Production method of zirconium oxide block

Abstract

The invention belongs to the technical field of zirconia block production, and particularly relates to a zirconia block production method, which comprises: S1, raw material selection: selecting treated zirconia powder, a dispersant and an adhesive, and carrying out proportioning and pretreatment according to a certain ratio to obtain zirconia pressed powder; in the step S1, raw material pretreatment specifically comprises the following steps: S11, yttrium oxide with the addition amount of 0.5%-1% is selected as zirconium oxide powder, ammonium polyacrylate is adopted as a dispersing agent, and polyvinyl alcohol is adopted as a binding agent; and S12, putting the zirconium oxide powder and water or ethanol into a ball milling tank, grinding for 24-48 hours by taking the zirconium oxide balls as a grinding medium, taking out the zirconium oxide powder, and separating out the zirconium oxide balls and grinding liquid. The inner wall of the mold can be changed into an inclined state, friction force between powder and the mold wall is reduced, and pressure transmission is more uniform.

Description

Technical Field

[0001] This invention belongs to the field of zirconia block production technology, and specifically relates to a method for producing zirconia blocks. Background Technology

[0002] Zirconia blocks are high-performance inorganic non-metallic material products with zirconium oxide (ZrO2) as the main component. Due to their excellent physicochemical properties, they are widely used in many fields.

[0003] Pure zirconium oxide is a monoclinic phase at room temperature, but it transforms into tetragonal and cubic phases at high temperatures. Adding stabilizers can maintain the tetragonal or cubic phase at room temperature, avoiding volume expansion and cracking caused by phase transformation, and improving the strength and stability of the material.

[0004] In the current production process of zirconia blocks, zirconia often needs to be placed in a mold for high-pressure shaping. However, the metal molds traditionally used are often cylindrical molds. When the cylindrical mold is used for unidirectional pressing, the pressure is transmitted to the powder through the upper die punch, while the lower die punch only serves a supporting function. Due to the friction between the powder and the mold wall, the pressure decreases significantly along the axial direction, resulting in a situation where the density of the upper surface of the billet is high and the density of the lower surface is low.

[0005] In addition, the vertical cylindrical mold wall causes the friction between the powder and the mold wall to be transmitted radially inward, resulting in a large pressure loss at the edge and a relatively high pressure at the center, forming a radial density gradient of "low density at the edge and high density at the center". Therefore, the processed zirconia blocks often have uneven density during testing. Summary of the Invention

[0006] The purpose of this invention is to provide a method for producing zirconia blocks, which can change the inner wall of the mold to an inclined state, reduce the friction between the powder and the mold wall, and make the pressure transmission more uniform.

[0007] The specific technical solution adopted by this invention is as follows:

[0008] A method for producing zirconium oxide blocks, the method comprising the following steps:

[0009] S1: Raw material selection: Select the treated zirconia powder, dispersant, and binder, and mix and pretreat them according to the proportions to obtain zirconia pressed powder;

[0010] In step S1, the raw material pretreatment specifically includes the following steps:

[0011] S11: The zirconium oxide powder is selected with an addition amount of 0.5%-1% of yttrium oxide, the dispersant is ammonium polyacrylate, and the binder is polyvinyl alcohol;

[0012] S12: Place zirconia powder, water or ethanol in a ball mill jar, use zirconia balls as the grinding medium, grind for 24-48 hours, then remove the zirconia powder and separate the zirconia balls and grinding liquid.

[0013] S13: After the milled zirconium oxide powder is dried in a dryer, it is broken up and sieved. The zirconium oxide powder with larger particle size is then fed back into the next ball milling process.

[0014] In step S13, after sieving, the particle size of the zirconium oxide powder is 0.4-1 μm.

[0015] S14: After uniformly mixing zirconium oxide powder with dispersant and binder, zirconium oxide pressed powder with a purity ≥99% is obtained.

[0016] S2: Zirconia powder is packed into a specific metal mold and extruded using cold isostatic pressing to obtain zirconia billet.

[0017] In step S2, the specific metal mold is a cylindrical mold, and the inner wall of the cylindrical mold is inclined from top to bottom towards the central axis, with an inclination of 1-5°. A high-pressure resistant metal pad is provided at the bottom of the inner cavity of the cylindrical mold, and both the cylindrical mold and the high-pressure resistant metal pad are made of tungsten steel.

