3D printing ceramic material sintering performance judgment method based on ultrahigh-temperature heating stage

Abstract

The invention relates to the technical field of high-temperature material test characterization and additive manufacturing process optimization, and discloses a 3D printing ceramic material sintering performance judgment method based on an ultrahigh-temperature heating stage, which comprises the steps of sample preparation, sample placement, experimental parameter setting, in-situ real-time observation and picture shooting, image analysis and sintering behavior quantitative evaluation. According to the method, continuous in-situ recording of degreasing, shrinkage and densification behaviors in the sintering process of the ceramic material is realized, key sintering processes such as neck formation and pore evolution can be directly represented, and the limitation that only states before and after sintering can be obtained and a sintering dynamic evolution mechanism is difficult to reveal in a traditional technology is broken through; whether a certain ceramic is over-burnt or under-burnt can be judged within ten minutes, so that the trial and error cost is greatly reduced; in addition, height, width and area changes are measured at the same time, and the dilatometer is more comprehensive than a push rod type dilatometer and suitable for complex 3D printed pieces; the temperature rise of the ultrahigh-temperature heating stage is hundreds of times faster than that of a large furnace, the research and development efficiency is remarkably improved, and the device is suitable for various ceramic materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-temperature material testing characterization and additive manufacturing process optimization, in particular to a 3D printed ceramic material sintering performance judgment method based on an ultra-high temperature hot stage. BACKGROUND

[0002] 3D printed ceramic materials must be sintered at high temperature after forming to obtain the final dense structure, and the sintering window, densification rate, and softening and melting behavior directly determine the dimensional stability and mechanical properties. Traditional sintering research mainly relies on resistance furnace heating methods such as muffle furnace or tube furnace, and the final morphology after sintering is observed by SEM, optical microscope, etc., and the thermal effect information is obtained by combining DSC, TG, etc. thermal analysis instruments, but these means have obvious limitations.

[0003] The heating process of traditional furnace sintering is closed and invisible, only the sintering "result" can be obtained, but the "process itself" cannot be seen, and the key deformation information such as volume evolution, pore shrinkage, softening sagging, and collapse of the material during the heating process is completely missing. Researchers often need to speculate the best sintering schedule through repeated trial sintering, and one experiment usually takes several hours or even longer, which not only wastes time and effort, but also easily leads to under-sintering or over-sintering due to improper parameter selection.

[0004] Although imaging devices such as microscopes can obtain the microstructure after sintering, they can only observe after the fact and cannot capture the dynamic evolution of the material during the heating process, nor can they quantitatively calculate important parameters such as shrinkage rate and softening temperature. Thermal analysis instruments (DSC / TG) also only provide mass change or heat flow signals, and cannot provide intuitive visual information on the overall densification behavior of complex 3D printed structures. Therefore, the present application provides a 3D printed ceramic material sintering performance judgment method based on an ultra-high temperature hot stage to solve the above problems. SUMMARY

[0005] The 3D printed ceramic material sintering performance judgment method based on an ultra-high temperature hot stage provided by the present application realizes the synchronous heating and imaging of an open hot stage, which not only allows real-time observation of the morphology evolution of the ceramic during the heating process, but also quickly obtains key parameters such as sintering starting temperature, densification stage, and softening interval, significantly shortens the process exploration time, and significantly improves the accuracy of sintering schedule optimization, solving the problems mentioned in the above background technology, such as the inability to observe the sintering process in situ, the inability to quickly determine whether the process parameters are reasonable, the inability to quantitatively analyze the shrinkage behavior and softening interval, and the inability to efficiently guide the actual sintering process development of 3D printed ceramics.

[0006] The present application provides the following technical solutions:

[0007] The method for judging sintering performance of 3D printed ceramic material based on super-high temperature hot stage comprises the following steps:

[0008] S1, sample preparation: select representative ceramic samples and pretreat them;

[0009] S2, sample placement: place the prepared sample on the hot stage for sintering observation;

[0010] S3, experimental parameter setting: set the temperature rising program according to the material properties and experimental purpose;

[0011] S4, in-situ real-time observation and picture shooting: start the in-situ high-temperature microscope camera system at the beginning of the temperature rising program, and record the shape and size changes of the sample during the sintering process in real time;

[0012] S5, image analysis: after the sintering experiment is finished, the continuous image data during the whole temperature rising period are obtained, and the image processing software is used to quantitatively analyze each frame of image;

[0013] S6, quantitative evaluation of sintering behavior: extract the key sintering characteristic temperature, and quantitatively evaluate the sintering behavior of the material.

