Preparation method of zirconia ceramic with gradient layered structure

Abstract

The invention discloses a preparation method of zirconia ceramic with a gradient layered structure, which comprises the following steps: firstly, screening out a surface modifier capable of effectively reducing the refractive index difference of zirconia ceramic particles, and increasing the curing depth of the surface modifier; the applicant compares rheological properties, dynamic stability, wettability and photocuring properties of the zirconium oxide ceramic slurry before and after modification, and reveals a photocuring forming mechanism of the modified zirconium oxide ceramic slurry. By utilizing the mechanism, the rheological property, the dynamic stability, the wettability and the photocuring property of the zirconium oxide ceramic slurry are improved, and the zirconium oxide ceramic with high density, hardness and fracture toughness can be prepared.

Description

Technical Field

[0001] The invention relates to the technical field of zirconia ceramic forming, in particular to a method for preparing zirconia ceramic with a gradient layered structure. Background Art

[0002] Zirconia ceramics have high hardness, low thermal expansion coefficient and high fracture toughness, making zirconia ceramic components such as exhaust valves, valve springs, bucket tappets, rocker pads, etc. widely used in the industrial field. Zirconia ceramics have high wear resistance and thermal shock resistance, which makes it widely used in the field of mechanical processing. Due to its excellent thermoelectric properties and corrosion resistance, it has also been widely used in thermal conductors, valves, catalyst carriers, spark plugs and other motor fields. In addition, its excellent comprehensive physical properties make it a candidate material for high-temperature gas-cooled reactors and nuclear fusion reactors. At the same time, the performance of the zirconia ceramic sandwich structure as a missile radome directly affects the guidance performance of the missile, among which the radome wall structure with wide-band and high wave transmission performance is mainly a sandwich structure.

[0003] However, the traditional mechanical processing method for manufacturing complex ceramic parts has problems such as long cycle, high processing cost, and heavy dependence on molds. In comparison, additive manufacturing technology can realize the preparation of complex ceramic parts without molds. Among them, photocuring has incomparable advantages in the preparation of high-precision and complex ceramic parts, and has been applied to the fields of medicine and biology (such as tooth and bone repair), microtechnology (such as sensors, piezoelectric elements and photonic crystals) and mechanical heat-resistant structures. Photocuring forming technology is a slurry mixed with photosensitive resin and ceramic powder, which is polymerized by ultraviolet light beam irradiation to form a solidified body. However, there are relatively few reports on photocuring forming technology for oxide ceramics, especially gray or dark ceramics. This is because zirconia ceramics have high ultraviolet light absorption, high refractive index, strong scattering, low curing depth of slurry, and are difficult to form. At the same time, the strong covalent bond characteristics of oxide ceramics also make it difficult to sinter and densify. Only Huang et al. oxidized the zirconium oxide powder to form a nano-SiO2 film on its surface, reducing the refractive index difference with the premixed liquid and preparing Si3N4 ceramics with a density of 97.84%. However, the presence of SiO2 can lead to a significant decrease in its mechanical properties. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the above-mentioned prior art: to provide a method for preparing a gradient layered structure zirconia ceramic, which effectively improves the rheological properties, dynamic stability, wetting properties and photocuring properties of the zirconia ceramic slurry, and can prepare zirconia ceramics with high density, hardness and fracture toughness.

[0005] The technical solution of the present invention is as follows: A method for preparing a gradient layered structure zirconia ceramic comprises the following specific steps:

[0006] 1) Weighing a surface modifier and zirconia powder, mixing and ball milling for 10-20 minutes, and then drying to obtain modified zirconia powder; wherein, by weight: 2-5 parts of surface modifier, 60-100 parts of zirconia powder;

[0007] 2) Weighing a diluent and an initiator, mixing them and stirring them at a high speed in vacuum to obtain a premixed solution, wherein the stirring speed is 1000-1350 r / min and the stirring time is 10-30 min; wherein, by weight: 30-100 parts of diluent and 1-10 parts of initiator;

[0008] 3) stirring and mixing the modified zirconium oxide powder prepared in step 1) and the premixed liquid prepared in step 2) to prepare at least two light-cured zirconium oxide slurries with different solid contents, respectively, wherein the stirring speed is 2000-2300 r / min;

