Conductive zirconia ceramic and method of additive manufacturing thereof and applications thereof

Abstract

This invention provides a conductive zirconia ceramic, a method for preparing it using additive manufacturing, and its applications. The method includes: mixing zirconia powder, a surface modifier, and a solvent; sequentially ball-milling and drying the mixture; heating and stirring the resulting first mixture, then mixing in a binder and further stirring under pressure to obtain a second mixture; sequentially cooling and crushing the second mixture to obtain zirconia particles, which are then additively manufactured to obtain a green body; the green body is degreased, and the degreased workpiece is sintered under nitrogen-containing conditions to obtain the conductive zirconia ceramic. This invention allows for the fabrication of ZrO2 conductive ceramics without the addition of other impurity phases and can prepare complex porous structures. It offers advantages such as simple operation, low cost, high strength, stable chemical properties, and stable conductivity.

Description

Technical Field

[0001] This invention relates to the field of conductive ceramic materials technology, and in particular to a conductive zirconia ceramic, a method for preparing it by additive manufacturing, and its applications. Background Technology

[0002] Zirconia (ZrO2) ceramics are structural ceramic materials with advantages such as high melting point, high hardness, excellent chemical stability, low thermal conductivity, and good wear resistance. They are often used in engine parts, chemical industry, biomedical devices, bulletproof armor, abrasives and other fields.

[0003] However, ZrO2 ceramics have a wide bandgap and generally exhibit extremely poor electrical conductivity, being non-conductive at room temperature. This significantly limits their application in conductive materials fields such as high-voltage, high-heat devices, electronics, and automation control. In recent years, with the development of science and technology, the requirements for materials have gradually increased. We not only need to leverage the excellent high-temperature resistance and corrosion resistance of ZrO2 ceramics, but also need to address its shortcomings in electrical conductivity to provide better material options for cutting-edge technology fields.

[0004] Currently, the conductivity of ZrO2 ceramics is mainly achieved through two methods. One method is to add charge carrier-conducting dopants, such as MgO, ZnO, WO3, and TiN. However, ZrO2 ceramics with added MgO, ZnO, and WO3 phases only meet the requirements for electrostatic dissipation at room temperature, and their room temperature conductivity is not ideal. The other method is to achieve the conductivity of ZrO2 ceramics by coating conductive materials such as TiN and ZrN through chemical vapor deposition or physical vapor deposition.

[0005] In material preparation, the carrier-conductive doped phase exhibits sintering porosity, and the sintered host phase and doped phase may form a physical interface rather than a metallurgical interface, leading to performance degradation. The chemical stability of the doped phase relative to the overall structure requires further investigation. Chemical vapor deposition (CVD) conductive coatings typically involve a gas-solid phase reaction involving decomposition and thermal bonding at 950℃-1050℃ to grow a solid deposition layer on a heated substrate surface; however, this process requires stringent conditions and is costly. Physical vapor deposition (PVD) uses a process where the workpiece surface is purified by particle bombardment at 300℃-500℃, the coating material melts and atomizes, ionizes in the plasma region, and deposits on the substrate. This method produces coatings with high purity and density, but requires expensive equipment and has a long coating cycle. Furthermore, deposition coatings are not suitable for surface conductivity modification of internally porous and complex structures. In summary, both carrier-conductive doped phases and deposition coatings present complex operational processes and high costs.

[0006] Therefore, there is a need to develop new methods for preparing conductive zirconia ceramics. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides a conductive zirconia ceramic and a method for preparing it by additive manufacturing and its application. By using the Zr element in ZrO2 and the nitrogen-containing gas or the surface coating with nitrogen-containing elements to generate a conductive layer in situ in a carbon deposition atmosphere, a uniform metallurgical bond between the surface and the conductive layer is achieved. The zirconia conductive ceramic formed by this method does not require the addition of other impurity phases and can be used to prepare complex porous structures. It has the advantages of simple operation, low cost, high strength, stable chemical properties and stable conductivity.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing conductive zirconia ceramics by additive manufacturing, the method comprising the following steps:

[0010] (1) A first mixture is obtained by ball milling and drying a mixture of zirconium oxide powder, surface modifier and solvent; the first mixture is heated and stirred, and a binder is mixed in and then stirred under pressure to obtain a second mixture.

[0011] (2) The second mixture is cooled and crushed in sequence to obtain zirconia granules; the zirconia granules are then processed by additive manufacturing to obtain a green body;

[0012] (3) The green blank is degreased, and the degreased workpiece is sintered under nitrogen-containing conditions to obtain conductive zirconia ceramic.

[0013] The additive manufacturing method for preparing conductive zirconia ceramics provided by this invention first uses additive manufacturing to prepare zirconia green blanks, avoiding the material waste and high costs associated with subtractive manufacturing, and is applicable to products of various shapes. Simultaneously, in-situ composite formation of ZrN, ZrCN, or ZrNO phases is used on the surface of the zirconia, achieving a metallurgical bonding interface with the ZrO2 matrix, resulting in enhanced, toughened, and conductive effects. The bonding strength between the two is high, and the performance is excellent. The method provided by this invention has the advantages of simple operation, low cost, high strength, stable chemical properties, and stable conductivity.

