KR20210085581A - Manufacturing method for shaping of ceramics by 3D printing and container for slurry - Google Patents

Abstract

The present invention relates to a method for producing a ceramic compact by a three-dimensional printing method and a ceramic slurry container. More specifically, the method comprises the steps of: mixing the ceramic slurry and the photoinitiator to prepare main slurry and low concentration slurry having a relatively low concentration compared to the main slurry; applying the low-concentration slurry to a platform of a 3D printer; and performing three-dimensional printing by laminating the present slurry on dried low-concentration slurry. According to the present invention, the method can be expected that the effect of securing the smoothness of manufacturing a molded body through the improvement of adhesion between ceramic slurry and a metal molding plate mounted on a 3D printer can be expected.

Description

A method for manufacturing a ceramic formed body by a three-dimensional printing method and a container for accommodating a ceramic slurry {Manufacturing method for shaping of ceramics by 3D printing and container for slurry}

The present invention relates to a method for manufacturing a ceramic compact by a three-dimensional printing method and a ceramic slurry receiving container, and more particularly, to a low-concentration slurry having a relatively low concentration compared to the present slurry and the present slurry by mixing a ceramic slurry and a photoinitiator. preparing each; applying the low-concentration slurry to a platform of a 3D printer; and performing three-dimensional printing by laminating the present slurry on the dried low-concentration slurry.

Due to their excellent properties, ceramics are used in a wide range of fields including chemistry, machinery, electronics, aerospace, and biotechnology. These properties are attributed to high mechanical strength and hardness, excellent thermal and chemical stability, and optical, electrical, electronic and magnetic performance. Ceramic parts are generally based on raw materials in the form of binder-free powders or mixtures with binders and other additives, by injection molding, die pressing, tape casting or gel casting. It is molded through methods such as casting), and then, through high-temperature densification and processing, dimension processing and surface treatment are completed. When a flow path connected to the inside of the component exists or has a complex external shape rather than a simple shape, ceramic component manufacturing has a limitation in that a long process time is required for the forming process or the cost due to post-processing increases rapidly.

Recently, various products are manufactured using 3D printers, and 3D printers are attracting attention due to their low facility construction cost and manufacturing cost, high precision, and similarity comparable to products manufactured by other processes.

3D printing, also called additive manufacturing (AM), is an advanced manufacturing technology that decomposes a 3D CAD model into a digital cross-section of a 2D plane, and builds up each layer while molding. It can flexibly manufacture precise structures with complex shapes that are difficult to implement with conventional casting and machining, and can increase productivity by making multiple parts in one run.

If 3D printing is applied to the manufacture of ceramic parts, there is a possibility that the disadvantages of the existing ceramic process mentioned above can be easily solved, and many researchers are currently interested. Ceramic 3D printing can be classified into slurry-based, powder-based, and bulk-based materials according to the material. Among them, the slurry-based material ranges from a low-viscosity slurry with a low ceramic solid content of 30 vol% to a high solid content of up to 60 vol%. Use a high-viscosity paste with a high content. Slurry-based 3D printing is generally used by preparing a slurry in which ceramic fine powder is dispersed in a liquid polymer in the form of a monomer, and the slurry contains a photoinitiator as one of the additives and is polymerized by light having a wavelength in the ultraviolet region. The composition is designed to cause a reaction.

As a method of irradiating light having a wavelength in the ultraviolet region, stereolithography (SL), which scans the laser analogously on a two-dimensional plane, and digital light processing ( Digital Light Processing (DLP).

The ceramic SL process has been extensively studied by Halloran since 1994, using high-concentration slurries up to 65 vol % containing silica, alumina and silicon nitride. The key variables that must be satisfied for product output include the homogeneous dispersion and long-term stability of the slurry, and depending on the selection of the printing material and process, the viscosity of the slurry, the solid content, the powder particle size, and the difference in refractive index between the monomer and the powder are considered. should be On the other hand, in order to secure the x and y-axis dimensional accuracy of the product, the slurry must be designed to minimize light scattering in the slurry, and control of the curing depth is required for the z-axis dimensional accuracy. The ceramic DLP process uses a digital micro-mirror (DMD) from Texas Instruments in 2001, which is a chip composed of an array of hundreds of thousands of micro-reflectors corresponding to pixels of an image to be displayed. The DMD driven by electrostatic force is capable of high-speed switching at an angle of 10 to 12 degrees, and the micro-reflectors receiving the on signal reflect the incident light in the direction of the lens to form a desired image. Because DLP has a faster process speed than SL, process time is greatly reduced, and excellent resolution down to several micrometers can be obtained. It has been reported that the alumina parts produced by this method have a relative density of 90% or more, and the output resolution is 25×25×25 μm ^{3 .}