[0009] 4) performing periodic lamination curing on the at least two solid content photocurable zirconium oxide slurries prepared in step 3) in descending or ascending order of solid content on a photocuring machine to form a gradient layered structure blank cured by layers of zirconium oxide slurries with different solid contents, wherein the exposure time of each layer is 3-8s, the thickness of each layer is 0.03-0.06mm, and the total number of layers is determined according to the total thickness requirement of the gradient layered structure blank; for example, there are three solid content photocurable zirconium oxide slurries of 1vol.%, 2vol.%, and 3vol.%, which are periodically laminated and cured from the lower layer to the upper layer in ascending order of solid content to form a material including 7 cured layers, and the layered structure composition is 1vol.%-2vol.%-3vol.%-1vol.%-2vol.%-3vol.%-1vol.%;

[0010] 5) The obtained gradient layered structure green body is degreased and sintered in sequence to obtain a gradient layered structure zirconia ceramic; wherein the degreasing temperature is 500-800°C, and the heating rate of the degreasing temperature is 0.1-0.5°C / min; the sintering pressure is 0.1-0.2MPa, the sintering temperature is 1600-1700°C, the sintering heating rate is 1-5°C / min, and the sintering time is 18-24h.

[0011] As a preferred solution of the preparation method of the gradient layered structure zirconia ceramic, the method comprises the following specific steps:

[0012] 1) Weighing a surface modifier and zirconia powder, mixing and ball milling for 10-20 minutes, and then drying to obtain modified zirconia powder; wherein, by weight: 2-5 parts of surface modifier, 60-100 parts of zirconia powder;

[0013] 2) Weighing a diluent and an initiator, mixing them and stirring them at a high speed in vacuum to obtain a premixed solution, wherein the stirring speed is 1000-1350 r / min and the stirring time is 10-30 min; wherein, by weight: 30-100 parts of diluent and 1-10 parts of initiator;

[0014] 3) The modified zirconium oxide powder prepared in step 1) is stirred and mixed with the premixed liquid prepared in step 2) to prepare light-cured zirconium oxide slurries with two solid contents of 25-35 vol.% and 40-45 vol.%, respectively, and the stirring speed is 2000-2300 r / min;

[0015] 4) performing periodic stacking and curing of the two solid content photocurable zirconium oxide slurries of 25-35 vol.% and 40-45 vol.% prepared in step 3) in a 405 nm light curing machine in a decreasing or increasing order of solid content, respectively, to form a gradient layered structure blank cured by two solid content zirconium oxide slurry layers, wherein the exposure time of each layer is 3-8 s, the thickness of each layer is 0.03-0.06 mm, and the total number of layers is determined according to the total thickness requirement of the gradient layered structure blank;

[0016] 5) The obtained gradient layered structure green body is degreased and sintered in sequence to obtain a gradient layered structure zirconia ceramic; wherein the degreasing temperature is 500-800°C, and the heating rate of the degreasing temperature is 0.1-0.5°C / min; the sintering pressure is 0.1-0.2MPa, the sintering temperature is 1700-1800°C, the sintering heating rate is 1-5°C / min, and the sintering time is 18-24h.

[0017] As an optimization, the surface modifier is one or more of KH550, KH560, and KH570.

[0018] As an optimization, the diluent is one or more of HEA, HDDA, and TMPTA.

[0019] As an optimization, the initiator is one or more of TPO, 819, and 184.

[0020] As an optimization, the particle size of the zirconium oxide powder is 200-800 nm.

[0021] As an optimization, in step 5), the debinding temperature is 500°C, and the heating rate of the debinding temperature is 0.1°C / min; the sintering pressure is 0.1MPa, the sintering temperature is 1650°C, the sintering heating rate is 1°C / min, and the sintering time is 24h.