[0014] As a preferred technical scheme of the present application, the sample is a 0.1-5mm diameter disc green body obtained by punching sampling from the 3D printed ceramic blank.

[0015] As a preferred technical scheme of the present application, the hot stage is made of platinum-rhodium alloy.

[0016] As a preferred technical scheme of the present application, the temperature rising program comprises temperature rising rate, temperature stage, holding time and atmosphere condition, the temperature rising rate is 0-300℃ / s; the temperature stage is 0-1800℃; the holding time is 1-1000000s; the atmosphere condition is one of air, inert gas, reducing gas and oxidizing gas.

[0017] As a preferred technical scheme of the present application, the high-temperature microscope camera system mainly comprises a high-temperature optical microscope, a CCD camera, image acquisition and control software, an optical adapter and a terminal display device, the high-temperature optical microscope adopts a telecentric lens, the magnification is 1.0x-2.0x, the working distance focal length is 80-150mm, and the aperture is F / 8-F / 11; the CCD camera acquisition rate is 1-150fps.

[0018] As a preferred technical scheme of the present application, the quantitative analysis specifically comprises:

[0019] The outline of the sample is extracted by threshold segmentation or edge detection method;

[0020] measure the size parameters in each frame of image;

[0021] Convert the pixel length into actual physical length in combination with the microscope calibration coefficient;

[0022] Calculate the shrinkage and deformation index of the sample according to the initial size and real-time size.

[0023] The size parameters include the height, width and projected area of the sample.

[0024] Compared with the prior art, the present application provides a 3D printed ceramic material sintering performance judgment method based on an ultrahigh temperature hot stage, which has the following beneficial effects:

[0025] The 3D printed ceramic material sintering performance judgment method based on an ultrahigh temperature hot stage realizes continuous in-situ recording of the debinding, shrinkage and densification behavior in the ceramic sintering process for the first time, solves the problem that the traditional technology cannot see the "sintering process itself", and can judge whether a certain ceramic is overburned or underburned within ten minutes, greatly reducing the trial and error cost. In addition, the height, width and area changes are measured at the same time, which is more comprehensive than the push rod type dilatometer and is suitable for complex 3D printed parts. The ultrahigh temperature hot stage can be heated up to several 300℃ / s, which is several hundred times faster than large furnaces, significantly improves the research and development efficiency, and is suitable for multiple types of ceramic materials.

[0026] The synchronization of heating and imaging is realized by the hot stage, the morphology evolution of the ceramic in the whole debinding and sintering process can be observed in real time, and key process parameters such as the debinding completion temperature zone, the sintering starting temperature, the densification stage characteristic temperature zone, the structure instability starting interval and the edge rounding temperature can be quickly obtained, thereby significantly shortening the debinding-sintering process exploration period and effectively improving the accuracy and controllability of sintering system optimization. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the specific embodiments or prior art description will be briefly introduced as follows.

[0028] Figure 1 It is a method flow chart of the present application;

[0029] Figure 2 It is an experimental image of printing LAP bioceramics;

[0030] Figure 3 It is a cordierite ceramic experimental image;

[0031] Figure 4 It is a high temperature microscope camera system workflow diagram. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work are within the protection scope of the present application.

[0033] Embodiment one:

[0034] Referring to Figures 1-4 A method for judging sintering performance of 3D printed ceramic material based on an ultrahigh-temperature hot stage, comprising the following steps:

[0035] S1, sample preparation: representative ceramic samples are selected, and the preparation materials include slurry, powder, ink and the like. The sample is a 1mm-diameter disc green body obtained from a 3D-printed ceramic blank by punching sampling, and appropriate pretreatment is performed before heating, such as low-temperature drying or curing, to remove excess solvent or to preliminarily solidify the precursor, so as to ensure that the sample surface is flat and clean, without obvious defects and impurities, so as to improve the accuracy of subsequent deformation observation.