Ceramic tools are a product that has been researched a lot in the field of special cutting. In particular, in the case of a heat-resistant alloy such as Inconel, which is a difficult-to-cut material, it is difficult to process, so a ceramic tool with high hardness is required. However, since ceramic tools are manufactured by multiaxial molding, they have limitations in producing complex shapes. In addition, in the tool industry with a small quantity and variety of features, the cost of manufacturing an expensive press mold is considerable. However, the use of 3D printing not only increases the degree of freedom in design, but it is advantageous in terms of cost because there is no need to manufacture a press mold, and it is possible to produce an internal flow path that cannot be produced by the press method, which has a great advantage in efficiency improvement. . For example, the helix drill with coolant channel, designed to facilitate cooling of the drill tip and discharge of the workpiece, has a complex internal and external shape and is difficult to manufacture by the press method. If it can be manufactured through a simple post-processing process, it can be said that there is sufficient product competitiveness.

In this regard, Republic of Korea Patent No. 2028327 "Ceramic 3D printer" has been disclosed, the technology relates to a ceramic 3D printer, the body portion and provided inside the body portion to transfer the work bed in the X-axis An X-axis transfer unit for making a shovel, a Y-axis transfer unit coupled with the X-axis transfer unit to transfer the work bed to the Y-axis, a ceramic material is filled therein, and 3D printing data is used to produce a three-dimensional sculpture. By including a nozzle part for compressing and discharging a ceramic material, and a Z-axis transport part coupled to the body part and the nozzle part to transport the Z-axis, it is possible to effectively manufacture a three-dimensional electronic component using the ceramic material.

However, this technology compresses and discharges the ceramic material while transporting it along the X-axis, Y-axis, and Z-axis according to the three-dimensional printing data, so that a three-dimensional electronic component can be effectively manufactured using the ceramic material. In addition, by providing a stirring propeller at the end of the compression screw for compressing the ceramic material filled inside the filling cylinder, it is possible to prevent the ceramic material from curing in advance by stirring the ceramic material even when the 3D printing operation is stopped. made to be

However, this technology uses a slurry in manufacturing a ceramic molded body, and while the method for performing molding when using the slurry is mentioned, there is a problem that a methodology for removing errors that may occur in the molding process is not presented. have.

Republic of Korea Patent No. 2028327

The present invention has been devised to solve the problems of the prior art described above, and the present invention can secure smoothness of manufacturing a molded body through improved adhesion between a ceramic slurry and a metal molding plate mounted on a 3D printer. An object of the present invention is to provide a method for manufacturing a ceramic compact by a three-dimensional printing method and a container for accommodating a ceramic slurry.

In addition, the present invention is a ceramic by a 3D printing method to solve the problem of scratches caused by a polymer sheet occupying the bottom surface of the VAT (container) that accommodates the slurry required for 3D printing in the 3D printing process by replacing it with a glass sheet Another object of the present invention is to provide a method for manufacturing a molded body and a container for accommodating a ceramic slurry.

In addition, the present invention provides a method for producing a ceramic molded body by a three-dimensional printing method that smoothes flow characteristics by lowering the viscosity of the slurry by controlling the temperature of the slurry by applying a glass sheet with a transparent electrode patterned on the bottom of the VAT, and a ceramic slurry It is another object to provide a receiving container.

In order to achieve the above object, the present invention comprises the steps of preparing a low concentration slurry having a relatively low concentration compared to the present slurry and the present slurry by mixing a ceramic slurry and a photoinitiator; applying the low-concentration slurry to a platform of a 3D printer; and performing three-dimensional printing by laminating the present slurry on the dried low-concentration slurry.

The slurry is preferably a slurry containing alumina, zirconia, silicon nitride, sialon or cemented carbide (WC).

When the step of performing 3D printing by applying the present slurry on the dried low-concentration slurry; is intermittent, it is preferable to heat the main slurry in order to lower the viscosity of the main slurry and secure fluidity.