[0022] The beneficial effects of the present invention are as follows: the present invention first screens out a surface modifier that can effectively reduce the refractive index difference of zirconia ceramic particles and increase their curing depth. The applicant compares the rheological properties, dynamic stability, wettability and photocuring properties of zirconia ceramic slurry before and after modification, and reveals the photocuring forming mechanism of modified zirconia ceramic slurry. The results show that the Y group in the surface modifier is an epoxy group (-CH(O)CH-), which will undergo ring opening under certain temperature and pH conditions and react with the hydroxyl group (-OH) on the surface of the copolymer to form an ether covalent bond (ROR). The surface modifier is bridged with the acrylic premix, which can make the dispersion effect of submicron zirconia particles in the premix more significant, thereby significantly improving the rheological properties and dynamic stability of the ceramic slurry. At the same time, the ether covalent bond formed between the surface-modified zirconia particles and the diluent reduces the surface tension of the ceramic slurry and improves the wettability of the ceramic slurry to the cured layer. Finally, a thin EA shell is formed on the surface of the zirconia particles, which significantly reduces the refractive index difference between the ceramic powder and the premix, and improves the photocuring performance of the ceramic slurry. Then, by using this as raw material and combining it with zirconium oxide slurry layers with different solid contents to solidify into a gradient layered structure, zirconium oxide ceramics with high density, hardness and fracture toughness can be prepared. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below with specific examples, but the present invention is not limited to the following specific examples.

[0024] Example

[0025] The gradient layered structure zirconia ceramics were prepared according to the following specific steps:

[0026] 1) Weighing silane coupling agent KH570 and zirconium oxide powder with a particle size of 200 nm, mixing and ball milling for 20 minutes, and then drying in a drying oven at a drying temperature of 30° C. for a drying time of 48 hours to obtain modified zirconium oxide powder; wherein, by weight: 3 parts of silane coupling agent KH570 and 100 parts of zirconium oxide powder;

[0027] 2) Weighing the diluent HDDA and the initiator TPO, mixing them and stirring them at a high speed in vacuum to obtain a premixed solution, wherein the stirring speed is 1350 r / min and the stirring time is 30 min; wherein, by weight: 40 parts of the diluent HDDA and 4 parts of the initiator TPO;

[0028] 3) The modified zirconium oxide powder prepared in step 1) and the premixed liquid prepared in step 2) were stirred and mixed to prepare light-cured zirconium oxide slurries with two solid contents of 25 vol.% and 45 vol.%, respectively, and the stirring speed was 2300 r / min;

[0029] 4) on a 405 nm light curing machine, the two solid content light-cured zirconium oxide slurries of 25 vol.% and 45 vol.% prepared in step 3) are respectively cured in ascending order of solid content from lower layer to upper layer to form a material including 7 cured layers, wherein the slurry concentration of the gradient cured layers is 25 vol.%-45 vol.%-25 vol.%-45 vol.%-25 vol.%-45 vol.%-25 vol.% from lower layer to upper layer, respectively, to form a gradient layered structure blank cured by zirconia slurry layers with different solid contents, the exposure time of each layer is 5 s, and the thickness of each layer is 0.05 mm;

[0030] 5) The obtained gradient layered structure green body is degreased and sintered in sequence to obtain a gradient layered structure zirconia ceramic; wherein the degreasing temperature is 500°C, and the heating rate of the degreasing temperature is 0.1°C / min; the sintering pressure is 0.1MPa, the sintering temperature is 1650°C, the sintering heating rate is 1°C / min, and the sintering time is 24h.

[0031] The density, microhardness and fracture toughness of the gradient layered zirconia ceramics prepared in this embodiment were measured to be 6.10 g / cm 3 , 14.43±0.2GPa and 795±2MPa·m 1 / 2 .

[0032] The above are only examples of the features of the present invention and do not constitute any limitation on the protection scope of the present invention. Any technical solution formed by equivalent exchange or equivalent replacement falls within the protection scope of the present invention.

