A method for preparing black zirconia by reduction

Abstract

The application provides a method for preparing black zirconia by reduction, which is a method for preparing black zirconia pieces by adding a single colorant auxiliary material and sintering by reduction, comprising the following steps: mixing and sintering, preparing yttrium stabilized zirconia slurry by using purified water; mixing the slurry with praseodymium oxide according to a proportion and then performing ball milling; adding a dispersing agent in the ball milling to make the mixed slurry uniform and not precipitate, and adding a small amount of ammonia water to adjust pH, so as to ensure the granulation effect and perform granulation; forming a blank by tabletting and injection molding, and sintering; performing secondary reduction sintering in a hydrogen atmosphere; and performing grinding and polishing to obtain a finished product. The black zirconia prepared by the process has fewer added components, the process is easier to control, the sintered product has more uniform color and grain, has higher density and can reach more than 6.05 g / cm3, has high bending strength and can reach more than 1200 MPa. The added elements are non-toxic and harmless, and can be better applied to related industries.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of zirconia powder preparation process, and particularly relates to a method for preparing black zirconia by a reduction method. BACKGROUND

[0002] Zirconia ceramic ornaments are characterized by gloss, high hardness, no rust and discoloration, no contamination and stable chemical properties. For example, ceramic watches use zirconia ceramic materials for watch cases and watch bands, and compared with stainless steel materials, the hardness of the zirconia ceramic materials is about 10 times that of the stainless steel materials, and the zirconia ceramic materials have good rust and heat resistance, high hardness, never wear, never fade and no damage to the skin. The application of the zirconia ceramic materials is continuously expanded in other ornament applications.

[0003] At present, the production methods of black zirconia mainly include solid phase mixing method, chemical coprecipitation method and liquid phase impregnation method.

[0004] The solid phase mixing method has the advantages of simple process, low cost, convenient operation and easy industrialization, but cannot overcome the agglomeration of nano particles, and the coloring phase and the substrate nano particles are not uniformly mixed, and the ball milling time is long, and the ball milling medium or the atmosphere may cause serious pollution to the powder;

[0005] The chemical coprecipitation method has the advantages of high purity and excellent performance of the obtained powder, but has a complex process;

[0006] The liquid phase impregnation method is more simple in process, and the prepared colored zirconia ceramic has obvious advantages in color uniformity and physical properties, but a large amount of metal salt solution is needed, and the treatment of production tailings is troublesome.

[0007] The existing disclosed technology for doping black color materials all uses two or more composite color materials, and some contain heavy metals such as Cr.

[0008] Therefore, a new type of more environmentally friendly black zirconia production method is developed, which does not add any health-hazardous elements, is more simple, achieves the uniformity of other methods through the solid phase mixing method, has excellent performance, avoids the performance decline caused by the addition of multiple elements, and better meets the market demand and fills the blank of black series applications. SUMMARY

[0009] Technical scheme: In order to solve the problems of the three methods used in the industry, such as the non-uniformity of the solid phase mixing method, the process complexity and uncontrollability of the chemical coprecipitation method, the high pollution of the liquid phase impregnation method, and the control difficulty caused by the addition of multiple components, a single praseodymium oxide is added, and a black zirconia is prepared by an atmosphere reduction method, so as to solve the above problems. The method comprises the following steps:

[0010] 2.5-5mol% yttrium stabilized zirconia is added into a ball mill tank, 45-65% purified water is added, stirred uniformly, 0.1-3% nano praseodymium oxide Pr6O 11， 0.01-0.3% water-based dispersant S is added, and ball milling is performed for 4-10 min.

[0011] A small amount of ammonia water is added to adjust the viscosity to 600-800 mPa·s, and ball milling is performed for mixing, and the raw materials are ball milled for 20-40 min.

[0012] The inlet temperature is 180-240 DEG C, and the outlet temperature is 95-110 DEG C for granulation.

[0013] Taking dry pressing as an example, the pressure is 3-5T, and the subcooling isostatic pressing is performed at a pressure of 180-200 MPa to increase the green strength and process forming. The powder produced by the method is a glue-free powder, and because the components are simple, the application type is good, and the granulation powder is suitable for various processing methods such as dry pressing and injection molding.

[0014] The machined blank product is pre-sintered at 1300-1500 DEG C for 80-120 min.