It is preferable that the stirring of the slurry is performed simultaneously during the heating.

The heating is preferably made by a glass patterned with a transparent electrode installed on the bottom of the container.

The heating is preferably controlled according to a preset temperature and time so that the concentration of the slurry does not change during the heating process.

applying the low-concentration slurry to a platform of a 3D printer; After that, drying the low-concentration slurry; it is preferable to further include.

The slurry is preferably defoamed before molding.

After the low-concentration slurry is applied to the platform, it is preferable to perform a curing treatment before 3D printing molding.

The curing treatment is preferably performed by UV (Ultra Violet).

In addition, the present invention provides a container for accommodating a ceramic slurry of a 3D printer device, a glass sheet is installed on the bottom surface of the container so as to be in direct contact with the ceramic slurry, so that it is not eroded by the slurry, It provides a container for manufacturing a ceramic molded body by a three-dimensional printing method, characterized in that the light source irradiated from the light source is not scattered.

It is preferable that the said glass sheet is a transparent glass sheet.

The transparent glass sheet is preferably patterned with a transparent electrode for heating the slurry.

According to the present invention as described above, it is possible to expect the effect of securing the smoothness of manufacturing the molded body through the improvement of the adhesion between the ceramic slurry and the metal molding plate mounted on the 3D printer.

In addition, the present invention can be expected to solve the problem of scratches caused by the polymer sheet occupying the bottom surface of the VAT (container) that accommodates the slurry required for 3D printing in the 3D printing process by replacing it with a glass sheet.

In addition, the present invention can be expected to have the effect of smoothing the flow characteristics by controlling the temperature of the slurry and lowering the viscosity of the slurry by applying the glass sheet with the transparent electrode patterned on the bottom of the VAT.

1 is a flowchart showing a method of manufacturing a ceramic molded body by a three-dimensional printing method according to an embodiment of the present invention;
2 is a schematic diagram showing a three-dimensional printer;
3 is a schematic diagram showing VAT and a plastic film, which are components of a three-dimensional printer according to the prior art;
4 is a schematic diagram showing a glass sheet printed with VAT and transparent electrodes, which are components of a 3D printer according to an embodiment of the present invention;
5 is atmospheric sintering or HIP sintering (b, d) of a specimen manufactured by three-dimensional printing prepared according to an embodiment of the present invention, after uniaxial pressure molding, and then atmospheric sintering or HIP sintering (a , a graph showing the comparison of the relative densities of c),
Figure 6 is normal pressure sintering or HIP sintering (b, d) of a specimen manufactured by three-dimensional printing prepared according to an embodiment of the present invention, after uniaxial pressure molding, atmospheric sintering, or HIP sintering (a) , c) compared to electron micrographs,
7 is an atmospheric pressure sintering or HIP sintering (b, d) of a specimen manufactured by three-dimensional printing manufactured according to an embodiment of the present invention after uniaxial pressure molding, followed by atmospheric sintering or HIP sintering (a , a graph showing a comparison of the Vickers hardness of c),
8 is atmospheric pressure sintering or HIP sintering (b, d) of a specimen prepared by three-dimensional printing prepared according to an embodiment of the present invention, followed by uniaxial pressure sintering, or HIP sintering (a) , c) a graph showing the comparison of fracture toughness,
9 is a photograph of a part for a cutting tool made of an alumina material manufactured according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail based on preferred embodiments and the accompanying drawings.

In the present invention, an alumina slurry is mainly exemplified, but other materials are also possible. For example, the slurry is preferably a slurry containing zirconia, silicon nitride, sialon or cemented carbide (WC).

The present invention comprises the steps of preparing a low-concentration slurry having a relatively low concentration compared to the present slurry and the present slurry by mixing a ceramic slurry and a photoinitiator; applying the low-concentration slurry to a platform of a 3D printer; and performing three-dimensional printing by laminating the present slurry on the dried low-concentration slurry.

In the present invention, it was checked whether the physical properties of a ceramic tool manufactured by 3D printing differ from that of a ceramic tool manufactured by the conventional press method. For this purpose, an alumina insert, which is a simple shape but a representative ceramic tool, was produced by 3D printing. The insert molded body manufactured by 3D printing was sintered under atmospheric pressure, and some specimens were processed by hot isostatic pressing (HIP). Coupon specimens subjected to CIP (cold isostatic press) were prepared as reference specimens, and some specimens were HIP-treated, and the relative density, microstructure, hardness, and fracture toughness of these specimens were measured and analyzed for comparison.

