniform mixing of the metal oxide powder.

[0023] In one embodiment, the ball mill is a planetary ball mill.

[0024] In this invention, the particle size of the metal oxide powder before ball milling is preferably ≤50nm; the purity of the metal oxide powder is preferably ≥99%.

[0025] In this invention, the drying temperature is preferably 80~100℃; the drying time is preferably 10~15h. As one embodiment, the drying is performed by forced-air drying.

[0026] In this invention, the grinding time is preferably 1 to 2 hours. As one embodiment, the grinding is carried out in an agate mortar.

[0027] In this invention, the sieving time is preferably 1 to 2 hours.

[0028] In this invention, the mesh size of the sieved metal oxide powder is preferably ≥100 mesh.

[0029] In this invention, the metal oxide powder is a mixture of yttrium oxide and zirconium oxide.

[0030] In this invention, the mass ratio of yttrium oxide to zirconium oxide in the mixed powder of yttrium oxide and zirconium oxide is preferably 1:(10~12), more preferably 1:(11~12), and even more preferably 1:11.5.

[0031] In this invention, the pressing pressure is preferably 50-100 MPa; the holding time is preferably 1-10 min. As one embodiment, the pressing pressure can specifically be 50 MPa, 60 MPa, 70 MPa, 80 MPa, 90 MPa, or 100 MPa; the holding time can specifically be 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, or 10 min.

[0032] In one embodiment, the present invention places 1-2g of metal oxide powder into a mold with a diameter of 15-18mm and presses it using a uniaxial pressure of 50-100MPa for 1-10 minutes.

[0033] In this invention, the coarse metal oxide powder obtained after sieving is preferably coated onto the pressed green body before sintering. This coating with coarse metal oxide powder prevents the volatilization of the metal oxides during sintering.

[0034] In this invention, the sintering temperature is preferably 1300~1600℃; the sintering holding time is preferably 5~15h; and the heating rate to the sintering temperature is preferably 1~5℃ / min. As one embodiment, the sintering temperature can specifically be 1300℃, 1350℃, 1400℃, 1450℃, 1500℃, 1550℃, or 1600℃; the sintering holding time can specifically be 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, or 15h; and the heating rate to the sintering temperature can specifically be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, or 5℃ / min. By controlling the sintering parameters within the above ranges, this invention can obtain a uniform and dense bulk material, thereby further improving the mechanical properties of the ceramic material.

[0035] In one implementation, the sintering is carried out in a muffle furnace.

[0036] After sintering, the present invention preferably cools the sintered product to obtain a bulk material.

[0037] In one implementation, the cooling is performed by cooling the furnace to room temperature.

[0038] After obtaining the bulk material, the present invention heat-treats the bulk material in an atmosphere containing water vapor to obtain a ceramic material.

[0039] In this invention, the water vapor atmosphere preferably includes a water vapor atmosphere or a mixture of water vapor and air; the volume content of water vapor in the water vapor atmosphere is preferably 10-100%. As one embodiment, the volume content of water vapor in the water vapor atmosphere can specifically be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%.

[0040] In this invention, the flow rate of the water vapor atmosphere is preferably 0.1~1L / min.

[0041] In one implementation, the water vapor is generated by a precision water vapor generator.

[0042] In this invention, the heat treatment temperature is preferably 1000~1600℃; the heat treatment holding time is preferably 1~500h; and the heating rate to the heat treatment temperature is preferably 1~5℃ / min. As one embodiment, the heat treatment temperature can specifically be 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, 1450℃, 1500℃, 1550℃, or 1600℃; the heat treatment holding time can specifically be 1h, 50h, 100h, 150h, 200h, 250h, 300h, 350h, 400h, 450h, or 500h; and the heating rate to the heat treatment temperature can specifically be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, or 5℃ / min. This invention involves heat treatment (water-oxygen corrosion) under high-temperature water vapor and controlling the parameters of the heat treatment. Under high-temperature water vapor, due to the decrease in oxygen partial pressure, lattice oxygen overflows to form oxygen vacancies, which promotes the formation of metastable tetragonal phase (t') and stabilizes the high-temperature phase of yttrium-stabilized zirconia (YSZ). Furthermore, the high-temperature water vapor lowers the phase transformation temperature of YSZ martensitic transformation (tm), refines the martensite laths, and the increased lath interfaces promote crack deflection and bridging. In addition, the t' phase formed under high-temperature water vapor introduces an additional ferroelastic domain transformation toughening mechanism, thereby significantly improving the fracture toughness of YSZ.

[0043] In one embodiment, the heat treatment is carried out in a zirconia crucible to avoid the crucible reacting with the bulk material under high temperature and moisture to form impurities that contaminate the material; the crucible is placed in the center of the tube furnace tube to ensure that the bulk material is heated evenly.

[0044] In one embodiment, the test surface of the bulk material is placed facing upwards during the heat treatment.

[0045] After heat treatment, the product of the heat treatment is preferably cooled to obtain a ceramic material.

