A method for preparing a zirconia-based medical composite ceramic material

Abstract

This invention relates to the field of medical ceramic materials technology, and more particularly to a method for preparing a zirconia-based medical composite ceramic material. The method includes: adjusting the target number of cycles in response to the slurry mixing state, or compensatingly adjusting the spray granulation process parameters based on slurry state parameters; determining whether the current batch of green bodies has a risk of closed pores based on the green body characteristics, and determining an adjustment feature point based on the actual shrinkage rate variation; stopping the sintering heating and adding a holding stage in response to the adjustment feature point, and determining the intermediate holding temperature and the holding stage duration; obtaining the sintered body phase to determine the tetragonal zirconia retention rate, and determining whether the sintering adjustment strategy matches the characteristics of the current batch of slurry based on the sintered body performance; and adjusting the intermediate holding temperature of subsequent sintering processes based on the tetragonal phase retention rate deviation in response to the sintered body performance. This invention improves the performance of ceramic implants by adjusting the sintering temperature curve based on the characteristics of zirconia-based powder.

Description

Technical Field

[0001] This invention relates to the field of medical ceramic materials technology, and in particular to a method for preparing a zirconia-based medical composite ceramic material. Background Technology

[0002] Zirconia ceramics, especially yttrium-stabilized tetragonal zirconia, are widely used in medical fields, particularly in dental restorations (such as crowns and bridges) and orthopedic implants (such as femoral heads), due to their high strength, high fracture toughness, good wear resistance, and excellent biocompatibility. Their core toughening mechanism lies in the stress-induced martensitic transformation from the tetragonal phase to the monoclinic phase, i.e., "phase transformation toughening." However, pure Y-TZP carries the risk of low-temperature aging (LTD), meaning that during long-term use in humid environments, the metastable tetragonal phase will transform into the monoclinic phase, leading to microcracks and performance degradation. Furthermore, its fracture toughness is still relatively high compared to human bone, and its bioactivity is insufficient.

[0003] Chinese Patent Publication No. CN109574634A discloses a medical alumina ceramic composite material and its preparation method, comprising the following steps: mixing 98-99.75% vol alumina ceramic with 0.25-2% vol graphene, pressing the mixture into a green body, sintering the green body at 1450-1650℃, and then cooling it. The medical alumina ceramic composite material prepared by this method has advantages such as being less prone to aging, having good wear resistance, high flexural strength, good fracture toughness, and good biocompatibility. However, the medical alumina ceramic composite material and its preparation method have the following problems:

[0004] Composite systems with added alumina or other second-phase materials introduce heterogeneous phase interfaces, which may become crack sources, affect optical properties, or interfere with the phase transformation toughening effect of zirconia. Summary of the Invention

[0005] Therefore, the present invention provides a method for preparing medical composite ceramic materials based on zirconia, in order to overcome the problem that the introduction of heterogeneous phase interfaces in the prior art interferes with the phase transformation toughening effect of zirconia.

[0006] To achieve the above objectives, the present invention provides a method for preparing a zirconia-based medical composite ceramic material, comprising:

[0007] The slurry is cyclically wet ball-milled according to the target number of cycles to obtain one of the particle size distribution characteristic values ​​of the slurry and the actual slurry viscosity to determine the slurry dispersibility index, so as to determine the slurry mixing state;

[0008] The target number of cycles is adjusted in response to the slurry mixing state, or the spray granulation process parameters are adjusted compensatorily based on the slurry state parameters.

[0009] The dynamic sintering activity index is determined by combining the powder filling characteristic parameters and the initial compaction density of the green body with the slurry dispersity index, so as to determine the green body characteristics of the current batch of green bodies.

[0010] Based on another particle size distribution characteristic value of the slurry, the sintering driving force of the green body in the sintering process is predicted, the heating rate of the sintering process is adjusted, and the sintering adjustment strategy of the sintering process is dynamically adjusted based on the dynamic sintering activity index in response to the green body characteristics.

[0011] Based on the characteristics of the green body, determine whether there is a risk of grain coarsening in the sintering process, and obtain the actual relative density of the green body to adjust the temperature stage and sintering temperature of the sintering process.

[0012] Based on the characteristics of the green blank, determine whether there is a risk of closed pores in the current batch of green blanks, and determine the adjustment feature point in combination with the degree of change in the actual shrinkage rate. In response to the adjustment feature point, stop the sintering heating and add a heat preservation stage, and determine the intermediate heat preservation temperature and the heat preservation stage duration.

[0013] The sintered body phase is obtained to determine the tetragonal zirconia retention rate. Based on the sintered body properties, it is determined whether the sintering adjustment strategy matches the characteristics of the current batch of slurry. In response to the sintered body properties, the intermediate holding temperature of the subsequent sintering process is adjusted according to the tetragonal phase retention rate deviation.

[0014] Furthermore, the slurry in the grinding chamber is sampled and tested to obtain the particle size distribution characteristic value and the actual slurry viscosity to determine the slurry dispersibility index;

[0015] When the slurry dispersibility index is greater than or equal to the first index threshold, the slurry is determined to be in the first mixing state, and the slurry fineness and fluidity meet the requirements. The current number of cycles of wet ball milling is set as the target number of cycles.

[0016] When the slurry dispersity index is less than the first index threshold and greater than or equal to the second index threshold, the slurry is determined to be in a second mixed state. The slurry state has an adjustable deviation, and compensatory adjustments are made to subsequent processes.

[0017] When the slurry dispersibility index is less than the second index threshold, the slurry is determined to be in the third mixing state. The slurry state does not meet the requirements, and the target number of wet ball milling is increased.

[0018] The particle size distribution characteristics of the slurry include the D90 value and the median particle size D50 value.

[0019] Furthermore, when the slurry is in the second mixing state, the spray granulation process parameters are adjusted according to the slurry state parameters, which include viscosity ratio and fineness ratio;

[0020] If the actual slurry viscosity is greater than the target slurry viscosity, the liquid-solid content of the spray granulation material is reduced proportionally according to the ratio of the target slurry viscosity to the actual slurry viscosity.

[0021] If the particle size distribution characteristic value is greater than the target characteristic value, the atomization pressure of spray granulation is increased according to the ratio of the particle size distribution characteristic value to the target characteristic value.

[0022] Furthermore, the dynamic sintering activity index is calculated by obtaining the powder filling characteristic parameters and the initial compaction density of the green body to reflect the green body characteristics of the current batch of green bodies. The powder filling characteristic parameters are the actual tap density of the powder.

[0023] When the dynamic sintering activity index exceeds the calibrated index range, it is determined that the current batch of green blanks has the characteristics of intrinsic activity and green blank microstructure exceeding the range, and the sintering driving force and densification rate exceed the preset range.

