WO2024014759A1 - Two-color zirconia-alumina ceramic composite and method for manufacturing same - Google Patents

Abstract

Disclosed are a two-color zirconia-alumina composite having a clear two-color boundary and improved mechanical properties, and a method for manufacturing same. The disclosed two-color zirconia-alumina ceramic composite comprises: 55-65 wt% of zirconia spherical particles; and 35-45 wt% of aluminum oxide.

Description

Two-color zirconia-alumina ceramic composite and its manufacturing method

The present invention relates to a two-color zirconia-alumina ceramic composite and a manufacturing method thereof, and more specifically, to a high-strength ceramic composite with bright and clear two-color boundaries and a manufacturing method thereof.

When ceramic materials undergo rapid temperature changes, cracks occur on the surface due to internal stress and changes in volume, ultimately leading to destruction. Therefore, when it comes to various heat-resistant or insulating devices or materials, resistance to thermal shock, that is, heat-resistant characteristics, is of utmost importance.

Therefore, among ceramic materials, zirconia, which has excellent structural properties, is widely used as a structural ceramic. Zirconium dioxide (ZrO2), also called zirconia, is a white crystalline oxide and is the ceramic material closest to metal. Zirconia has excellent material properties such as high heat resistance, low thermal conductivity, chemical stability, high strength, high hardness, and high fracture toughness, so it is used as a heat-resistant material for melting glass and making iron and steel.

On the other hand, zirconia has limitations in its application range due to the high brittleness of ceramic materials. However, after it was discovered that brittleness, a drawback of ceramics, can be improved, zirconia is being used in a variety of fields, and is widely used in thread guides, various dies, and nozzles. Recently, attempts are being made to color zirconia ceramics in various colors and apply them to decorative items such as watch bezels, cases, and watch bands that require excellent mechanical properties, as well as substrates for various mechanical and electronic components.

In addition, with the improvement of living standards, zirconia is used not only in watches but also in decorative items such as jewelry, and the demand for zirconia of various colors is increasing. Meanwhile, when coloring zirconia with various colors, the color must be maintained even when fired at high temperatures without affecting the excellent physical and chemical properties. The various colors of zirconia developed so far are colored by adding metal pigments to zirconia, but this method has the disadvantage of destroying the stabilization of zirconia and lowering its mechanical properties.

In particular, zirconia is stable in the monoclinic structure from room temperature to 1170°C, but has the property of changing into a tetragonal or cubic structure as the temperature rises. Therefore, zirconia, which has become tetragonal by sintering above 1500℃, undergoes a phase transition to monoclinic when cooled below 950℃, accompanied by a change in volume, exceeding the deformation resistance, and causing cracks.

Therefore, zirconia has the disadvantage of not being able to maintain its colored color due to cracking as well as deterioration of the properties of zirconia due to metallic pigments. In order to complement the structural characteristics of zirconia, research is being actively conducted on materials with excellent thermal shock resistance by dissolving aluminum oxide (Al2O3) in zirconia. In addition, research is being conducted on a composite of stabilized zirconia mixed with aluminum oxide by adding a metal stabilizer to zirconia.

Patent Document 1 below discloses a method for manufacturing two-color zirconia ceramics, and Patent Document 2 discloses a method for producing colored, especially orange-colored items made from zirconia, and decorative colored items made from zirconia obtained according to this method. It has been disclosed. The invention disclosed in Patent Documents 1 and 2 manufactures colored zirconia ceramics by including aluminum oxide and pigments in zirconia, but is lacking in terms of mechanical properties and color vividness.

The present invention was created in consideration of the above-described points. By mixing zirconia spherical particles and aluminum oxide and then implementing a ceramic composite developed in various colors at high temperature, a two-color zirconia with not only mechanical properties but also clear color and color boundaries is created. -The purpose is to provide an alumina ceramic composite and a manufacturing method thereof.

In order to achieve the above object, the two-color zirconia-alumina ceramic composite according to the present invention includes spherical zirconia particles; and aluminum oxide.

The zirconia spherical particles are prepared by dissolving 93 to 95 wt% of partially stabilized zirconia powder, 1 to 4 wt% of polyvinyl alcohol-based binder, 2 to 3 wt% of ammonium polycarboxylate salt-based dispersant, and 1 to 2 wt% of polyether-based defoaming agent in water. preparing a mixture; and spray drying the mixture at 150 to 230°C.

The partially stabilized zirconia powder is a powder obtained by adding a small amount of a metal stabilizer to zirconia powder, and the metal stabilizer is selected from yttria (Y2O3), magnesium oxide (MgO), calcium oxide (CaO), and cerium oxide (Ce2O3). It can include at least one or more.

As a result of analyzing the color change after heating the two-color zirconia-alumina ceramic composite in cooking oil at a predetermined temperature for 24 hours, the color difference (△E) before and after heating was 0.10 to 0.20.

The two-color zirconia-alumina ceramic composite further includes a pigment, and the pigment may include at least one selected from magnesium oxide, zinc oxide, nickel oxide, cobalt oxide, manganese oxide, iron oxide, and copper oxide.

In order to achieve the above object, the method for manufacturing two-color zirconia-alumina ceramics according to the present invention includes the steps of preparing a precursor by mixing 55 to 65 wt% of zirconia spherical particles with 35 to 45 wt% of aluminum oxide, a pigment reaction catalyst, and the following steps: ; manufacturing a molded body by pressure molding the precursor material; Degreasing heat treatment of the molded body; Adding a solution in which a pigment is dissolved to a portion of the degreased heat-treated molded body to partially color it through a color reaction between the pigment and aluminum oxide, which is the pigment reaction catalyst; Sintering the partially colored molded body; And it may include the step of naturally cooling the sintered molded body.

The zirconia spherical particles are prepared by dissolving 93 to 95 wt% of partially stabilized zirconia powder, 1 to 4 wt% of polyvinyl alcohol-based binder, 2 to 3 wt% of ammonium polycarboxylate salt-based dispersant, and 1 to 2 wt% of polyether-based defoaming agent in water. preparing a mixture; and spray drying the mixture at 150 to 230°C.

The partially stabilized zirconia powder is a powder obtained by adding a small amount of a metal stabilizer to zirconia powder, and the metal stabilizer is yttria (Y2O3), magnesium oxide (MgO), calcium oxide (CaO), and cerium oxide (Ce2O3). It may include at least one selected.

