Black zirconia ceramic and method for manufacturing the same

Abstract

A black zirconia ceramic is composed of a colorant and a base material, characterized in that the mass percentage of the colorant is 2.0-5.0%, and the mass percentage of the base material is 95.0-98.0%; the colorant is composed of CoO, NiO and Fe2O3, and the mass ratio of CoO, NiO and Fe2O3 in the colorant is CoO:NiO:Fe2O3=0.5-1:14-18:32-36; and the base material is 3mol% yttria partially stabilized zirconia. The application further provides a preparation method of the black zirconia ceramic. The black zirconia ceramic has uniform and stable color, excellent mechanical properties, and relatively low preparation cost.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, specifically to a black zirconia ceramic and its preparation method. Background Technology

[0002] With the rapid development of internet technology, smart terminal devices have experienced explosive growth, leading to increasingly higher demands for the performance and appearance of their protective materials. Currently, the mainstream protective materials for smart terminals on the market are mainly metal and plastic: although metal materials have good heat dissipation performance, their high thermal conductivity can easily cause the device to overheat, affecting its use, and their surfaces often rely on anodizing or multi-color paint spraying, making them prone to paint peeling after impact, seriously affecting their aesthetics; plastic materials, on the other hand, have inherent defects such as poor heat dissipation and low dielectric constant, limiting their application range.

[0003] Ceramic materials, with their excellent mechanical strength, moderate thermal conductivity, good dielectric properties, and controllable appearance and color, have become an ideal choice for protective materials in smart terminals. Among them, black zirconia ceramics are highly favored by the market due to their stable and beautiful appearance. Existing black zirconia ceramics are mostly prepared by doping with coloring ions. Although this achieves a good black color, it generally suffers from the following problems: First, the colorant system is singular or the ratio is unreasonable, resulting in poor color stability and easy color deviation and fading; second, the composite ceramic structure is complex, impairing mechanical properties, and the bending strength is difficult to meet the requirements of high-end applications; third, the high cost of colorants or excessively high doping ratios increase the preparation cost, hindering industrialization. Therefore, developing a black zirconia ceramic that combines high mechanical properties, excellent color stability, and relatively low cost is of significant practical importance. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a black zirconia ceramic and its preparation method. This black zirconia ceramic has a uniform and stable color, excellent mechanical properties, and relatively low preparation cost. The technical solution adopted is as follows:

[0005] A black zirconia ceramic, composed of a colorant and a matrix material, is characterized in that: the mass percentage of the colorant is 2.0-5.0%, and the mass percentage of the matrix material is 95.0-98.0%; the colorant is composed of CoO, NiO, and Fe2O3, and the mass ratio of CoO, NiO, and Fe2O3 in the colorant is CoO:NiO:Fe2O3=0.5-1:14-18:32-36; the matrix material is 3 mol% yttrium-stabilized zirconia.

[0006] The key to this invention lies in using three metal oxides, CoO, NiO, and Fe2O3, as composite colorants, which are pretreated and then doped into 3 mol% yttrium oxide partially stabilized zirconium oxide to prepare black zirconium oxide ceramics (for example, black zirconium oxide ceramics are prepared by high-temperature solid-state method).

[0007] Using 3 mol% yttrium oxide partially stabilized zirconium oxide as the matrix material, it has excellent mechanical properties and chemical stability, and can provide good matrix support for ceramics.

[0008] In the preferred embodiment, the mass percentage of the colorant in the aforementioned black zirconia ceramic is 2.5%, and the mass percentage of the matrix material is 97.5%.

[0009] In the preferred embodiment, the mass ratio of CoO, NiO and Fe2O3 in the above-mentioned pigment is CoO:NiO:Fe2O3 = 0.8:14-18:32-36.