[0014] Preferably, the heating and stirring temperature in step (1) is 60~260℃, for example, it can be 60℃, 76℃, 92℃, 105℃, 125℃, 135℃, 155℃, 165℃, 185℃, 200℃, 210℃, 250℃ or 260℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0015] Preferably, the heating and stirring time is 30 to 240 minutes, for example, it can be 30 minutes, 55 minutes, 75 minutes, 100 minutes, 125 minutes, 145 minutes, 170 minutes, 195 minutes, 215 minutes or 240 minutes, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] Preferably, the mass ratio of the adhesive to the first mixture is 1:3 to 4.5, for example, it can be 1:3, 1:3.1, 1:3.2, 1:3.5, 1:3.8, 1:4.0, 1:4.2 or 1:4.5, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] Preferably, the adhesive comprises any one or a combination of at least two of stearic acid, polyethylene glycol, phenolic resin, epoxy resin, ethyl cellulose, polystyrene, polypropylene, polyethylene, polyvinyl alcohol, polyvinyl butyral, or paraffin wax, wherein typical but not limiting combinations are combinations of polyethylene glycol and phenolic resin, combinations of epoxy resin and phenolic resin, combinations of polyethylene glycol and epoxy resin, combinations of ethyl cellulose and phenolic resin, and combinations of polyethylene glycol and ethyl cellulose.

[0018] Preferably, the pressure of the pressurized stirring is 10~120MPa, for example, it can be 10MPa, 20MPa, 30MPa, 40MPa, 50MPa, 60MPa, 80MPa, 100MPa, 110MPa or 120MPa, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] Preferably, the pressurized stirring time is 1 to 10 hours, for example, it can be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] Preferably, the mass ratio of zirconium oxide powder to surface modifier in step (1) is 10 to 25:1, for example, it can be 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 21:1, 22:1, 23:1, 24:1 or 25:1, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] Preferably, the surface modifier comprises stearic acid and / or calcium lignosulfonate.

[0022] Preferably, a stabilizer is also added to the mixture in step (1).

[0023] Preferably, the mass ratio of the stabilizer to the zirconium oxide powder is 1 to 4:100, for example, it can be 1:100, 1.2:100, 1.5:100, 1.8:100, 2.0:100, 2.2:100, 2.3:100, 2.5:100, 2.8:100, 3.0:100, 3.2:100, 3.5:100 or 4.0:100, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] In this invention, the sintering and nitriding of zirconium oxide powder without added stabilizer leads to a significant decrease in the ZrN phase content and an increase in the proportion of O-containing phase, resulting in a decrease in surface conductivity. In addition, when the mass ratio of added stabilizer is too high, it will lead to the formation of a new stabilizer nitriding phase, which will affect the formation of the ZrN phase.

[0025] Preferably, the stabilizer comprises yttrium oxide.

[0026] Preferably, the solvent includes ethanol and / or water.

[0027] Preferably, the volume ratio of the total volume of the zirconium oxide powder, surface modifier and stabilizer to the volume of the solvent is 0.5 to 1.2:1, for example, it can be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1 or 1.2:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] Preferably, the rotational speed of the ball mill is 100~500 r / min, for example, it can be 100 r / min, 120 r / min, 150 r / min, 180 r / min, 200 r / min, 220 r / min, 250 r / min, 280 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min or 500 r / min, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0029] Preferably, the ball milling time is 1 to 20 hours, for example, it can be 1 hour, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours or 20 hours.

[0030] Preferably, the drying temperature is 50~100℃, for example, it can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃ or 100℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] Preferably, the drying time is 2 to 24 hours, for example, it can be 2 hours, 3 hours, 5 hours, 10 hours, 12 hours, 13 hours, 15 hours, 18 hours, 20 hours, 22 hours or 24 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] Preferably, the cooling in step (2) is cooling to room temperature.

[0033] Preferably, the particle size of the zirconia particles obtained after crushing is 1~10mm, for example, it can be 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm or 10mm, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0034] Preferably, the size of the additively manufactured nozzle is 0.05~3mm, for example, it can be 0.05mm, 0.38mm, 0.71mm, 1.04mm, 1.37mm, 1.69mm, 2.02mm, 2.35mm, 2.68mm or 3mm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] Preferably, the thickness of the additive manufacturing layer is 0.05~0.35mm, for example, it can be 0.05mm, 0.09mm, 0.12mm, 0.15mm, 0.19mm, 0.22mm, 0.25mm, 0.29mm, 0.32mm or 0.35mm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] Preferably, the printing speed of the additive manufacturing is 5~100mm / s, for example, it can be 5mm / s, 16mm / s, 27mm / s, 37mm / s, 48mm / s, 58mm / s, 69mm / s, 79mm / s, 90mm / s or 100mm / s, etc., but is not limited to the listed values, and other unlisted values ​​in this range are also applicable.