[0018] In step S2, the specific steps of extrusion molding are as follows:

[0019] S21: First, place the metal high-pressure resistant pad at the bottom of the mold cavity, and then fill the mold with zirconium oxide pressed powder according to the weight.

[0020] S22: Place the filled mold on a vibratory machine for compaction, for initial shaping;

[0021] S23: Next, place the mold on the press, inject auxiliary liquid, apply pressure to the press to extrude the zirconium oxide powder in the mold, the pressure is 100-400MPa, and the pressure is held for 10-50 minutes.

[0022] S24: After the pressure holding is completed, remove the mold and press the metal high-pressure resistant pad upward to remove the zirconia from the mold and obtain the zirconia block blank.

[0023] S3: Sinter the zirconia block blank to obtain the initial zirconia block;

[0024] In step S3, the specific steps of sintering are as follows:

[0025] S31: Place the zirconia billet blanks one by one onto the Luoyang Institute of Materials Technology and Engineering (Luoyang Institute of Materials Technology and Engineering) support, and place the Luoyang Institute of Materials Technology and Engineering support into the combustion furnace one by one, with a gap of 0.02-0.05m between two adjacent Luoyang Institute of Materials Technology and Engineering support;

[0026] S32: Firing temperature is 1000℃-1700℃, firing time is 10-18h, and holding time is 48-98h;

[0027] During the firing process, the heating rate shall not exceed 5℃-8℃ / min.

[0028] S4: Shape and test the initial zirconia block to obtain the finished zirconia block.

[0029] In step S4, the specific steps for shaping the initial zirconia block are as follows:

[0030] S41: Place the initial zirconia block on the grinding table and use a zirconia step turner to grind the edges and corners of the initial zirconia block to eliminate burrs or depressions at the edges and corners of the initial zirconia block. The surface roughness after grinding is less than 0.1μm.

[0031] S42: A protective layer is deposited on the surface of the initial zirconia block using chemical vapor deposition. The protective layer is any one of the following: a TiN metal layer, an antibacterial layer, or a wear-resistant layer.

[0032] In S4, the initial zirconia block inspection uses Archimedes' displacement method to perform density testing.

[0033] The compressive strength was tested using the three-point bending method.

[0034] SEM was used to observe the grain state and detect its distribution.

[0035] The technical effects achieved by this invention are as follows:

[0036] The present invention provides a method for producing zirconia blocks that can change the inner wall of the mold to an inclined state, reduce the friction between the powder and the mold wall, make the pressure transmission more uniform, reduce pressure loss, and help reduce the density difference between the axial and radial sides of the blank, resulting in high density consistency of the zirconia blocks after molding. Attached Figure Description

[0037] Figure 1 This is a flowchart of the present invention;

[0038] Figure 2 This is a schematic diagram of the structure of a specific metal mold of the present invention. Detailed Implementation

[0039] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention.

[0040] like Figures 1-2As shown, a method for producing zirconium oxide blocks includes the following steps:

[0041] S1: Raw material selection: Select treated zirconia powder, dispersant, and binder, and mix and pretreat them according to the ratio to obtain zirconia pressed powder, which is used to improve powder flowability and molding performance.

[0042] In S1, the raw material pretreatment specifically includes the following steps:

[0043] S11: The zirconium oxide powder is made of 0.5%-1% yttrium oxide, the dispersant is ammonium polyacrylate, and the binder is polyvinyl alcohol. Yttrium oxide can effectively inhibit the volume change of zirconium oxide during the phase transformation process, prevent material cracking, and improve the stability and toughness of zirconium oxide blocks.

[0044] Ammonium polyacrylate, as a dispersant, contains a large number of hydrophilic groups in its molecular structure, which can be adsorbed on the surface of zirconium oxide powder. Through electrostatic repulsion and steric hindrance, it effectively prevents powder agglomeration, so that the powder is evenly dispersed during the grinding process, thereby improving grinding efficiency and powder quality.

[0045] Polyvinyl alcohol has good adhesion and film-forming properties, which can make the zirconium oxide powder particles tightly bonded during subsequent molding processes, ensuring the strength and shape stability of the blank, and facilitating the processing and transportation of the blank.

