Zirconium oxide coating material and preparation method thereof

Abstract

The invention belongs to the field of coating materials, and discloses a zirconium oxide coating material and a preparation method thereof.The preparation method of the zirconium oxide coating material comprises the steps that zirconium oxide powder and zirconium powder are ball-milled and mixed, pure water is added, and then material covering is conducted to obtain a first mixture; the first mixture is subjected to cold pressing and cold isostatic pressing in sequence, a second green body is obtained, then the second green body is screened after being crushed in sequence, and a second mixture is obtained; and sequentially carrying out primary sintering, cooling, secondary sintering and cooling on the mixture II to obtain the zirconium oxide coating material. A small amount of zirconium powder is added to inhibit abnormal growth of zirconium oxide grains, and the optimized preparation process is matched, so that the density of the prepared zirconium oxide coating material is close to the theoretical density, the phenomena of large air release amount and splashing in the melting process can be effectively avoided, the coating density is improved, and the coating quality is further improved.

Description

Technical Field

[0001] The present invention belongs to the field of coating materials, and relates to a target for coating, in particular to a zirconia coating material and a preparation method thereof. Background Art

[0002] Zirconia has a relatively high refractive index, low absorption rate in the range from near ultraviolet to mid-infrared, and the zirconia film has high hardness, good thermal stability and mechanical properties, and is widely used in various optical coating fields.

[0003] The density of zirconia particles is relatively low. When using zirconia particles for evaporation coating, splashing is likely to occur, resulting in uneven film layers and affecting product quality. Summary of the Invention

[0004] In view of the defects and deficiencies existing in the prior art, on the one hand, the present invention provides a preparation method of a zirconia coating material; on the other hand, the present invention provides a zirconia coating material.

[0005] On the one hand, the present invention provides a preparation method of a zirconia coating material, comprising the following steps: Step 1, ball-milling and mixing zirconia powder and zirconium powder to obtain a mixed powder, and then adding pure water to the mixed powder to obtain a first mixture; Step 2, cold-pressing the first mixture to obtain a first green body, and then cold isostatic pressing the first green body to obtain a second green body; Step 3, crushing and screening the second green body to obtain a second mixture; Step 4, sintering the second mixture once in air, cooling to obtain an intermediate product; Step 5, transferring the intermediate product to a vacuum atmosphere for secondary sintering, cooling to obtain the zirconia coating material; In Step 1, the molar ratio of zirconia powder to zirconium powder is 97.5-99:1-2.5.

[0006] Preferably, in Step 1, the mass ratio of the mixed powder to pure water is 9-9.5:0.5-1.

[0007] Preferably, in Step 1, after adding pure water to the mixed powder, it is left standing for 10-20 h to obtain a first mixture.

[0008] Preferably, in Step 1, the ball-milling speed is 300-500 r / min, and the ball-milling time is 10-15 h.

[0009] Preferably, in Step 2, during cold-pressing, the pressure is 20-50 MPa, and the pressing time is 3-5 s.

[0010] Preferably, in step 2, during cold isostatic pressing, the pressure is 100 - 200 MPa and the pressure holding time is 180 - 300 s.

[0011] Preferably, in step 3, the particle size of the second mixture is 1 - 3 mm.

[0012] Preferably, in step 4, during the first sintering, the sintering temperature is 900 - 1200 °C, the sintering time is 2 - 4 h; the heating rate is 3 - 5 °C / min.

[0013] Preferably, in step 5, during the second sintering, heat up to 1200 - 1400 °C at a heating rate of 2 - 4 °C / min, and then heat up to 1700 - 1900 °C at 5 - 9 °C, and hold for 2 - 4 h.

[0014] In a second aspect, a zirconia coating material is obtained by the above preparation method.

[0015] Compared with the prior art, the present invention has at least one of the following beneficial effects: (1) When preparing the zirconia coating material, adding a small amount of zirconium powder inhibits the abnormal growth of zirconia grains. Combined with the optimized preparation process, the density of the obtained zirconia coating material is close to the theoretical density, which can effectively avoid the large gas evolution and sputtering phenomena during the pre-melting process, improve the coating density, and thus improve the coating quality; at the same time, by optimizing the preparation process, no organic binder needs to be added, which can effectively save the debinding time, improve efficiency, and reduce production costs.