[0010] This invention also provides a method for preparing the above-mentioned black zirconia ceramic, characterized by comprising the following steps in sequence:

[0011] (1) Metal oxide pretreatment: Weigh the metal oxides CoO, NiO and Fe2O3 according to the mass ratio CoO:NiO:Fe2O3=0.5-1:14-18:32-36, grind and dry them; then put the ground and dried metal oxides into a muffle furnace and calcine them at 1050-1100℃ to obtain pretreated pigments;

[0012] (2) Mixing and granulation: The pretreated pigment obtained in step (1) is mixed into 3 mol% yttrium oxide partially stabilized zirconium oxide. The mass percentage of the pretreated pigment is 2.0-5.0%, and the mass percentage of 3 mol% yttrium oxide partially stabilized zirconium oxide is 95.0-98.0% to obtain a mixture. The mixture is then ground, and a binder is added and the mixture is slurry dispersed during the grinding process to obtain a slurry with a viscosity of 500-1000 mPa·s. The slurry is then spray-granulated using a spray granulator, and the moisture content of the granules is controlled to be 0.8-1.5%, and the loose density is 1.20-1.60 g / cm³ to obtain zirconium oxide granulated powder.

[0013] (3) Molding and sintering: The zirconia granulated powder obtained in step (2) is molded into ceramic green body by dry pressing machine, and then the ceramic green body is subjected to cold isostatic pressing treatment; the ceramic green body after cold isostatic pressing treatment is placed in tunnel furnace and solid-phase sintering is carried out at 1400-1450℃ to obtain black zirconia ceramic.

[0014] Typically, the purity of the aforementioned three metal oxides, CoO, NiO, and Fe2O3, is chemically pure.

[0015] In the preferred step (1), the grinding is carried out by wet roller grinding for 3 hours, wherein the ratio of metal oxide to water is 1:3, the grinding medium is φ3mm composite zirconia grinding media, and the material is passed through a 60-mesh sieve after discharge. Particle refinement and uniform mixing are achieved by wet roller grinding.

[0016] In preferred step (1), the ground metal oxide is placed in a drying oven and dried at 120°C for 3 hours.

[0017] In step (1), calcination causes a solid-state reaction in the metal oxide, forming a stable coloring precursor, which improves the stability and coloring ability of the pigment. Preferably, the calcination time in step (1) is 3-3.5 hours.

[0018] In step (2), the pretreated pigment is mixed and ground with the zirconium oxide matrix to ensure uniform dispersion of the pigment. Preferably, in step (2), the mixture is first roller-ground for 3 hours and then transferred to a ball mill for ball milling for 1 hour.

[0019] In step (2), after adding the binder to adjust the slurry, spray granulation is carried out to obtain granulated powder with good flowability and uniform particle size, which provides a guarantee for subsequent molding.

[0020] In preferred step (2), the binder is a polyvinyl alcohol aqueous solution with a mass percentage concentration of 10%, and the solid content of the added binder is 1% of the mass of the mixture.

[0021] In preferred step (2), the inlet air temperature of the spray granulator is 250°C and the outlet air temperature is 82°C.

[0022] In preferred step (3), a dry pressing machine is used to pre-form the ceramic green body under a pressure of 20 MPa; then the ceramic green body is placed in a cold isostatic press and held under a pressure of 200 MPa for 3 minutes to further densify it.

[0023] In step (3), solid-state sintering is carried out at 1400-1450℃ to fully densify the ceramic particles, while the colorant and the matrix form a stable bond, ensuring the mechanical properties and color stability of the ceramic.

[0024] In preferred step (3), the solid-state sintering process is as follows: after placing the ceramic green body treated by cold isostatic pressing in a tunnel furnace, the temperature is raised to 1400-1450℃ at a heating rate of 5℃ / min, held for 180-240 minutes, and then cooled to room temperature at a cooling rate of 3℃ / min. After taking it out, black zirconia ceramic is obtained.

[0025] The main mechanism of action of this invention is as follows:

[0026] 1. Principle of single metal oxide coloring:

[0027] 1-1. CoO, as a transition metal oxide, can form Co in a zirconium oxide matrix. 2+ Co 3+ Isochromatic ions absorb visible light of specific wavelengths through ion transitions, exhibiting blue or bluish-black hues. However, when doped in a single color, the color is lighter and the stability is poor.

[0028] 1-2. Fe in Fe2O3 3+ Ions can form stable coloring centers in the zirconium oxide lattice, which absorb visible light and appear brownish-red or dark red, making it difficult to achieve a pure black effect when used alone.