[0046] S12: Placing zirconia powder, water, or ethanol in a ball mill jar can prevent the introduction of impurities during the grinding process, which would affect the purity of the zirconia powder. Using zirconia balls as the grinding medium, after grinding for 24-48 hours, the zirconia powder is removed to separate the zirconia balls and grinding liquid, thereby homogenizing the powder particle size and removing impurities.

[0047] The ball-to-powder ratio (mass ratio of spheres to zirconium oxide powder) is controlled between 5:1 and 10:1, and the rotation speed is set to 200-300 r / min. A suitable ball-to-powder ratio and rotation speed ensure effective impact and grinding of the powder by the spheres, resulting in better uniformity of powder particle size.

[0048] S13: After the milled zirconium oxide powder is dried in a dryer, it is broken up and sieved to facilitate subsequent molding. The zirconium oxide powder with larger particle size is then re-involved in the next ball milling.

[0049] A vacuum dryer is selected for drying in a vacuum environment, which lowers the boiling point of water or ethanol, accelerates the drying process, and prevents the zirconium oxide powder from oxidizing or agglomerating at high temperatures. The drying temperature is set at 60-80℃, and the drying time is adjusted according to the moisture content of the powder, generally 2-4 hours.

[0050] The process involves using a combination of a vibrating screen and a centrifuge to separate zirconia spheres from the grinding liquid. The vibrating screen can initially separate larger spheres, while the centrifuge can more thoroughly separate smaller particles and liquid, ensuring effective separation and improving the recovery rate of spheres and the purity of the powder.

[0051] In S13, the dried zirconia powder may clump together. An air jet disperser is used to disperse the clumps by using the impact force of high-speed airflow. After sieving, the particle size of the zirconia powder is 0.4-1μm.

[0052] S14: After uniformly mixing zirconium oxide powder with dispersant and binder, zirconium oxide pressed powder with a purity ≥99% is obtained.

[0053] S2: Zirconia powder is packed into a specific metal mold and extruded using cold isostatic pressing to obtain zirconia billet.

[0054] Specifically, a double-cone mixer is used. Its unique structural design enables three-dimensional movement of materials during the mixing process, ensuring thorough and uniform mixing of zirconia powder, dispersant, and binder. The mixing time is set according to the amount of material and the mixer speed, preferably 30-60 minutes.

[0055] In S2, a specific metal mold is a cylindrical mold, and the inner wall of the cylindrical mold slopes downwards towards the central axis, with an inclination of 1-5°. A high-pressure resistant metal pad is installed at the bottom of the inner cavity of the cylindrical mold, and both the cylindrical mold and the high-pressure resistant metal pad are made of tungsten steel.

[0056] In some embodiments, the cylindrical mold is designed with its inner wall inclined at 1-5° from top to bottom towards the central axis. This inclined structure facilitates better filling of the mold by the zirconia powder under pressure during the extrusion molding process, reducing air residue and improving the density of the preform. At the same time, the inclined inner wall makes it easier to remove the preform during demolding, reducing the probability of preform damage.

[0057] In addition, a high-pressure resistant metal backing plate, made of tungsten steel, is placed at the bottom of the mold cavity. Tungsten steel is characterized by high hardness and high compressive strength, capable of withstanding the high pressure applied by the press, ensuring that the backing plate does not deform during extrusion, thereby ensuring the shape and dimensional accuracy of the billet bottom. The surface of the backing plate is polished, with a roughness controlled below 0.05μm, to prevent unevenness of the backing plate surface from affecting the quality of the billet bottom.

[0058] In S2, the specific steps of extrusion molding are as follows:

[0059] S21: First, place the metal high-pressure resistant pad at the bottom of the mold cavity, and then fill the mold with zirconium oxide pressed powder according to the weight.

[0060] S22: Place the filled mold on a vibratory machine for compaction, for initial shaping;

[0061] S23: Next, place the mold on the press, inject auxiliary liquid, and apply pressure to the press to extrude the zirconia powder inside the mold. The pressure is 100-400MPa, and the pressure is held for 10-50 minutes. During the holding pressure process, the continuous pressure further compacts the zirconia powder, making the bond between particles tighter and improving the strength and density of the blank.

[0062] S24: After the pressure holding is completed, remove the mold and press the metal high-pressure resistant pad upward to remove the zirconia from the mold and obtain the zirconia block blank.

[0063] The filled mold is placed on a vibrator with a vibration frequency of 50-100Hz and a vibration time of 3-5 minutes. The vibration compacts the powder to initially shape it, reduce the gaps between the powder particles, and increase the initial density of the green body.