[0024] When the dynamic sintering activity index is within the calibrated index range, it is determined that the green characteristics of the current batch of green blanks are within the preset range;

[0025] When the dynamic sintering activity index is lower than the calibrated index range, it is determined that the current batch of green blanks has porosity due to poor dispersion or poor pressing efficiency, resulting in high sintering resistance.

[0026] Furthermore, the sintering driving force coefficient was determined based on the median particle size D50 value;

[0027] When the sintering driving force coefficient is greater than the driving force warning threshold, it is determined that the current batch of slurry has a driving force risk of excessive densification rate under the current sintering parameters, and the heating rate of the sintering process is adjusted according to the sintering driving force coefficient.

[0028] Furthermore, if the current batch of green blanks possesses green blank characteristics of intrinsic activity and microstructure beyond the range, then the current batch of green blanks carries the risk of grain coarsening during the sintering process.

[0029] Obtain the initial volume, initial mass, and initial length of the green blank, and detect the linear shrinkage of the green blank in the axial or radial direction to determine the actual relative density;

[0030] When the actual relative density is greater than the critical relative density, it is determined that the current batch of green blanks has been densified to the critical density. The sintering temperature is then reduced to the preset adjustment range according to the maximum controllable temperature adjustment rate, and the temperature is kept for the preset holding time.

[0031] Furthermore, when the sintering resistance of the current batch of green billets is high, it is determined that there is a risk of forming closed pores in the current batch of green billets, and the adjustment characteristic point is determined based on the degree of change in the actual shrinkage rate.

[0032] Calculate the actual shrinkage rate based on the linear shrinkage amount, plot the actual shrinkage rate-actual sintering temperature curve, and obtain the maximum rate of the actual shrinkage rate-actual sintering temperature curve within a number of preset temperature ranges.

[0033] When the actual ratio of the maximum rate in the current preset temperature range to the average rate in the previous preset temperature range is greater than the minimum increase threshold, the maximum rate in the current preset temperature range is determined to meet the significance condition.

[0034] Furthermore, after determining the maximum rate of the interval that meets the significance condition, the linear fitting slope of the peak point corresponding to the maximum rate of the interval is calculated in the subsequent unit time. The contraction rate difference between several data points and the previous data point is obtained according to the preset temperature unit, and the proportion of the actual negative value of the contraction rate difference is calculated among the several contraction rate differences.

[0035] When the slope of the linear fitting is less than the slope threshold and the proportion of actual negative values ​​is greater than or equal to the proportion threshold, it is determined that the peak point corresponding to the maximum rate in the interval conforms to the continuous trend, and the dominant diffusion mechanism of the sintering stage corresponding to the current preset temperature interval exceeds the maximum rate period.

[0036] Furthermore, when the maximum rate in the interval meets the significance condition and the corresponding peak point meets the continuous trend, the heating is stopped and the sintering temperature is adjusted to the intermediate holding temperature, which is the actual sintering temperature corresponding to the maximum rate in the interval.

[0037] The actual shrinkage rate of the green body is detected in real time. When the actual shrinkage rate is less than the shrinkage rate evaluation value, it is determined that the porosity optimization through surface diffusion has ended, and the intermediate heat preservation stage is stopped to continue heating the green body for sintering. The shrinkage rate evaluation value is the product of the maximum rate in the interval and the calibrated percentage.

[0038] Furthermore, samples were taken from the sintered body after sintering, and the phase composition of the sintered body was analyzed to confirm the retention rate of tetragonal zirconium oxide.

[0039] When the tetragonal zirconium oxide retention rate is greater than or equal to the target retention rate, the sintered body performance is judged to meet the standard, and the sintering strategy is matched with the characteristics of the current batch of slurry.

[0040] When the tetragonal zirconium oxide retention rate is less than the target retention rate, it is determined that the sintered body performance is insecure due to insufficient tetragonal phase retention. The intermediate holding temperature of the subsequent sintering process is adjusted according to the deviation of the tetragonal phase retention rate.

[0041] Compared with existing technologies, the advantages of this invention lie in its ability to prepare ceramic implants using zirconium oxide as the main component through online slurry state diagnosis, dynamic prediction of sintering activity, and closed-loop control throughout the entire process. Compared with existing composite schemes that add alumina, this invention achieves a fundamental improvement in the material's resistance to low-temperature aging through high-purity component control and precise yttrium stabilization, fundamentally avoiding the risks of micro-stress and crack initiation at heterogeneous interfaces caused by the mismatch in thermal expansion coefficients of alumina and zirconium oxide. Simultaneously, this invention utilizes a dynamic sintering activity index intelligent matching sintering strategy, leveraging the higher phase transformation toughening potential of the pure zirconium oxide system while effectively suppressing grain coarsening and closed-pore formation through control methods such as "critical density triggering" and "shrinkage rate peak monitoring," ultimately obtaining a fine, dense, and uniform microstructure. The prepared implants maintain high strength and excellent biocompatibility, while exhibiting significantly better long-term service stability and reliability than zirconium oxide-alumina composite materials.

[0042] Furthermore, this method employs a circulating wet ball milling method to ensure that powders of different components achieve uniform mixing at the molecular level. Nanoparticles are prone to agglomerate into large "soft aggregates," and wet ball milling can effectively break up these aggregates, further reducing the particle size of the powder and increasing its specific surface area. This results in higher activity and easier densification of the powder during subsequent sintering. The spray granulation method involves adding a small amount of high-purity organic binder (such as polyvinyl alcohol) to the slurry after ball milling. The slurry is then placed in a spray granulator, sprayed through nozzles as droplets, and dried to obtain spherical granulated powder with good flowability and concentrated particle size distribution. By reducing surface energy, the flowability is improved, and the powder uniformly fills the mold, ensuring the subsequent automated molding process.

[0043] Furthermore, the slurry dispersibility index includes viscosity ratio and fineness ratio. The lower the measured viscosity (smaller η), the larger this ratio indicates better slurry flowability and potentially better dispersibility. The fewer the measured large particles (smaller D90), the larger this ratio indicates better grinding effect and effective breaking down of large particle agglomerates. This invention integrates "grinding fineness" and "flowability and dispersibility" to introduce a slurry dispersibility index to reflect the slurry state. Based on the actual dispersion state of the slurry, it can intelligently determine whether it is in an ideal, adjustable, or unqualified state based on the D90 value and viscosity calculation, and automatically make decisions to stop ball milling, compensate subsequent processes, or precisely increase the number of cycles. This method effectively avoids particle agglomeration caused by insufficient ball milling or pollution and energy waste caused by excessive ball milling, ensuring that the slurry has a highly uniform particle size distribution (D90 and D50) and excellent flowability, providing a stable and reliable precursor for subsequent spray granulation and sintering processes. It improves the uniformity and consistency of the microstructure of medical zirconia ceramic implants from the source, ultimately ensuring the mechanical properties and long-term reliability of the product.

