TW202229203A - Method for fabricating zirconia ceramics by aqueous gel-casting technology - Google Patents

Abstract

The present invention relates to a method for fabricating zirconia ceramics by aqueous gel-casting technology. The method includes: mixing yttria-stabilized zirconia with a dispersant to form a first mixture; mixing an organic monomer and a plasticizer with the first mixture to form a second mixture; mixing a polymerization initiator with the second mixture to form a third mixture; mixing a polymerization inhibitor with the third mixture to form a zirconia suspension; pouring the zirconia suspension into a mold and drying the zirconia suspension at temperature ranging from 45 DEG C to 60 DEG C for 11 to 13 hours to obtain a zirconia green body; sintering the zirconia green body at temperature ranging from 1250 DEG C to 1300 DEG C to form a zirconia ceramic. With the aqueous gel-casting technology, the dispersibility of zirconia suspension is improved so that the compactness of zirconia ceramics is improved.

Description

Method for making zirconia ceramics by water-based glue casting

The present invention relates to a method for producing zirconia ceramics by water-based glue casting, in particular to a zirconia slurry by mixing yttrium-stabilized zirconia with dispersant, organic monomer, plasticizer, polymerization initiator and polymerization inhibitor , and by controlling the drying temperature and time of the zirconia slurry in the mold to obtain the zirconia green body, and controlling the sintering temperature and time of the zirconia green body to obtain the invention of high-density zirconia ceramics.

Zirconia ceramics have the advantages of high melting point and high chemical stability, so zirconia ceramics are ceramic materials with great potential for industrial application. In addition, zirconia ceramics are also widely used in ceramic substrates due to their excellent mechanical properties and wear resistance, such as high mechanical strength, high toughness, and high hardness (Mohs hardness of 8.5, second only to diamond and corundum).

In addition to the above advantages, zirconia ceramics also have the characteristics of scratch resistance, no signal shielding, excellent heat dissipation performance, and good appearance. Therefore, it has become a new type of mobile phone body material after plastic, metal and glass. At present, the application of zirconia ceramics is mainly in the backplane and fingerprint recognition cover of mobile phones. The advantages of zirconia ceramics as mobile phone backplanes are as follows:

(1) Mechanical strength: A small amount of yttrium oxide is added to the widely used yttrium-stabilized zirconia (Y-TZP), which causes residual compressive internal stress inside the ceramic material. When the ceramic body is impacted, the added tensile stress will offset the residual compressive internal stress, so that the toughness of the zirconia ceramic is improved and it is not easy to be broken.

(2) Signal penetration: In the future, mobile phones will move towards the 5G generation. 5G communication will use the spectrum above 3Ghz, the wavelength of millimeter wave is very short, and the interference from metal is very strong. The antenna layout of the existing mobile phone terminals is full. To re-layout the 5G antenna with strict requirements, it is necessary to change the material of the existing metal casing. Zirconia ceramics has an "innate advantage", which can allow the signal to easily pass through the casing and reach the internal antenna. Make the signal strength transmitted or received stronger.

(3) Heat conduction: When the internal parts of the mobile phone generate heat, the traditional glass or plastic mobile phone casing will make the user feel hot and uncomfortable. When using a zirconia ceramic case, it can achieve better heat dissipation because of better heat conduction, and it feels warmer and skin-friendly.

(4) Hardness: The hardness of zirconia ceramics is second only to diamond and corundum, which also means that its anti-scratch ability is extremely strong. When zirconia ceramics are used as mobile phone shells, it can greatly reduce the generation of scratches and maintain the integrity of the appearance of mobile phones. .

The conventional zirconia ceramics are made by wet forming method, for example, as shown in the Republic of China Invention Patent Publication No. I576094 "Coloring Method of Zirconia Green Body". This case discloses that the zirconia manufacturing steps include: wet mixing a mixture to prepare a mixed slurry, and the mixture contains zirconia powder, alumina powder, mica powder, ferric nitrate powder and an adhesive; drying the mixed slurry , in order to obtain agglomerates, and the agglomerates are composed of zirconia powder, alumina powder, ferric nitrate powder and mica powder bonded to each other through an adhesive; grinding and sieving the agglomerates to form powders ; Press-molding the powder to form a block; and calcining the block at 800 to 1100° C. to obtain a zirconia green body.