[0036] S2, sample placement: place the prepared sample on the appropriate position of the ultrahigh-temperature rapid heating platinum-rhodium alloy hot stage for sintering observation. Use tweezers to place the sample lightly on the center of the hot stage, so that the sample is in the center field of view of the microscope observation window. Adjust the relative positions of the hot stage and the microscope, so that the entire sample is clearly focused in the center of the field of view, to ensure that the sample is always in the camera field of view during the whole temperature rising process, and to obtain accurate temperature readings.

[0037] S3, experimental parameter setting: according to the material properties and experimental purposes, set the temperature rising program. For example, for the light-cured LAP bioceramic, the program is set as follows: in an air environment, heat the sample from 25-600℃ and keep it for 100s to complete the debinding and pre-sintering; then heat at a speed of 10℃ / s, and raise the temperature from 600℃ to 750℃, to make the material begin to sinter and shrink by slow heating; then heat at a speed of 1℃ / s for 300s, and raise the temperature from 750℃ to 1150℃ (target sintering temperature); finally, keep the temperature at 1150℃ for 2h to fully densify the microstructure.

[0038] S4, in-situ real-time observation and picture shooting: start the in-situ high-temperature microscope camera system at the beginning of the temperature rising program, to record the shape and size changes of the sample during the sintering process in real time.

[0039] The high-temperature microscope camera system mainly includes a high-temperature optical microscope, a CCD camera, image acquisition and control software, an optical adapter and a terminal display device,

[0040] The high-temperature optical microscope adopts a telecentric lens, the magnification of which is 2.0x, the working distance focal length is 100 mm, the aperture is F / 81, and a quartz glass isolation window is arranged below the lens, which allows visible light to pass through but blocks part of the infrared heat radiation, and inert gas is used to purge the lens to prevent the lens from fogging or oxidizing at high temperature;

[0041] The CCD camera has an active cooling function, and the acquisition rate is 20 fps in the heating stage and 15 fps in the observation stage;

[0042] The high-temperature optical microscope, CCD camera, image acquisition and control software, and optical adapter are closely coordinated through optical path, mechanical interface and data communication to realize in-situ, real-time and high-resolution imaging and recording of the ceramic sintering process at high temperature.

[0043] S5, image analysis: after the sintering experiment is completed, continuous image data during the entire heating period is obtained, and image processing software is used to quantitatively analyze each frame of image;

[0044] The threshold segmentation or edge detection method is used to extract the contour of the sample;

[0045] The height, width and projected area of the sample in each frame of image are measured;

[0046] The pixel length is converted into actual physical length combined with the microscope calibration coefficient;

[0047] The shrinkage rate and deformation index of the sample are calculated according to the initial size and real-time size;

[0048] Then, the following parameters are calculated according to the above data:

[0049] Linear shrinkage rate: the shortening ratio of a linear dimension of the sample at each time relative to the initial value;

[0050] According to the following formula:

[0051]

[0052]

[0053] In the formula:

[0054] D(t) is the equivalent diameter at time t;

[0055] D(0) is the equivalent diameter at the initial time;

[0056] A(t) is the projected area of the sample obtained by image segmentation at time t;

[0057] Linear shrinkage at time t;

[0058] Volume shrinkage: the shrinkage ratio of the total volume of the sample at each time relative to the initial volume;

[0059] According to the following formula:

[0060] In the formula:

[0061] Volume shrinkage at time t, indicating the volume reduction ratio of the sample relative to the initial state;

[0062] At time t, the projected area of the sample obtained from image segmentation;

[0063] At the initial time t = 0, the projected area, i.e. the original projected area of the sample before sintering.

[0064] In addition, the linear shrinkage and volume shrinkage have the following relationship:

[0065]

[0066] Shrinkage rate: the derivative of the shrinkage rate with respect to temperature, reflecting the speed of sample shrinkage at each temperature segment (e.g. the percentage of shrinkage per 1℃ increase);

[0067] According to the following formula:

[0068]

[0069] Softening starting temperature: the temperature point at which the sample begins to show obvious deformation (such as rapid height drop or shape instability) during the heating process.

[0070] Melting / collapse temperature: the temperature point at which the sample completely loses its original shape and collapses as a whole.

[0071] S6, quantitative evaluation of sintering behavior: extraction of key sintering feature temperatures, quantitative evaluation of the sintering behavior of the material,

[0072] The following feature temperatures and their physical meanings are mainly concerned:

[0073] Sintering starting temperature: the temperature at which the sample begins to shrink significantly, i.e. the starting point of the obvious mutation on the shrinkage curve, usually corresponding to the temperature at which the particles begin to approach each other after the binder is burned out, such as the sudden increase in linear shrinkage of ceramic green body at about 900℃, indicating that sintering shrinkage begins at this point.