The metal stabilizer is yttria, and the yttria may contain 3 to 4 mol% based on the total mol% of the zirconia powder.

The degreasing heat treatment step may be characterized by primary heating at 155 to 175°C for 30 to 40 hours, followed by secondary heating at 650 to 850°C for 30 to 40 hours.

In the partial coloring step, the amount of pigment reacting with the pigment reaction catalyst of the molded body may be 0.05 to 0.10 wt% based on the total wt% of the colored portion of the molded body.

The sintering step may be characterized in that the partially colored molded body is heated from room temperature to a sintering temperature of 1550 to 1600°C for 10 to 15 hours, and then heated at the elevated temperature for 15 to 20 hours.

The density of the sintered zirconia-alumina ceramic composite may be 5.80 to 6.10 g/cm ³ .

The two-color zirconia-alumina composite according to the present invention provides a ceramic composite with excellent strength, corrosion resistance, and chemical resistance properties by using a mixture of spherical zirconia particles and aluminum oxide.

In addition, the method for manufacturing a two-color zirconia-alumina composite according to the present invention is to manufacture zirconia spherical particles by spray drying the mixture by adding a binder, antifoaming agent, and propellant to zirconia powder containing a metal stabilizer, and then producing zirconia spherical particles. By molding a mixture of aluminum oxide and aluminum oxide to produce a molded body, degreasing heat treatment of the molded body, partial coloring by the coloring reaction of the pigment, sintering, and cooling, not only are the colors colored at high temperatures bright, the two-color border is clear, and the material has excellent mechanical properties. , provides a manufacturing step that does not discolor.

Figure 1 is a flow chart showing the manufacturing steps of a two-color zirconia-alumina composite according to an embodiment of the present invention.

Figure 2 is a graph showing the density of the sintered body of a two-color zirconia-alumina ceramic composite according to an embodiment of the present invention.

Figure 3 is a scanning electron microscope (SEM) photograph of a two-color zirconia-alumina ceramic composite according to an embodiment of the present invention.

Figures 4 to 7 are photographs showing a two-color zirconia-alumina ceramic composite whose color was changed by varying the pigment according to an embodiment of the present invention.

All terms described in this specification are general terms that are currently widely used in consideration of the functions of the present invention, but these may vary depending on the intention of a person skilled in the art, custom, or the emergence of new technologies. Additionally, if the inventor specifies any term in the present invention, its meaning will be described in the description of the invention. Therefore, the terms used in the present invention should not be interpreted simply as the names of the terms, but should be interpreted based on the actual meaning of the term and the overall content described in the description of the present invention.

Hereinafter, a two-color zirconia-alumina ceramic composite and a method for manufacturing the same according to an embodiment of the present invention will be described in detail with reference to the attached drawings. In order to clearly explain the present invention in the drawings, parts not related to the description are omitted, and the same reference numerals are used for identical or similar components throughout the specification.

The present invention provides a two-color zirconia-alumina ceramic composite and a method for manufacturing the same. In the present invention, the use of the two-color zirconia-alumina ceramic composite is not limited. In the present invention, the zirconia-alumina ceramic composite can be applied, for example, to decorative items, substrates for electronic components, etc. Specifically, the two-color zirconia-alumina composite according to the present invention is a ceramic part and product that satisfies both gloss and strength as aesthetic requirements, and is used in watch cases, watch bands, watch faces, tie pins, buttons, and jewelry. It can be used in Ceramic electronic components such as decorative items, mechanical parts of various structural materials, and substrates for electronic components.

The two-color zirconia-alumina ceramic composite according to an embodiment of the present invention may include zirconia spherical particles and aluminum oxide.

The two-color zirconia-alumina ceramic composite according to an embodiment of the present invention includes spherical zirconia particles. The zirconia spherical particles may contain 55 to 65 wt% based on the total wt% of the ceramic composite. The zirconia spherical particles are a mixture of 93 to 95 wt% of partially stabilized zirconia powder, 1 to 4 wt% of polyvinyl alcohol-based binder, 2 to 3 wt% of ammonium polycarboxylate salt-based dispersant, and 1 to 2 wt% of polyether-based antifoaming agent dissolved in water. After preparing, the mixture can be obtained through spray drying at 150 to 230°C. The particle size of the zirconia spherical particles may be 20 to 30㎛.

The zirconia spherical particles may include partially stabilized zirconia powder. The partially stabilized zirconia powder can be produced by adding a small amount of a metal stabilizer to pure zirconia powder. Zirconium dioxide (ZrO2), also called zirconia, is a white crystalline oxide and is the ceramic material closest to metal. The zirconia has a density of 5.68 g/cm ³ , a melting point of 2715°C, and a boiling point of 400°C, and has excellent material properties such as high heat resistance, low thermal conductivity, chemical stability, high strength, high hardness, and high fracture toughness.

On the other hand, zirconia has the same chemical composition, but its structure changes depending on temperature, so its physical properties can change. That is, the zirconia can change into a monoclinic structure from room temperature to 1170°C, and into a tetragonal or cubic structure as the temperature rises. Therefore, zirconia, which has become tetragonal by sintering above 1500℃, undergoes a phase transition to monoclinic when naturally cooled below 950℃. The phase-transformed zirconia is accompanied by a volume change of 3 to 5%, and the resulting stress exceeds the deformation resistance of zirconia, which may cause cracks.

Therefore, in order to alleviate the problem of cracks occurring during natural cooling after sintering of zirconia, partially stabilized zirconia powder can be manufactured by adding a small amount of metal stabilizer to zirconia powder in an embodiment of the present invention. The metal stabilizer may be selected from at least one of yttria (Y2O3), magnesium oxide (MgO), calcium oxide (CaO), and cerium oxide (Ce2O3). Therefore, the yttria may contain 3 to 4 mol% based on the total mol% of the zirconia powder. Additionally, magnesium oxide may contain 8 to 9 mol% based on the total mol% of the zirconia powder, and calcium oxide may contain 8 to 9 mol% based on the total mol% of the zirconia powder. In an embodiment of the present invention, yttria may be mainly selected as the metal stabilizer.