[0029] 1-3. Ni in NiO 2+ Ions can enter the zirconium oxide lattice to form a solid solution. They absorb light through charge transfer and dd transitions, resulting in a grayish-black tone. When doped with a single element, the blackness is insufficient and a grayish tint is easily observed.

[0030] 2. The synergistic mechanism of the three metal oxides: The three metal oxides form a multi-component solid solution in the zirconium oxide matrix, and their synergistic effect is mainly reflected in the following three aspects:

[0031] 2-1. Complementary Tones: The bluish-black of CoO, the brownish-red of Fe2O3, and the grayish-black of NiO form complementary tones. By adjusting the proportions of these three, the color deviation defects of a single pigment can be offset, achieving a pure black. For example, the brownish-red of Fe2O3 can be neutralized by the bluish-black of CoO and the grayish-black of NiO, preventing ceramics from appearing reddish or grayish.

[0032] 2-2. Enhanced coloring intensity: The three metal ions form multiple coloring centers in the zirconium oxide lattice, which expands the absorption range of visible light, significantly improves the blackness and color saturation, and makes the ceramics appear bright black with a metallic luster.

[0033] 2-3. Improved stability: During the calcination process, the three metal oxides undergo a solid-phase reaction to form a stable composite oxide coloring phase (such as Co-Ni-Fe-O solid solution). This coloring has strong bonding force and is not prone to fading or color shift due to changes in the external environment. At the same time, it enhances the compatibility between the colorant and the zirconium oxide matrix, avoiding the decline in mechanical properties caused by colorant agglomeration.

[0034] Compared with existing technologies, this invention has the following advantages: 1. Excellent color performance: Through the synergistic effect of the ternary composite colorants CoO, Fe2O3, and NiO, the color tones are complementary, achieving a uniform bright black color with a metallic luster. The color remains stable after damp heat and aging tests, without any color deviation or fading. 2. Outstanding mechanical properties: Low-proportion colorant doping (2.0-5.0%) avoids damage to the matrix structure. The prepared black zirconia ceramic has a flexural strength >1500MPa and a density >6.00g / cm³, superior to existing similar products. 3. Controllable cost: Using inexpensive chemically pure metal oxides with a low doping ratio reduces raw material costs by more than 30% compared to rare earth doping schemes. 4. The process uses conventional equipment and procedures (high-temperature solid-state method combined with conventional grinding and calcination processes), without any special complex steps. The process is simple, with high production efficiency, and easy to industrialize. 5. The process is stable and reliable, with excellent product repeatability and consistency, meeting the requirements of industrial mass production.

[0035] The black zirconia ceramic of the present invention is particularly suitable for applications such as smart terminal protection materials where high requirements are placed on both color stability and mechanical properties. Detailed Implementation

[0036] I. Examples and Product Performance Testing

[0037] Example 1: In this example, a black zirconia ceramic is composed of a colorant and a matrix material, characterized in that: the mass percentage of the colorant is 2.5%, and the mass percentage of the matrix material is 97.5%; the colorant is composed of CoO, NiO and Fe2O3, and the mass ratio of CoO, NiO and Fe2O3 in the colorant is CoO:NiO:Fe2O3=0.8:16:34; the matrix material is 3 mol% yttrium partially stabilized zirconia.

[0038] In this embodiment, the preparation method of black zirconia ceramic includes the following steps in sequence:

[0039] (1) Metal oxide pretreatment: Weigh the metal oxides CoO, NiO and Fe2O3 according to the mass ratio CoO:NiO:Fe2O3=0.8:16:34, grind them and then dry them; then put the ground and dried metal oxides into a muffle furnace and calcine them at 1050℃ for 3 hours to obtain pretreated pigments;

[0040] In this step (1), the grinding is carried out by wet roller grinding for 3 hours, wherein the ratio of metal oxide to water is 1:3, the grinding medium is φ3mm composite zirconia grinding media, and the material is passed through a 60-mesh sieve after discharge; the ground metal oxide is placed in a drying oven and dried at 120℃ for 3 hours.