[0074] Densification completion temperature: the temperature point at which the sample is substantially sintered and densified, and the shrinkage tends to be saturated, i.e. the shrinkage curve changes from rapid decline to a flat platform region, and this temperature reflects the minimum temperature required for the material to reach near maximum density, for example, the shrinkage of 3D-printed cordierite ceramic tends to stop after being kept at about 1480℃ for 2 hours, indicating that the densification is completed.

[0075] Softening deformation temperature: the temperature at which the sample starts to soften and collapse, when the temperature is too high and exceeds the appropriate range of material sintering, the sample may change shape due to partial melting or gravity, which is manifested as a sharp decline in the height curve, and the softening point reflects the start of overfiring, which can be used to determine the upper limit of the temperature.

[0076] Melting temperature: the temperature at which the sample completely melts or collapses, i.e. the temperature at which the material outline completely collapses and loses its original solid structure in the image, which is usually higher than the softening point, indicating that the sample has been severely overfired or melted.

[0077] By comparing these characteristic temperatures with the preset sintering schedule, it can be quickly determined whether the current sintering process is appropriate. For example, if the densification completion temperature of the sample is much higher than the actual maximum sintering temperature, there may be underfiring (insufficient sintering); on the contrary, if the softening deformation temperature appears below the target temperature, it indicates that overfiring or insufficient material refractoriness occurs; therefore, by combining the sintering start temperature, the densification completion temperature, and the softening and melting temperatures, the sintering quality of the material under the current sintering conditions can be evaluated to determine whether it is fully sintered, normal or defective.

[0078] In summary, in the present application, the continuous recording of shrinkage, softening and melting behavior during ceramic sintering is realized for the first time, solving the problem that the traditional technology cannot see the "sintering process itself"; and it can be determined within ten minutes whether a certain ceramic is overfired or underfired, greatly reducing the cost of trial and error; in addition, the height, width and area changes are measured simultaneously, which is more comprehensive than the push rod type dilatometer and is suitable for complex 3D printed parts; and the ultra-high temperature hot stage can be heated up to dozens to hundreds of ℃ / s, which is several hundred times faster than large furnaces, significantly improving the research and development efficiency and being suitable for multiple types of ceramic materials.

[0079] Example Two:

[0080] Referring to Figure 1 , Figure 2 and Figure 4 , the sample preparation: take the solidified LAP bioceramic sample, and use the punching sampling method to prepare a LAP bioceramic disc with a diameter of 1mm;

[0081] Sample placement: Use tweezers to gently place the round sample in the center of the hot stage, so that the sample is in the center of the microscope observation window, adjust the relative position of the hot stage and microscope, so that the whole sample is clearly focused in the central field of view, ensure that the sample is always in the camera field of view during the whole temperature rising process, and obtain accurate temperature readings;

[0082] Set heating program: according to the properties of photocured LAP bioceramics and the characteristics of the hot stage, the sample is heated from 25°C to 600°C and kept for 100s to complete the debinding and pre-sintering; then heated to 750°C at a rate of 10°C / s and kept for 1000s, finally the temperature is increased from 750°C to 1500°C at a rate of 1°C / s and kept for 2h;

[0083] In-situ observation: turn on the high temperature camera system of the microscope, the high temperature optical microscope uses a telecentric lens, the magnification is 2.0x, the working distance focal length is 100mm, the aperture is F / 81, the CCD camera acquisition rate is 20fps in the heating stage and 15fps in the observation stage, and the shape change of the sample during heating is recorded in real time;

[0084] Data calculation and judgment: at 600°C, the sample pores increase, organic groups decompose into small molecule gases, accompanied by volume shrinkage, and carbon residues gradually carbonize, the sample gradually turns black, and complete ceramicization is completed at 1150°C to form ceramic.