[0015] The sintered product is transferred into an atmosphere sintering furnace, the reduction sintering temperature is 1300-1500 DEG C, and the time is 10-50 h; the reduction hydrogen is precisely controlled to be 30-150 sccm, and the black zirconia product is prepared.

[0016] Beneficial effects: the process method provided by the present application has the following advantages compared with the existing conventional method:

[0017] 1. Only one kind of nano oxide is added, the process is simpler, the color is better, and the cost is lower. The color system can be adjusted by adjusting the concentration.

[0018] 2. The pollution of heavy metals is avoided, and the problems and pollution caused by the post-processing of other metal salts and cleaning water are avoided.

[0019] 3. The oxide Pr6O 11 has a density of 6.5 g / cm³, and the properties are close to yttrium stabilized zirconia, and the performance advantages of zirconia are better maintained. DETAILED DESCRIPTION

[0020] Figure 1 The sintered body morphology and original crystal size of the present application under 10000 times are shown.

[0021] Figure 2 The sample sheet of the finished product of the present application before calcination and polishing.

[0022] Figure 3 The sample sheet of the finished product of the present application after calcination and polishing. DETAILED DESCRIPTION

[0023] The specific embodiments of the present application are described in further detail below in conjunction with examples. The following examples are intended to illustrate the present application and are not intended to limit the scope of the present application. Example

[0024] (1) 3 mol% yttrium stabilized zirconia was added to a ball mill tank, 50% purified water was added, stirred evenly, and 0.2% nano praseodymium oxide Pr6O 11， 0.05% aqueous dispersant S was added, and ball milling was performed for 5 min.

[0025] (2) A small amount of ammonia water was added to adjust the viscosity to 600 mPa s, and ball milling was performed for mixing. Since the raw materials are all nano, ball milling was performed for 30 min.

[0026] (3) The inlet temperature was 190°C, and the outlet temperature was 105°C for granulation.

[0027] (4) Taking dry pressing as an example, the pressure was 5T, and the subcooling isostatic pressing was performed at a pressure of 180 MPa to increase the green strength. The product was processed and formed. The powder produced by this method is a glue-free powder, and since the components are simple, the application type is good, and the granulated powder is suitable for various processing methods such as dry pressing, injection molding, etc.

[0028] (5) The machined blank product was pre-sintered at 1450°C for 100 min.

[0029] (6) The sintered product was transferred to an atmosphere sintering furnace, and the reduction sintering temperature was 1500°C for 50 h; the reduction hydrogen was precisely controlled to 80 sccm, and a black zirconia product was prepared.

[0030] The black zirconia sheet produced according to this procedure was sintered at 1450°C and reduced at 1500°C. The sample sheet had a density of 6.08, a three-point bending strength of 1300 kn / m2, a color difference L value of 5.0, and was suitable for various ceramic elements. Example

[0031] (1) 3.5 mol% yttrium stabilized zirconia was added to a ball mill tank, 55% purified water was added, stirred evenly, and 0.6% nano praseodymium oxide Pr6O 11， 0.1% aqueous dispersant S was added, and ball milling was performed for 10 min.

[0032] (2) A small amount of ammonia water was added to adjust the viscosity to 650 mPa s, and ball milling was performed for mixing. Since the raw materials are all nano, ball milling was performed for 20 min.

[0033] (3) The inlet temperature was 180°C, and the outlet temperature was 95°C for granulation.

[0034] (4) Take dry pressing as an example, the pressure is 4.5T, the undercooling isostatic pressing, the pressure is 190MPa, the green strength is increased. The powder produced by this method is glue-free powder, and the components are simple, the application type is good, and the granulated powder is suitable for various processing methods such as dry pressing and injection molding.

[0035] (5) The processed blank product is pre-sintered at 1300℃ for 80min.

[0036] (6) The sintered product is transferred into an atmosphere sintering furnace, the reduction sintering temperature is 1400℃, the time is 40h; the reduction hydrogen is precisely controlled to be 100sccm, and the black zirconia product is prepared.

[0037] The black zirconia sheet produced according to this step is sintered at 1300℃ and reduced at 1400℃, the sample sheet density is 6.09, the three-point bending strength is 1265kn / m㎡, the color difference L value is 3.0, and it is suitable for various ceramic elements. Embodiment

[0038] (1) 4mol% yttrium stabilized zirconia is added into a ball mill tank, 55% purified water is added, and 1.5% nano praseodymium oxide Pr6O 11， 0.05% water-based dispersant S is added, and ball milling is performed for 4min.