[0044] Furthermore, this invention utilizes the refinement parameters of the slurry dispersibility index—viscosity ratio and fineness ratio—to precisely compensate for and control the spray granulation process of slurries in an adjustable deviation state. For excessively high viscosity, the system proportionally reduces the solid content of the liquid material, effectively ensuring atomization effect and drying uniformity; for excessively coarse particle size, the atomization pressure is proportionally increased to crush soft agglomerates and optimize particle size distribution. This dynamic adjustment mechanism overcomes the insufficient adaptability of fixed process parameters to precursor state fluctuations, significantly improving the flowability and filling uniformity of the granulated powder, laying a reliable powder foundation for the subsequent sintering process of preparing high-density, high-performance zirconia ceramic implants.

[0045] Furthermore, composite powders are more likely to achieve high density and rapid densification during sintering. Meanwhile, fine pores need to be eliminated through grain boundary diffusion or volume diffusion in the later stages of sintering. Insufficient temperature leaves residual micropores, while excessively high temperature or prolonged sintering time causes grains to grow rapidly and engulf pores, requiring timely suppression of grain growth. This invention constructs a dynamic sintering activity index to correlate the precursor slurry state with the green body forming characteristics, accurately predicting the green body sintering behavior in the sintering process. It comprehensively reflects the intrinsic activity of the powder, the slurry dispersion, the microstructure density of the green body, and the pressing efficiency, enabling early identification of grain coarsening risks caused by high activity or closed-pore defects caused by low density. Personalized pre-setting and dynamic control of the sintering process overcomes the industry problem that fixed sintering curves cannot adapt to batch fluctuations in raw materials, improving the uniformity and density of the zirconia implant microstructure.

[0046] Furthermore, the sintering driving force is inversely proportional to the powder particle size. Green bodies composed of composite powders have extremely high sintering driving forces. If the heating rate is not properly controlled, excessively high driving forces can lead to excessively fast sintering rates, potentially causing premature surface densification and "shell formation," which blocks the channels for internal pores to escape and ultimately forms closed pores. Therefore, it is necessary to adjust the heating rate based on the powder particle size. This method predicts the sintering driving force of the green body during the sintering process by using the particle size distribution characteristics of the slurry, actively slowing down the input of heat energy, providing more time for material diffusion, especially the migration of internal materials, balancing the densification process of the surface and the interior, and preventing "shell formation" procedurally. This serves as a refined management measure before subsequent control measures, avoiding the risk of shell formation and closed pores.

[0047] Furthermore, a high DSAI value signifies extremely high intrinsic sintering activity and excellent initial microstructure, resulting in strong sintering driving force. Under traditional single-heating sintering curves, the densification rate is too fast, leading to rapid grain boundary migration and grain coarsening. Closed pores are encapsulated by grains, forming difficult-to-eliminate "intragranular pores" that become crack sources. The core of this method lies in actively separating the densification process from the grain growth process in time. Through a real-time density feedback triggering adjustment strategy, the rate of grain boundary migration is greatly suppressed after temperature adjustment due to its higher activation energy, while atomic diffusion along the grain boundaries can still proceed effectively. This allows the material to be continuously transported to the closed pores, causing them to gradually shrink and disappear. However, since the grain boundaries hardly move, the grain size is maintained at the small state at the end of the first step. By utilizing the high activity of the material to achieve rapid initial densification, and through a precise "density-triggered cooling" mechanism, the negative effects of high activity are avoided, ultimately obtaining a high-performance microstructure with fine grains, complete densification, and no intragranular pores.

[0048] Furthermore, a low DSAI value indicates the presence of large, irregularly shaped pores in the green body. The matrix material will sinter rapidly, leading to premature densification. Blocking the connection between large pores and the external environment, as well as the shrinkage path, reduces the material's density and reliability. This method intelligently identifies the significant peak and continuous downward trend of the shrinkage rate curve, accurately capturing the key node of the sintering mechanism's transition from surface diffusion to grain boundary diffusion. Based on this, it automatically triggers intermediate heat preservation, prioritizing the pretreatment and repair of potential large pores before the microstructure is "locked up." At temperatures where grains have not yet begun to grow significantly, the surface diffusion mechanism is used to smooth the pore surface and reduce pore size, providing sufficient time for surface diffusion-dominated pore optimization. This effectively eliminates the risk of closed pores formed due to premature closure of large pores in low-activity green bodies. By dynamically determining the heat preservation termination point based on the rate peak ratio, the optimal balance between pore repair and energy efficiency is achieved.

[0049] Furthermore, a low tetragonal phase retention rate usually indicates that the second-step holding temperature in sintering is too high or the holding time is too long, leading to excessive transformation of the metastable tetragonal phase into the stable cubic phase. This invention achieves closed-loop control of the long-term phase stability of the material by establishing a negative feedback adjustment mechanism between the tetragonal phase zirconia retention rate and sintering process parameters. When insufficient tetragonal phase retention rate is detected, the intermediate holding temperature of subsequent batches can be automatically reduced proportionally, effectively suppressing the excessive transformation of the tetragonal phase into the cubic phase, thereby significantly improving the low-temperature aging resistance of the implant. By setting a lower temperature limit, the risk of over-adjustment is avoided, ensuring that the product maintains excellent densification while achieving high phase stability, providing a key guarantee for the long-term clinical reliability of zirconia implants. Attached Figure Description

[0050] Figure 1This is a schematic flowchart of the method for preparing a zirconia-based medical composite ceramic material in an embodiment of the present invention;

[0051] Figure 2 This is a schematic diagram of the internal structure of the wet ball mill in an embodiment of the present invention;

[0052] Figure 3 This is a schematic diagram of the circulating wet ball milling process in an embodiment of the present invention;

[0053] Figure 4 This is a schematic diagram of the process for determining the slurry mixing state in an embodiment of the present invention;

[0054] In the diagram: 1-Wet grinding mill, 2-Circulating pump, 3-Circulating tank, 11-Material inlet, 12-Rotating shaft, 13-Grinding chamber, 14-Main shaft, 15-Slurry outlet, 16-Ball mill slurry, 17-Grinding balls. Detailed Implementation

[0055] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0056] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0057] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0058] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0059] Please see Figures 1-4 As shown, Figure 1 This is a schematic flowchart of the method for preparing a zirconia-based medical composite ceramic material in an embodiment of the present invention; Figure 2This is a schematic diagram of the internal structure of the wet ball mill in an embodiment of the present invention; Figure 3 This is a schematic diagram of the circulating wet ball milling process in an embodiment of the present invention; Figure 4 This is a schematic diagram of the process for determining the mixing state of the slurry in an embodiment of the present invention.