In this way, the density of the partially stabilized zirconia powder is 6.1 g/cm ^{3 ,} which increases not only the density but also the hardness compared to the zirconia powder. Therefore, the partially stabilized zirconia powder can improve the density and sinterability of the two-color zirconia-alumina ceramic composite of the present invention. In addition, the partially stabilized zirconia powder has a rectangular structure and exhibits high toughness at room temperature, thereby mitigating the occurrence of cracks when naturally cooled after sintering the molded body and minimizing changes in physical properties and color when coloring by pigments, which will be described later.

Additionally, the zirconia spherical particles may include a binder. The binder not only binds each component, but also softens the mixture to increase fluidity, allowing the powder to fill empty spaces and improve density. Therefore, the binder can affect the production of molded bodies with high density. In embodiments of the present invention, polyvinyl alcohol-based binder can be mainly selected. In spheronizing the zirconia powder, the polyvinyl alcohol-based binder may contain 1 to 4 wt% based on the total weight % of the zirconia spherical particles. The polyvinyl alcohol system is water-soluble and can be dissolved in water to bind the partially stabilized zirconia powder particles.

Additionally, the zirconia spherical particles may include a dispersant. The dispersing agent can uniformly disperse each component and make the composition of each sphere uniform. In other words, when the dispersant turns large particles and aggregated particles into smaller particles, it can prevent the generated micro particles from re-agglomerating. Therefore, the dispersant may use an absorbent material such as a surfactant or a polymer material. In embodiments of the present invention, ammonium polycarboxylate salts can be mainly selected as the dispersant. In spheronizing the zirconia powder, the polycarboxylic acid ammonium salt-based dispersant may contain 2 to 3 wt% based on the total weight % of the zirconia spherical particles. In addition, the polycarboxylic acid ammonium salt-based dispersant does not contain sulfur and may not adversely affect the molded product.

Additionally, the zirconia spherical particles may contain an antifoaming agent. The antifoaming agent is capable of removing harmful foam and has an excellent superfoam suppression effect. Therefore, the antifoaming agent may be selected from organic phosphates, alcohols, etc. In embodiments of the present invention, polyether-based dispersants may be mainly selected, but the present invention is not limited thereto. In spheronizing the zirconia powder, the polyether-based antifoaming agent may be included in an amount of 1 to 2 wt% based on the total weight % of the zirconia spherical particles.

The two-color zirconia-alumina ceramic composite according to an embodiment of the present invention includes aluminum oxide. The aluminum oxide may contain 35 to 45 wt% based on the total wt% of the ceramic composite. The aluminum oxide has the highest strength among oxides based on strong ionic bonds. Additionally, aluminum oxide is known to have excellent corrosion and chemical resistance properties. Therefore, in order to complement the structural characteristics of zirconia, thermal shock resistance can be improved by dissolving aluminum oxide (Al2O3) in zirconia spherical particles.

The two-color zirconia-alumina ceramic composite according to an embodiment of the present invention may further include a pigment. The pigment may be selected from at least one selected from magnesium oxide, zinc oxide, nickel oxide, cobalt oxide, manganese oxide, iron oxide, and copper oxide.

The pigment can react with aluminum oxide as a pigment reaction catalyst to form a spinel structure and develop color. Specifically, magnesium oxide and zinc oxide are white, nickel oxide and cobalt oxide are blue, manganese oxide is yellow-brown, iron oxide is yellowish brown, and copper oxide is blue, red, green, pink, gray, black, etc. depending on the particle size. You can. In the present invention, “spinel structure” refers to a ceramic with a molecular structure of AB2X4 (A and B are metal elements, do. The spinel structure is a cubic lattice with a regular octahedral appearance and is filled with oxygen atoms in almost cubic close packing. That is, between the oxygen atoms, the B atom is surrounded by six oxygens in an octahedral shape, and the A atom is surrounded by four oxygens in a tetrahedral shape. Therefore, compounds with a spinel-type structure are stable at high temperatures and can easily form hybrid crystals, thereby ensuring various color development and vivid colors.

In addition, the structure formed by the reaction of pigment and aluminum oxide in the present invention can not only improve the mechanical properties of zirconia, especially corrosion resistance, but also improve aesthetics. Additionally, the spinel structure can stabilize the colored color by suppressing color tone changes after sintering.

In this way, the two-color zirconia-alumina ceramic composite not only stabilizes the colored color, but also provides a ceramic composite with excellent strength, corrosion resistance, and chemical resistance properties.

Figure 1 is a flowchart showing the manufacturing steps of a two-color zirconia-alumina ceramic composite according to the present invention.

Referring to FIG. 1, the manufacturing step of a two-color zirconia-alumina ceramic composite according to an embodiment of the present invention may largely consist of six processes. That is, preparing a precursor by mixing 55 to 65 wt% of zirconia spherical particles and 35 to 45 wt% of aluminum oxide (S10), manufacturing a molded body by pressure molding the precursor (S20), and degreasing heat treatment (S30). ), partial coloring step (S40), sintering step (S50), and natural cooling step (S60).

Step S10 is a step of preparing a precursor by mixing 55 to 65 wt% of zirconia spherical particles and 35 to 45 wt% of aluminum oxide, a pigment reaction catalyst.

In the step of preparing the precursor (S10), the precursor contains 55 to 65 wt% of spherical zirconia particles.

The zirconia spherical particles are a mixture of 93 to 95 wt% of partially stabilized zirconia powder, 1 to 4 wt% of polyvinyl alcohol-based binder, 2 to 3 wt% of ammonium polycarboxylate salt-based dispersant, and 1 to 2 wt% of polyether-based antifoaming agent dissolved in water. After preparing, the mixture can be obtained through spray drying at 150 to 230°C. Specifically, the zirconia spherical particles are prepared by first wet mixing for 20 hours by dissolving 93 to 95 wt% of partially stabilized zirconia powder, 2 to 3 wt% of polycarboxylic acid ammonium salt-based dispersant, and 1 to 2 wt% of polyether-based antifoaming agent in water. You can. To increase the cohesion of the first wet mixed powder, 1 to 4 wt% of polyvinyl alcohol (PVA) binder can be added and the mixture can be prepared by second wet mixing for 4 hours. It can be prepared by spray drying the secondary wet mixed mixture at 150 to 230°C.

The particle size of the zirconia spherical particles prepared in this way may be 20 to 30㎛.