[0039] (2) A small amount of ammonia water is added to adjust the viscosity to 750mPa·s, and ball milling is performed for 25min because the raw materials are all nano.

[0040] (3) The inlet temperature is 200℃, and the outlet temperature is 105℃ for granulation.

[0041] (4) Take dry pressing as an example, the pressure is 4T, the undercooling isostatic pressing, the pressure is 185MPa, the green strength is increased. The powder produced by this method is glue-free powder, and the components are simple, the application type is good, and the granulated powder is suitable for various processing methods such as dry pressing and injection molding.

[0042] (5) The processed blank product is pre-sintered at 1500℃ for 120min.

[0043] (6) The sintered product is transferred into an atmosphere sintering furnace, the reduction sintering temperature is 1500℃, the time is 10h; the reduction hydrogen is precisely controlled to be 50sccm, and the black zirconia product is prepared.

[0044] The black zirconia sheet produced according to this step is sintered at 1500℃ and reduced at 1500℃, the sample sheet density is 6.10, the three-point bending strength is 1205kn / m㎡, the color difference L value is 1.0, and it is suitable for various ceramic elements. Embodiment

[0045] (1) Put 2.5 mol% yttrium stabilized zirconia into a ball mill tank, add 45% purified water, stir evenly, add 2.6% nano praseodymium oxide Pr6O 11， Add 0.2% aqueous dispersant S, ball mill for 7 min.

[0046] (2) Add a small amount of ammonia water to adjust the viscosity to 700 mPa·s, ball mill and mix, and ball mill for 30 min because the raw materials are all nano.

[0047] (3) The inlet temperature is 240℃ and the outlet temperature is 100℃ for granulation.

[0048] (4) Take dry pressing as an example, the pressure is 3.5T, and the green strength is increased by subcooling isostatic pressing at a pressure of 195MPa. Process forming. The powder produced by this method is a glue-free powder, and because the components are simple, it is suitable for various processing methods such as dry pressing, injection molding, etc.

[0049] (5) The machined blank product is pre-sintered at 1350℃ for 110 min.

[0050] (6) The sintered product is transferred to a gas atmosphere sintering furnace, and the reduction sintering temperature is 1450℃ for 30h; the reduction hydrogen is precisely controlled at 120sccm to obtain a black zirconia product.

[0051] The black zirconia sheet produced according to this procedure is sintered at 1350℃ and reduced at 1450℃, with a sample density of 6.07, a three-point bending strength of 1315 kn / m㎡, and a color difference L value of 2.0, suitable for various ceramic elements. Example

[0052] (1) Put 2.5 mol% yttrium stabilized zirconia into a ball mill tank, add 45% purified water, stir evenly, add 2.6% nano praseodymium oxide Pr6O 11， Add 0.2% aqueous dispersant S, ball mill for 7 min.

[0053] (2) Add a small amount of ammonia water to adjust the viscosity to 700 mPa·s, ball mill and mix, and ball mill for 30 min because the raw materials are all nano.

[0054] (3) The inlet temperature is 240℃ and the outlet temperature is 100℃ for granulation.

[0055] (4) Take dry pressing as an example, the pressure is 3.5T, and the green strength is increased by subcooling isostatic pressing at a pressure of 195MPa. Process forming. The powder produced by this method is a glue-free powder, and because the components are simple, it is suitable for various processing methods such as dry pressing, injection molding, etc.

[0056] (5) The machined blank product is pre-sintered at 1350℃ for 110 min.

[0057] (6) The sintered product is transferred into an atmosphere sintering furnace, and the reduction sintering temperature is 1500 DEG C, and the time is 20h; the reduction hydrogen is precisely controlled to be 150sccm, and the black zirconia product is prepared.

[0058] The black zirconia sheet produced according to the step is sintered at 1450 DEG C, and reduced at 1500 DEG C, the sample sheet density is 6.09, the three-point bending strength is 1295 kn / m2, the color difference L value is 2.1, and is suitable for various ceramic elements.

[0059] In order to analyze the performance of the zirconia product of the above embodiment, the following experiments and test results are made.