[0037] Preferably, the feed flow rate for additive manufacturing is 70-100%, for example, it can be 70%, 74%, 77%, 80%, 84%, 87%, 90%, 94%, 97% or 100%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0038] Preferably, step (2) further includes polishing the surface of the green blank.

[0039] Preferably, the surface roughness Ra after polishing is 0.1 to 1.6, for example, it can be 0.1, 0.2, 0.3, 0.5, 0.8, 1.0, 1.1, 1.5 or 1.6, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0040] Preferably, the degreasing method in step (3) includes solvent degreasing and / or thermal degreasing.

[0041] Preferably, the solvent used for solvent degreasing includes any one or a combination of at least two of water, ethanol, n-heptane, kerosene, diesel oil, or edible oil, wherein typical but non-limiting combinations are combinations of water and ethanol, n-heptane and ethanol, water and n-heptane, kerosene and ethanol, and edible oil and ethanol.

[0042] Preferably, the thermal degreasing includes heating to a first temperature at a first heating rate and holding at that temperature for a first time, then heating to a second temperature at a second heating rate and holding at that temperature for a second time, then heating to a third temperature at a third heating rate and holding at that temperature for a third time, and then heating to a fourth temperature at a fourth heating rate and holding at that temperature for a fourth time.

[0043] Preferably, the first heating rate is 0.2~5℃ / min, for example, it can be 0.2℃ / min, 0.74℃ / min, 1.27℃ / min, 1.8℃ / min, 2.34℃ / min, 2.87℃ / min, 3.4℃ / min, 3.94℃ / min, 4.47℃ / min or 5℃ / min, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0044] Preferably, the first temperature is 60~100℃, for example, it can be 60℃, 65℃, 69℃, 74℃, 78℃, 83℃, 87℃, 92℃, 96℃ or 100℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] Preferably, the first time is 30 min to 10 h, for example, it can be 30 min, 40 min, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h or 10 h, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] Preferably, the second heating rate is 0.2~5℃ / min, for example, it can be 0.2℃ / min, 0.74℃ / min, 1.27℃ / min, 1.8℃ / min, 2.34℃ / min, 2.87℃ / min, 3.4℃ / min, 3.94℃ / min, 4.47℃ / min or 5℃ / min, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0047] Preferably, the second temperature is 180~220℃, for example, it can be 180℃, 185℃, 189℃, 194℃, 198℃, 203℃, 207℃, 212℃, 216℃ or 220℃, etc., but is not limited to the listed values, and other unlisted values ​​in this range are also applicable.

[0048] Preferably, the second time is 30 min to 12 h, for example, it can be 30 min, 40 min, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h or 12 h, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] Preferably, the third heating rate is 0.2~5℃ / min, for example, it can be 0.2℃ / min, 0.74℃ / min, 1.27℃ / min, 1.8℃ / min, 2.34℃ / min, 2.87℃ / min, 3.4℃ / min, 3.94℃ / min, 4.47℃ / min or 5℃ / min, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0050] Preferably, the third temperature is 380~420℃, for example, it can be 380℃, 385℃, 389℃, 394℃, 398℃, 403℃, 407℃, 412℃, 416℃ or 420℃, etc., but is not limited to the listed values, and other unlisted values ​​in this range are also applicable.

[0051] Preferably, the third time is 30 min to 12 h, for example, it can be 30 min, 40 min, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h or 12 h, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] Preferably, the fourth heating rate is 0.2~5℃ / min, for example, it can be 0.2℃ / min, 0.74℃ / min, 1.27℃ / min, 1.8℃ / min, 2.34℃ / min, 2.87℃ / min, 3.4℃ / min, 3.94℃ / min, 4.47℃ / min or 5℃ / min, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0053] Preferably, the fourth temperature is 550~600℃, for example, it can be 550℃, 556℃, 562℃, 567℃, 573℃, 578℃, 584℃, 589℃, 595℃ or 600℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0054] Preferably, the fourth time is 30 min to 8 h, for example, it can be 30 min, 40 min, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h or 8 h, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0055] Preferably, the conditions for the nitrogen-containing element in step (3) include: coating the surface with a nitrogen-containing element, introducing nitrogen gas, or placing a nitrogen-containing compound, or a combination of at least two of these.

[0056] Preferably, the heating rate of the sintering treatment is 0.5~10℃ / min, for example, it can be 0.5℃ / min, 1.6℃ / min, 2.7℃ / min, 3.7℃ / min, 4.8℃ / min, 5.8℃ / min, 6.9℃ / min, 7.9℃ / min, 9℃ / min or 10℃ / min, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0057] Preferably, the final temperature of the sintering treatment is 1500~2000℃, for example, it can be 1500℃, 1550℃, 1600℃, 1650℃, 1700℃, 1750℃, 1800℃, 1850℃, 1900℃, 1950℃ or 2000℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0058] In this invention, if the sintering temperature is too high, the overall structure will deform, affecting its use; if the sintering temperature is too low, the ZrN phase will not be formed, and its electrical conductivity will not be achieved.