[0060] This invention provides a method for preparing a zirconia-based medical composite ceramic material, comprising:

[0061] Step S1: The slurry is cyclically wet ball-milled according to the target number of cycles to obtain one of the particle size distribution characteristic values ​​of the slurry and the actual slurry viscosity to determine the slurry dispersibility index, so as to determine the slurry mixing state;

[0062] Step S2: Adjust the target number of cycles in response to the slurry mixing state or adjust the spray granulation process parameters compensatorily based on the slurry state parameters;

[0063] Step S3: Obtain the powder filling characteristic parameters and the initial compaction density of the green body, and combine them with the slurry dispersion index to determine the dynamic sintering activity index, so as to determine the green body characteristics of the current batch of green bodies.

[0064] Step S4: Based on another particle size distribution characteristic value of the slurry, predict the sintering driving force of the green body in the sintering process, adjust the heating rate of the sintering process, and dynamically adjust the sintering adjustment strategy of the sintering process based on the dynamic sintering activity index in response to the green body characteristics.

[0065] Step S5: Based on the characteristics of the green body, determine whether there is a risk of grain coarsening in the sintering process, and obtain the actual relative density of the green body to adjust the temperature stage and sintering temperature of the sintering process.

[0066] Step S6: Based on the characteristics of the green blank, determine whether there is a risk of closed pores in the current batch of green blanks, and determine the adjustment feature point in combination with the degree of change in the actual shrinkage rate to stop sintering and heating and add a heat preservation stage in response to the adjustment feature point, and determine the intermediate heat preservation temperature and the heat preservation stage duration.

[0067] Step S7: Obtain the tetragonal zirconia retention rate of the sintered body phase to determine whether the sintering adjustment strategy matches the characteristics of the current batch of slurry based on the sintered body performance. In response to the sintered body performance, adjust the intermediate holding temperature of the subsequent sintering process according to the tetragonal phase retention rate deviation.

[0068] In this embodiment, the medical composite ceramic material is a ceramic implant with zirconium oxide as the main component. The chemical composition percentages in the medical composite ceramic material are as follows: ZrO2+HfO2+Y2O3≥99.0%, Y2O3>4.5%≤6.0%, HfO2≤5%, Al2O3≤0.5%, and other oxides≤0.5%.

[0069] The chemical and mechanical properties of qualified medical composite ceramic materials should meet the material performance requirements in YY / T 1715-2020.

[0070] Specifically, this invention uses zirconium oxide as the main component to prepare ceramic implants through online slurry state diagnosis, dynamic prediction of sintering activity, and closed-loop control throughout the entire process. Compared to existing composite schemes that add alumina, this invention achieves a fundamental improvement in the material's resistance to low-temperature aging through high-purity component control and precise yttrium stabilization, fundamentally avoiding the risks of micro-stress and crack initiation at heterogeneous interfaces caused by the mismatch in thermal expansion coefficients of alumina and zirconium oxide. Simultaneously, this invention utilizes a dynamic sintering activity index intelligent matching sintering strategy, taking advantage of the higher phase transformation toughening potential of the pure zirconium oxide system, and effectively suppressing grain coarsening and closed-pore formation through control methods such as "critical density triggering" and "shrinkage rate peak monitoring," ultimately obtaining a fine, dense, and uniform microstructure. The prepared implants maintain high strength and excellent biocompatibility, while exhibiting significantly better long-term service stability and reliability than zirconium oxide-alumina composite materials.

[0071] In this embodiment, yttrium-stabilized zirconia composite powder prepared by co-precipitation is selected as the main raw material, providing a method for preparing yttrium-stabilized zirconia composite powder by co-precipitation, including but not limited to.

[0072] Specifically, a salt solution containing zirconium, hafnium, and yttrium ions, such as zirconium oxychloride and yttrium nitrate, is mixed in the required stoichiometric ratio. Then, a precipitant, such as ammonia, is added to precipitate all the metal ions simultaneously and synchronously, forming a homogeneous hydroxide or carbonate precursor. After washing, drying, and calcination, yttrium-stabilized zirconium oxide composite powder is obtained.

[0073] To further ensure absolute homogeneity of the components and to break down soft agglomerates, the powder was mixed with anhydrous ethanol and trace amounts of a dispersant such as ammonium polyacrylate in a specific ratio to form a slurry. This slurry was then wet-milled using zirconia grinding balls and a planetary ball mill for 12 to 24 hours. This process achieved further nano-sizing and uniform mixing of the powder while avoiding the introduction of aluminum impurities exceeding standard levels.

[0074] Specifically, the preparation process of medical composite ceramic materials includes co-precipitation method for preparing yttrium-stabilized zirconia composite powder, wet ball milling, spray granulation, implant molding, high-temperature sintering, and post-treatment;

[0075] In this embodiment, a circulating wet ball milling method is used to wet ball mill the ball mill slurry 16 using a wet grinding mill 1. The ball mill slurry 16 to be dispersed is put into the cylindrical grinding chamber 13 containing grinding balls 17 through the material inlet 11 and continuously transported by the circulating pump 2. By adjusting the rotation of the rotary shaft 12 and other aspects, the operating parameters of the main shaft 14 are changed, so that the shear force and collision force between the grinding balls 17 are applied, and the ball mill slurry 16 is wet dispersed and output from the slurry outlet 15.

[0076] During implementation, the ball mill slurry 16 enters the circulation tank 3 through the slurry outlet 15, and is circulated to the material inlet 11 of the wet mill 1 by the output of the circulation pump 2, and then enters the grinding chamber 13.

[0077] Specifically, the circulating wet ball milling method ensures that powders of different components achieve uniform mixing at the molecular level. Nanoparticles are prone to agglomerate into large "soft aggregates". Wet ball milling can effectively break up these aggregates, further reduce the particle size of the powder, and increase its specific surface area, thereby making the powder more active and easier to densify in the subsequent sintering process. The spray granulation method adds a small amount of high-purity organic binder (such as polyvinyl alcohol) to the slurry after ball milling. The slurry is put into a spray granulator and sprayed into droplets through the nozzle and then dried to obtain spherical granulated powder with good flowability and concentrated particle size distribution. By reducing the surface energy, the flowability is improved and the powder is uniformly filled into the mold, which provides a guarantee for subsequent automated molding.