[0060] The zirconia products of embodiments 1-5 are tested by the drainage method, and the density is tested by using a 0.0001mg electronic scale, and the sample density range is 6.10-6.07, and it can be seen that the sintered product of the above formula has good porcelain effect, and the sintering density reaches the theoretical requirement.

[0061] The obtained product is tested by a scanning electron microscope, and the scanning electron microscope test results are shown in the following table 2. Figure 1 The morphology and primary crystal size of the zirconia powder under 10000 times of the application are shown in the following table 2. Figure 1 It can be seen that the primary crystal size obtained by the application is between 60-80nm, and the morphology structure is very uniform.

[0062] The obtained product is tested by a three-point strength testing machine according to the fine ceramic bending strength test method of GB / T6569, and the following table 1 is the data of 11 groups of randomly obtained parallel products.

[0063] Table 1 fine ceramic bending strength test method of 11 groups of products

[0064] Num Max force N Bending strength MPa Max deformation mm Elastic modulus Gpa Elastic ratio 1 817.23 1109.44 6.03 510.54 7324.13 2 649.63 913.34 4.87 584.61 7989.37 3 1075.88 1474.34 7.35 989.00 14008.25 4 836.37 1153.88 6.06 551.79 7736.95 5 968.61 1327.35 6.82 1090.34 15443.68 6 1055.94 1443.18 7.40 1080.94 15351.29 7 1165.94 1636.90 8.12 1089.34 14959.08 8 796.15 1117.75 5.87 581.41 7984.11 9 1047.57 1425.92 7.15 502.99 7196.61 10 878.45 1238.36 6.45 606.34 8264.14 11 936.76 1326.04 6.82 593.34 8026.19 Average value 929.87 1287.86 6.63 743.69 10389.44

[0065] From the above table 1, it can be seen that the average bending strength of all the products is more than 1200MPa, the average value of the maximum deformation is 6.63, the average value of the elastic modulus is 743.69, and the average value of the elastic ratio is 10389.44.

[0066] The above embodiments only express several embodiments of the application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the application, some modifications and improvements can be made, which belong to the protection scope of the application. Therefore, the protection scope of the patent of the application should be subject to the appended claims.

Claims

1. A method for preparing black zirconia by reduction, characterized by: The preparation method mixes by ball milling, and sintering by hydrogen reduction, and the method comprises the following steps: (1) uniformly stirring yttrium stabilized zirconium oxide slurry prepared by purified water; the yttrium stabilized zirconium oxide is zirconium oxide with a yttrium content of 2.5-5 mol%, and the mass percentage of the purified water is 45-65%; (2) mixing the yttrium stabilized zirconium oxide slurry with praseodymium oxide in a proportion and then ball milling; the added mass percentage of the praseodymium oxide is 0.1-3%, and the praseodymium oxide is nano praseodymium oxide; (3) adding a dispersing agent to make the mixed slurry uniform and non-deposited during the ball milling process, and adjusting pH by adding ammonia water to ensure the granulation effect; (4) granulating the ball-milled slurry in the above (3) by using a granulation tower; (5) forming a blank by tabletting and injection molding of the granulated (4); (6) sintering the formed blank in the above (5); the sintering temperature is 1300-1500℃, and the holding time is 80-120 min; (7) performing secondary reduction sintering on the sintered product in the above step (6) under a hydrogen atmosphere; the reduction sintering temperature is 1300-1500℃, and the time is 10-50 h; the reduction hydrogen is precisely controlled to be 30-150 sccm; (8) obtaining a finished product by grinding and polishing the product in step (7).

2. The method of claim 1 for the preparation of black zirconia by reduction, characterized in that: The dispersing agent in the step (3) is selected from water-based dispersing agents, and the concentration is 0.01-0.3%, and the adjusted pH is 6-8.

3. The method of claim 1, wherein the method of preparing black zirconia by reduction is characterized by: After the step (4) of granulation, D50=60-90μm, the inlet temperature of the granulation is 180-240℃, and the outlet temperature is 95-110℃.

4. The method of claim 1, wherein the method of preparing black zirconia by reduction is characterized by: The step (5) adopts dry pressing forming, the pressure is 3-5T, and over-cooled isostatic pressing, the pressure is 180-200MPa, so as to increase the strength of the green body and process forming.

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