A MgO-CaO-Al2O3-SiO2 microcrystalline opaque glaze and its preparation method

Abstract

The application discloses a MgO-CaO-Al2O3-SiO2 system microcrystalline opalescent glaze and a preparation method thereof. A large number of augite and quartz crystals are precipitated in the glaze by optimizing the formula design, so that the reflection and scattering of incident light are increased, the hardness of the glaze surface is improved, the opalescent glaze with high whiteness and high hardness is obtained, and the cost of the opalescent glaze is reduced by introducing talc and calcium carbonate as main raw materials. The introduced raw materials do not contain radioactive elements, and the opalescent glaze has the characteristics of low cost and green environmental protection.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials, and in particular to a high-whiteness microcrystalline opaque glaze and its preparation method. Background Technology

[0002] Opacity glaze has excellent decorative properties on ceramic surfaces. Its high opacity can effectively cover the color and defects of the body, thus reducing the requirements for the body color and expanding the source of raw materials. It is widely used in the sanitary ceramics and building ceramics industries.

[0003] To achieve the desired opacifying effect, a second phase (i.e., an opacifier) ​​with a refractive index different from the base glass is often added to opacified glazes. This causes phenomena such as reflection, refraction, and diffuse scattering of incident light, leading to glaze devitrification. Commonly used opacifiers include titanium dioxide, tin oxide, and zirconium silicate. Titanium dioxide is generally used for ceramic products fired below 1000℃ because at high temperatures it exists as a rutile crystal phase, causing the glaze to yellow. Traditional sanitary ceramics and building ceramics are fired at around 1200℃, so titanium dioxide is rarely used as an opacifier. Tin oxide has a high refractive index and low solubility in glazes, resulting in excellent opacifying effects, but its high cost limits its widespread use in the ceramics industry. Zirconium silicate has advantages such as high refractive index, high hardness, and insensitivity to atmosphere, making it the most widely used opacifier. However, my country has relatively scarce zirconium resources, and the price of zirconium silicate raw materials has risen rapidly in recent years. Furthermore, zircon is associated with radioactive elements such as thorium and uranium, which are difficult to remove during later processing and pose health risks. Therefore, developing green, environmentally friendly, and inexpensive zirconium-free opaque glazes is of great practical significance. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a MgO-CaO-Al2O3-SiO2 system microcrystalline opaque glaze. Through optimized formula design, a large amount of pyroxene and quartz crystals can precipitate in the glaze, thereby increasing the reflection and scattering of incident light, improving the glaze surface hardness, and obtaining an opaque glaze with high whiteness and high hardness. Furthermore, by introducing talc and calcium carbonate as the main raw materials, costs are effectively reduced, achieving a low-cost opaque glaze. Another objective of this invention is to provide a method for preparing the aforementioned microcrystalline opaque glaze.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] The present invention provides a microcrystalline opaque glaze based on MgO-CaO-Al2O3-SiO2, the raw material composition of which is: 25-40 wt% quartz, 10-25 wt% talc, 10-16 wt% albite, 2-8 wt% zinc oxide, 15-25 wt% calcite, and 5-15 wt% clay.

[0007] In the above scheme, the chemical composition of the opaque glaze of the present invention is 60-75wt% SiO2, 4-12wt% Al2O3, 5-14wt% CaO, 4-12wt% MgO, 3-8wt% ZnO, 0.1-1wt% K2O, and 0.5-4wt% Na2O.

[0008] Another objective of this invention is achieved through the following technical solution:

[0009] The method for preparing the above-mentioned MgO-CaO-Al2O3-SiO2 microcrystalline opaque glaze provided by the present invention includes the following steps:

[0010] (1) The raw materials are prepared and mixed according to the above composition, heated and melted, and then the melt is poured into water and quenched to obtain a frit. The frit powder is obtained by ball milling and drying.

[0011] (2) The frit powder is mixed with clay, water, carboxymethyl cellulose and sodium tripolyphosphate in a mass ratio of frit powder: clay: water: carboxymethyl cellulose: sodium tripolyphosphate = 100: 2~8: 50~70: 0.1~0.3: 0.1~0.3. The resulting material is then placed in a ball mill for ball milling. After sieving and iron removal, water is added to adjust the mixture and obtain a glaze slurry.

[0012] (3) Apply the glaze slurry to the surface of the green or bisque-fired body and fire it at 1160-1250℃ for 40-120 min to obtain a microcrystalline opaque glaze surface based on MgO-CaO-Al2O3-SiO2 system.

[0013] Furthermore, in the preparation method of the present invention, the melting temperature in step (1) is 1500–1600℃, and the holding time is 30–180 min. In step (2), the material is ball-milled until the particle size is 0.1–300 μm and the density of the glaze slurry is 1.5–1.8 g / cm³. 3 The flow rate is 22–35 s.