To prepare an alumina slurry, an acrylate monomer (HDDA, SigmaAdrich, USA) and a silane coupling agent (KBM, ShinEtsu, Japan) were stirred to prepare a vehicle. The prepared vehicle and nano-sized alumina powder (AKP-30) were mixed, and ball milled at a speed of 200 rpm for 24 hours. The content of the alumina powder was 73% by weight. The ball mill used high-purity alumina balls to minimize contamination. The viscosity of the alumina slurry was measured, and the alumina solid content was reconfirmed using TG-DTA (SDT Q 600, TA Instruments, Korea).

To prepare the photosensitive alumina slurry, the photoinitiator was put into the alumina slurry 6 hours before 3D printing, and mixed at room temperature with a magnetic stirrer. Thereafter, in order to remove air bubbles in the photosensitive alumina slurry, it was placed in a vacuum chamber and treated under reduced pressure (de-foaming process).

For 3D printing, a DLP printer for containers (IM-2, CARIMA, KOREA) was used. The UV light source 121 was custom-made to use a UV light source of 365 nm wavelength instead of the UV light source of 405 nm wavelength, which is most often used in general-purpose 3D printers. The structure of the printer is the same as that of FIG. 2 . Unlike the SLA method in which a new layer is continuously formed on the surface of the slurry, a new layer of the molded body 112 is continuously output from the bottom of the container 110 . For this, the bottom of the container 110 should be optically transparent and flexible at the same time, so it is usually made of a plastic film. However, in the present invention, the plastic film was replaced with the glass sheet 111 .

On the other hand, if the step of performing three-dimensional printing by applying the slurry on the dried low-concentration slurry; is performed intermittently, it is preferable to heat the main slurry in order to lower the viscosity of the main slurry and secure fluidity, For this, a transparent electrode was applied to the glass sheet (see 111'), and the slurry (S) accommodated in the container 110 was heated by the transparent electrode to further secure fluidity.

It is preferable that the stirring of the slurry is performed simultaneously during the heating, and the heating is controlled according to a preset temperature and time so that the concentration of the slurry does not change during the heating process.

In the case of a plastic film, it can be easily eroded by a ceramic slurry of high hardness. In this case, transparency is greatly inhibited and light scattering occurs, thus increasing the possibility of errors in 3D printing. Therefore, in the present invention, a glass sheet is applied instead of a plastic film to effectively cope with this.

The optical system consists of a UV light source, a DMD chip, and a lens, and more than one million micromirrors in the DMD chip are individually driven by software to form a desired image on the film located at the bottom of the container. The 3D printer used in the present invention adjusted the optical system so that the size of one pixel was 30 μm.

After 200 g of the photosensitive alumina slurry is put into the container, the metal platform 113 comes down to the bottom of the container 110, and the space between the bottom of the container 110 and the platform 113 is 25 μm. A three-dimensional model of a tool insert designed in CAD was cut at intervals of 25 μm, and the digitized two-dimensional image was sequentially exported to the DMD chip 122 so that the molded body 112 was continuously generated from the bottom of the container. The finished molded body 112 was washed with ethanol and put into a curing machine for post-treatment to remove the unreacted slurry remaining on the surface.

The metal platform 113 has poor wettability to the ceramic slur, making it difficult to form the first layer. Therefore, in the present invention, a low-concentration slurry having a relatively lower concentration than the ceramic slurry (this slurry) for manufacturing a molded body is applied to the surface of the platform to serve as a mediating layer or a buffer layer between the present slurry and the platform (not shown).

The low-concentration slurry is applied to the platform with a thickness of 100-200㎛. In a specific method, a small amount of the low-concentration slurry is poured on the platform surface and horizontally moved with an applicator for tape casting to form a liquid coating film. The platform on which the liquid slurry is applied is carefully placed in a UV curing machine with the application side facing up, and cured. After UV treatment, the low-concentration slurry is cured on the surface of the platform and adheres in the form of a hard thick foil. In the subsequent 3D printing process, this slurry comes into contact with the cured low-concentration slurry for the first time. can be avoided Since the low copper slurry is hardened, dissolution or dissolution does not occur even when it comes into contact with the liquid main slurry. Alternatively, drying sufficiently is also a method, but curing is superior in terms of stability.