[0064] Specific mold design and scientific extrusion molding process improve the forming quality and production efficiency of the green body. The inclined structure of the mold and the use of high-pressure resistant pads ensure the density and dimensional accuracy of the green body, reducing defects and scrap rates. Precise control of filling, compaction, and extrusion parameters ensures stable green body quality, providing a good foundation for subsequent sintering processes.

[0065] S3: Sinter the zirconia block blank to obtain the initial zirconia block;

[0066] In S3, the specific sintering steps are as follows:

[0067] S31: Place the zirconia billets one by one onto the Luoyang Institute of Technology (RI) support, and then place the RI support into the combustion furnace one by one. The interval between two adjacent RI support should be 0.02-0.05m. This spacing is conducive to the uniform circulation of hot gas in the furnace, ensuring that the billets have enough space for heat exchange and gas discharge during the sintering process, and ensuring that the billets on each tray are heated evenly, avoiding local overheating or undercooling. The surface of the tray should be flat and smooth, with a roughness controlled below 0.1μm, to ensure that the zirconia billets are placed stably on the tray.

[0068] S32: Firing temperature is 1000℃-1700℃, firing time is 10-18h, and holding time is 48-98h;

[0069] During firing, the heating rate should not exceed 5℃-8℃ / min. Slow heating allows for the full expulsion of moisture and organic matter from the blank, preventing cracking or deformation of the blank due to excessively rapid heating.

[0070] S4: Shape and test the initial zirconia block to obtain the finished zirconia block.

[0071] In S4, the specific steps for shaping the initial zirconia block are as follows:

[0072] S41: Place the initial zirconia block on the grinding table and use a zirconia step turner to grind the edges and corners of the initial zirconia block to eliminate burrs or depressions at the edges and corners of the initial zirconia block. The surface roughness after grinding is less than 0.1μm.

[0073] During the grinding process, a combination of rough grinding and fine grinding is used. In the rough grinding stage, a coarser-grit zirconia step-turning wheel is used to quickly remove burrs and large depressions from the edges and corners of the initial zirconia block. In the fine grinding stage, a finer-grit grinding wheel is used to further improve the surface finish. Throughout the grinding process, the grinding dimensions and surface quality are monitored in real time to ensure that the dimensional accuracy and surface quality of the ground zirconia block meet the requirements.

[0074] S42: A protective layer is deposited on the surface of the initial zirconia block using chemical vapor deposition. The protective layer is any one of the following: a TiN metal layer, an antibacterial layer, or a wear-resistant layer.

[0075] Taking TiN metal layer coating as an example, an initial zirconia block is placed in a vacuum chamber, and reactive gases (such as TiCl4 and N2) are introduced. Under the action of plasma, the reactive gases undergo a chemical reaction, depositing a TiN metal layer on the surface of the zirconia block. By controlling parameters such as the flow rate of the reactive gases, deposition time, and temperature, the thickness and quality of the TiN metal layer can be precisely controlled. Generally, the thickness of the TiN metal layer is controlled between 0.5-2 μm, giving it good wear resistance, corrosion resistance, and decorative properties.

[0076] In S4, the initial zirconia block inspection uses Archimedes' displacement method for density testing. The initial zirconia block is completely immersed in water, the volume of water displaced is measured, and the density of the zirconia block is calculated using the density formula. By comparing the density with the theoretical density, the compactness of the zirconia block is determined. If the density is lower than the standard value, there may be defects such as internal pores, requiring further analysis of the cause.

[0077] The compressive strength test was conducted using the three-point bending method. A zirconia block was placed on two support points of the testing equipment, and pressure was applied at the middle position. The maximum pressure value at which the zirconia block fractured was recorded, and the compressive strength was calculated using the formula. Compressive strength is an important indicator for evaluating the mechanical properties of zirconia blocks; this test ensures that the product's strength meets usage requirements.

[0078] SEM (Scanning Electron Microscopy) was used to observe and detect the grain morphology and distribution. Zirconia block samples were surface-treated and then observed under a scanning electron microscope. SEM images clearly show the size, shape, and distribution of the grains, allowing for an assessment of the impact of the sintering process on the grain structure and providing a basis for optimizing the production process.