The partially stabilized zirconia powder can be produced by adding a small amount of a metal stabilizer to pure zirconia powder. Zirconium dioxide (ZrO2), also called zirconia, is a white crystalline oxide and is the ceramic material closest to metal. The zirconia has a density of 5.68 g/cm ³ , a melting point of 2715°C, and a boiling point of 4000°C, and has excellent material properties such as high heat resistance, low thermal conductivity, chemical stability, high strength, high hardness, and high fracture toughness.

On the other hand, zirconia has the same chemical composition, but its structure changes depending on temperature, so its physical properties can change. That is, the zirconia can change into a monoclinic structure from room temperature to 1170°C, into a tetragonal structure as the temperature rises, and into a cubic structure at 2370°C. Therefore, zirconia, which has become tetragonal by sintering above 1500℃, undergoes a phase transition to monoclinic when naturally cooled below 950℃. The phase-transformed zirconia is accompanied by a volume change of 3 to 5%, and the resulting stress exceeds the deformation resistance of zirconia, which may cause cracks.

Therefore, in order to alleviate the problem of cracks occurring during natural cooling after sintering of zirconia, partially stabilized zirconia powder can be manufactured by adding a small amount of metal stabilizer to zirconia powder in an embodiment of the present invention. The metal stabilizer may be selected from at least one of yttria (Y2O3), magnesium oxide (MgO), calcium oxide (CaO), and cerium oxide (Ce2O3). Therefore, the yttria may contain 3 to 4 mog% based on the total mol% of the zirconia powder. Additionally, the magnesium oxide may contain 8 mol% based on the total mol% of the zirconia powder, and the calcium oxide may contain 8 mol% based on the total mol% of the zirconia powder. In an embodiment of the present invention, yttria may be mainly selected as the metal stabilizer. Meanwhile, if the content of the metal stabilizer added to pure zirconia powder is less than the above-mentioned range, it is insufficient for stabilizing zirconia, and if it exceeds it, it may be meaningless in terms of stabilizing zirconia.

On the other hand, if the content of the partially stabilized zirconia powder in the present invention is less than 93wt%, it may be a problem in demonstrating the physical properties of zirconia, and if it is more than 95wt%, it causes a decrease in the content of other components, resulting in unevenness and a decrease in density of each component. It may cause problems such as:

In this way, the density of the partially stabilized zirconia powder is 6.1 g/cm ^{3 ,} which increases not only the density but also the hardness compared to the zirconia powder. Therefore, the partially stabilized zirconia powder can improve the density and sinterability of the two-color zirconia-alumina ceramic composite of the present invention. In addition, the partially stabilized zirconia powder has a rectangular structure and exhibits high toughness at room temperature, thereby mitigating the occurrence of cracks when naturally cooled after sintering the molded body and minimizing changes in physical properties and color when coloring by pigments, which will be described later.

Additionally, the zirconia spherical particles may include a binder. The binder not only binds each component, but also softens the mixture to increase fluidity, allowing the powder to fill empty spaces and improve density. Therefore, the binder can affect the production of molded bodies with high density. In embodiments of the present invention, polyvinyl alcohol-based binder can be mainly selected. In spheronizing the zirconia powder, the polyvinyl alcohol-based binder may contain 1 to 4 wt% based on the total weight % of the zirconia spherical particles. The polyvinyl alcohol system is water-soluble and can be dissolved in water to bind the partially stabilized zirconia powder particles.

On the other hand, if the content of the polyvinyl alcohol-based binder is less than this range, the fluidity of the mixture is low and the powder cannot fill the empty space, making it impossible to manufacture a high-density zirconia-alumina ceramic composite. If the content of the polyvinyl alcohol-based binder exceeds the range, the molded body may be quickly hardened before the binder is uniformly dispersed within the powder. Additionally, the density of the zirconia-alumina ceramic composite may decrease due to gas evaporating from the polyvinyl alcohol-based binder itself.

Additionally, the zirconia spherical particles may include a dispersant. The dispersing agent can uniformly disperse each component and make the composition of each sphere uniform. In other words, the dispersant can prevent the fine particles generated when large particles and aggregated particles are converted into smaller particles from re-agglomeration. Therefore, the dispersant may use an absorbent material such as a surfactant or a polymer material. In embodiments of the present invention, ammonium polycarboxylate salts can be mainly selected as the dispersant. In spheronizing the zirconia powder, the polycarboxylic acid ammonium salt-based dispersant may contain 2 to 3 wt% based on the total weight % of the zirconia spherical particles. The polycarboxylic acid ammonium salt-based dispersant does not contain sulfur and may not adversely affect the molded product.

Additionally, the zirconia spherical particles may contain an antifoaming agent. The antifoaming agent is capable of removing harmful foam and has an excellent superfoam suppression effect. Therefore, the antifoaming agent may be selected from organic phosphates, alcohols, etc. In embodiments of the present invention, polyether-based dispersants may be mainly selected, but the present invention is not limited thereto. In spheronizing the zirconia powder, the polyether-based antifoaming agent may be included in an amount of 1 to 2 wt% based on the total weight % of the zirconia spherical particles.

On the other hand, if the content of the zirconia spherical particles is less than 55wt%, the physical properties of zirconia may be deteriorated. In addition, when the content of spherical particles of zirconia exceeds 65 wt%, a decrease in the content of aluminum oxide may cause color change after coloring due to a color reaction with pigments, which will be described later.

In this way, the zirconia spherical particles can achieve the effect of improving formability by increasing the packing density when manufacturing a molded body, achieving uniform coloring, and reducing the generation of pores during the sintering process.

In the step of preparing the precursor (S10), the precursor contains aluminum oxide (Al2O3).

The aluminum oxide may contain 35 to 45 wt% based on 55 to 65 wt% of the zirconia spherical particles. The aluminum oxide has the highest strength among oxides based on strong ionic bonds. In addition, the aluminum oxide is known to have excellent corrosion resistance and chemical resistance properties. Therefore, in order to complement the structural characteristics of zirconia, thermal shock resistance can be improved by dissolving aluminum oxide (Al2O3) in zirconia spherical particles. In addition to improving thermal shock resistance, adding aluminum oxide to zirconia spherical particles to produce a two-color zirconia-alumina ceramic composite not only improves physical properties compared to manufacturing colored zirconia alone, but also minimizes colored color changes. there is.