The separated three-dimensional insert molded body was subjected to a degreasing process, which was raised to 600° C. at a temperature increase rate of 1° C./min, maintained for 4 hours, and then furnace cooled. The degreased specimens were sintered under normal pressure at 1500° C. for 3 hours using an electric furnace. Thereafter, as necessary, hot isotropic press (HIP) was performed, and the conditions at this time were maintained at 1300° C. under 1,500 atmospheres for 1 hour. A coupon-type specimen was prepared for comparison with the three-dimensionally printed specimen. As a starting material for the coupon specimen, high-purity alumina (AKP-30), which was used to prepare alumina slurry for 3D printing (this slurry), was used identically.

The powder was charged into a mold having a diameter of 10 mm, and a coupon-shaped shape was formed by pressing it lightly with a uniaxial press, and then cold isostatic pressing (CIP, Cold isotatic press) was performed at a pressure of 150 MPa for 300 seconds. The molded specimen was sintered and HIP-treated under the same conditions as the three-dimensional printing specimen. Forming and heat treatment conditions for the specimens prepared in the present invention are summarized in Table 1, and a series of these process processes is shown in FIG. 1 .

A. Press Coupon B. 3D insert C. HIP coupon D. HIP Insert Press, CIP ○ ○ 3D Printing ○ ○ sintering ○ ○ ○ ○ HIP ○ ○

The sintered specimen was surface polished to 3 μm using a diamond abrasive. The relative density was obtained through image analysis based on the SEM image of the micropolished surface. SEM images were obtained by randomly selecting a location in a specific specimen, and the number of pixels in the area visible as pores and the number of pixels in the entire image were detected using commercial software, and the relative density was calculated. The relative density was measured for 10 images per each condition, the average value of the relative density was calculated, and the standard deviation was calculated and displayed as an error bar on the graph.

Indentation marks were made on the micro-polished surface of the specimen using a micro Vickers indenter, and hardness and fracture toughness were measured. The average values of hardness and fracture toughness were measured from 10 indentation marks per specimen, and the standard deviation was calculated and displayed in the form of error bars on the graph.

Specimens after measuring mechanical properties were destroyed, and the fracture surface generated at this time was observed with SEM to qualitatively estimate the particle size.

5 shows the relative density of specimens prepared according to an embodiment of the present invention. Specimen A is a specimen sintered under atmospheric pressure after uniaxial molding, and its relative density is 99.55%. HIP-treated this specimen is Specimen C, and the relative density is 99.66%. After 3D printing, atmospheric pressure sintering was completed in specimen B, and the relative density was 99.00%. Specimen B treated with HIP was Specimen D, and the relative density was 99.54%. Sumitomo's AKP-30 is known to have a relative density of about 99.0% or more when sintered at 1500°C for 2 hours under atmospheric pressure, so in terms of relative density, there seems to be no problem in the manufacturing process for all specimens.

When the relative densities of specimen A and specimen C were compared, the central value of specimen C subjected to HIP slightly increased, and dispersion of measured values was also reduced, suggesting that the effect of HIP treatment exists. In the case of the 3D printed specimen B, the relative density value was significantly lower than that of the CIP molded specimen A, which is due to the difference in initial molding density between the two specimens. That is, the basic assumption suggested by the traditional solid-state sintering theory is that there should be as many contacts as possible between the powders inside the compact for material movement to occur. However, there is a possibility that the agglomerated powders create large pores by mutual frictional force, so that non-contact between the powder particles occurs. The large pores of the molded body may be collapsed by a pressure of 150 MPa or more provided in the CIP process, and finally, this pressing process becomes a favorable condition for securing a high relative density. From the same point of view, the ceramic powder fixed inside the molded body by UV curing during the 3D printing process is relatively disadvantageous in making maximum contact with neighboring powders. It has a lower initial molding density than a CIP-treated molded article in the case of a three-dimensional printed article, and has a relatively low relative density when sintered for the same time. Specimen D treated with HIP after sintering the 3D printed specimen showed a higher relative density than specimen B, and the densification behavior by high pressure sintering was clearly seen.