[0016] (2) When the present invention prepares the zirconia coating material, a one-stage sintering is adopted during high-temperature vacuum sintering, and no heat preservation section is set except for heat preservation at the highest sintering temperature. By adjusting the heating rate, the formation of a sintered compact is promoted. Reducing the heating rate at the low-temperature stage is beneficial to the discharge of moisture inside the particles and the growth of sintering necks, and increasing the heating rate at the high-temperature stage is beneficial to crystal growth, preventing its abnormal growth and saving the preparation time. Description of the Drawings

[0017] Figure 1 It is a physical diagram of the zirconia coating material obtained in Example 1. Detailed Embodiments

[0018] The present invention provides the following specific technical solutions.

[0019] In a first aspect, the present invention provides a preparation method of a zirconia coating material; in a second aspect, the present invention provides a zirconia coating material.

[0020] In a first aspect, the present invention provides a preparation method of a zirconia coating material, including the following steps: Step 1: Ball-mill zirconia powder and zircon powder to obtain a mixed powder, and then add pure water to the mixed powder to obtain a first mixture. Step 2: Cold-press the first mixture to obtain a first green body, and then cold isostatically press the first green body to obtain a second green body. Step 3: Crush and screen the second green body to obtain a second mixture. Step 4: Sinter the second mixture in air for the first time, and then cool it to obtain an intermediate product. Step 5: Transfer the intermediate product to a vacuum atmosphere for secondary sintering, and then cool it to obtain the zirconia coating material. In Step 1, the molar ratio of zirconia powder to zircon powder is 97.5 - 99:1 - 2.5.

[0021] The inventor found through research that when preparing the zirconia coating material at high temperature, the high temperature will cause abnormal grain growth of zirconia, affecting the density and hardness of zirconia. In the present invention, by adopting a high-temperature sintering process and adding zircon powder, a strong driving force can be provided for the sintering of zirconia particles without causing abnormal grain growth, so that the density of the prepared zirconia coating material is close to the theoretical density, effectively avoiding the large gas evolution and sputtering phenomena during the pre-melting process during coating, improving the coating density, and further improving the coating quality. At the same time, by optimizing the preparation process, no organic binder needs to be added, effectively saving the debinding time, improving the efficiency, and reducing the production cost.

[0022] Preferably, in Step 1, the mass ratio of the mixed powder to pure water is 9 - 9.5:0.5 - 1.

[0023] Preferably, in Step 1, after adding pure water to the mixed powder, let it stand for 10 - 20 h to obtain a first mixture.

[0024] Letting it stand and stuffy can make the powder and water fully contact, improve the adhesion between powders, and facilitate forming.

[0025] Preferably, in Step 1, the ball-milling speed is 300 - 500 r / min, and the ball-milling time is 10 - 15 h.

[0026] Preferably, in Step 2, during cold pressing, the pressure is 20 - 50 MPa, and the pressing time is 3 - 5 s.

[0027] Preferably, in Step 2, during cold isostatic pressing, the pressure is 100 - 200 MPa, and the pressure holding time is 180 - 300 s.

[0028] Preferably, in Step 3, the particle size of the second mixture is 1 - 3 mm.

[0029] Preferably, in Step 4, during the first sintering, the sintering temperature is 900 - 1200 °C, the sintering time is 2 - 4 h; the heating rate is 3 - 5 °C / min.

[0030] Preferably, in step 5, during the secondary sintering, the temperature is raised to 1200 - 1400 °C at a heating rate of 2 - 4 °C / min, and then raised to 1700 - 1900 °C at a rate of 5 - 9 °C and held for 2 - 4 h.