Claims

1. A method for preparing a gradient layered structure zirconia ceramic, characterized in that: The specific steps include: 1) Weighing a surface modifier and zirconia powder, mixing and ball milling for 10-20 minutes, and then drying to obtain modified zirconia powder; wherein, by weight: 2-5 parts of surface modifier, 60-100 parts of zirconia powder; 2) Weighing a diluent and an initiator, mixing them and stirring them at a high speed in vacuum to obtain a premixed solution, wherein the stirring speed is 1000-1350 r / min and the stirring time is 10-30 min; wherein, by weight: 30-100 parts of diluent and 1-10 parts of initiator; 3) stirring and mixing the modified zirconium oxide powder prepared in step 1) and the premixed liquid prepared in step 2) to prepare at least two light-cured zirconium oxide slurries with different solid contents, respectively, wherein the stirring speed is 2000-2300 r / min; 4) performing periodic lamination curing on the at least two solid content photocurable zirconium oxide slurries prepared in step 3) in a light curing machine in a decreasing or increasing order of solid content to form a gradient layered structure blank cured by layers of zirconium oxide slurries with different solid contents, wherein the exposure time of each layer is 3-8s, the thickness of each layer is 0.03-0.06mm, and the total number of layers is determined according to the total thickness requirement of the gradient layered structure blank; 5) The obtained gradient layered structure green body is degreased and sintered in sequence to obtain a gradient layered structure zirconia ceramic; wherein the degreasing temperature is 500-800°C, and the heating rate of the degreasing temperature is 0.1-0.5°C / min; the sintering pressure is 0.1-0.2MPa, the sintering temperature is 1600-1700°C, the sintering heating rate is 1-5°C / min, and the sintering time is 18-24h.

2. The method for preparing the gradient layered structure zirconia ceramic according to claim 1, characterized in that: The specific steps include: 1) Weighing a surface modifier and zirconia powder, mixing and ball milling for 10-20 minutes, and then drying to obtain modified zirconia powder; wherein, by weight: 2-5 parts of surface modifier, 60-100 parts of zirconia powder; 2) Weighing a diluent and an initiator, mixing them and stirring them at a high speed in vacuum to obtain a premixed solution, wherein the stirring speed is 1000-1350 r / min and the stirring time is 10-30 min; wherein, by weight: 30-100 parts of diluent and 1-10 parts of initiator; 3) The modified zirconium oxide powder prepared in step 1) is stirred and mixed with the premixed liquid prepared in step 2) to prepare light-cured zirconium oxide slurries with two solid contents of 25-35 vol.% and 40-45 vol.%, respectively, and the stirring speed is 2000-2300 r / min; 4) performing periodic stacking and curing of the two solid content photocurable zirconium oxide slurries of 25-35 vol.% and 40-45 vol.% prepared in step 3) in a 405 nm light curing machine in a decreasing or increasing order of solid content, respectively, to form a gradient layered structure blank cured by two solid content zirconium oxide slurry layers, wherein the exposure time of each layer is 3-8 s, the thickness of each layer is 0.03-0.06 mm, and the total number of layers is determined according to the total thickness requirement of the gradient layered structure blank; 5) The obtained gradient layered structure green body is degreased and sintered in sequence to obtain a gradient layered structure zirconia ceramic; wherein the degreasing temperature is 500-800°C, and the heating rate of the degreasing temperature is 0.1-0.5°C / min; the sintering pressure is 0.1-0.2MPa, the sintering temperature is 1600-1700°C, the sintering heating rate is 1-5°C / min, and the sintering time is 18-24h.

3. The method for preparing the gradient layered structure zirconia ceramic according to claim 1 or 2, characterized in that: The surface modifier is one or more of KH550, KH560 and KH570.

4. The method for preparing the gradient layered structure zirconia ceramic according to claim 1 or 2, characterized in that: The diluent is one or more of HEA, HDDA and TMPTA.

5. The method for preparing the gradient layered structure zirconia ceramic according to claim 1 or 2, characterized in that: The initiator is one or more of TPO, 819, and 184.

6. The method for preparing the gradient layered structure zirconia ceramic according to claim 1 or 2, characterized in that: The particle size of the zirconium oxide powder is 200-800 nm.

7. The method for preparing the gradient layered zirconia ceramic according to claim 1 or 2, characterized in that: In step 5), the degreasing temperature is 500° C., and the heating rate of the degreasing temperature is 0.1° C. / min.

8. The method for preparing the gradient layered zirconia ceramic according to claim 1 or 2, characterized in that: In step 5), the sintering pressure is 0.1 MPa, the sintering temperature is 1650° C., the sintering heating rate is 1° C. / min, and the sintering time is 24 h.