6 shows the fracture surfaces of the specimens manufactured according to an embodiment of the present invention. 6(a) is a specimen A, which is a specimen sintered under atmospheric pressure after CIP. Considering that the average particle size of the initial powder is 200 nm, it can be seen that the particle growth has progressed considerably. Most of the particles are 2-3 μm in size, but particles larger than 5 μm are also found. Particles with large particle sizes appear to be broken by intragranular destruction, and micropores trapped inside the particles during particle growth are observed on this fracture surface. 6(b) shows the fracture surface of the specimen B, which is sintered under atmospheric pressure after 3D printing, and most of the particles have a size of 1 μm or less, and mainly exhibit a pattern of intergranular fracture. Also, pores on the order of particle size are observed. Figure 6(c) is a fracture surface of the specimen C, the fracture surface of the specimen A HIP-treated specimen. The size of the particles is not significantly different from that of Specimen A. Most of the particles are 2-3 μm in size, and particles of 5 μm or larger are also identified. Particles larger than 5 μm exhibit intragranular fracture behavior. 6(d) is a cross-sectional view of specimen D, showing a microstructure similar to that of specimen B. Most of the particles have a size of 1 μm or less, and mainly have a grain boundary fracture pattern. Specimen C and Specimen D treated with HIP hardly showed grain growth compared to normal pressure sintered specimens. This is because the HIP treatment temperature of 1,300° C. is a low temperature for active grain growth, and only the driving force for densification by gas pressure exists. Only an increase in density is observed.

7 shows Vickers hardness of specimens prepared according to an embodiment of the present invention. Among the physical properties that a cutting tool must satisfy, hardness has the most important meaning. In the case of CIP-treated specimen A, it has a hardness of 17.90 GPa, and shows a value similar to 17.80 GPa, which is the hardness of specimen B, which is 3D printed. Factors affecting hardness based on the same material include relative density and particle size. The relative density is a factor that determines the size of the plastic deformation region when pressed with an indenter. In order for a polycrystalline ceramic material to undergo plastic deformation, it is necessary to collapse the pores between the grains and intergrain microcracks due to intragranular twin/slip. It is an intuitively understandable phenomenon that the pores of the multi-porous ceramics collapse by external pressure to cause plastic deformation. On the other hand, plastic deformation due to grain boundary microcracks needs to be considered in existing studies. According to F. Guiberte et al., the occurrence of grain boundary microcracks differs depending on the size of the alumina particles, and in the case of Hertzian contact damage, plastic deformation due to intergranular microcracks was observed in specimens having particles of 3 μm or more in size. It is reported that The particle size is related to the amount of displacement due to twin/slip under compressive stress, and it is explained that the relationship between this amount of displacement and grain boundary toughness is a criterion for causing grain boundary microcracks.

Interpreting the results of the present invention from the two viewpoints described above, it is as follows. That is, in the case of polycrystalline alumina, since specimen A shows a higher relative density value than specimen B in terms of relative density, the plastic region due to pore collapse does not develop, so it should have a relatively high hardness value. Since the particles of A are larger than that of specimen B, plastic deformation due to microcracks at the grain boundary easily occurs, so it should have a lower hardness. As such, it can be estimated that specimens A and B show similar hardness values due to the conflicting effects of the two factors affecting the hardness-related plastic deformation. Of course, there is no confirmation about the quantitative comparison of the effect of the two factors, so it is difficult to clearly explain the experimentally obtained hardness.

On the other hand, after the same HIP treatment, the changes in hardness of specimen A and specimen B are different from each other. That is, in the case of specimen A subjected to atmospheric pressure sintering after CIP, when HIP treatment is performed, the hardness increases, whereas in the case of specimen B subjected to atmospheric pressure sintering after 3D printing, the hardness value decreases when HIP treatment is performed. Referring to the relative density measurement result of FIG. 5, since the relative density of specimen C showed a tendency to increase, the increase in hardness can be explained. On the other hand, in the case of Specimen D, despite showing a higher relative density than Specimen B, it shows a low hardness value, which can be explained by grain boundary segregation of carbon due to contamination by carbon during the HIP process. According to E. Marquis et al., as a result of compositional analysis of the interface of polycrystalline alumina contaminated with carbon using a probe, it was reported that a higher concentration of carbon was detected at the grain boundary than inside the grain. F. Inam et al., who studied carbon/alumina composites, showed that the alumina specimen containing carbon showed a lower hardness value than the specimen not containing carbon, which was due to the lubrication of nano-sized carbon particles contained in the composite, and indenter (indenter). ) because it reduces the friction between the surface and the surface of the polished surface, resulting in deeper indenter marks. Even in the present invention, during the HIP treatment, contaminated carbon segregated at the grain boundary of the specimen, and the hardness measurement value can be lowered due to the lubrication effect, and this effect can be explained largely in the 3D printed specimen with small particles.