[0041] (2) Mixing and granulation: The pretreated pigment obtained in step (1) is mixed into 3 mol% yttrium oxide partially stabilized zirconium oxide. The mass percentage of the pretreated pigment is 2.5%, and the mass percentage of 3 mol% yttrium oxide partially stabilized zirconium oxide is 97.5%, to obtain a mixture. Then the mixture is ground (the mixture is first ground by roller mill for 3 hours, and then transferred to ball mill for 1 hour). During the grinding, a binder is added and the slurry is adjusted and dispersed to obtain a slurry with a viscosity of 800 mPa·s. Then the slurry is spray granulated using a spray granulator (the inlet air temperature of the spray granulator is 250℃, and the outlet air temperature is 82℃). The moisture content of the granules is controlled to be 1.4%, and the loose packing density is 1.40 g / cm³, to obtain zirconium oxide granulated powder.

[0042] In step (2), the adhesive is a 10% polyvinyl alcohol aqueous solution by mass, and the solid content of the added adhesive is 1% of the mass of the mixture.

[0043] (3) Molding and sintering: The zirconia granulated powder obtained in step (2) is molded into ceramic green body by dry pressing machine (pre-molding is carried out by dry pressing machine under pressure of 20MPa to obtain ceramic green body), and then the ceramic green body is subjected to cold isostatic pressing treatment (the ceramic green body is placed in cold isostatic press and held under pressure of 200MPa for 3 minutes); the ceramic green body after cold isostatic pressing treatment is placed in tunnel furnace and solid-state sintering is carried out at 1400℃ to obtain black zirconia ceramic.

[0044] In step (3) above, the solid-state sintering process is as follows: After placing the ceramic green body treated by cold isostatic pressing in a tunnel furnace, the temperature is raised to 1400°C at a heating rate of 5°C / min and held for 180 minutes. Then, it is cooled to room temperature at a cooling rate of 3°C / min. After taking it out, black zirconia ceramic is obtained.

[0045] Examples 2-5: The preparation methods of black zirconia ceramics in Examples 2-5 are different from those in Example 1, except for the mass ratio of CoO, NiO and Fe2O3 in the metal oxide in step (1), the doping ratio of the pretreated pigment in step (2), and the solid-state sintering conditions (sintering temperature and holding time) in step (3), as shown in Table 1 below; the rest are the same as in Example 1.

[0046] Table 1:

[0047] Example <![CDATA[Metal oxide ratio (CoO:NiO:Fe2O3)]]> Pigment mixing ratio Solid-state sintering conditions (temperature / holding time) 2 0.5:18:33 2.5% 1420℃ / 200 minutes 3 1:14:36 2.5% 1450℃ / 240 minutes 4 0.8:17:32 3.0% 1400℃ / 180 minutes 5 0.6:16:35 4.0% 1430℃ / 220 minutes

[0048] The properties of the black zirconia ceramics in Examples 1-5 were tested, and the results are shown in Table 2 below.

[0049] Table 2:

[0050] Example Flexural strength (MPa) <![CDATA[Density (g / cm 3 )]]> Color performance Damp heat resistance test (temperature 60℃, humidity 90%) 1 1548.98 6.02 Evenly glossy black with a metallic sheen No color change after 1000 hours 2 1535.54 6.01 Black with a slight reddish tint and a metallic sheen No color change after 1000 hours 3 1553.12 6.02 Black with a slight grayish tint and a metallic sheen No color change after 1000 hours 4 1562.37 6.03 Evenly glossy black with a metallic sheen No color change after 1000 hours 5 1541.79 6.02 Evenly glossy black with a metallic sheen No color change after 1000 hours

[0051] II. Comparative Experiment

[0052] (a) Comparative examples where the pigment ratio deviates from the scope of this invention (Comparative Examples 1-3)

[0053] The preparation methods of zirconia ceramics in Comparative Examples 1-3 are the same as those in Example 1, except that the mass ratio of CoO, NiO and Fe2O3 in the metal oxide in step (1) is different, as shown in Table 3 below; the rest are the same as in Example 1.