[0085] Example three:

[0086] Referring to Figure 1 , Figure 3 and Figure 4 , sample preparation: take 1mm sample from 3D printed cordierite ceramic to prepare 1mm cordierite disc green body;

[0087] Sample placement: place the 1mm cordierite disc green body on the B-type thermocouple metal sheet in the center of the ultra-high temperature hot stage, and adjust the position of the hot stage so that the green body is completely in the center of the observation window of the camera system;

[0088] Set heating program: according to the properties of cordierite and the characteristics of the hot stage, the sample is rapidly heated from 0-400°C and kept for 60s to complete debinding and pre-sintering; then heated at a rate of 0.5°C / s for 700s, the temperature is increased from 400°C to 750°C; then heated at a rate of 1°C / s for 730s, the temperature is increased from 750°C to 1480°C, finally kept at 1480°C for 2h to fully densify the microstructure;

[0089] In-situ observation: turn on the high temperature camera system, the high temperature optical microscope adopts a telecentric lens, the magnification is 2.0x, the working distance focal length is 100mm, the CCD camera acquisition rate: 20fps in the heating stage, 15fps in the observation stage, the shape change of the sample during heating process is recorded in real time;

[0090] Data calculation and judgment: 400-600℃, the sample pores increase (decomposition of the degreasing produces carbon dioxide), accompanied by volume shrinkage, at the same time, the carbon residue gradually carbonizes, the sample gradually turns black; 750℃, the residual carbon reacts with air, the sample gradually turns white; 1480℃, the sample sintering shrinks for 2h, until the sintering is completed.

[0091] The components not described in detail in the present application are prior art.

[0092] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for judging the sintering performance of 3D printed ceramic materials based on an ultra-high temperature hot stage, characterized in that, Includes the following steps: S1. Sample preparation: Select representative ceramic samples and pretreat them. S2. Sample Placement: Place the prepared sample on the hot stage for sintering observation; S3. Experimental parameter setting: Set the heating program according to the material properties and experimental purpose; S4. In-situ real-time observation and image capture: At the start of the heating program, the in-situ high-temperature microscope imaging system is activated to record the changes in the shape and size of the sample during the sintering process in real time. S5. Image Analysis: After the sintering experiment, continuous image data during the entire heating period was acquired, and each frame of the image was quantitatively analyzed using image processing software. S6. Quantitative evaluation of sintering behavior: Extract key sintering characteristic temperatures and quantitatively evaluate the sintering behavior of the material.

2. The method for judging the sintering performance of 3D printed ceramic materials based on an ultra-high temperature hot stage according to claim 1, characterized in that, The samples were obtained from the 3D-printed ceramic blanks using a drilling sampling method.

3. The method for judging the sintering performance of 3D printed ceramic materials based on an ultra-high temperature hot stage according to claim 1, characterized in that, The sample is a circular green embryo with a diameter of 0.1-5 mm.

4. The method for judging the sintering performance of 3D printed ceramic materials based on an ultra-high temperature hot stage according to claim 1, characterized in that, The heating stage is made of platinum-rhodium alloy.

5. The method for judging the sintering performance of 3D printed ceramic materials based on an ultra-high temperature hot stage according to claim 1, characterized in that, The heating process includes heating rate, temperature stages, holding time, and atmospheric conditions. The heating rate is 0-300℃ / s; The temperature range is 0-1800℃; The heat preservation time is 1-1,000,000 seconds; The atmospheric conditions are one of air, inert gas, reducing gas, and oxidizing gas.

6. The method for judging the sintering performance of 3D printed ceramic materials based on an ultra-high temperature hot stage according to claim 1, characterized in that, The high-temperature microscope imaging system mainly includes a high-temperature optical microscope, a CCD camera, image acquisition and control software, an optical adapter, and a terminal display device. The high-temperature optical microscope uses a telecentric lens with a magnification of 1.0x-2.0x, a working distance focal length of 80-150mm, and an aperture of F / 8-F / 11. The CCD camera has an acquisition rate of 1-150fps.

7. The method for judging the sintering performance of 3D printed ceramic materials based on an ultra-high temperature hot stage according to claim 1, characterized in that, The quantitative analysis specifically includes: The contour of the sample is extracted using threshold segmentation or edge detection methods; Measure the size parameters in each frame of the image; By combining microscope calibration coefficients, the pixel length is converted into the actual physical length; The shrinkage rate and deformation index of the specimen were calculated based on the initial and real-time dimensions.

8. The method for judging the sintering performance of 3D printed ceramic materials based on an ultra-high temperature hot stage according to claim 7, characterized in that, The dimensional parameters include the height, width, and projected area of ​​the sample.

Images