[0046] In one implementation, the cooling is performed by cooling the furnace to room temperature.

[0047] As one implementation method, after the heat treatment is completed, the precision steam generator is turned off to avoid water accumulation in the furnace tubes during the cooling process, which could lead to cracking.

[0048] This invention performs heat treatment under high-temperature water vapor, which, compared to high-temperature air heat treatment, achieves synergistic optimization of phase stability and fracture toughness.

[0049] The present invention also provides ceramic materials prepared by the preparation method described in the above technical solution.

[0050] The present invention also provides the application of the ceramic material described in the above technical solution in the thermal barrier coating for hydrogen co-fueling engines.

[0051] The present invention does not impose any special limitations on the operation of the application, and any technical solution known to those skilled in the art can be used.

[0052] The present invention also provides an apparatus for preparing ceramic materials with both high-temperature phase stability and high fracture toughness as described in the above technical solution, including a precision steam generator, a gas cylinder, a flow meter, a tube furnace, and an anti-backflow device.

[0053] The device provided by the present invention includes a precision steam generator.

[0054] In one embodiment, the precision steam generator includes a constant flow dual plunger pump and an FD-HG generator; the constant flow dual plunger pump is connected to a water bottle; the water bottle contains purified water.

[0055] In one embodiment, the precision steam generator has a voltage of 220V, a frequency of 50Hz, and a power of 500W.

[0056] In one embodiment, the vaporization temperature of the precision steam generator is 100~180℃.

[0057] The device provided by the present invention also includes a gas cylinder.

[0058] In one embodiment, the gas cylinder is equipped with a pressure reducing valve; the precision steam generator is connected to the pressure reducing valve of the gas cylinder; and the gas cylinder is filled with compressed air.

[0059] In one embodiment, the heating device of the precision steam generator vaporizes liquid water into steam, which is then introduced into a tubular furnace or introduced into a tubular furnace together with compressed air from a gas cylinder. The amount of steam introduced is controlled by adjusting the flow meter.

[0060] The device provided by the present invention also includes a flow meter.

[0061] The apparatus provided by this invention also includes a tubular furnace.

[0062] In one embodiment, the air inlet of the tubular furnace is connected to a precision steam generator; the air outlet of the tubular furnace is connected to an anti-backflow device.

[0063] In one embodiment, the tube connecting the air inlet of the tubular furnace to the precision steam generator is insulated with heat tracing tape to prevent steam condensation; the temperature of the heat tracing tape is 100~180℃.

[0064] The device provided by the present invention also includes an anti-backflow device.

[0065] In one embodiment, the anti-backflow device consists of a funnel and a conduit that are inverted on the surface of the absorbent liquid (water).

[0066] The present invention does not impose any special limitations on the material, size and source of the components in the device; any components well known to those skilled in the art can be used.

[0067] Images of the device provided by this invention are shown below. Figure 1 As shown.

[0068] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0069] Example 1 A method for preparing a ceramic material is as follows: (1) Weigh 4g of yttrium oxide (particle size ≤ 50nm) and 46g of zirconium oxide (particle size ≤ 50nm), heat them in a muffle furnace at a rate of 5℃ / min to 800℃ for 3h, cool them, and then place them in a ball mill jar. Use isopropanol as the ball milling medium, and 5mm zirconium oxide large balls and 2mm zirconium oxide small balls as grinding balls. According to the total mass of yttrium oxide and zirconium oxide and the mass ratio of 5mm zirconium oxide large balls and 2mm zirconium oxide small balls 1:2:4, ball mill them in a planetary ball mill at 400r / min for 20h, then dry them in a forced air at 90℃ for 12h, grind them in an agate mortar for 2h, and pass them through a 200-mesh sieve for 1h to obtain metal oxide powder and coarse powder. (2) Place 1.5g of metal oxide powder in a mold with a diameter of 16mm and press it under a uniaxial pressure of 70MPa for 5min to obtain a green body. Cover the surface of the green body with coarse powder and sinter at a rate of 2℃ / min to 1400℃ for 10h. Cool it to room temperature in the furnace to obtain a bulk material. (3) Connect the inlet of the precision steam generator to the gas cylinder, and connect the outlet pipe to the inlet of the tube furnace with a heat tracing cable. Connect the outlet of the tube furnace to the anti-backflow device. The vaporization temperature of the precision steam generator is 150℃, and the heat tracing temperature is 150℃. Heat the tube furnace to 200℃ to remove the moisture in the tube furnace. Place the block material face up in the zirconia crucible. Place the crucible in the center of the tube furnace tube. Open the gas cylinder valve, adjust the flow meter to 0.8L / min, and the liquid inlet to 0.16L / min (i.e., the water vapor volume content is 20%). After the water vapor is introduced, heat the tube furnace to 1400℃ at a rate of 2℃ / min for 100h. At the same time, observe whether there are bubbles and condensate flowing out of the anti-backflow device to ensure the introduction of water vapor. After the heat treatment is completed, turn off the precision steam generator and cool it to room temperature with the furnace. Mark the front and back of the block material, turn off the compressed air, and obtain the ceramic material.