On the other hand, if the content of aluminum oxide, which is a pigment reaction catalyst, is less than 35 wt%, a spinel-structured compound that stably exhibits color may not be sufficiently formed. If the content of aluminum oxide exceeds 45 wt%, the stability of the pigment may decrease, which may reduce not only color development but also physical properties of the zirconia-alumina ceramic composite produced.

In this way, color can be expressed stably even at high temperatures by mixing aluminum oxide, a pigment reaction catalyst, with zirconia spherical particles and molding them, then reacting them with pigments to be described later to color the zirconia.

Step S20 will be described in detail as a step of manufacturing a molded body by pressure molding the precursor material.

A molded body can be manufactured by pressure molding a precursor material that is a mixture of the zirconia spherical particles and aluminum oxide. The molded body can be manufactured in a plate shape and is not limited to its shape, such as a polygon such as a triangle or pentagon, a circle, a ring, or a rod.

Step S30 will be described in detail as a degreasing heat treatment step for the molded body.

The physical properties of the two-color zirconia-alumina composite depend on the uniformity of the mixture. Therefore, the degreasing heat treatment step can create a uniform mixture by minimizing foreign substances. That is, in the production of zirconia spherical particles, the organic components of the binder, dispersant, antifoaming agent, and organic components that may be contained in the precursor may cause pores or cracks in the sintering step described later, so organic materials, etc. must be removed through degreasing heat treatment. You can.

Therefore, the degreasing heat treatment step may include primary heating at 155 to 175°C for 30 to 40 hours, followed by secondary heating at 650 to 850°C for 30 to 40 hours. During the first heating, moisture in the molded body can be removed, and during the second heating, organic components within the molded body can be removed. This stepwise heating suppresses the thermal stress of the molded body and prevents the bending phenomenon in which the molded body bends.

On the other hand, if the temperature and time are below the range in the degreasing heat treatment step, there may be a risk of cracks occurring in the sintering step due to residual organic matter. Additionally, if the temperature and time range are exceeded during the degreasing heat treatment step, bending or damage to the molded body may occur.

Step S40 will be described in detail as a step of adding a solution in which a pigment is dissolved to a portion of the degreased heat-treated molded body to partially color it through a color reaction between the pigment and aluminum oxide, which is the pigment reaction catalyst.

The pigment may include at least one selected from magnesium oxide, zinc oxide, nickel oxide, cobalt oxide, manganese oxide, and iron oxide. The pigment can react with aluminum oxide as a pigment reaction catalyst to form a spinel structure and develop color. Specifically, magnesium oxide and zinc oxide are white, nickel oxide and cobalt oxide are blue, manganese oxide is yellow-brown, iron oxide is yellowish brown, and copper oxide is blue, red, green, pink, gray, black, etc. depending on the particle size. You can. In the present invention, “spinel structure” refers to a ceramic with a molecular structure of AB2X4 (A and B are metal elements, do. The spinel structure is a cubic lattice with a regular octahedral appearance and is filled with oxygen atoms in almost cubic close packing. That is, between the oxygen atoms, the B atom is surrounded by six oxygens in an octahedral shape, and the A atom is surrounded by four oxygens in a tetrahedral shape. Therefore, compounds with a spinel-type structure are stable at high temperatures and can easily form hybrid crystals, thereby ensuring various color development and vivid colors.

Coloring of the ceramic composite of the present invention can be accomplished by dissolving the pigment in water to prepare an aqueous solution and then spraying or applying it to the colored part of the degreased heat-treated molded body or immersing the molded body in the aqueous solution. The concentration of the pigment in the aqueous solution is not limited, but the higher the concentration, the shorter the coloring time. Therefore, the concentration of the pigment can be increased by increasing the solubility by increasing the temperature of the water. Therefore, the content of the pigment that reacts with aluminum oxide, which is the pigment reaction catalyst of the molded body, may include 0.05 to 0.10 wt% based on the total wt% of the colored portion of the molded body. The content of the pigment may vary in weight depending on the shape of the colored part of the molded body. Additionally, the spray amount, application amount, or immersion time can be adjusted depending on the concentration of the aqueous solution in which the pigment is dissolved so that the amount of the pigment can participate in the reaction.

On the other hand, if the content of the pigment is below this range, the color of the molded body cannot be maintained stably. Additionally, if the content of the pigment exceeds the range, the physical properties of the zirconia-alumina ceramic composite may deteriorate due to unreacted pigment material.

In this way, the structure formed by the reaction of pigment and aluminum oxide in the present invention can not only improve the physical properties of zirconia, especially corrosion resistance, but also improve aesthetics.

Step S50 will be described in detail as a step of sintering the partially colored molded body.

The sintering step (S50) refers to a process of applying sufficient temperature and pressure to turn particles with a large specific surface area into a more dense mass. Through sintering, the sintering density becomes denser, which not only increases the strength and toughness of the molded body, but also stabilizes the color of the colored molded body by reacting the pigment with aluminum oxide, which is a pigment reaction catalyst. In addition, since zirconia that has been spheronized by adding a metal stabilizer to zirconia powder is used, the structural characteristics of zirconia are complemented and cracking of the molded body can be prevented even at high sintering temperatures.

Therefore, in the sintering, a zirconia-alumina ceramic composite can be manufactured by raising the temperature of the partially colored molded body from room temperature to a sintering temperature of 1550°C to 1600°C for 10 to 15 hours and then heating it at the elevated temperature for 15 to 20 hours.

On the other hand, if the sintering temperature is below this range, it may be difficult for the molten powder to penetrate into the interior, which may inhibit densification of the colored zirconia-alumina ceramic composite. If the sintering temperature exceeds the range, not only may physical properties such as densification be impaired due to gas generation, but the pigment may be decomposed and discoloration problems may occur.

Figure 2 is a graph showing the density of the sintered body of a two-color zirconia-alumina ceramic composite according to an embodiment of the present invention.

Referring to FIG. 2, the density of the sintered body of the zirconia-alumina ceramic composite for which the sintering step (S50) has been completed may be 5.80 to 6.10 g/cm ³ .

Step S60 is a step of naturally cooling the sintered molded body.

In the natural cooling step (S60), natural cooling can occur inside the sintering furnace while the heat source of the sintering furnace is blocked. This can prevent distortion of the molded body structure due to rapid temperature changes.