8 shows the fracture toughness of the prepared specimen. CIP-molded specimen A showed a fracture toughness value of 4.11 MPa·m ^1/2 , which is typical of high-purity alumina, and HIP-treated specimen C showed a slightly increased value to ^{4.37 MPa·m 1/2.} The 3D printed specimen ^{showed a relatively high value of 6.85 MPa·m 1/2} , which can explain the relationship between alumina particle size and fracture toughness by existing studies. When the fracture toughness is measured with a Vickers indenter, the fracture toughness value changes according to the load value. At a low load, the fracture toughness value of a specimen with a small particle size is high, and at a high load, the fracture toughness of a specimen with a large particle size is high. has been reported The 9.8N load carried out in the present invention corresponds to a low load, and the crack formed as shown in the indenter mark at the bottom of FIG. 8 is a short crack. In a situation where particle pull-out by grain bridging, which is one of the fracture toughness enhancement mechanisms in polycrystalline ceramics, dominates, fracture by small cracks is considered to be a phenomenon that occurs because the resistance of small particles is large in specimens. . Since densification by HIP treatment is not significantly related to particle size change, there appears to be no significant change in fracture toughness due to HIP treatment.

100: 3D printer 110: upper container
111: glass sheet 111': glass sheet coated with a transparent electrode
112: molded body 113: platform
120: enclosure 121: UV light source
123: lens 124: glass substrate
130: lower container

Claims (13)

mixing the ceramic slurry and the photoinitiator to prepare the main slurry and the low-concentration slurry having a relatively low concentration compared to the main slurry;
applying the low-concentration slurry to a platform of a 3D printer; and
performing three-dimensional printing by laminating the present slurry on the dried low-concentration slurry;
A method of manufacturing a ceramic compact by a three-dimensional printing method, characterized in that it comprises a. According to claim 1,
The slurry is a method of manufacturing a ceramic compact by a three-dimensional printing method, characterized in that the slurry containing alumina, zirconia, silicon nitride, sialon or carbide (WC). According to claim 1,
3D printing, characterized in that the present slurry is heated in order to lower the viscosity of the main slurry and secure fluidity when performing 3D printing by applying the main slurry on the dried low concentration slurry; A method for producing a ceramic compact by the method. 4. The method of claim 3,
A method of manufacturing a ceramic molded body by a three-dimensional printing method, characterized in that the stirring of the slurry is made simultaneously during the heating. 4. The method of claim 3,
The heating is a method of manufacturing a ceramic molded body by a three-dimensional printing method, characterized in that the transparent electrode installed on the bottom of the container is made of patterned glass. 4. The method of claim 3,
The heating is controlled according to a preset temperature and time so that the concentration of the slurry does not change during the heating process. According to claim 1,
applying the low-concentration slurry to a platform of a 3D printer; Thereafter, drying the low-concentration slurry;
Method of manufacturing a ceramic compact by a three-dimensional printing method, characterized in that it further comprises. According to claim 1,
The slurry is a method of manufacturing a ceramic molded body by a three-dimensional printing method, characterized in that the defoaming process is performed before molding. According to claim 1,
After the low-concentration slurry is applied to the platform, a method of manufacturing a ceramic molded body by a three-dimensional printing method, characterized in that a curing treatment is performed before the three-dimensional printing molding. 10. The method of claim 9,
The curing treatment is a method of manufacturing a ceramic molded body by a three-dimensional printing method, characterized in that performed by UV (Ultra Violet). In the container for accommodating the ceramic slurry of the three-dimensional printer device,
A glass sheet is installed on the bottom of the container so as to be in direct contact with the ceramic slurry, so as not to be eroded by the slurry, so that the light source irradiated from the light source below is not scattered by erosion. A container for producing a ceramic compact. 12. The method of claim 11,
The glass sheet is a container for manufacturing a ceramic molded body by a three-dimensional printing method, characterized in that the transparent glass sheet. 12. The method of claim 11,
A container for manufacturing a ceramic molded body by a three-dimensional printing method, characterized in that the transparent glass sheet is patterned with a transparent electrode for heating the slurry.

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