[0070] Comparative Example 1 The water vapor in Example 1 was omitted, that is, the heat treatment was carried out in an air atmosphere, and all other parameters were the same as in Example 1, to obtain a ceramic material.

[0071] Example 2 The heat treatment time in Example 1 was modified to 300 hours, while other parameters remained the same as in Example 1, resulting in a ceramic material.

[0072] Comparative Example 2 The water vapor in Example 2 was omitted, that is, the heat treatment was carried out in an air atmosphere, and all other parameters were the same as in Example 2, to obtain a ceramic material.

[0073] Example 3 The heat treatment time in Example 1 was modified to 500 hours, while other parameters remained the same as in Example 1, resulting in a ceramic material.

[0074] Comparative Example 3 The water vapor in Example 3 was omitted, that is, the heat treatment was carried out in an air atmosphere, and all other parameters were the same as in Example 3, to obtain a ceramic material.

[0075] The XRD patterns of the bulk material prepared in Example 1, and the ceramic materials prepared in Examples 1-3 and Comparative Examples 1-3 are shown below. Figure 2 As shown, (a) is the XRD pattern, and (b) and (c) are magnified views of (a). The Raman spectra of the bulk material prepared in Example 1, and the ceramic materials prepared in Examples 1-3 and Comparative Examples 1-3 are shown below. Figure 3 As shown, the phase content diagrams of the bulk material prepared in Example 1, and the ceramic materials prepared in Examples 1-3 and Comparative Examples 1-3, obtained from XRD and Raman plot fitting, are as follows: Figure 4 As shown. From Figures 2-4As can be seen, with the increase of sintering time, the t phase gradually decreases, while the m and c phases gradually increase. Compared with sintering in air, the content of the m phase in steam sintering is significantly lower than that in air, while the content of the t and c phases is higher. This indicates that high-temperature steam is beneficial to the stability of the high-temperature t and c phases, thus promoting the superior high-temperature phase stability of YSZ.

[0076] SEM images of the bulk material prepared in Example 1, and the ceramic materials prepared in Examples 1-3 and Comparative Examples 1-3 are shown below. Figure 5 As shown. From Figure 5 As can be seen, when sintered in air, the sample develops a large number of fine cracks, mainly intergranular fracture, and the crack density is significantly higher than that in water vapor; when sintered in water vapor, the number of cracks decreases significantly, but the crack width increases, mainly transgranular fracture.

[0077] The fracture toughness of the bulk material prepared in Example 1, and the ceramic materials prepared in Examples 1-3 and Comparative Examples 1-3 are as follows: Figure 6 As shown. From Figure 6 As can be seen, after heat treatment in steam, the fracture toughness of ceramic materials increases compared to bulk materials. With the extension of heat treatment time, the fracture toughness of ceramic materials gradually decreases, but it is always higher than or basically the same as that of bulk materials. However, after heat treatment in air, when the heat treatment time is 100 hours, the fracture toughness of ceramic materials increases compared to bulk materials. But with further increases in heat treatment time, the fracture toughness of ceramic materials decreases significantly and is significantly lower than that of bulk materials. Moreover, after heat treatment in steam, the fracture toughness of ceramic materials is 2 to 3 times that of heat treatment in air, that is, the fracture toughness in steam is significantly higher than that in air.

[0078] In summary, the ceramic material prepared by this invention has higher fracture toughness and high-temperature phase stability.

[0079] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a ceramic material, comprising the following steps: (1) The metal oxide powder is pressed and sintered in sequence to obtain a bulk material; the metal oxide powder is a mixture of yttrium oxide and zirconium oxide. (2) The bulk material obtained in step (1) is heat-treated in an atmosphere containing water vapor to obtain ceramic material.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of yttrium oxide to zirconium oxide in the mixed powder of yttrium oxide and zirconium oxide is 1:(10~12).

3. The preparation method according to claim 1, characterized in that, The metal oxide powder in step (1) has a mesh size ≥ 100 mesh.

4. The preparation method according to claim 1, characterized in that, The pressing pressure in step (1) is 50~100MPa, and the pressing holding time is 1~10min.

5. The preparation method according to claim 1, characterized in that, In step (1), the sintering temperature is 1300~1600℃, the sintering holding time is 5~15h, and the rate of heating to the sintering temperature is 1~5℃ / min.

6. The preparation method according to claim 1, characterized in that, The atmosphere containing water vapor in step (2) includes a water vapor atmosphere or a mixture of water vapor and air.

7. The preparation method according to claim 6, characterized in that, In step (2), the volume content of water vapor in the atmosphere containing water vapor is 10-100%.

8. The preparation method according to claim 1, characterized in that, In step (2), the heat treatment temperature is 1000~1600℃, the heat treatment holding time is 1~500h, and the rate of heating to the heat treatment temperature is 1~5℃ / min.

9. The ceramic material prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the ceramic material of claim 9 in a thermal barrier coating for a hydrogen co-fuel engine.

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