Due to the formulation problem in the above wet molding method, the viscosity of the slurry is high and it is not easy to disperse, so that the solid content of the slurry cannot be too high. In addition, most of the solvents used in the wet molding method are mainly organic solvents with high cost.

In view of this, the present invention provides a method for manufacturing zirconia ceramics by water-based glue casting, comprising: stirring and mixing a yttrium-stabilized zirconia and a dispersant to form a first mixture. An organic monomer and a plasticizer are added to the first mixture and mixed into a second mixture. A polymerization initiator is added to the second mixture and mixed into a third mixture. A polymerization inhibitor is added to the third mixture and mixed into a zirconia slurry. The zirconia slurry is poured into a mold, and dried at a temperature between 45 degrees Celsius and 60 degrees Celsius, and the drying time is between 11 hours and 13 hours, so as to obtain a green zirconia body. The zirconia green body is taken out from the mold, and the zirconia green body is sintered at a temperature between 1250 degrees Celsius and 1300 degrees Celsius, so that the zirconia green body is formed into a zirconia ceramic.

Further, the yttrium-stabilized zirconia solid content of the zirconia slurry is between 35% and 45% by volume.

Further, the particle size of the yttrium-stabilized zirconia is between 80 and 100 nanometers.

Further, the weight part of the yttrium-stabilized zirconia is between 150 and 200, and the weight part of the dispersant is between 0.5 and 1. Preferably, the weight ratio of the yttrium-stabilized zirconia to the dispersant is 1000:4.

Further, the parts by weight of the organic monomer are between 10 and 15, the parts by weight of the plasticizer are between 8 and 10, the parts by weight of the polymerization initiator are between 5 and 8, the polymerization inhibitor The weight part of the agent is between 0.05 and 0.1.

Further, the zirconia green body is sintered in two stages, the sintering temperature of the first stage is between 1250 degrees Celsius and 1300 degrees Celsius, and the holding time is between 1 minute and 30 minutes; the sintering temperature of the second stage is between 1 minute and 30 minutes. Between 1200 degrees Celsius and 1240 degrees Celsius, the holding time is between 20 hours and 30 hours.

Further, the dispersant is polyammonium methacrylate (Dolapix CE64), the organic monomer is ethylene glycol diglycidyl ether (EGDGE), the plasticizer is glycerin (GLY), and the polymerization initiator is imine Dipropylamine (DPTA), the polymerization inhibitor is hydroquinone (HQ).

Further, the relative density of the zirconia ceramic is between 99.0 and 99.5%

The above technical features have the following advantages:

1. In the present invention, the viscosity of the zirconia slurry is lower through water-based glue casting, and the dispersibility of the yttrium-stabilized zirconia in the zirconia slurry is improved, so the solid content of the zirconia slurry is high, and the zirconia slurry can be sintered. The compactness of zirconia ceramics, and the cost of water-based chemicals is lower than that of organic solvents, which reduces the production cost.

2. The present invention further improves the compactness of zirconia ceramics after sintering by sintering green zirconia embryos in two stages, and the relative density of zirconia ceramics can be increased to about 99.0% to 99.5% after testing.

3. By controlling the drying temperature and time of the zirconia slurry in the mold, the present invention can improve the strength of the zirconia green body and reduce the defects generated during drying when the zirconia slurry is solidified and reacted to form a zirconia green body.

In view of the above technical features, the main effects of the method for producing zirconia ceramics by water-based glue casting of the present invention can be clearly shown in the following examples.

Referring to the first figure, the present invention provides a method for manufacturing zirconia ceramics by water-based glue casting. The steps include:

A first mixture is prepared by stirring and mixing a yttrium-stabilized zirconia between 150 g and 200 g and a dispersing agent between 0.15 g and 0.5 g in a weight part at a shear rate of 0.1 Hz. , the viscosity of the first mixture is between 0.24 poise and 10 poise, and the weight ratio of the yttrium-stabilized zirconia to the dispersant is 1000:4.