[0059] Preferably, the sintering treatment is carried out at the final temperature for 1 to 8 hours, for example, 1 hour, 1.8 hours, 2.6 hours, 3.4 hours, 4.2 hours, 4.9 hours, 5.7 hours, 6.5 hours, 7.3 hours or 8 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0060] As a preferred technical solution of the present invention, the method includes the following steps:

[0061] (1) Mix zirconium oxide powder, surface modifier, stabilizer and solvent, and ball mill at a speed of 100~500 r / min for 1~20 h. The mass ratio of zirconium oxide powder to surface modifier is 10~25:1, the mass ratio of stabilizer to zirconium oxide powder is 2~4:96~98, the volume ratio of total volume of zirconium oxide powder to stabilizer to volume of solvent is 0.5~1.2:1, and the time is 1~20 h; to obtain the first mixture;

[0062] The first mixture is heated and stirred at 60~200℃ for 30~240 min, and then mixed with a binder and stirred under pressure of 10~120MPa for 1~10 h to obtain the second mixture;

[0063] The mass ratio of the adhesive to the first mixture is 1:3~4.5;

[0064] (2) The second mixture is cooled to room temperature and crushed in sequence to obtain zirconia particles with a particle size of 1~10mm; the zirconia particles are additively manufactured with a nozzle size of 0.05~3mm, a layer thickness of 0.05~0.35mm, a printing speed of 5~100mm / s, and a feed flow rate of 70~100% to obtain a green blank; the surface of the green blank is polished to make the surface roughness Ra of the polished surface 0.1~1.6;

[0065] (3) The green blank is degreased, and the degreased workpiece is heated to 1500~2000℃ under nitrogen-containing conditions at a heating rate of 0.5~10℃ / min, and sintered at the final temperature for 1~8h to obtain conductive zirconia ceramic.

[0066] In a second aspect, the present invention provides a conductive zirconia ceramic, wherein the conductive zirconia ceramic is prepared by the additive manufacturing method described in the first aspect.

[0067] Preferably, the ZrN content in the conductive zirconia ceramic is 60-100%, for example, it can be 60%, 70%, 75%, 80%, 85%, 90%, 95% or 100%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0068] Preferably, the ZrCN content in the conductive zirconia ceramic is 0~20%, for example, it can be 0.1%, 1%, 2%, 3%, 4%, 5%, 8%, 9%, 10%, 12%, 13%, 15%, 18% or 20%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0069] Preferably, the ZrNO content in the conductive zirconia ceramic is 0~20%, for example, it can be 0.1%, 1%, 2%, 3%, 4%, 5%, 8%, 9%, 10%, 12%, 13%, 15%, 18% or 20%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0070] Preferably, the thickness of the conductive zirconia ceramic is 0.5~5μm, for example, it can be 0.5μm, 1μm, 1.2μm, 1.5μm, 2.0μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm or 5μm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0071] Thirdly, the present invention relates to the application of the conductive zirconia ceramic described in the second aspect in engine parts, chemical industry, biomedical devices, bulletproof armor, or abrasives.

[0072] Compared with the prior art, the present invention has at least the following beneficial effects:

[0073] (1) The additive manufacturing method for preparing conductive zirconia ceramics provided by the present invention is simple to operate and has low cost;

[0074] (2) The conductive zirconia ceramic prepared by the additive manufacturing method provided by the present invention has a metallurgical alloy interface between the conductive layer and the zirconia matrix layer, with high bonding strength and achieving the effect of strengthening, toughening and conductivity. Its resistivity is 3.1×10 4 Below μΩ·cm, preferably below 1.0×10 4 Below μΩ·cm. Attached Figure Description

[0075] Figures 1-2 This is a SEM image of the conductive zirconia ceramic prepared in Example 1 of this invention before sintering.

[0076] Figures 3-4 This is a SEM image of the conductive zirconia ceramic obtained in Example 1 of this invention after sintering.

[0077] Figure 5 These are XRD phase analysis diagrams of two different regions of the conductive zirconia ceramic prepared in Example 1 of this invention. Detailed Implementation

[0078] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0079] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0080] Example 1

[0081] This embodiment provides a method for preparing conductive zirconia ceramics by additive manufacturing, the method comprising the following steps:

[0082] (1) Mix 100g of zirconium oxide powder, 2.5g of stearic acid, 2g of yttrium oxide and ethanol. The total volume ratio of zirconium oxide powder, stearic acid and yttrium oxide to solvent (ethanol) is 1:1. Put the mixture into a ball mill jar, seal it and ball mill at 260r / min for 2h. Place the ball-milled powder in a drying oven at 80℃ for 2h to obtain the first mixture.