[0078] In the preparation of advanced ceramics, granulation is also essential, as it has a direct impact on the quality of the finished ceramic product. For example, from the perspective of firing, the finer the ceramic powder, the better. However, due to its high surface energy and poor fluidity, fine powder often does not easily fill the mold evenly during pressing and molding, resulting in problems such as voids, loose edges and corners, delamination, and elastic aftereffects in the molded parts. Granulation can solve this problem.

[0079] Granulated powder is precisely filled into a mold shaped like an implant, and axially dry-pressed to obtain an implant preform (green preform). The dry-pressed preform is then sealed in a high-elasticity rubber mold and placed in a cold isostatic press.

[0080] The green blank is placed in a high-temperature sintering furnace for sintering. Initially, the temperature is raised to 600 degrees Celsius at a slow rate and held for 1 to 2 hours.

[0081] In the densification sintering stage, the temperature is raised to the final sintering temperature at a relatively fast rate. The final sintering temperature is determined through process optimization and is between 1350 degrees Celsius and 1500 degrees Celsius. The temperature is held for 1 to 2 hours to achieve grain diffusion and complete densification of the material.

[0082] During the cooling stage, the furnace is cooled along with the furnace or slowly according to a set program to release internal stress.

[0083] The post-processing steps involve sandblasting or acid etching the implant surface to increase surface roughness and promote osseointegration.

[0084] In the wet ball milling process of this embodiment, the wet ball milling device performs circulating wet ball milling on the slurry according to a preset target number of cycles.

[0085] According to the initial testing cycle, the slurry in the grinding chamber during the wet ball milling process is sampled and tested to obtain the particle size distribution characteristic value and the actual slurry viscosity, and the slurry dispersity index is calculated.

[0086] Slurry dispersibility index = (target slurry viscosity / actual slurry viscosity) × (target characteristic value / particle size distribution characteristic value);

[0087] In practice, the particle size distribution characteristic values ​​are the D90 value and the median particle size D50 value in the particle size distribution of the slurry, and the target characteristic value is the target D90 value.

[0088] When the slurry dispersibility index is greater than or equal to the first index threshold, the slurry is determined to be in the first mixing state, and the slurry fineness and fluidity meet the requirements. The current number of cycles of wet ball milling is set as the target number of cycles.

[0089] When the slurry dispersity index is less than the first index threshold and greater than or equal to the second index threshold, the slurry is determined to be in a second mixed state. The slurry state has an adjustable deviation, and compensatory adjustments are made to subsequent processes.

[0090] When the slurry dispersibility index is less than the second index threshold, the slurry is determined to be in the third mixing state. The slurry state does not meet the requirements, and the target number of wet ball milling is increased.

[0091] Specifically, the target number of wet ball milling is increased by the integer value of the product of the ratio of the second index threshold to the slurry dispersity index and the target number of cycles.

[0092] In practice, the target slurry viscosity is preferably in the range of 200-400 mPa·s, the target D90 value is preferably in the range of 0.3-0.6 μm, the first exponent threshold is 1.0, and the second exponent threshold is 0.7.

[0093] Specifically, the slurry dispersibility index includes viscosity ratio and fineness ratio. The lower the measured viscosity (smaller η), the larger this ratio indicates better slurry flowability and potentially better dispersibility. The fewer the measured large particles (smaller D90), the larger this ratio indicates better grinding effect and effective breaking down of large particle agglomerates. This invention integrates "grinding fineness" and "flowability and dispersibility" to introduce a slurry dispersibility index to reflect the slurry state. Based on the actual dispersion state of the slurry, it can intelligently determine whether it is in an ideal, adjustable, or unqualified state based on the D90 value and viscosity calculation, and automatically make decisions to stop ball milling, compensate subsequent processes, or precisely increase the number of cycles. This method effectively avoids particle agglomeration caused by insufficient ball milling or pollution and energy waste caused by excessive ball milling, ensuring that the slurry has a highly uniform particle size distribution (D90 and D50) and excellent flowability, providing a stable and reliable precursor for subsequent spray granulation and sintering processes. It improves the uniformity and consistency of the microstructure of medical zirconia ceramic implants from the source, ultimately ensuring the mechanical properties and long-term reliability of the product.

[0094] When the slurry is in the second mixing state, the process parameters of spray granulation are dynamically adjusted according to the actual state of each parameter of the slurry.

[0095] When the slurry is in the second mixing state, the preset process parameters of the spray granulation process are adjusted according to the slurry state parameters. The slurry state parameters include viscosity ratio and fineness ratio. The viscosity ratio is (target slurry viscosity / actual slurry viscosity), and the fineness ratio is (target characteristic value / particle size distribution characteristic value).

[0096] Specifically, if the actual slurry viscosity is greater than the target slurry viscosity, the liquid-solid content of the spray granulation is reduced proportionally according to the ratio of the target slurry viscosity to the actual slurry viscosity to ensure atomization effect and droplet drying uniformity.

[0097] If the particle size distribution characteristic value is greater than the target characteristic value, the atomization pressure of spray granulation is increased according to the ratio of the particle size distribution characteristic value to the target characteristic value to crush any possible soft agglomerates and obtain a narrower particle size distribution.

[0098] Specifically, this invention utilizes the refinement parameters of the slurry dispersibility index—viscosity ratio and fineness ratio—to precisely compensate for and control the spray granulation process of slurries in an adjustable deviation state. For slurries with excessively high viscosity, the system proportionally reduces the solid content of the liquid material, effectively ensuring atomization effect and drying uniformity. For slurries with excessively coarse particle size, the atomization pressure is proportionally increased to crush soft agglomerates and optimize particle size distribution. This dynamic adjustment mechanism overcomes the insufficient adaptability of fixed process parameters to fluctuations in the precursor state, significantly improving the flowability and filling uniformity of the granulated powder, laying a reliable powder foundation for the subsequent sintering process of preparing high-density, high-performance zirconia ceramic implants.

[0099] The tap density of the spray-granulated powder is tested to obtain the actual tap density, which is used to reflect the filling characteristics of the granulated powder. The actual tap density is a powder filling characteristic parameter of the granulated powder.

[0100] After dry pressing, the initial compact density of the green body is measured using non-destructive testing methods. The dynamic sintering activity index is calculated to reflect the green body characteristics of the current batch of green bodies. The dynamic sintering activity index = slurry dispersion index. 第一权重 × (Initial compaction density / Actual tapped density) 第二权重 ;

[0101] It is understandable that the higher the slurry dispersion index, the more thoroughly the original powder agglomerates are broken up, and the higher the intrinsic sintering activity. (Initial compact density / actual tap density) is the compaction efficiency ratio. The higher the ratio, the better the granulated powder is filled under pressure, the stronger the particle rearrangement and deformation ability, and the more contact points inside the green blank. This indicates that the material transport path during the sintering process is better and the densification driving force is stronger.