The yttrium-stabilized zirconia of the present invention is a commercial yttrium-stabilized zirconia powder (3YTZ) prepared by a hydrothermal method, and the yttrium-stabilized zirconia powder contains 3 mol% of yttrium oxide, and the particle size of the yttrium-stabilized zirconia is between 80 and 100 Between nanometers, although yttrium-stabilized zirconia powder is easier to make into polycrystalline ceramics ranging from nanometers to sub-micrometers, due to the smaller particle size of the powder, the van der Waals force is more attractive, which makes the yttrium-stabilized zirconia powder dispersed and The molding process is difficult. It should be noted that due to the large van der Waals force attraction between the particle sizes of yttrium-stabilized zirconia powder, it is necessary to pay attention to each step of zirconia slurry production in order to successfully produce high density, less agglomeration and small pores Zirconia slurry. In this embodiment, polyammonium methacrylate (Dolapix CE64) is used as the dispersant, and through this dispersant, the van der Waals force between the particle sizes of the yttrium-stabilized zirconia powder can be reduced to achieve uniform dispersion without agglomeration.

Then, an organic monomer between 10 g and 15 g by weight and a plasticizer between 8 g and 10 g by weight are added to the first mixture and mixed to form a second mixture. In this embodiment, the organic monomer is selected from ethylene glycol diglycidyl ether (EGDGE), and the plasticizer is selected from glycerin (GLY). The organic monomer helps the subsequently formed zirconia green body to have a certain strength to facilitate subsequent machining, and the plasticizer helps to reduce the glass transition temperature of the macromolecular polymer in the subsequently formed zirconia green body, so that the It is beneficial to carry out cold equalization to further increase the density of green zirconia.

A polymerization initiator in parts by weight between 5 grams and 8 grams is added to the second mixture and mixed into a third mixture. In this embodiment, the polymerization initiator is selected from imine dipropylamine (DPTA). Wherein the polymerization initiator can induce the cleavage of the epoxy group of the organic monomer and polymerize with the short chain of the organic monomer to form a network polymer to increase the strength.

A polymerization inhibitor between 50 mg and 100 mg by weight is added to the third mixture and mixed to form a zirconia slurry, and the solid content of the zirconia slurry can reach between 35% and 45%. In this embodiment, the polymerization inhibitor is selected from hydroquinone (HQ). The polymerization reaction of the zirconia slurry is slowed down by the polymerization inhibitor, so as to facilitate the subsequent shaping of the zirconia slurry.

The zirconia slurry was poured into a mold. The mold can be made according to the desired shape and size. The mold with the zirconia slurry is placed in a drying space for drying, the drying temperature is between 45 degrees Celsius and 60 degrees Celsius, and the drying time is between 11 and 13 hours, so that the zirconia in the mold is dried. The slurry undergoes a curing reaction to form a green zirconia body. After the zirconia green body is taken out from the mold, the zirconia green body is placed in a cold isostatic pressing machine (CIP), and the zirconia green body is subjected to cold isopress forming, so that the zirconia green body is compressed more densely , reduce porosity and increase density.

The zirconia green body is subjected to two-stage sintering at high temperature. The sintering temperature of the first stage is between 1250 degrees Celsius and 1300 degrees Celsius, and the holding time is between 1 minute and 30 minutes; the sintering temperature of the second stage is between 1200 degrees Celsius and 1240 degrees Celsius, and the holding time Between 20 hours and 30 hours, the zirconia green body is allowed to form a zirconia ceramic. Among them, the heating curve of the first stage sintering is to raise the temperature at a heating rate of 1°C per minute to 500°C and hold the temperature for 2 hours to degrease, and then raise the temperature to 1300°C at a heating rate of 5°C per minute and hold the temperature for 30 minutes. Inside; the heating curve of the second stage sintering is maintained at a heating rate of 5 degrees Celsius per minute to 1240 degrees Celsius for 24 hours. Therefore, the relative density of the zirconia ceramic after sintering can reach between 99.0 and 99.5%.