[0083] Heat the rollers of the stirring device to 160°C, add 100g of the first mixture to the rollers and stir for 30 minutes, then mix in the binder (3g stearic acid, 8g paraffin, 15g polyethylene (n=100000), 6g resin (C8H) 14 O2) n After mixing 4g of polyethylene glycol (n=600) and then stirring under pressure of 30MPa for 6 hours (while maintaining the original roller temperature), a second mixture was obtained.

[0084] (2) The second mixture is cooled to room temperature and cut into 2-3 mm zirconia particles; the zirconia particles are additively manufactured, and the workpiece is made by heating and extruding the zirconia particles according to the solid slice model. The nozzle size is 0.4 mm, the layer thickness is 0.152 mm, the printing speed is 20 mm / s, and the feed flow rate is 100% to obtain a green blank; the surface of the green blank is polished so that the surface roughness Ra after polishing is 0.31.

[0085] (3) The green blank is placed in a heat treatment furnace and heated to 80℃ at 0.5℃ / min and held for 5 hours. Then, it is heated to 180℃ at 0.5℃ / min and held for 10 hours. Then, it is heated to 260℃ at 0.5℃ / min and held for 8 hours. Then, it is heated to 380℃ at 0.5℃ / min and held for 8 hours. After the temperature drops by 70℃ at 1℃ / min, it is cooled to room temperature in the furnace for degreasing. The degreased workpiece is wrapped in graphite paper and placed in a carbon atmosphere furnace. After evacuation, nitrogen gas is introduced and the temperature is raised to 1800℃ at a rate of 5℃ / min. The workpiece is then held at the final temperature for 2 hours for sintering to obtain conductive zirconia ceramic.

[0086] The surface morphology of the conductive zirconia ceramic prepared in this embodiment before sintering is as follows: Figure 1 As shown, the surface morphology of the cross-section before sintering is as follows: Figure 2 As shown, the surface morphology of the sintered conductive zirconia ceramic is as follows: Figure 3 As shown, the cross-sectional surface morphology of the sintered conductive zirconia ceramic is as follows: Figure 4 As shown, the surface microstructure of conductive zirconia ceramic is uniformly distributed, with no obvious pore defects, and the overlapping structure of the printing path is stable without deformation.

[0087] Furthermore, the surface phase analysis of the conductive zirconia ceramic prepared in this embodiment is as follows: Figure 5 As shown, from Figure 5 It can be seen that ZrN, ZrO2 and ZrNO are formed on its surface.

[0088] Example 2

[0089] This embodiment provides a method for preparing conductive zirconia ceramics by additive manufacturing, the method comprising the following steps:

[0090] (1) Mix 100g of zirconium oxide powder, 2.5g of stearic acid, 4g of yttrium oxide and ethanol. The volume ratio of the total volume of zirconium oxide powder, stearic acid and yttrium oxide to the volume of solvent (ethanol) is 1.1:1. Put the mixture into a ball mill jar, seal it and ball mill at 130r / min for 18h. Place the ball-milled powder in a drying oven at 75℃ for 3h to obtain the first mixture.

[0091] Heat the rollers of the stirring device to 230°C, add 132.5g of the first mixture to the rollers and stir for 15 minutes, then mix in the binder (4g stearic acid, 5g paraffin, 20g polyethylene (n=120000), 7g resin (C8H4O)). 14 O2) n After mixing 4g of polyethylene glycol (n=500) with n=90000, the mixture was further stirred under pressure of 50MPa for 5 hours (while maintaining the original roller temperature) to obtain the second mixture.

[0092] (2) The second mixture is cooled to room temperature and cut into zirconia particles of 3-5 mm. The zirconia particles are then processed by additive manufacturing. The workpiece is made by heating and extruding the zirconia particles according to the solid slice model. The nozzle size is 3 mm, the layer thickness is 0.25 mm, the printing speed is 55 mm / s, and the feed flow rate is 80%. A green blank is obtained. The surface of the green blank is polished so that the surface roughness Ra after polishing is 1.2.

[0093] (3) The green blank is placed in a heat treatment furnace and heated to 90°C at 3°C / min and held for 3 hours. Then, it is heated to 190°C at 0.2°C / min and held for 8 hours. Then, it is heated to 420°C at 0.5°C / min and held for 12 hours. Then, it is heated to 600°C at 5°C / min and held for 1 hour. After the temperature drops to 78°C at 2°C / min, it is cooled to room temperature in the furnace for degreasing. Urea is placed around the degreased workpiece and it is placed in the furnace together. The temperature is increased to 2000°C at a rate of 8°C / min and held at the final temperature for 2 hours for sintering to obtain conductive zirconia ceramic.