[0102] When the dynamic sintering activity index exceeds the calibrated index range, it is determined that the current batch of green blanks has the characteristics of high intrinsic activity and excellent green blank microstructure, strong sintering driving force, and fast densification rate.

[0103] When the dynamic sintering activity index is within the calibrated index range, it is determined that the green characteristics of the current batch of green blanks are within the preset range;

[0104] When the dynamic sintering activity index is lower than the calibrated index range, it is determined that the current batch of green blanks has porosity due to poor dispersion or poor pressing efficiency, resulting in high sintering resistance.

[0105] In practice, the first weight ranges from 0.4 to 0.6, the second weight ranges from 0.4 to 0.6, the sum of the weights is one, and the calibration index ranges from (0.85 to 1.15).

[0106] Specifically, composite powders are more likely to achieve high density and rapid densification during sintering. Meanwhile, fine pores need to be eliminated through grain boundary diffusion or volume diffusion in the later stages of sintering. Insufficient temperature leaves residual micropores, while excessively high temperature or prolonged time causes grains to grow rapidly and engulf pores, requiring timely suppression of grain growth. This invention correlates the precursor slurry state with green body forming characteristics by constructing a dynamic sintering activity index, accurately predicting the green body sintering behavior in the sintering process. It comprehensively reflects the intrinsic activity of the powder, the slurry dispersion, the microstructure density of the green body, and the pressing efficiency, enabling early identification of grain coarsening risks caused by high activity or closed-pore defects caused by low density. Personalized pre-setting and dynamic control of the sintering process overcomes the industry problem of fixed sintering curves being unable to adapt to batch fluctuations in raw materials, improving the uniformity and density of the zirconia implant microstructure.

[0107] Specifically, the driving force of the sintering process comes almost entirely from the reduction of surface energy and grain boundary energy (densification), without consuming additional energy and time for long-range component homogenization diffusion. This allows for a lower sintering initiation temperature, a faster densification rate, and easier attainment of high density at lower temperatures.

[0108] Based on the particle size distribution characteristics of the slurry, the sintering driving force of the green body in the sintering process is predicted, and the heating rate of the sintering process is adjusted.

[0109] In obtaining the particle size distribution characteristic values ​​of the slurry, the median particle size D50 value in the particle size distribution of the slurry is obtained, and the sintering driving force coefficient is calculated. The sintering driving force coefficient = target median particle size / median particle size D50 value.

[0110] When the sintering driving force coefficient is greater than the driving force warning threshold, it is determined that the current batch of slurry has an ultra-high sintering driving force, and there is a high driving force risk of excessive densification rate under the current sintering parameters, so the heating rate of the sintering process is adjusted.

[0111] Specifically, when there is a high risk of driving force, the heating rate of the sintering process is reduced before the start of the sintering process according to the ratio of a to the sintering driving force coefficient.

[0112] In practice, the preferred range of the target median particle size is 0.05-0.15 μm, and the driving force warning threshold is 1.2.

[0113] Specifically, the sintering driving force is inversely proportional to the powder particle size. Green bodies composed of composite powders have extremely high sintering driving forces. If the heating rate is not properly controlled, excessively high driving forces can lead to excessively fast sintering rates, potentially causing premature surface densification and "shell formation," which blocks the channels for internal pores to escape and ultimately forms closed pores. Therefore, it is necessary to adjust the heating rate based on the powder particle size. This method predicts the sintering driving force of the green body during the sintering process by using the particle size distribution characteristics of the slurry, actively slowing down the input of heat energy, providing more time for material diffusion, especially the migration of internal materials, balancing the densification process of the surface and the interior, and preventing "shell formation" procedurally. This serves as a refined management measure before subsequent control measures, avoiding the risk of shell formation and closed pores.

[0114] Based on the dynamic sintering activity index, the sintering adjustment strategy of the sintering process is dynamically adjusted.

[0115] When the current batch of green blanks has the characteristics of high intrinsic activity and excellent green blank microstructure, it is judged that there is a risk of grain coarsening in the current batch of green blanks during the sintering process. The temperature stage of the sintering process is adjusted according to the critical density of the green blank.

[0116] Specifically, the initial volume, initial mass, and initial length of the green billet are obtained before the sintering process. The linear shrinkage of the green billet in the axial or radial direction is detected in real time using a non-contact laser displacement sensor, and the actual sintering temperature in the sintering furnace is detected simultaneously.

[0117] Actual volume of green body = initial volume × (1 - linear shrinkage / initial length) 3 Actual density = initial mass / actual volume; actual relative density = (actual density / theoretical density) × 100%.

[0118] When the actual relative density is greater than the critical relative density, it is determined that the current batch of green blanks has been densified to the critical density, the sintering temperature is reduced and heat preservation is performed.

[0119] Specifically, when the actual relative density of the current batch of green blanks reaches the critical relative density, the sintering temperature is reduced to the preset adjustment range according to the maximum controllable temperature adjustment rate, and the heat preservation time is preset.

[0120] In practice, the theoretical density is the required theoretical density of the green body prepared from zirconia composite powder after sintering, in g / cm³. The critical relative density is preferably 80%-85%, but is 82% in practice. The preset adjustment range is 150-250℃, and the preset heat preservation time is 2-5h.

[0121] Specifically, the critical relative density is established experimentally. When the relative density is below this range, the open pore network in the green body is not yet completely closed, and premature cooling will lead to insufficient densification. When the relative density is above this range (e.g., >90%), the grains have already begun to grow rapidly, and cooling to suppress grain boundary migration is too late. At a relative density of 82%, the open pores just disappear and transform into closed pores, and the grain boundary network initially forms but has not yet begun to migrate violently. Cooling at this point is the optimal window for separating the densification and grain growth processes.

[0122] Specifically, a high DSAI value signifies extremely high intrinsic sintering activity and excellent initial microstructure, resulting in strong sintering driving force. Under traditional single-heating sintering curves, the densification rate is too fast, leading to rapid grain boundary migration and grain coarsening. Closed pores are encapsulated by grains, forming difficult-to-eliminate "intragranular pores" that become crack sources. The core of this method lies in actively separating the densification process from the grain growth process in time. Through a real-time density feedback triggering adjustment strategy, the rate of grain boundary migration is greatly suppressed after temperature adjustment due to its higher activation energy, while atomic diffusion along the grain boundaries can still proceed effectively. This allows the material to be continuously transported to the closed pores, causing them to gradually shrink and disappear. However, since the grain boundaries hardly move, the grain size is maintained at the small state at the end of the first step. By utilizing the high activity of the material to achieve rapid initial densification, and through a precise "density-triggered cooling" mechanism, the negative effects of high activity are avoided, ultimately obtaining a high-performance microstructure with fine grains, complete densification, and no intragranular pores.