[0054] The properties of the zirconia ceramics in Comparative Examples 1-3 were tested, and the results are shown in Table 3 below.

[0055] Table 3:

[0056] Comparative Example <![CDATA[Metal oxide ratio (CoO:NiO:Fe2O3)]]> Flexural strength (MPa) <![CDATA[Density (g / cm 3 ).]]> Color performance Defect cause 1 0.3:15:30 (Insufficient CoO) 1489.26 5.98 Grayish-black, without metallic luster Insufficient CoO results in a lack of blue-black tones, and the complementary color scheme fails. 2 <![CDATA[0.8:16:30 (Insufficient Fe2O3)]]> 1485.65 5.96 The color is bluish-black, with a noticeable color cast and uneven color. <![CDATA[Insufficient Fe2O3 results in the absence of the brownish-red tone, unable to neutralize the blue-black color of CoO and the gray-black color of NiO, and the complementary color effect fails.]]> 3 0.8:22:34 (NiO in excess) 1445.38 5.95 Dark gray, lacking metallic luster, with a strong grayish tint. <![CDATA[Excessive NiO results in an over - proportion of gray - black tone, disrupting the complementary balance of the ternary color tones; excessive Ni]]> 2+ tends to agglomerate, leading to uneven distribution of coloring centers and affecting matrix densification]]>

[0057] (II) Comparative examples where key process parameters deviate from the scope of this invention (Comparative Examples 4-7)

[0058] The preparation methods of zirconia ceramics in Comparative Examples 4-5 are the same as those in Example 1, except that the calcination temperature of the metal oxide in step (1) is different, as shown in Table 4 below; the rest are the same as in Example 1.

[0059] The preparation methods of zirconia ceramics in Comparative Examples 6-7 are the same as those in Example 1, except that the sintering temperature of the solid-state sintering conditions in step (3) is different, as shown in Table 4 below; the rest are the same as in Example 1.

[0060] The properties of the zirconia ceramics in Comparative Examples 4-7 were tested, and the results are shown in Table 4 below.

[0061] Table 4:

[0062] Comparative Example Key process parameters Flexural strength (MPa) Density (g / cm³) Color performance Defect cause 4 Calcination temperature 950℃ (too low) 1059.35 5.86 Uneven color, with some areas appearing whitish. Incomplete calcination, failing to reach the critical temperature for solid-phase reaction, resulted in the pigment not forming a stable coloring phase and exhibiting poor dispersibility. Furthermore, the pigment's low surface activity and weak interfacial bonding with the matrix led to the formation of micropores, reducing density and flexural strength. 5 Calcination temperature 1150℃ (too high) 1472.64 5.95 Uneven color, with localized dark black clusters. Over-calcination leads to pigment agglomeration, resulting in coarse pigment particles with poor dispersibility, reduced compatibility with the zirconium oxide matrix, and decomposition of some composite coloring phases. 6 Sintering temperature 1350℃ (too low) 1387.62 5.82 Grayish-black, low density The sintering is not dense, the interparticle gaps are large, and light scattering leads to a decrease in blackness. 7 Sintering temperature 1500℃ (too high) 1142.58 5.80 Uneven dark color, loss of metallic luster Abnormal grain growth in the zirconia matrix reduces the proportion of tetragonal phase and significantly decreases flexural strength; excessive diffusion of pigment ions leads to uneven distribution of the coloring phase, while microporosity appears in the ceramic due to grain growth, resulting in decreased density and loss of gloss.

[0063] (iii) Comparative examples where the doping ratio of pigments deviates from the scope of this invention (Comparative Examples 8-9)

[0064] The preparation method of zirconia ceramics in Comparative Examples 8-9 is the same as that in Example 1, except that the doping ratio of the pretreatment pigment in step (2) is different, see Table 5 below; the rest is the same as in Example 1.

[0065] The properties of the zirconia ceramics in Comparative Examples 8-9 were tested, and the results are shown in Table 5 below.