[0094] Example 3

[0095] This embodiment provides a method for preparing conductive zirconia ceramics by additive manufacturing, the method comprising the following steps:

[0096] (1) Mix 100g of zirconium oxide powder, 3g of stearic acid, 2.5g of yttrium oxide and ethanol. The volume ratio of the total volume of zirconium oxide powder, stearic acid and yttrium oxide to the volume of solvent (ethanol) is 0.8:1. Place the mixture in a ball mill jar, seal it and ball mill at 350r / min for 2.5h. Place the ball-milled powder in a drying oven at 65℃ for 4h to obtain the first mixture.

[0097] Heat the rollers of the stirring device to 110°C, add 90g of the first mixture to the rollers and stir for 70 minutes, then mix in the binder (4g stearic acid, 5g paraffin, 20g polyethylene (n=130000), 7g resin (C8H) 14 O2) n After mixing 4g of polyethylene glycol (n=600) and then pressurizing and stirring at 25MPa for 9 hours (while maintaining the original roller temperature), a second mixture was obtained.

[0098] (2) The second mixture is cooled to room temperature and cut into 2-5 mm zirconia particles; the zirconia particles are additively manufactured, and the workpiece is made by heating and extruding the zirconia particles according to the solid slice model. The nozzle size is 1 mm, the layer thickness is 0.15 mm, the printing speed is 20 mm / s, and the feed flow rate is 75% to obtain a green blank; the surface of the green blank is polished so that the surface roughness Ra after polishing is 0.4.

[0099] (3) The green body is degreased by ethanol solvent (the sample is placed in a beaker containing ethanol solvent and heated to 55°C in a water bath or oil bath for 4.5h). The degreased workpiece is wrapped in graphite paper and placed in a carbon atmosphere furnace. After vacuuming, nitrogen gas is introduced and heated to 1600°C at a heating rate of 2.5°C / min. The workpiece is then sintered at the final temperature for 5h to obtain conductive zirconia ceramic.

[0100] Example 4

[0101] This embodiment provides a method for preparing conductive zirconia ceramics by additive manufacturing. Except for the mass ratio of zirconia powder to yttrium oxide being 100:6, the method is the same as in Example 1 and will not be repeated here.

[0102] In this embodiment, the YN content in the subsequently obtained conductive zirconia ceramic increases, causing the conductive zirconia ceramic to decompose in a humid environment at room temperature and pressure, generating Y(OH)3, which is not conducive to subsequent use.

[0103] Example 5

[0104] This embodiment provides a method for preparing conductive zirconia ceramics by additive manufacturing. Except for the mass ratio of zirconia powder to yttrium oxide being 100:0.5, the method is the same as in Example 1 and will not be repeated here.

[0105] In this embodiment, the amount of ZrN formed in the subsequently obtained conductive zirconia ceramic is reduced, resulting in decreased conductivity and a resistivity as high as 31.0 × 10⁻⁶. 3 μΩ·cm.

[0106] As can be seen from Examples 1 and 4-5, by controlling the mass ratio of zirconium oxide powder and yttrium oxide within a specific range, the present invention is more conducive to ensuring the composition of the in-situ composite ceramic and the conductivity of the final composite ceramic.

[0107] Example 6

[0108] This embodiment provides a method for preparing conductive zirconia ceramics by additive manufacturing. Except for the final temperature of 2100℃ in step (3), the method is the same as that in Example 1, and will not be repeated here.

[0109] In this embodiment, the macroscopic structure was damaged due to the excessively high final temperature, resulting in deformation of the overall structure.

[0110] Example 7

[0111] This embodiment provides a method for preparing conductive zirconia ceramics by additive manufacturing. Except for the final temperature of 1400℃ in step (3), the method is the same as that in Example 1, and will not be repeated here.

[0112] In this embodiment, the final temperature is too low, resulting in the inability to generate the ZrN phase and thus the inability to achieve the desired electrical conductivity.

[0113] As can be seen from Examples 1 and 6-7, the additive manufacturing method for preparing conductive zirconia ceramics provided by the present invention can only improve the strength and thermal conductivity of the product if the final temperature is controlled within a specific range.

[0114] Comparative Example 1

[0115] This comparative example provides a method for preparing conductive zirconia ceramics. Except for the absence of the sintering treatment in step (3), the method is the same as that in Example 1, and will not be repeated here.

[0116] In this comparative example, the workpiece surface showed obvious powder shedding, was loose and had extremely low strength, and could not achieve electrical conductivity.

[0117] Comparative Example 2

[0118] This comparative example provides a method for preparing conductive zirconia ceramics. Except for the sintering process in step (3) where nitrogen is not introduced, the method is the same as in Example 1 and will not be repeated here.

[0119] In this comparative example, no nitrogen gas was introduced, resulting in no ZrN phase being formed and no electrical conductivity.

[0120] As can be seen from Example 1 and Comparative Examples 1-2, the present invention can promote the formation of ZrN in the presence of a nitrogen-containing gas source or a nitrogen-containing compound, which is beneficial to the realization of electrical conductivity.