In the embodiment of the present invention, the yttrium-stabilized zirconia and the zirconia ceramics are subjected to material analysis:

Please refer to the second picture A and the second picture B, the yttrium stabilized zirconia is placed under a scanning electron microscope (SEM), the image of the yttrium stabilized zirconia is shown in the second picture A; as shown in the second B picture, through the The second graph A calculates and statistically makes a cumulative distribution of powder particle size. The average particle size (d50) of the zirconia slurry is about 94 nanometers.

Please refer to the spectrum of the yttrium-stabilized zirconia shown in Figure 3A, which is a spectrum of the yttrium-stabilized zirconia placed on an X-ray diffractometer (XRD). More monoclinic phase. By heating the yttrium-stabilized zirconia to a temperature higher than the phase transition temperature and cooling it to room temperature, the monoclinic phase of the yttrium-stabilized zirconia is transformed into a tetragonal phase and retained. The two-stage heated zirconia ceramic was placed in an X-ray diffractometer (XRD), and it can be seen that after the two-stage high-temperature sintering and cooling to room temperature, a large number of meso-stable tetragonal crystal phases remained in the zirconia ceramics, especially not all All of them exist as tetragonal crystal phase or there is some monoclinic crystal phase, and these many monoclinic crystal phases indicate that their relative tetragonal crystals are relatively unstable and tend to be transformed into monoclinic crystal phases at any time. When subjected to crack tensile stress, The tetragonal crystal phase will expand in volume due to the transformation of the stress-induced phase into the monoclinic crystal phase, and the compressive stress and the tensile stress of the crack will cancel each other out, thereby preventing the extension of the crack and increasing the drop resistance of the ceramic body.

In the embodiment of the present invention, the viscosity and dispersibility analysis of adding different contents of dispersants to the zirconia slurry of the same solid content:

Please refer to the fourth figure, when the solid content of the zirconia slurry is 45vol% and the addition amount of the dispersant is 0.15wt%, the viscosity exceeds 10 poise (Pa.s) when the shear rate is 0.1 Hz (1/s). ), the measured viscosity is too high, which indicates that the amount of dispersant added is insufficient. When the amount of the dispersant added was increased from 0.2 to 0.3 wt%, the viscosity decreased significantly. However, when the amount of the dispersant was increased to 0.5wt%, the excessive amount of the dispersant increased the viscosity again. Therefore, the optimum amount of the dispersant added to the zirconia slurry is about 0.2 wt %, which has a viscosity of 0.24 poise (Pa.s) at a shear rate of 0.1 Hz (1/s).

Please refer to Fig. 5A and Fig. 5B, the zirconia slurry with a solid content of 45vol% was added with 0.2wt% of the dispersant and placed in a laser particle size analysis. The zirconia was measured through the results of the laser particle size analysis. The particle size of the slurry is about 165 nanometers, which is not much different from the size of the original powder, and no agglomeration is produced. From this, it can be known that the yttrium-stabilized zirconia of the zirconia slurry can be uniformly dispersed through the dispersant without obvious powder agglomeration.

Referring to Figure 6, when the polymerization inhibitor is mixed with the organic monomer of the zirconia slurry, even if the dispersant is contained in the zirconia slurry, no obvious polymerization reaction will occur. The polymerization agent can indeed prevent the problem of the dispersant promoting the polymerization of the organic monomer. However, the monitoring mixing time was prolonged, and the polymerization inhibitory effect of the polymerization inhibitor was continuously observed, and no hydroxyl peak produced by the polymerization reaction of the organic monomer and the polymerization initiator was found. It is thus known that adding the polymerization inhibitor to the zirconia slurry can indeed increase the residence time of the polymerization reaction, thereby increasing the stability of the zirconia slurry and the working time of injection molding.