[0014] In the above scheme, the crystalline phase of the glaze obtained by the preparation method of the present invention is pyroxene and quartz, and the particle size of the precipitated crystals is 1-5 μm; the whiteness of the glaze is 60-75, the surface gloss is 10°-20°, and the hardness of the glaze measured by Vickers hardness tester is 6.0-7.0 GPa.

[0015] The present invention has the following beneficial effects:

[0016] (1) This invention optimizes the formula design so that the chemical composition of the microcrystalline glaze is located in the MgO-CaO-Al2O3-SiO2 crystallization range, which promotes the precipitation of a large number of pyroxene and quartz crystals in the glaze, and controls the crystal size to be 1-5 μm. The refractive index of pyroxene crystals is about 1.71, which is greater than that of glass matrix (1.55). Therefore, a large number of small pyroxene crystal particles can increase the scattering of incident light and obtain a good opacifying effect. In addition, the precipitation of a large number of quartz crystals in the glaze can give the glaze surface high hardness, thereby obtaining a microcrystalline opacifying glaze with high whiteness and high hardness at the same time.

[0017] (2) This invention introduces inexpensive talc and calcium carbonate as the main raw materials, and none of the introduced raw materials contain radioactive elements, which has the characteristics of low cost and green environmental protection. Attached Figure Description

[0018] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings:

[0019] Figure 1 This is the XRD pattern of the MgO-CaO-Al2O3-SiO2 microcrystalline opaque glaze obtained in the embodiments of the present invention;

[0020] Figure 2 This is a SEM image of the MgO-CaO-Al2O3-SiO2 microcrystalline opaque glaze obtained in the embodiments of the present invention. Detailed Implementation

[0021] Example 1:

[0022] 1. This embodiment describes a MgO-CaO-Al2O3-SiO2 microcrystalline opaque glaze, the raw material composition of which is: quartz 38wt%, talc 12wt%, albite 14wt%, zinc oxide 5wt%, calcite 20wt%, and clay 11wt%. Its chemical composition is: SiO2 68.9wt%, Al2O3 7.4wt%, CaO 12.0wt%, MgO 4.6wt%, ZnO 5.6wt%, K2O 0.1wt%, and Na2O 1.4wt%.

[0023] 2. This embodiment describes a method for preparing a MgO-CaO-Al2O3-SiO2-based microcrystalline opaque glaze, the steps of which are as follows:

[0024] (1) Prepare and mix the raw materials according to the above composition, then put them into a high-alumina crucible and heat them to 1550°C and keep them at that temperature for 60 minutes until the raw materials are fully melted. Pour the resulting melt into water and quench it to obtain a frit. After wet ball milling and drying, frit powder is obtained.

[0025] (2) The frit powder, clay, water, carboxymethyl cellulose, and sodium tripolyphosphate were mixed in a mass ratio of 100:5:55:0.2:0.2. The resulting material was then ball-milled in a ball mill for 60 minutes until the particle size was 0.3–150 μm. After sieving and iron removal, water was added to adjust the density to 1.56 g / cm³. 3 25s flow rate glaze slurry;

[0026] (3) The above glaze slurry is applied to the surface of the green or bisque blank by spraying, and then fired in a roller kiln. The maximum firing temperature is 1200℃ and the firing cycle is 56min to obtain a microcrystalline opaque glaze surface of MgO-CaO-Al2O3-SiO2 system.

[0027] Example 2:

[0028] 1. This embodiment describes a MgO-CaO-Al2O3-SiO2 microcrystalline opaque glaze, the raw material composition of which is: quartz 35wt%, talc 18wt%, albite 14wt%, zinc oxide 4wt%, calcite 23wt%, and clay 6wt%. Its chemical composition is: SiO2 67.7wt%, Al2O3 5.6wt%, CaO 13.9wt%, MgO 6.8wt%, ZnO 4.5wt%, K2O 0.1wt%, and Na2O 1.4wt%.

[0029] 2. This embodiment describes a method for preparing a MgO-CaO-Al2O3-SiO2-based microcrystalline opaque glaze, the steps of which are as follows:

[0030] (1) Prepare and mix the raw materials according to the above composition, then put them into a high-alumina crucible and heat them to 1500℃ and keep them at that temperature for 60 minutes until the raw materials are fully melted. Pour the resulting melt into water and quench it to obtain a frit. After wet ball milling and drying, frit powder is obtained.