[0121] Comparative Example 3

[0122] This comparative example provides a method for preparing conductive zirconia ceramics. Except for skipping the pressurized stirring in step (1) and the cooling and crushing in step (2), the method is the same as in Example 1, except that the binder is directly mixed in and ball-milled to obtain zirconia particles with an average particle size of 2-3 mm. The rest of the method is the same as in Example 1 and will not be repeated here.

[0123] Because the comparative example does not perform the pressurized stirring in step (1) and the cooling and crushing in step (2), it is difficult to form zirconia ceramics with a conductive structure.

[0124] As can be seen from Example 1 and Comparative Examples 1-3, the present invention combines the steps of ball milling, drying, heating and stirring, pressurizing and stirring, cooling and crushing. These steps work in a specific order to obtain ceramic products with higher bonding strength and higher conductivity.

[0125] Test methods: The cross-sectional thickness of conductive zirconia ceramics was observed and measured using scanning electron microscopy. The ZrN, ZrCN, ZrCN and zirconia contents on the upper surface of the conductive zirconia ceramics were analyzed semi-quantitatively using XRD. The conductivity of the conductive zirconia ceramics was tested using the four-probe method. The presence of obvious cracks and pores or other defects at the interface of the conductive zirconia ceramics was observed using scanning electron microscopy.

[0126] The test results of the above embodiments and comparative examples are shown in Table 1.

[0127] Table 1

[0128] Thickness μm Zirconia content % ZrN content % ZrCN content % ZrNO content % Whether an alloy interface is formed Resistivity (μΩ·cm) Example 1 1.65 10 90 0 0 yes <![CDATA[5.0×10 3 ]]> Example 2 1.8 0 100 0 0 / <![CDATA[3.0×10 3 ]]> Example 3 1.1 30 60 5 15 yes <![CDATA[9.1×10 3 ]]> Example 4 1.5 20 60 0 0 yes <![CDATA[8.2×10 3 ]]> Example 5 0.8 40 30 0 30 yes <![CDATA[31.0×10 3 ]]>

[0129] The following points can be observed from Table 1:

[0130] As can be seen from Examples 1-3, the additive manufacturing method for preparing conductive zirconia ceramics provided by the present invention can produce conductive zirconia ceramics with excellent performance, strong bonding strength, and resistivity of 1×10⁻⁶. 4 Below μΩ·cm.

[0131] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing conductive zirconia ceramics by additive manufacturing, characterized in that, The method includes the following steps: (1) Zirconia powder, surface modifier and solvent are mixed, ball-milled and dried in sequence to obtain a first mixture; the first mixture is heated and stirred, and a binder is mixed in and then stirred under pressure to obtain a second mixture; a stabilizer is also added to the mixture in step (1); the stabilizer includes yttrium oxide; the mass ratio of the stabilizer to the zirconia powder is 1~4:100; the pressure of the stirring is 10~120MPa; (2) The second mixture is cooled and crushed in sequence to obtain zirconia granules; the zirconia granules are then processed by additive manufacturing to obtain a green body; (3) The green blank is degreased, and the degreased workpiece is sintered under nitrogen-containing conditions to obtain conductive zirconia ceramic; The final temperature of the sintering process is 1600~2000℃.

2. The method according to claim 1, characterized in that, The heating and stirring temperature in step (1) is 60~200℃.

3. The method according to claim 1, characterized in that, The heating and stirring time is 30~240 minutes.

4. The method according to claim 1, characterized in that, The mass ratio of the adhesive to the first mixture is 1:3 to 4.

5.

5. The method according to claim 1, characterized in that, The adhesive comprises any one or a combination of at least two of polyethylene glycol, phenolic resin, epoxy resin, ethyl cellulose, polystyrene, polypropylene, polyethylene, polyvinyl alcohol, polyvinyl butyral, or paraffin.

6. The method according to claim 1, characterized in that, The pressurized stirring time is 1 to 10 hours.

7. The method according to claim 1, characterized in that, The mass ratio of zirconium oxide powder to surface modifier in step (1) is 10~25:

1.

8. The method according to claim 1, characterized in that, The surface modifiers include stearic acid and / or calcium lignosulfonate.

9. The method according to claim 1, characterized in that, The solvent includes ethanol and / or water.

10. The method according to claim 1, characterized in that, The volume ratio of the total volume of the zirconium oxide powder, surface modifier and stabilizer to the volume of the solvent is 0.5~1.2:

1.

11. The method according to claim 1, characterized in that, The ball mill rotates at a speed of 100~500 r / min.

12. The method according to claim 1, characterized in that, The ball milling time is 1 to 20 hours.

13. The method according to claim 1, characterized in that, The drying temperature is 50~100℃.

14. The method according to claim 1, characterized in that, The drying time is 2 to 24 hours.

15. The method according to claim 1, characterized in that, The cooling mentioned in step (2) is cooling to room temperature.

16. The method according to claim 1, characterized in that, The particle size of the zirconia particles obtained after crushing is 1~10mm.

17. The method according to claim 1, characterized in that, The thickness of the additive manufacturing layer is 0.05~0.35mm.