In this way, the two-color zirconia-alumina ceramic composite according to the embodiment of the present invention is manufactured by spheroidizing partially stabilized zirconia powder, so not only does it improve physical properties by preventing cracking during sintering, but also the pigment is aluminum oxide, which is a pigment reaction catalyst. It is a colored complex that reacts with , and the color is vivid and does not discolor at the boundary between the two colors, so it can be applied to a variety of household items as well as decorative items such as watches, bracelets, and rings.

<Manufacturing example>

[Preparation Example 1] - Partially stabilized zirconia powder

Partially stabilized zirconia powder (Y-TZP, yttria-stabilized tetragonal zirconium polycrystal) was prepared by coprecipitation by adding 3 mol% of yttria, a metal stabilizer, to the total mol% of pure zirconia powder.

[Preparation Example 2] - Zirconia spherical particles

93 wt% of partially stabilized zirconia powder prepared according to Preparation Example 1, 3 wt% of ammonium polycarboxylate salt-based dispersant, and 2 wt% of polyether-based defoamer were dissolved in water and first wet mixed for 20 hours. To increase the cohesion of the first wet mixed powder, 2 wt% of polyvinyl alcohol (PVA) binder was added and the mixture was prepared by second wet mixing for 4 hours. The secondary wet mixed mixture was spray dried at 210°C to produce zirconia spherical particles.

<Examples and Comparative Examples>

[Example 1]

45 wt% of aluminum oxide was mixed with 55 wt% of zirconia spherical particles prepared according to Preparation Example 2, and pressure molded using a dry compression molding method to prepare a molded body having a ring-shaped plate shape. The molded body was first heated at 155°C for 30 hours to remove impurities, and then secondarily heated at 650°C for 30 hours to remove organic substances. The degreased heat-treated molded body was colored in two colors using a solution in which the pigment, cobalt chloride, was dissolved in water at 25°C, and a solution in which the pigment, zinc oxide, was dissolved in water at 25°C. At this time, the contents of cobalt chloride and zinc oxide hydrate colored in the molded body were each 0.05 wt% based on the total wt% of the colored area. The colored molded body was heated to 1550°C over 10 hours, sintered at 1550°C for 15 hours, and then naturally cooled to produce a two-color zirconia-alumina ceramic composite.

[Example 2]

40 wt% of aluminum oxide was mixed with 60 wt% of zirconia spherical particles prepared according to Preparation Example 2, and pressure molded using a dry compression molding method to prepare a molded body having a ring-shaped plate shape. The molded body was first heated at 165°C for 35 hours to remove impurities, and then secondarily heated at 750°C for 35 hours to remove organic substances. The degreased heat-treated molded body was colored in two colors using a solution in which the pigment, copper oxide, was dissolved in water at 25°C and a solution in which the pigment, zinc oxide, was dissolved in water at 25°C. At this time, the content of copper oxide and zinc oxide hydrate colored in the molded body was each 0.05 wt% based on the total wt% of the colored area. The colored molded body was heated to 1600°C for 10 hours, then sintered at 1600°C for 15 hours and then naturally cooled to produce a two-color zirconia-alumina ceramic composite.

[Example 3]

65 wt% of zirconia spherical particles prepared according to Preparation Example 2 were mixed with 35 wt% of aluminum oxide, and pressure molded using a dry compression molding method to prepare a molded body having a ring-shaped plate shape. The molded body was first heated at 175°C for 40 hours to remove impurities, and then secondarily heated at 850°C for 40 hours to remove organic substances. The degreased heat-treated molded body was immersed in a solution of zinc oxide, a pigment, dissolved in water at 25°C for 10 seconds to partially color the molded body. At this time, the content of zinc oxide hydrate colored in the molded body was set to 0.05 wt% based on the total wt% of the colored area. The colored molded body was heated to 16,000°C for 15 hours, then sintered at 16,000°C for 20 hours and then naturally cooled to produce a two-color zirconia-alumina ceramic composite.

[Comparative Example 1]

In Preparation Example 2, zirconia spherical particles were manufactured using pure zirconia powder instead of using partially stabilized zirconia powder containing a metal stabilizer, and then mixed with aluminum oxide to produce a molded body. The same method as Example 1. A two-color zirconia-alumina ceramic composite was manufactured.

[Comparative Example 2]

Two-color zirconia ceramics were manufactured in the same manner as Example 1, except that the molded body was manufactured by pressure molding using only zirconia spherical particles.

[Comparative Example 3]

Pure zirconia powder (without metal stabilizer) was used instead of the mixture of 99.52wt% zirconia spherical particles, 0.4wt% aluminum oxide, and 0.08wt% cobalt chloride hydrate in Example 1 and the stabilized zirconia powder in Preparation Example 3. The manufactured zirconia spherical particles were charged in half to a mold having a ring-shaped plate shape and then pressed and molded to produce a molded body in which the mixture of zirconia spherical particles-aluminum oxide-cobalt chloride hydrate and the zirconia spherical particles each formed half of a ring shape. The molded body was first heated at 165°C for 35 hours to remove impurities, and then secondarily heated at 750°C for 35 hours to remove organic substances. The sintered body was heated to 1600°C for 10 hours, then sintered at 1600°C for 15 hours and then naturally cooled to produce two-color zirconia ceramics.

Table 1 shows the component contents in the production of two-color zirconia-alumina ceramic composites and two-color zirconia ceramics according to examples and comparative examples of the present invention.

Example
and
Comparative example metal stabilizer
(mol%) zirconia
Spherical particles (wt%) aluminum oxide
(wt%) pigment
(wt%) Example 1 3mol% 55wt% 45wt% 0.05wt% Example 2 3mol% 60wt% 40wt% 0.05wt% Example 3 3mol% 65wt% 35wt% 0.05wt% Comparative Example 1 - 55wt% 45wt% 0.05wt% Comparative Example 2 3mol% 100wt% - 0.05wt% Comparative Example 3 3mol% 99.52wt% 0.4wt% 0.08wt%

<Test example>

[Test Example 1] - Density, fracture strength, fracture toughness and hardness of sintered body

The two-color zirconia-alumina ceramics composite and two-color zirconia ceramics specimens prepared according to the above examples and comparative examples were manufactured and the density, fracture strength, fracture toughness, and hardness of the sintered body were measured.