[0031] (2) The frit powder, clay, water, carboxymethyl cellulose, and sodium tripolyphosphate were mixed in a mass ratio of 100:8:60:0.2:0.2. The resulting material was then ball-milled in a ball mill for 70 minutes until the particle size was 0.2–140 μm. After sieving and iron removal, water was added to adjust the density to 1.60 g / cm³. 3 28s flow rate of glaze slurry;

[0032] (3) The above glaze slurry is applied to the surface of the green or bisque blank by spraying, and then fired in a roller kiln. The maximum firing temperature is 1180℃ and the firing cycle is 60min to obtain a microcrystalline opaque glaze surface of MgO-CaO-Al2O3-SiO2 system.

[0033] Example 3:

[0034] 1. This embodiment describes a MgO-CaO-Al2O3-SiO2 microcrystalline opaque glaze, the raw material composition of which is: quartz 27wt%, talc 20wt%, albite 15wt%, zinc oxide 3wt%, calcite 20wt%, and clay 15wt%. Its chemical composition is: SiO2 65.9wt%, Al2O3 9.3wt%, CaO 12.0wt%, MgO 7.6wt%, ZnO 3.4wt%, K2O 0.3wt%, and Na2O 1.5wt%.

[0035] 2. This embodiment describes a method for preparing a MgO-CaO-Al2O3-SiO2-based microcrystalline opaque glaze, the steps of which are as follows:

[0036] (1) Prepare and mix the raw materials according to the above composition, then put them into a high-alumina crucible and heat them to 1550°C and keep them at that temperature for 90 minutes until the raw materials are fully melted. Pour the resulting melt into water and quench it to obtain a frit. After wet ball milling and drying, frit powder is obtained.

[0037] (2) The frit powder, clay, water, carboxymethyl cellulose, and sodium tripolyphosphate were mixed in a mass ratio of 100:5:50:0.2:0.2. The resulting material was then ball-milled in a ball mill for 60 minutes until the particle size was 0.1–200 μm. After sieving and iron removal, water was added to adjust the density to 1.78 g / cm³. 3 1. Glaze slurry with a flow rate of 32s;

[0038] (3) Apply the above glaze slurry to the surface of the green or bisque-fired body by glazing and fire it in a roller kiln. The maximum firing temperature is 1210℃ and the firing cycle is 65min to obtain a microcrystalline opaque glaze surface of MgO-CaO-Al2O3-SiO2 system.

[0039] like Figure 1 As shown, the crystalline phases of the glaze obtained in the embodiments of the present invention are pyroxene and quartz, and the particle size of the precipitated crystals is 1-5 μm (see...). Figure 2 The performance metrics for each embodiment are shown in Table 1.

[0040] Table 1 Performance indicators of the glaze obtained in various embodiments of the present invention

[0041]

[0042] Note: The hardness of the glaze was measured using a Vickers hardness tester.

Claims

1. A method for preparing a MgO-CaO-Al2O3-SiO2-based microcrystalline opaque glaze, characterized in that: The raw material composition of the microcrystalline opaque glaze is 27-38 wt% quartz, 12-20 wt% talc, 14-15 wt% albite, 3-5 wt% zinc oxide, 20-23 wt% calcite, and 6-15 wt% clay; The chemical composition of the microcrystalline opaque glaze is as follows: SiO2 65.9–68.9 wt%, Al2O3 5.6–9.3 wt%, CaO 12–13.9 wt%, MgO 4.6–7.6 wt%, ZnO 3.4–5.6 wt%, K2O 0.1–0.3 wt%, Na2O 1.4–1.5 wt%. The preparation method includes the following steps: (1) The raw materials are prepared and mixed according to the above composition, heated and melted, and then the melt is poured into water and quenched to obtain a frit. The frit powder is obtained by ball milling and drying. (2) The frit powder is mixed with clay, water, carboxymethyl cellulose, and sodium tripolyphosphate in a mass ratio of 100:2-8:50-70:0.1-0.3:0.1-0.

3. The resulting material is then ball-milled until the particle size is 0.1-300 μm. After sieving and iron removal, water is added to adjust the density to 1.5-1.8 g / cm³. 3 22-35s flow rate of glaze slurry; (3) The glaze slurry is applied to the surface of the green or bisque-fired body and fired at 1160-1250℃ for 40-120 min to obtain a microcrystalline opaque glaze of MgO-CaO-Al2O3-SiO2 system. The crystal phase of the obtained glaze is pyroxene and quartz, and the particle size of the precipitated crystals is 1-5 μm. The whiteness of the glaze is 60-75, the surface gloss is 10°-20°, and the hardness of the glaze is 6.0-7.0 GPa when measured with a Vickers hardness tester.

2. The method for preparing the MgO-CaO-Al2O3-SiO2 microcrystalline opaque glaze according to claim 1, characterized in that: The melting temperature in step (1) is 1500-1600℃, and the holding time is 30-180min.

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