18. The method according to claim 1, characterized in that, The printing speed of the additive manufacturing is 5~100mm / s.

19. The method according to claim 1, characterized in that, The feed flow rate for additive manufacturing is 70-100%.

20. The method according to claim 1, characterized in that, Step (2) also includes polishing the surface of the green blank.

21. The method according to claim 20, characterized in that, The surface roughness Ra after polishing is 0.1~1.

6.

22. The method according to claim 1, characterized in that, The conditions for nitrogen-containing elements mentioned in step (3) include: introducing nitrogen gas and / or placing a nitrogen-containing compound.

23. The method according to claim 1, characterized in that, The heating rate of the sintering process is 0.5~10℃ / min.

24. The method according to claim 1, characterized in that, The sintering process involves holding the sample at the final temperature for 1 to 8 hours.

25. The method according to claim 1, characterized in that, The degreasing method described in step (3) includes solvent degreasing and / or thermal degreasing.

26. The method according to claim 25, characterized in that, The solvent used for solvent degreasing includes any one or a combination of at least two of the following: water, ethanol, n-heptane, kerosene, diesel oil, or edible oil.

27. The method according to claim 25, characterized in that, The thermal degreasing process includes heating to a first temperature at a first heating rate and holding for a first time, then heating to a second temperature at a second heating rate and holding for a second time, then heating to a third temperature at a third heating rate and holding for a third time, and then heating to a fourth temperature at a fourth heating rate and holding for a fourth time.

28. The method according to claim 27, characterized in that, The first heating rate is 0.2~5℃ / min.

29. The method according to claim 27, characterized in that, The first temperature is 60~100℃.

30. The method according to claim 27, characterized in that, The first time period is 30 min to 10 h.

31. The method according to claim 27, characterized in that, The second heating rate is 0.2~5℃ / min.

32. The method according to claim 27, characterized in that, The second temperature is 180~220℃.

33. The method according to claim 27, characterized in that, The second time is 30 minutes to 12 hours.

34. The method according to claim 27, characterized in that, The third heating rate is 0.2~5℃ / min.

35. The method according to claim 27, characterized in that, The third temperature is 380~420℃.

36. The method according to claim 27, characterized in that, The third time period is 30 minutes to 12 hours.

37. The method according to claim 27, characterized in that, The fourth heating rate is 0.2~5℃ / min.

38. The method according to claim 27, characterized in that, The fourth temperature is 550~600℃.

39. The method according to claim 27, characterized in that, The fourth time period is 30 minutes to 8 hours.

40. The method according to claim 1, characterized in that, The method includes the following steps: (1) Mix zirconium oxide powder, surface modifier, stabilizer and solvent, and ball mill at a speed of 100~500 r / min for 1~20 h. The mass ratio of zirconium oxide powder to surface modifier is 10~25:1, the mass ratio of stabilizer to zirconium oxide powder is 1~4:100, the volume ratio of total volume of zirconium oxide powder, surface modifier and stabilizer to volume ratio of solvent is 0.5~1.2:1, and the time is 1~20 h; to obtain the first mixture; The first mixture is heated and stirred at 60~200℃ for 30~240 min, and then mixed with a binder and stirred under pressure of 10~120MPa for 1~10 h to obtain the second mixture; The mass ratio of the adhesive to the first mixture is 1:3~4.5; (2) The second mixture is cooled to room temperature and crushed in sequence to obtain zirconia particles with a particle size of 1~10mm; the zirconia particles are additively manufactured with a nozzle size of 0.05~3mm, a layer thickness of 0.05~0.35mm, a printing speed of 5~100mm / s, and a feed flow rate of 70~100% to obtain a green blank; the surface of the green blank is polished to make the surface roughness Ra of the polished surface 0.1~1.6; (3) The green blank is degreased, and the degreased workpiece is heated to 1500~2000℃ under nitrogen-containing conditions at a heating rate of 0.5~10℃ / min, and sintered at the final temperature for 1~8h to obtain conductive zirconia ceramic.

41. A conductive zirconia ceramic, characterized in that, The conductive zirconia ceramic is prepared by the additive manufacturing method for preparing conductive zirconia ceramic as described in any one of claims 1 to 40.

42. The conductive zirconia ceramic according to claim 41, characterized in that, The ZrN content in the conductive zirconia ceramic is 60~100%.

43. The conductive zirconia ceramic according to claim 41, characterized in that, The ZrCN content in the conductive zirconia ceramic is 0~20%.

44. The conductive zirconia ceramic according to claim 41, characterized in that, The ZrNO content in the conductive zirconia ceramic is 0~20%.

45. The conductive zirconia ceramic according to claim 41, characterized in that, The thickness of the conductive zirconia ceramic is 0.5~5μm.

46. ​​The use of a conductive zirconia ceramic according to any one of claims 41-45 in engine parts, chemical industry, biomedical devices, bulletproof armor or abrasives.

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