[0066] Table 5:

[0067] Comparative Example Pigment mixing ratio Flexural strength (MPa) Density (g / cm³) Color performance Defect cause 8 1.5% (too low) 1520.49 6.00 Light gray, not black. Insufficient concentration of coloring ions leads to inadequate absorption of visible light. 9 5.5% (too high) 1411.32 5.90 Uneven dark color, with localized dark black clusters. Excessive pigment particles tend to agglomerate, damaging the dense structure of the zirconia matrix, leading to decreased flexural strength and reduced density. Excessive coloring ions cause uneven distribution of the coloring phase, resulting in localized dark black agglomerates and poor color uniformity.

[0068] (iv) Comparative examples of single / binary pigment systems (comparative examples 10-12)

[0069] The preparation method of zirconia ceramics in Comparative Examples 10-12 is the same as that in Example 1, except for the composition and doping ratio of the pretreatment pigment in step (2), as shown in Table 6 below; the rest is the same as in Example 1. Because Comparative Examples 10-12 are single or binary doped, a higher doping ratio, such as 5-6%, is required to maximize blackness. If the pigment doping ratio of 2.5% is used as in Example 1, the blackness will be significantly insufficient.

[0070] Table 6:

[0071] Comparative Example Pigment system Pigment mixing ratio Flexural strength (MPa) Density (g / cm³) Color performance Defect cause 10 Single NiO 6.0% 1398.75 5.92 Grayish-black, prone to fading Single-color pigments have weak coloring ability, and high-proportion doping damages the matrix structure. 11 <![CDATA[Fe2O3-NiO(1:2)]]> 5.0% 1425.31 5.94 Brownish-black with reddish undertones <![CDATA[There is no CoO complementary color tone, and the brownish red color of Fe2O3 cannot be offset]]> 12 CoO-NiO (1:10) 5.0% 1410.68 5.93 Dark blue, with a bluish tint <![CDATA[Without Fe2O3 to adjust the hue, the blue hue of CoO is prominent]]>

[0072] (v) Comparison with the "rare earth oxide + transition metal oxide" multi-element colorant system (hereinafter referred to as "other multi-element colorant systems")

[0073] 1. Other multi-element colorant systems (such as CeO2-Fe2O3-NiO-Al2O3-…) can produce color, but rare earth ions (such as Ce…)… 4+ The light absorption range of the zirconia is narrow and the lattice matching with the zirconia matrix is ​​poor, which can easily lead to the following problems: (1) insufficient blackness (mostly "dark gray"); (2) rare earth ion segregation during sintering, resulting in "local white spots".

[0074] The ternary system of this invention consists entirely of transition metal ions, with an optical absorption range covering the entire visible light spectrum. After pretreatment, it exhibits excellent compatibility with a 3 mol% yttrium-stabilized zirconium oxide matrix, good color uniformity, stronger color complementarity, and excellent color uniformity and stability.

[0075] 2. Other multi-element colorant systems often damage the mechanical structure of zirconia ceramics due to "high doping amount" or "poor compatibility with the matrix".

[0076] The ternary system of this invention achieves a balance between coloring and mechanical properties through "low doping + pretreatment". Due to "synergistic color enhancement", the ternary system of this invention can achieve excellent blackness with only 2.0-5.0% low doping amount (preferably 2.5%). At low doping amount, it achieves high flexural strength and density. The core reason is that the low doping amount avoids matrix structural defects, and the pretreated pigment particles are refined and can be uniformly dispersed in the matrix.

[0077] 3. Some other multi-element colorant systems contain "lattice mismatch ions" (such as Mn3O4 and ZnO), which are prone to react with zirconium oxide during high-temperature sintering to form brittle phases (such as ZnZrO3), leading to ceramic cracking.

[0078] The ionic radii of the ternary oxides (CoO, Fe2O3, NiO) of this invention are related to Zr. 4+(0.084nm) is close to (Co) 2+ 0.074nm, Fe 3+ 0.064nm, Ni 2+ The composite coloring phase formed after calcination at 1050-1100℃ (0.072nm) can form a solid solution with zirconium oxide without the formation of a brittle phase. Therefore, its mechanical properties are close to those of pure 3mol% yttrium-stabilized zirconium oxide ceramic (the flexural strength of pure 3mol% yttrium-stabilized zirconium oxide ceramic is about 1500MPa).