[0031] The inventors found through research that when preparing the zirconia coating material, during high-temperature vacuum sintering, one-stage sintering is adopted. Except for holding at the highest sintering temperature, no holding section is set during the process. By adjusting the heating rate, the formation of a sintered dense body is promoted. Reducing the heating rate in the low-temperature stage is beneficial to the discharge of moisture inside the particles and the growth of sintering necks. Increasing the heating rate in the high-temperature stage is beneficial to crystal growth, preventing its abnormal growth and saving preparation time.

[0032] In a second aspect, a zirconia coating material is obtained by the above preparation method.

[0033] To make the technical problems, technical solutions, and technical advantages to be solved by the present invention clearer, the following will be described in detail with specific examples, but the protection scope of the present invention is not limited to the following specific embodiments.

[0034] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0035] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0036] Example 1: A preparation method of a zirconia coating material includes the following steps: In step 1, zirconia powder and zirconium powder are ball-milled and mixed to obtain a mixed powder. The molar ratio of zirconium powder to zirconia powder is 1:99. Ball milling is carried out using a pot mill with a material-to-ball ratio of 1:3, a ball milling speed of 315 r / min, and a time of 12 h. Then, pure water is added to the mixed powder and left to soak for 12 h to obtain a first mixture. The mass ratio of the mixed powder to pure water is 9:1; In step 2, the first mixture is cold-pressed at a pressure of 20 MPa for 3 s to obtain a first green body with a size of D27.5*8 mm; then, the first green body is cold isostatically pressed at 150 MPa for 180 s to obtain a second green body; In step 3, the second green body is crushed and screened to obtain a second mixture with a particle size of 1 - 3 mm; In step 4, the second mixture is transferred to a crucible and heated to 1000 °C at a rate of 4 °C / min under normal atmospheric pressure of air, held for 2 h, and then cooled to obtain an intermediate product; Step 5: Place the intermediate product in a graphite crucible. In a vacuum graphite furnace, first heat it at a rate of 2.5 °C / min to 1300 °C, and then heat it at a rate of 5.5 °C / min to 1750 °C. Keep it at this temperature for 2 h for secondary sintering. After cooling with the furnace to room temperature, a zirconia coating material is obtained.

[0037] Figure 1 Fig. [0000100] is a physical picture of the zirconia coating material prepared in Example 1. It can be seen from Figure 1 that there is no slag falling in the zirconia coating material prepared by the preparation method provided by the present invention, which can prove from the side that the density of the zirconia coating material is relatively high.

[0038] Comparative Example 1: A preparation method of a zirconia coating material includes the following steps: Step 1: Ball mill zirconia powder. Use a pot mill for ball milling. The material-to-ball ratio is 1:3, the ball milling speed is 315 r / min, and the time is 12 h. Then add pure water to the mixed powder and let it stand for 12 h to obtain Material 1. Step 2: Cold press Material 1 at a pressure of 20 MPa for 3 s to obtain a green compact 1 with a size of D27.5*8 mm; then cold isostatically press green compact 1 at 150 MPa for 180 s to obtain a green compact 2. Step 3: After crushing, screen green compact 2 to obtain a mixed material 2, and the particle size of the mixed material 2 is 1 - 3 mm. Step 4: Transfer the mixed material 2 to a crucible. Under the condition of normal air pressure, heat it at a rate of 4 °C / min to 1000 °C, keep it at this temperature for 2 h, and then cool it to obtain an intermediate product. Step 5: Place the intermediate product in a graphite crucible. In a vacuum graphite furnace, first heat it at a rate of 2.5 °C / min to 1300 °C, and then heat it at a rate of 5.5 °C / min to 1750 °C. Keep it at this temperature for 2 h for secondary sintering. After cooling with the furnace to room temperature, a zirconia coating material is obtained.