In the embodiment of the present invention, the drying temperature is controlled to observe the solidification reaction of the zirconia slurry and the density analysis of the zirconia green body with or without cold isostatic pressing:

Please refer to Figure 7. If the zirconia slurry is kept at room temperature, the viscosity of the zirconia slurry does not increase significantly when measured for a long time, which means that the molecular weight of the organic monomer of the zirconia slurry does not increase. In addition, the polymerization reaction hardly occurs, which is not suitable for practical application, because the curing reaction time of the zirconia slurry at room temperature is too long. Therefore, in the present invention, in order to improve the curing reaction, the zirconia slurry is heated to 45 degrees Celsius to 60 degrees Celsius to obviously find that the viscosity of the zirconia slurry increases significantly, indicating that the zirconia slurry is undergoing curing reaction. The curing reaction of the zirconia slurry at 60 degrees Celsius is more severe than that at 45 degrees Celsius, and the curing reaction time of the zirconia slurry is shortened to form the zirconia green body.

Referring to Figure 8, the zirconia green body is heated directly and then compressed by a cold equalizing press (CIP). , so that the pores become smaller and the density is increased, which is beneficial to the subsequent heating to make the zirconia ceramic more dense.

In the embodiment of the present invention, the zirconia green body is sintered into the microstructure and relative density analysis of the zirconia ceramic:

Please refer to Fig. 9, during the sintering of the zirconia green body into the zirconia ceramic, a dilatometer analysis (DIL) is performed to obtain a data graph of the relative density of the zirconia green body at different temperatures. The zirconia green body is sintered in two stages, the sintering temperature of the first stage is between 1250 degrees Celsius and 1300 degrees Celsius, and the temperature holding time is between 1 minute and 30 minutes; the first stage sintering can make the zirconia The green body is densified, and the relative density can reach 90%; the sintering temperature in the second stage is between 1200 degrees Celsius and 1240 degrees Celsius, and the holding time is between 20 hours and 30 hours to inhibit the growth of grains and continue to Densification was performed to densify the formed zirconia ceramic to a relative density of 99.5%.

Please refer to Figure 10A, the zirconia ceramic fracture surface image is taken with a scanning electron microscope (SEM), it can be seen that the relative density of the zirconia ceramic reaches 99%, and it can also be seen from the figure that the zirconia ceramic The ceramic has been densified almost completely, and the pores have been eliminated. Referring to Figure 10 B, it can be known that the grain size of the zirconia ceramic is about 195 nm, and thus it can be known that the zirconia ceramic is densified to a relative density of more than 99.5%.

Mechanical property analysis of this zirconia ceramic in the embodiment of the present invention:

Referring to Figure 11A, the fracture toughness of the zirconia ceramic is calculated by three-point bending resistance, and then the average value is 770.9MPa and the standard deviation is 209.65 through statistical analysis of multiple sets of data.

Referring to Fig. 11B, the Vickers hardness of the zirconia ceramic is calculated by Vickers indentation. The average value was 15.2GPa and the standard deviation was 0.29 through statistical analysis of multiple groups of data.

Referring to Figure 11 C, the KIC value of the fracture toughness was calculated by the indentation method of the zirconia ceramic. The indentation shape and crack length obtained by the Vickers hardness machine were calculated and the statistical analysis of multiple sets of data obtained the average value of 7.8MPa*m ^1/2 and the standard deviation of 1.63.

Based on the descriptions of the above embodiments, one can fully understand the operation, use and effects of the present invention, but the above-mentioned embodiments are only preferred embodiments of the present invention, which should not limit the implementation of the present invention. Scope, that is, simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the contents of the description of the invention, all fall within the scope of the present invention.