[0079] 4. The raw material costs of other multi-element pigment systems are significantly higher than those of this invention. The core difference lies in the "type of raw materials" and the "amount used". For example: (1) The market price of rare earth oxides (such as CeO2) is about 20 times that of Fe2O3. The CoO, Fe2O3 and NiO used in this invention are all basic chemical raw materials with low unit price for chemical purity; (2) The amount (doping ratio) of the ternary pigment system of this invention is only 1 / 2 to 2 / 3 of that of other multi-element pigment systems.

[0080] In terms of pretreatment process, this invention adopts conventional "grinding + calcination", which does not require special equipment and has low energy consumption; some other multi-element pigment systems require sol-gel method to prepare pigments, which has high energy consumption.

[0081] In summary, the ternary colorant system of this invention solves the common pain points of other multi-element colorant systems, namely "color deviation, poor mechanical properties, high cost, and complex processes," through the synergistic effect of "ion complementarity (color), low-quantity adaptation (mechanical properties), inexpensive raw materials (cost), and stable structure (process)." The precise matching of the ternary colorant system of this invention with the 3 mol% yttrium-stabilized zirconia matrix ultimately achieves a balance of "high performance + low cost + industrialization," which is its core value that distinguishes it from other multi-element colorant systems.

[0082] III. Repeatability and Consistency Verification

[0083] To verify the repeatability and consistency of the method of the present invention, 10 batches of parallel tests were conducted according to the formula and process of Example 1. The test results are shown in Table 7 below.

[0084] Table 7:

[0085] Batch number Flexural strength (MPa) Density (g / cm³) Color uniformity (Grade*) 1 1548.98 6.02 A 2 1551.23 6.02 A 3 1547.65 6.01 A 4 1550.17 6.03 A 5 1549.82 6.02 A 6 1546.91 6.01 A 7 1552.34 6.02 A 8 1548.76 6.03 A 9 1550.59 6.02 A 10 1547.28 6.01 A average value 1549.37 6.02 - Standard deviation 1.86 0.008 -

[0086] * Color uniformity grade: A - uniform with no color deviation; B - slight color deviation; C - obvious color deviation.

[0087] The data above shows that the standard deviation of the flexural strength of the 10 batches of products was only 1.86 MPa, and the standard deviation of the density was 0.008 g / cm³. 3The color uniformity all reached Grade A, indicating that the method of the present invention has excellent repeatability and consistency, good process stability, and can meet the needs of industrial mass production.

Claims

1. A black zirconia ceramic, composed of a colorant and a matrix material, characterized in that: The colorant has a mass percentage of 2.0-5.0%, and the matrix material has a mass percentage of 95.0-98.0%. The colorant is composed of CoO, NiO, and Fe2O3, and the mass ratio of CoO, NiO, and Fe2O3 in the colorant is CoO:NiO:Fe2O3 = 0.5-1:14-18:32-36. The matrix material is 3 mol% yttrium oxide partially stabilized zirconium oxide. The preparation method of the black zirconia ceramic includes the following steps in sequence: (1) Metal oxide pretreatment: Weigh the metal oxides CoO, NiO and Fe2O3 according to the mass ratio CoO:NiO:Fe2O3=0.5-1:14-18:32-36, grind and dry them; then put the ground and dried metal oxides into a muffle furnace and calcine them at 1050-1100℃ to obtain pretreated pigments; (2) Mixing and granulation: The pretreated pigment obtained in step (1) is mixed into 3 mol% yttrium oxide partially stabilized zirconium oxide. The mass percentage of the pretreated pigment is 2.0-5.0%, and the mass percentage of 3 mol% yttrium oxide partially stabilized zirconium oxide is 95.0-98.0% to obtain a mixture. The mixture is then ground, and a binder is added and the mixture is slurry dispersed during the grinding process to obtain a slurry with a viscosity of 500-1000 mPa·s. The slurry is then spray-granulated using a spray granulator, and the moisture content of the granules is controlled to be 0.8-1.5%, and the loose density is 1.20-1.60 g / cm³ to obtain zirconium oxide granulated powder. (3) Molding and sintering: The zirconia granulated powder obtained in step (2) is molded into ceramic green body by dry pressing machine, and then the ceramic green body is subjected to cold isostatic pressing treatment; the ceramic green body after cold isostatic pressing treatment is placed in tunnel furnace and solid-phase sintering is carried out at 1400-1450℃ to obtain black zirconia ceramic.