[0039] Comparative Example 2: A preparation method of a zirconia coating material includes the following steps: Step 1: Ball mill a mixture of zirconia powder and zirconium powder to obtain a mixed powder. The molar ratio of zirconium powder to zirconia powder is 1:99. Use a pot mill for ball milling. The material-to-ball ratio is 1:3, the ball milling speed is 315 r / min, and the time is 12 h. Then add pure water to the mixed powder and let it stand for 12 h to obtain a mixed material 1. The mass ratio of the mixed powder to pure water is 9:1. Step 2: Cold press the mixed material 1 at a pressure of 20 MPa for 3 s to obtain a green compact 1 with a size of D27.5*8 mm; then cold isostatically press green compact 1 at 150 MPa for 180 s to obtain a green compact 2. Step 3, screening the green body 2 after crushing to obtain a mixture 2, wherein the particle size of the mixture 2 is 1-3 mm; Step 4, transfer the mixed material 2 to a vacuum graphite furnace, first heat it to 1300°C at a rate of 2.5°C / min, then heat it to 1750°C at a rate of 5.5°C / min, keep it warm for 2 hours for secondary sintering, and cool it to room temperature in the furnace to obtain the zirconium oxide coating material.

[0040] Comparative Example 3: A method for preparing a zirconium oxide coating material is different from that of Example 1 in that, in step 1, the molar ratio of zirconium powder to zirconium oxide powder is 7:3.

[0041] Embodiment 2: A method for preparing a zirconium oxide coating material comprises the following steps: Step 1, ball milling mixed zirconium oxide powder and zirconium powder to obtain a mixed powder, the molar ratio of zirconium powder to zirconium oxide powder is 2.5:97.5, using a pot mill for ball milling, the material-ball ratio is 1:3, the ball milling speed is 315r / min, the time is 10h, and then pure water is added to the mixed powder and the mixture is placed for 12h to obtain a mixed material 1, the mass ratio of the mixed powder to pure water is 9.5:0.5; Step 2, cold pressing the mixture at a pressure of 20 MPa for 4 seconds to obtain a green body 1 with a size of D27.5*8 mm; then cold isostatic pressing the green body at 100 MPa for 250 seconds to obtain a green body 2; Step 3, screening the green body 2 after crushing to obtain a mixture 2, wherein the particle size of the mixture 2 is 1-3 mm; Step 4, transferring the mixed material 2 into a crucible, heating the mixture to 900° C. at a rate of 3° C. / min under normal air pressure, keeping the temperature for 3 h, and then cooling the mixture to obtain an intermediate product; Step 5, placing the intermediate product in a graphite sagger, heating it to 1200°C at a rate of 3°C / min in a vacuum graphite furnace, then heating it to 1700°C at a rate of 6°C / min, keeping it warm for 2 hours for secondary sintering, and cooling it to room temperature in the furnace to obtain a zirconium oxide coating material.

[0042] Embodiment 3: A method for preparing a zirconium oxide coating material comprises the following steps: Step 1, ball milling zirconium oxide powder and zirconium powder to obtain a mixed powder, the molar ratio of zirconium powder to zirconium oxide powder is 1.5:98.5, using a pot mill for ball milling, the material-ball ratio is 1:3, the ball milling speed is 315r / min, the time is 15h, and then pure water is added to the mixed powder and the mixture is placed for 12h to obtain a mixed material 1, the mass ratio of the mixed powder to pure water is 9.3:0.7; Step 2: Cold press the first mixture at a pressure of 30 MPa for 5 s to obtain the first green body with a size of D27.5*8 mm; then perform cold isostatic pressing on the first green body at 200 MPa for 300 s to obtain the second green body; Step 3: Crush and screen the second green body to obtain the second mixture, and the particle size of the second mixture is 3 mm; Step 4: Transfer the second mixture to a crucible, heat it from room temperature to 1200 °C at a rate of 5 °C / min under normal atmospheric pressure of air, hold for 4 h, and then cool to obtain the intermediate product; Step 5: Place the intermediate product in a graphite crucible, first heat it from room temperature to 1400 °C at a rate of 2 °C / min in a vacuum graphite furnace, and then heat it to 1800 °C at a rate of 5 °C / min, hold for 4 h for secondary sintering, and cool it to room temperature with the furnace to obtain the zirconia coating material.