[0123] When the sintering resistance of the current batch of green billets is high, it is determined that there is a risk of forming closed pores in the current batch of green billets. The adjustment characteristic point is determined according to the degree of change in the actual shrinkage rate, and the sintering temperature is adjusted accordingly.

[0124] Specifically, the actual shrinkage rate is calculated based on the linear shrinkage amount, the actual shrinkage rate-sintering actual temperature curve is plotted, and the maximum rate of the actual shrinkage rate-sintering actual temperature curve within a number of preset temperature ranges is obtained.

[0125] When the actual ratio of the maximum rate in the current preset temperature range to the average rate in the previous preset temperature range is greater than the minimum increase threshold, the maximum rate in the current preset temperature range is determined to meet the significance condition.

[0126] After determining the maximum rate of the interval that meets the significance condition, calculate the linear fitting slope of the peak point corresponding to the maximum rate of the interval in the subsequent unit time, and obtain the contraction rate difference between several data points and the previous data point according to the preset temperature unit, and calculate the proportion of the actual negative value of the contraction rate difference among several contraction rate differences.

[0127] When the linear fitting slope is less than the slope threshold and the proportion of actual negative values ​​is greater than or equal to the proportion threshold, it is determined that the peak point corresponding to the maximum rate in the interval conforms to the continuous trend, and the dominant diffusion mechanism of the sintering stage corresponding to the current preset temperature interval has passed its maximum rate period.

[0128] When the maximum rate in the interval meets the significance condition and the corresponding peak point meets the continuous trend, the heating is stopped and the sintering temperature is adjusted to the intermediate holding temperature, which is the actual sintering temperature corresponding to the maximum rate in the interval.

[0129] The sintering process is carried out at the intermediate holding temperature, and the surface diffusion mechanism continuously polishes and repairs the pores, while the actual shrinkage rate of the green body is detected in real time.

[0130] When the actual shrinkage rate is less than the shrinkage rate assessment value, it is determined that the porosity optimization through surface diffusion has ended, and the intermediate heat preservation stage is stopped to continue heating to sinter the green body. The shrinkage rate assessment value is the product of the maximum rate in the interval and the calibrated percentage.

[0131] In practice, the preset temperature range is 100℃, the average rate of the range is the average of the actual shrinkage rate within the preset temperature range, the preset temperature unit is 10℃, and the calibration percentage is 20%.

[0132] Specifically, a low DSAI value indicates the presence of large, irregularly shaped pores in the green body. The matrix material will sinter rapidly, leading to premature densification. This blocks the connection between the large pores and the external environment, and reduces the density and reliability of the material. This method intelligently identifies the significant peak and continuous downward trend of the shrinkage rate curve, accurately capturing the key node of the sintering mechanism's transition from surface diffusion to grain boundary diffusion. Based on this, it automatically triggers intermediate heat preservation, prioritizing the pretreatment and repair of potential large pores before the microstructure is "locked up." At a temperature before the grains begin to grow significantly, the surface diffusion mechanism is used to smooth the pore surface and reduce the pore size, providing sufficient time for surface diffusion-dominated pore optimization. This effectively eliminates the risk of closed pores formed due to premature closure of large pores in low-activity green bodies. By dynamically determining the heat preservation termination point based on the rate peak ratio, the optimal balance between pore repair and energy efficiency is achieved.

[0133] Sampling samples were taken from the sintered body, and X-ray diffraction (XRD) was used to analyze the phase composition of the sintered body to confirm the tetragonal zirconia retention rate. The tetragonal zirconia retention rate = (cubic phase content in the sintered body / total content of tetragonal and cubic phases) × 100%;

[0134] When the tetragonal zirconium oxide retention rate is greater than or equal to the target retention rate, the sintered body performance is judged to meet the standard, and the sintering strategy is matched with the characteristics of the current batch of slurry.

[0135] When the tetragonal zirconium oxide retention rate is less than the target retention rate, it is determined that the sintered body with insufficient tetragonal phase retention has potential performance problems. The intermediate holding temperature of the subsequent sintering process is adjusted according to the deviation of the tetragonal phase retention rate.

[0136] Specifically, the adjusted intermediate insulation temperature = current intermediate insulation temperature - adjustment gain coefficient × (target retention rate - tetragonal zirconia retention rate).

[0137] To avoid insufficient densification due to over-adjustment, a minimum lower temperature limit is set, such as 1250°C. If the adjusted intermediate insulation temperature is lower than the minimum lower temperature limit, the minimum lower temperature limit is used as the intermediate insulation temperature, and a front-end process alarm is generated.

[0138] In practice, the target retention rate is 97%, and the adjustment gain coefficient is 1℃ / %.

[0139] Specifically, a low tetragonal phase retention rate usually indicates that the holding temperature in the second sintering step was too high or the holding time too long, leading to an excessive transformation of the metastable tetragonal phase into the stable cubic phase. This invention achieves closed-loop control of the long-term phase stability of the material by establishing a negative feedback adjustment mechanism between the tetragonal phase zirconia retention rate and sintering process parameters. When insufficient tetragonal phase retention is detected, the intermediate holding temperature of subsequent batches can be automatically reduced proportionally, effectively suppressing the excessive transformation of the tetragonal phase into the cubic phase, thereby significantly improving the low-temperature aging resistance of the implant. By setting a lower temperature limit, the risk of over-adjustment is avoided, ensuring that the product maintains excellent densification while achieving high phase stability, providing a key guarantee for the long-term clinical reliability of zirconia implants.