The density of the sintered body was measured by the "Archimedes method", and the fracture strength was measured using UTM (Universal Testing Machine, Model No 4206, Instron, USA) at a crosshead speed of 0.5 mm/min and a span distance of 30 mm. It was measured through a bending strength test, and fracture toughness was measured using a Vickers hardness tester (AVK-C2, Mitutoyo, Japan) by applying a load of 10 kg and using the Vickers Indentation method. Additionally, hardness was measured with a micro beaker hardness tester under a load of 500 g.

Figure 2 is a graph showing the density of the sintered body of a two-color zirconia-alumina ceramic composite according to an embodiment of the present invention.

Figure 3 is a scanning electron microscope (SEM) photograph of a two-color zirconia-alumina ceramic composite according to an embodiment of the present invention.

Table 2 shows the results of physical property analysis according to the examples and comparative examples of the present invention.

Example
and comparative example Density of sintered body
(g/ ^cm3 ) Breaking strength
(MPa) Fracture toughness
(MPam ^1/2 ) Hardness
(kgf/ ^mm2 ) Example 1 5.80 793 9.3 1010 Example 2 5.93 821 10.2 1100 Example 3 6.02 820 11.0 1074 Comparative Example 1 5.10 625 8.2 998 Comparative Example 2 5.64 760 9.2 1025 Comparative Example 3 5.29 690 7.8 994

Referring to Figures 2, 3, and Table 2, it was found that the density of the sintered body was more improved in the zirconia spherical particles containing a metal stabilizer than in the ceramic composite that did not contain a metal stabilizer (Examples 1 to 3 and comparison Example 1, Comparative Example 3). In addition, the density of the sintered body was improved more by the ceramic composite mixed with zirconia spherical particles and aluminum oxide than by ceramics with only zirconia spherical particles (Examples 1 to 3 and Comparative Example 2), and the addition of aluminum oxide to the zirconia spherical particles increased the density of the sintered body. Accordingly, it was found that the density of the sintered body increased (Examples 1 to 3 and Comparative Example 3). In addition, it was found that as the content of zirconia spherical particles increases, the density of the sintered body improves, while the particle size decreases. Therefore, it was found that sintering properties were affected by the tetragonal/monoclinic ratio, which is a structural characteristic of zirconia present in the zirconia-alumina ceramics composite.

Hardness also has a similar tendency to the density of the sintered body, showing that it is more improved in the case of a ceramic composite mixed with zirconia spherical particles and aluminum oxide than in the case of ceramics containing only zirconia spherical particles (Examples 1 and 2), but the content of zirconia spherical particles It can be seen that as this increases, the composition ratio of zirconia spherical particles, which have lower hardness than aluminum oxide, increases, and the hardness decreases (Example 3) because microcracks occur in the material due to excessive grain growth.

In addition, with regard to fracture strength and fracture toughness, it was found that zirconia spherical particles containing a metal stabilizer improved fracture strength and fracture toughness compared to single zirconia spherical particles and zirconia spherical particles without a metal stabilizer (Examples 1 to 2) Example 3 and Comparative Example 1, Comparative Example 3). In addition, it was found that the fracture strength and fracture toughness of the ceramic composite mixed with zirconia spherical particles and aluminum oxide were improved compared to the case where only zirconia spherical particles were used (Examples 1 to 3 and Comparative Example 2).

[Test Example 2] - Color analysis

The color of the two-color zirconia-alumina ceramic composite prepared in the above examples and comparative examples was measured using an ultraviolet-visible spectrophotometer (UV-2401PC, Shimadzu, Japan) and measured by the Commission Internationale de I'Eclairage. , CIE) was analyzed using colorimetric values (L*, a*, b*).

Figures 4 to 7 are photographs showing a two-color zirconia-alumina ceramic composite whose color was changed by varying the pigment according to an embodiment of the present invention.

Table 3 shows the color analysis results according to the examples and comparative examples of the present invention.

Example
and comparative example sintered body L* a* b* Example 1 one side 39.56 34.28 -64.38 other side 91.66 -1.03 -4.21 Example 2 one side 64.78 24.09 -26.11 other side 91.66 -1.03 -4.21 Example 3 one side 100 0.00 0.00 other side - - - Comparative Example 1 one side 38.90 35.10 -65.47 other side 90.81 -1.68 -4.44 Comparative Example 2 one side 39.90 34.1 -63.2 other side 90.81 -1.68 -4.44 Comparative Example 3 one side 38.30 33.8 -61.2 other side - - -

Referring to FIGS. 4 to 7 and Table 3, in the present invention, “one side” of the sintered body refers to the blue, pink, or white portion, and “the other side” refers to milky gray, white, black, or no pigment. The part that is not included refers to the part of the metal itself. Example 1 was blue on one side and milky gray on the other side, Example 2 was pink on one side and milky gray on the other side, and Example 3 was white on one side and metallic color on the other side. In addition, it was confirmed that Comparative Examples 1 to 3 were dark blue on one side and dark gray on the other side, and each Comparative Example showed a slight difference in color.

In addition, when aluminum oxide is mixed with zirconia spherical particles containing a metal stabilizer according to the above examples and comparative examples, zirconia spherical particles containing no metal stabilizer (Comparative Examples 1 and 3), zirconia spherical particles alone (Comparative Examples Compared to the ceramic composite manufactured in Example 2) (Comparative Example 3), the sintered body was found to be uniformly colored and the two-color boundary line was clearer.

In addition, compared to Examples 1 to 3, the colors of Comparative Examples 1 to 3 were dark and not clear. In the case of Comparative Example 3, although a small amount of aluminum oxide was contained, the brightness was lower than that of Examples, so the feeling of darkness was greater, and 2 As the material was divided in half and pressure molded, it was confirmed that the boundary line between one side and the other side was not clear.

[Test Example 3] - Color difference analysis

The color change of the sintered body was analyzed after heating the two-color zirconia-alumina ceramic composite and the two-color zirconia ceramics prepared in the above Examples and Comparative Examples in cooking oil at 150°C for 24 hours, and the color difference (△E) compared to the sintered body before heating was analyzed. was calculated. The color before heating was based on Table 3 above, and the change in the colored part of the two colors of the sintered body was compared.

Table 4 shows color difference analysis according to examples and comparative examples of the present invention.

△E below is calculated by the formula below.