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[Figure 1] is a flow chart of the method of the present invention for producing zirconia ceramics by water-based glue casting. [The second picture A] is the SEM image of the original yttrium-stabilized zirconia powder of the present invention. [Second Figure B] is a graph showing the relationship between the grain size and the distribution ratio of the original yttrium-stabilized zirconia powder of the present invention. [The third picture A] is the XRD pattern of the original yttrium-stabilized zirconia powder of the present invention. [The third picture B] is the XRD pattern of the zirconia ceramics of the present invention. [Figure 4] is the relationship between the shear rate and the viscosity of the zirconia slurry of the present invention with different contents of dispersant added. [Fig. 5 A] is an analysis diagram of the laser particle size of the zirconia slurry of the present invention with 0.2wT% dispersant added. [Fig. 5 B] is a particle size distribution diagram of the yttrium-stabilized zirconia in the zirconia slurry of the present invention. [Fig. 6] is a spectrogram showing the effect of adding a polymerization inhibitor to the zirconia slurry of the present invention on the polymerization reaction. [Fig. 7] is a graph showing the viscosity of the zirconia slurry on the gelation time of the zirconia slurry at different drying temperatures of the present invention. [Figure 8] is a graph showing the relationship between the pore size and the pore area of the green zirconia embryo of the present invention with and without cold equalization. [Fig. 9] is a thermal analysis curve of thermal expansion in the process of sintering zirconia green embryos into zirconia ceramics according to the present invention. [10th Figure A] is an SEM image of the fractured surface of the zirconia ceramic of the present invention. [10th Figure B] is a graph showing the relationship between the grain size and the distribution ratio of the zirconia ceramics of the present invention. [Fig. 11 A] is a graph of the bending strength data of the zirconia ceramics of the present invention. [Fig. 11 B] is a graph of Vickers hardness data of the zirconia ceramics of the present invention. [Figure 11 C] is the fracture toughness data chart of the zirconia ceramics of the present invention.

Claims (9)

A method for making zirconia ceramics by water-based glue casting, comprising: stirring and mixing a yttrium-stabilized zirconia and a dispersant to form a first mixture; adding an organic monomer and a plasticizer to the first mixture and mixing into a second mixture; adding a polymerization initiator to the second mixture and mixing into a third mixture; adding a polymerization inhibitor to the third mixture to form a zirconia slurry; The zirconia slurry is poured into a mold, and dried at a temperature between 45 degrees Celsius and 60 degrees Celsius, and the drying time is between 11 hours and 13 hours to obtain green zirconia; The zirconia green body is taken out from the mold, and the zirconia green body is sintered at a temperature between 1250 degrees Celsius and 1300 degrees Celsius, so that the zirconia green body is formed into a zirconia ceramic. According to the method for producing zirconia ceramics by water-based glue casting according to claim 1, further, the solid content of yttrium-stabilized zirconia in the zirconia slurry is between 35% and 45% by volume. The method for manufacturing zirconia ceramics by water-based glue casting according to claim 2, wherein the particle size of the yttrium-stabilized zirconia is between 80 and 100 nanometers. The method for producing zirconia ceramics by water-based glue casting according to claim 2, wherein the weight part of the yttrium-stabilized zirconia is between 150 and 200, and the weight part of the dispersant is between 0.5 and 1 . The method for producing zirconia ceramics by water-based glue casting according to claim 4, wherein the weight ratio of the yttrium-stabilized zirconia to the dispersant is 1000:4. The method for producing zirconia ceramics by water-based glue casting according to claim 4, wherein the weight part of the organic monomer is between 10 and 15, the weight part of the plasticizer is between 8 and 10, The weight part of the polymerization initiator is between 5 and 8, and the weight part of the polymerization inhibitor is between 0.05 and 0.1. The method for producing zirconia ceramics by water-based glue casting according to claim 1, further, the zirconia green body is sintered in two stages, and the sintering temperature in the first stage is between 1250 degrees Celsius and 1300 degrees Celsius, The holding time is between 1 minute and 30 minutes; the sintering temperature in the second stage is between 1200 degrees Celsius and 1240 degrees Celsius, and the holding time is between 20 hours and 30 hours. The method for making zirconia ceramics by water-based glue casting according to claim 1, wherein the dispersant is polyammonium methacrylate (Dolapix CE64), and the organic monomer is ethylene glycol diglycidyl ether (EGDGE). , The plasticizer is glycerin (GLY), the polymerization initiator is iminodipropylamine (DPTA), and the polymerization inhibitor is hydroquinone (HQ). The method for producing zirconia ceramics by water-based glue casting according to claim 1, wherein the relative density of the zirconia ceramics is between 99.0 and 99.5%.

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