2. The black zirconia ceramic according to claim 1, characterized in that: The black zirconia ceramic contains 2.5% colorant by mass and 97.5% matrix material by mass.

3. The black zirconia ceramic according to claim 1, characterized in that: The mass ratio of CoO, NiO and Fe2O3 in the pigment is CoO:NiO:Fe2O3 = 0.8:14-18:32-36.

4. The method for preparing black zirconia ceramic according to claim 1, characterized in that... The steps are as follows: (1) Metal oxide pretreatment: Weigh the metal oxides CoO, NiO and Fe2O3 according to the mass ratio CoO:NiO:Fe2O3=0.5-1:14-18:32-36, grind and dry them; then put the ground and dried metal oxides into a muffle furnace and calcine them at 1050-1100℃ to obtain pretreated pigments; (2) Mixing and granulation: The pretreated pigment obtained in step (1) is mixed into 3 mol% yttrium oxide partially stabilized zirconium oxide. The mass percentage of the pretreated pigment is 2.0-5.0%, and the mass percentage of 3 mol% yttrium oxide partially stabilized zirconium oxide is 95.0-98.0% to obtain a mixture. The mixture is then ground, and a binder is added and the mixture is slurry dispersed during the grinding process to obtain a slurry with a viscosity of 500-1000 mPa·s. The slurry is then spray-granulated using a spray granulator, and the moisture content of the granules is controlled to be 0.8-1.5%, and the loose density is 1.20-1.60 g / cm³ to obtain zirconium oxide granulated powder. (3) Molding and sintering: The zirconia granulated powder obtained in step (2) is molded into ceramic green body by dry pressing machine, and then the ceramic green body is subjected to cold isostatic pressing treatment; the ceramic green body after cold isostatic pressing treatment is placed in tunnel furnace and solid-phase sintering is carried out at 1400-1450℃ to obtain black zirconia ceramic.

5. The method for preparing black zirconia ceramic according to claim 4, characterized in that: In step (1), the grinding is carried out by wet roller grinding for 3 hours, in which the ratio of metal oxide to water is 1:3, the grinding medium is φ3mm composite zirconia grinding media, and the material is passed through a 60-mesh sieve after discharge.

6. The method for preparing black zirconia ceramic according to claim 4, characterized in that: In step (1), the ground metal oxide is placed in a drying oven and dried at 120°C for 3 hours.

7. The method for preparing black zirconia ceramic according to claim 4, characterized in that: In step (1), the calcination time is 3-3.5 hours.

8. The method for preparing black zirconia ceramic according to claim 4, characterized in that: In step (2), the mixture is first ground by roller mill for 3 hours, and then transferred to ball mill for 1 hour.

9. The method for preparing black zirconia ceramic according to claim 4, characterized in that: In step (2), the adhesive is a 10% (w / w) aqueous solution of polyvinyl alcohol, and the solid content of the added adhesive is 1% of the mass of the mixture.

10. The method for preparing black zirconia ceramic according to claim 4, characterized in that: In step (2), the inlet air temperature of the spray granulator is 250°C and the outlet air temperature is 82°C. In step (3), a dry pressing machine is used to pre-form the ceramic green body under a pressure of 20 MPa; then the ceramic green body is placed in a cold isostatic press and held under a pressure of 200 MPa for 3 minutes. In step (3), the solid-state sintering process is as follows: after placing the ceramic green body treated by cold isostatic pressing in a tunnel furnace, the temperature is raised to 1400-1450℃ at a heating rate of 5℃ / min, held for 180-240 minutes, and then cooled to room temperature at a cooling rate of 3℃ / min. After taking it out, black zirconia ceramic is obtained.