[0079] High-precision grinding and coating processes improve the surface quality and performance of zirconia blocks, enabling them to meet diverse application requirements. Comprehensive testing methods accurately assess the quality of zirconia blocks, promptly identify product problems, ensure the reliability of finished zirconia blocks, and enhance the product's market competitiveness.

[0080] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A method of producing a zirconia block, characterized by: The production method comprises the following steps: S1: raw material selection: selecting treated zirconia powder, dispersant, and binder, and proportioning and pretreating to obtain zirconia pressing powder; S2: loading the zirconia pressing powder into a special metal mold and extruding into a shape by cold isostatic pressing to obtain a zirconia block blank; S3: sintering the zirconia block blank to obtain an initial zirconia block; S4: shaping and detecting the initial zirconia block to obtain a finished zirconia block.

2. A method of producing a zirconia block according to claim 1, characterized in that: In S1, the raw material pretreatment specifically comprises the following steps: S11: the zirconia powder is selected with an added amount of 0.5%-1% yttrium oxide, the dispersant is polyacrylamide, and the binder is polyvinyl alcohol; S12: the zirconia powder, water or ethanol is placed in a ball mill tank, zirconia spheres are used as grinding media, after grinding for 24-48h, the zirconia powder is taken out and the zirconia spheres and grinding liquid are separated; S13: after drying the ground zirconia powder by a dryer, it is scattered and sieved, and the zirconia powder with a larger particle size is reused for the next ball milling; S14: after mixing the zirconia powder with the dispersant and the binder uniformly, zirconia pressing powder with a purity of ≥99% is obtained.

3. A method of producing a zirconia block according to claim 2, characterized in that: In S13, after sieving, the particle size of the zirconia powder is 0.4-1μm.

4. The method of producing a zirconia block according to claim 1, characterized by: In S2, the special metal mold is a cylindrical mold, the inner wall of the cylindrical mold is inclined from top to bottom towards one side of the central axis, and a metal high-pressure-resistant pad is arranged at the bottom of the inner cavity of the cylindrical mold, and the materials of the cylindrical mold and the metal high-pressure-resistant pad are tungsten steel.

5. A method of producing a zirconia block according to claim 4, characterized in that: The inclination of the inner wall of the cylindrical mold is 1-5°.

6. The method of producing a zirconia block according to claim 1, characterized by: In S2, the extrusion molding specifically comprises the following steps: S21: first, place the metal high-pressure-resistant pad at the bottom of the inner cavity of the mold, and then load the zirconia pressing powder into the mold according to the gram weight; S22: place the loaded mold on a vibrating machine for vibration and compaction for preliminary shaping; S23: then place the mold on a press, inject an auxiliary liquid, and apply pressure to the mold by the press to extrude the zirconia pressing powder in the mold, the pressure is 100-400MPa, and the pressure is maintained for 10-50min; S24: after the pressure maintaining is completed, the mold is taken out, and the metal high-pressure-resistant pad is pressed upward to take out the zirconia from the mold to obtain a zirconia block blank.

7. The method of producing a zirconia block according to claim 1, characterized by: In S3, the sintering specifically comprises the following steps: S31: stack the zirconia block blanks on the LoNaiYuan support one by one, and place the LoNaiYuan supports in the combustion furnace one by one, and the adjacent two LoNaiYuan supports need to be spaced apart by 0.02-0.05m; S32: the sintering temperature is 1000℃-1700℃, the sintering time is 10-18h, and the holding time is 48-98h; During the sintering process, the temperature rising rate is not more than 5-8℃ / min.

8. The method of producing a zirconia block according to claim 1, characterized by: In S4, the shaping of the initial zirconia block specifically comprises the following steps: S41: place the initial zirconia block on a grinding table, use zirconia step turning to grind the edge and corner positions of the initial zirconia block to eliminate burrs or depressions at the edge and corner positions of the initial zirconia block, and the surface roughness after grinding is less than 0.1μm; S42: A protective layer is plated on the surface of the initial zirconia block by chemical vapor deposition, and the protective layer is any one of a TiN metal layer, an antibacterial layer, and a wear-resistant layer.

9. The method of producing a zirconia block according to claim 1, characterized by: In the S4, the initial zirconia block is subjected to density testing by the Archimedes drainage method. The compressive strength is tested by the three-point bending method. The grain state observation and distribution detection are performed by SEM.

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