[0140] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0141] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a zirconia-based medical composite ceramic material, characterized in that, include: To determine the slurry dispersion index, the particle size distribution characteristic value and the actual slurry viscosity are obtained from the slurry circulated according to the target number of cycles in the circulating wet ball milling process, so as to determine the slurry mixing state. The parameters of the spray granulation process of the slurry are adjusted in response to the slurry mixing state to determine the target number of cycles or to compensate for the slurry state parameters. Obtain the powder filling characteristic parameters and the initial compaction density of the green body, and determine the dynamic sintering activity index by combining the slurry dispersity index, so as to determine the green body characteristics of the current batch of green bodies; Based on another particle size distribution characteristic value of the slurry, the sintering driving force of the green body in the sintering process is predicted, the heating rate of the sintering process is adjusted, and the sintering adjustment strategy of the sintering process is dynamically adjusted based on the dynamic sintering activity index in response to the green body characteristics. The dynamic sintering activity index is calculated by obtaining the powder filling characteristic parameters and the initial compaction density of the green body to reflect the green body characteristics of the current batch of green bodies. The powder filling characteristic parameters are the actual tap density of the powder. When the dynamic sintering activity index exceeds the calibrated index range, it is determined that the current batch of green blanks has the characteristics of intrinsic activity and green blank microstructure exceeding the range, and the sintering driving force and densification rate exceed the preset range. When the dynamic sintering activity index is within the calibrated index range, it is determined that the green characteristics of the current batch of green blanks are within the preset range; When the dynamic sintering activity index is lower than the calibrated index range, it is determined that the current batch of green blanks has porosity due to poor dispersion or poor pressing efficiency, resulting in high sintering resistance. If the current batch of green blanks has the characteristics of intrinsic activity and microstructure of green blanks that exceed the range, then the current batch of green blanks has the risk of grain coarsening during the sintering process. Based on the characteristics of the green body, determine whether there is a risk of grain coarsening in the sintering process, and obtain the actual relative density of the green body to adjust the temperature stage and sintering temperature of the sintering process. Based on the characteristics of the green blank, determine whether there is a risk of closed pores in the current batch of green blanks. Combine the degree of change in the actual shrinkage rate to determine the adjustment feature point to stop sintering and add a heat preservation stage in response to the adjustment feature point. Also determine the intermediate heat preservation temperature and the heat preservation stage duration. Obtain the initial volume, initial mass, and initial length of the green blank, and detect the linear shrinkage of the green blank in the axial or radial direction to determine the actual relative density; When the actual relative density is greater than the critical relative density, it is determined that the current batch of green blanks has been densified to the critical density. The sintering temperature is then reduced to the preset adjustment range according to the maximum controllable temperature adjustment rate, and the temperature is held for the preset holding time. When the sintering resistance of the current batch of green billets is high, it is determined that there is a risk of forming closed pores in the current batch of green billets, and the adjustment characteristic point is determined according to the degree of change in the actual shrinkage rate. The sintered body phase is obtained to determine the tetragonal zirconia retention rate. Based on the sintered body properties, it is determined whether the sintering adjustment strategy matches the characteristics of the current batch of slurry. In response to the sintered body properties, the intermediate holding temperature of the subsequent sintering process is adjusted according to the tetragonal phase retention rate deviation. Calculate the actual shrinkage rate based on the linear shrinkage amount, plot the actual shrinkage rate-actual sintering temperature curve, and obtain the maximum rate of the actual shrinkage rate-actual sintering temperature curve within a number of preset temperature ranges. When the actual ratio of the maximum rate in the current preset temperature range to the average rate in the previous preset temperature range is greater than the minimum increase threshold, the maximum rate in the current preset temperature range is determined to meet the significance condition.

2. The method for preparing zirconia-based medical composite ceramic materials according to claim 1, characterized in that, The slurry in the grinding chamber is sampled and tested to obtain the particle size distribution characteristic value and the actual slurry viscosity to determine the slurry dispersity index; When the slurry dispersibility index is greater than or equal to the first index threshold, the slurry is determined to be in the first mixing state, and the slurry fineness and fluidity meet the requirements. The current number of cycles of wet ball milling is set as the target number of cycles. When the slurry dispersity index is less than the first index threshold and greater than or equal to the second index threshold, the slurry is determined to be in a second mixed state. The slurry state has an adjustable deviation, and compensatory adjustments are made to subsequent processes. When the slurry dispersibility index is less than the second index threshold, the slurry is determined to be in the third mixing state. The slurry state does not meet the requirements, and the target number of wet ball milling is increased. The particle size distribution characteristics of the slurry include the D90 value and the median particle size D50 value.

3. The method for preparing zirconia-based medical composite ceramic materials according to claim 2, characterized in that, When the slurry is in the second mixing state, the spray granulation process parameters are adjusted according to the slurry state parameters, including viscosity ratio and fineness ratio. If the actual slurry viscosity is greater than the target slurry viscosity, the liquid-solid content of the spray granulation material is reduced proportionally according to the ratio of the target slurry viscosity to the actual slurry viscosity. If the particle size distribution characteristic value is greater than the target characteristic value, the atomization pressure of spray granulation is increased according to the ratio of the particle size distribution characteristic value to the target characteristic value.

4. The method for preparing zirconia-based medical composite ceramic materials according to claim 1, characterized in that, The sintering driving force coefficient was determined based on the median particle size D50 value. When the sintering driving force coefficient is greater than the driving force warning threshold, it is determined that the current batch of slurry has a risk of excessive densification rate under the current sintering parameters, and the heating rate of the sintering process is adjusted according to the sintering driving force coefficient.

5. The method for preparing zirconia-based medical composite ceramic materials according to claim 1, characterized in that, After determining the maximum rate of the interval that meets the significance condition, calculate the linear fitting slope of the peak point corresponding to the maximum rate of the interval in the subsequent unit time, and obtain the contraction rate difference between several data points and the previous data point according to the preset temperature unit, and calculate the proportion of the actual negative value of the contraction rate difference among several contraction rate differences. When the slope of the linear fitting is less than the slope threshold and the proportion of actual negative values ​​is greater than or equal to the proportion threshold, it is determined that the peak point corresponding to the maximum rate in the interval conforms to the continuous trend, and the dominant diffusion mechanism of the sintering stage corresponding to the current preset temperature interval exceeds the maximum rate period.

6. The method for preparing zirconia-based medical composite ceramic materials according to claim 5, characterized in that, When the maximum rate in the interval meets the significance condition and the corresponding peak point meets the continuous trend, the heating is stopped and the sintering temperature is adjusted to the intermediate holding temperature, which is the actual sintering temperature corresponding to the maximum rate in the interval. The actual shrinkage rate of the green body is detected in real time. When the actual shrinkage rate is less than the shrinkage rate evaluation value, it is determined that the porosity optimization through surface diffusion has ended, and the intermediate heat preservation stage is stopped to continue heating the green body for sintering. The shrinkage rate evaluation value is the product of the maximum rate in the interval and the calibrated percentage.

7. The method for preparing zirconia-based medical composite ceramic materials according to claim 6, characterized in that, Sampling was performed on the sintered body, and the phase composition of the sintered body was analyzed to confirm the retention rate of tetragonal zirconium oxide. When the tetragonal zirconium oxide retention rate is greater than or equal to the target retention rate, the sintered body performance is judged to meet the standard, and the sintering strategy is matched with the characteristics of the current batch of slurry. When the tetragonal zirconium oxide retention rate is less than the target retention rate, it is determined that the sintered body performance is insecure due to insufficient tetragonal phase retention. The intermediate holding temperature of the subsequent sintering process is adjusted according to the deviation of the tetragonal phase retention rate.

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