△E = (△L* ² + △a* ² + △b* ² ) ^1/2

Example
and comparative example L* a* b* △E Example 1 39.61 34.32 -64.30 0.10 Example 2 64.88 24.15 -25.96 0.19 Example 3 100.06 0.08 0.08 0.12 Comparative Example 1 39.9 36.3 -64.57 1.8 Comparative Example 2 41.4 35.3 -62.03 2.24 Comparative Example 3 39.00 34.2 -60.0 1.44

Referring to Table 4, it was confirmed that the color difference (ΔE) of the two-color zirconia-alumina ceramic composite of the present invention was 0.10 to 0.20. In detail, a ceramic composite containing a mixture of zirconia spherical particles containing a metal stabilizer and aluminum oxide contains spherical particles without a metal stabilizer (Comparative Example 1), zirconia spherical particles alone (Comparative Example 2), and a small amount of aluminum oxide. The color change was less than that of a ceramic composite (Comparative Example 3), and the case where only zirconia spherical particles were used (Comparative Example 2) showed the greatest color difference. In addition, when zirconia spherical particles, aluminum oxide, and pigment (Comparative Example 3) were initially mixed, the color change was found to be greater than when coloring was performed by reacting the pigment with aluminum oxide, a pigment reaction catalyst, during the manufacturing step. Therefore, it was confirmed that the presence or absence of a metal stabilizer, the presence or absence of spheroidization of the zirconia powder, the reaction time between the pigment and aluminum oxide, which is a pigment reaction catalyst, and the content of aluminum oxide affect the color change.

In this way, the two-color zirconia-alumina ceramic composite manufacturing method according to the embodiment of the invention mixes zirconia spherical particles and aluminum oxide, which is a pigment reaction catalyst, molds them, and then partially reacts with the pigment to sinter, thereby providing excellent mechanical properties of the sintered body. In addition, the two-color border is clear and color changes can be minimized.

The embodiments described above are merely illustrative, and various modifications and equivalent embodiments can be made by those skilled in the art. Therefore, the true scope of technical protection of the present invention must be determined by the technical spirit of the invention described in the claims.

Claims (13)

In ceramic composites, Zirconia spherical particles 55 to 65 wt%; and Two-color zirconia-alumina ceramics composite containing 35 to 45 wt% of aluminum oxide. According to paragraph 1, The two-color zirconia-alumina ceramic composite further includes a pigment, The pigment is a two-color zirconia-alumina ceramic composite, characterized in that it contains at least one selected from magnesium oxide, zinc oxide, nickel oxide, cobalt oxide, manganese oxide, iron oxide, and copper oxide. According to paragraph 1, The zirconia spherical particles are, Preparing a mixture by dissolving 93 to 95 wt% of partially stabilized zirconia powder, 1 to 4 wt% of polyvinyl alcohol-based binder, 2 to 3 wt% of ammonium polycarboxylate salt-based dispersant, and 1 to 2 wt% of polyether-based defoamer in water; and A two-color zirconia-alumina ceramic composite manufactured by spray drying the mixture at 150 to 230°C. According to paragraph 3, The partially stabilized zirconia powder, A powder obtained by adding a small amount of metal stabilizer to zirconia powder, The metal stabilizer is a two-color zirconia-alumina ceramics composite, characterized in that it contains at least one selected from yttria (Y2O3), magnesium oxide (MgO), calcium oxide (CaO), and cerium oxide (Ce2O3). According to paragraph 2, As a result of analyzing the color change after heating the two-color zirconia-alumina ceramic composite in cooking oil at a predetermined temperature for 24 hours, the two-color zirconia-alumina is characterized in that the color difference (△E) before and after heating is 0.10 to 0.20. Ceramics composite. In the ceramic composite manufacturing method, Preparing a precursor by mixing 55 to 65 wt% of zirconia spherical particles with 35 to 45 wt% of aluminum oxide, a pigment reaction catalyst; manufacturing a molded body by pressure molding the precursor material; Degreasing heat treatment of the molded body; Adding a solution in which a pigment is dissolved to a portion of the degreased heat-treated molded body to partially color it through a color reaction between the pigment and aluminum oxide, which is the pigment reaction catalyst; Sintering the partially colored molded body; and A method of manufacturing a two-color zirconia-alumina ceramic composite comprising the step of naturally cooling the sintered molded body. According to clause 6, The zirconia spherical particles are, Preparing a mixture by dissolving 93 to 95 wt% of partially stabilized zirconia powder, 1 to 4 wt% of polyvinyl alcohol-based binder, 2 to 3 wt% of ammonium polycarboxylate salt-based dispersant, and 1 to 2 wt% of polyether-based defoaming agent in water; and A method for producing a two-color zirconia-alumina ceramic composite, characterized in that it is manufactured including the step of spray drying a mixture dissolved in water at 150 to 230 ° C. In clause 7, The partially stabilized zirconia powder, A powder obtained by adding a small amount of metal stabilizer to zirconia powder, A method for manufacturing a two-color zirconia-alumina ceramics composite, wherein the metal stabilizer includes at least one selected from yttria (Y2O3), magnesium oxide (MgO), calcium oxide (CaO), and cerium oxide (Ce2O3). According to clause 8, The metal stabilizer is yttria, A method for producing a two-color zirconia-alumina ceramics composite, characterized in that the yttria contains 3 to 4 mol% based on the total mol% of the zirconia powder. According to clause 6, The degreasing heat treatment step is, A method of manufacturing a two-color zirconia-alumina ceramics composite, characterized by primary heating at 155 to 175°C for 30 to 40 hours, and then secondary heating at 650 to 850°C for 30 to 40 hours. According to clause 6, A method for producing a two-color zirconia-alumina ceramics composite, characterized in that in the partial coloring step, the amount of pigment reacting with the pigment reaction catalyst of the molded body is 0.05 to 0.10 wt% based on the total wt% of the colored portion of the molded body. According to clause 6, The sintering step is, A method for producing a two-color zirconia-alumina ceramic composite, characterized in that the partially colored molded body is heated from room temperature to a sintering temperature of 1550°C to 1600°C for 10 to 15 hours, and then heated at the elevated temperature for 15 to 20 hours. According to clause 6, A method for manufacturing a two-color zirconia-alumina ceramics composite, characterized in that the density of the two-color zirconia-alumina ceramics composite after the sintering step is 5.80 to 6.10 g/cm ³ .

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