[0043] The theoretical density of zirconia is 5.98 g / cm 3 ; The relative density of the zirconia coating materials prepared in Examples 1-3 and Comparative Examples 1-3 was calculated by measuring their density through the wax-sealing method, and the zirconia coating materials prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to coating tests. The test data and phenomena are shown in Table 1.

[0044] Table 1 Density, relative density, coating phenomenon and film layer quality of the zirconia coating materials prepared in Examples 1-3 and Comparative Examples 1-3 By comparing the zirconia coating materials prepared in Example 1 and Comparative Example 1, it can be seen that by adding a small amount of zirconium powder in Example 1, the density of the zirconia coating material can be increased, which proves from the side that adding a small amount of zirconium powder can inhibit the abnormal crystal growth of zirconia at high temperature, and can reduce the gas evolution during melting and improve the coating quality.

[0045] By comparing the zirconia coating materials prepared in Example 1 and Comparative Example 2, it can be seen that in the preparation method provided by the present invention, the density of the zirconia coating material prepared by two-stage roasting is higher, there is no splashing during melting, and the coating is uniform.

[0046] By comparing the zirconia coating materials prepared in Example 1 and Comparative Example 3, it can be seen that when preparing the zirconia coating material, if an excessive amount of zirconium powder is added, the density of the zirconia coating material will decrease, the gas evolution during melting will increase, splashing will occur, resulting in uneven coating. The inventor speculates that the reason for the above situation may be that too high a proportion of zirconium powder will result in more low-valent zirconia, excessive reduction makes the composition of the zirconia coating material impure, and the coating process is uncontrollable, affecting the film layer performance.

[0047] The above-described embodiments are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope of the present invention, according to the technical solution and its concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a zirconium oxide coating material, characterized in that: The steps include: Step 1, ball milling and mixing zirconium oxide powder and zirconium powder to obtain mixed powder, and then adding pure water to the mixed powder to obtain a mixture 1; Step 2, cold pressing the mixed material 1 to obtain a green body 1, and then cold isostatically pressing the green body 1 to obtain a green body 2; Step 3, screening the green body 2 after crushing to obtain mixed material 2; Step 4, sintering the mixed material 2 in air once, cooling, and obtaining an intermediate product; Step 5, transferring the intermediate product to a vacuum atmosphere for secondary sintering and cooling to obtain the zirconium oxide coating material; In step 1, the molar ratio of zirconium oxide powder to zirconium powder is 97.5-99:1-2.

5.

2. The method for preparing the zirconium oxide coating material according to claim 1, characterized in that: In step 2, during cold pressing, the pressure is 20-50 MPa, and the pressing time is 3-5 s; during cold isostatic pressing, the pressure is 100-200 MPa, and the holding time is 180-300 s.

3. The method for preparing the zirconium oxide coating material according to claim 1, characterized in that: In step 3, the particle size of the mixture 2 is 1-3 mm.

4. The method for preparing the zirconium oxide coating material according to claim 1, characterized in that: In step 4, during the primary sintering, the sintering temperature is 900-1200°C, the sintering time is 2-4h, and the heating rate is 3-5°C / min.

5. The method for preparing the zirconium oxide coating material according to claim 1, characterized in that: In step 5, during the secondary sintering, the temperature is raised to 1200-1400°C at a heating rate of 3-5°C / min, then raised to 1700-1900°C at a heating rate of 6-10°C, and kept at this temperature for 2-4 hours.

6. The method for preparing the zirconium oxide coating material according to claim 1, characterized in that: In step 1, the mass ratio of the mixed powder to pure water is 9~9.5:0.5~1.

7. The method for preparing the zirconium oxide coating material according to claim 1, characterized in that: In step 1, pure water is added to the mixed powder and the mixture is allowed to stand for 10 to 20 hours to obtain a mixed material 1.

8. The method for preparing the zirconium oxide coating material according to claim 1, characterized in that: In step 1, the ball milling speed is 300-500 r / min, and the ball milling time is 10-15 h.

9. A zirconium oxide coating material, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

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