A method for low temperature preparation of deep brown glaze

Abstract

The application discloses a method for preparing deep brown glaze at low temperature, and a multi-component low-temperature eutectic system of K-Na-Ca-Mg-Fe-Sr-P is constructed by using manganese slag and chromium oxide, supplemented by titanium dioxide, calcium phosphate and strontium carbonate, so that firing at a temperature of 1150-1180 DEG C under an oxidizing atmosphere is realized; through the formation of iron-chromium spinel and manganese-chromium spinel crystal phases and the common action thereof, the overall glaze surface presents deep brown color under natural light. The application can be widely applied to various artistic ceramics, and the process of low-temperature firing and the use of solid waste materials save the cost of raw materials, and meet the needs of green environmental protection and circular economy development.

Description

Technical Field

[0001] This invention relates to the field of ceramic glaze technology, and in particular to a method for preparing a dark brown glaze for ceramic products. Background Technology

[0002] In the fields of ceramic art and industrial manufacturing, the color of glazes is closely related to firing temperature. Deep, stable brown glazes, due to their unique antique texture and artistic expression, enjoy enduring demand in daily-use ceramics, art decorations, and architectural ornamentation. Traditional techniques for obtaining high-quality brown glazes typically rely on high firing temperatures (generally above 1250℃), utilizing the valence change of coloring ions in a reducing atmosphere to form the brown glaze. However, this process is energy-intensive and places stringent requirements on kiln equipment and fuel control, resulting in high production costs and contradicting the current trend of green and low-carbon industrial development. To reduce energy consumption and costs, the development of low-temperature glazes has become an important research direction. However, simply lowering the firing temperature presents a series of severe technical challenges: at lower firing temperatures, the flux in the glaze composition is difficult to fully activate, the silicate network is not fully formed, often resulting in insufficient glaze maturity, manifested as low gloss, pinholes, orange glaze, and other defects; more importantly, iron-based compounds, as the main coloring source of brown, exhibit extremely unstable color development behavior in the low-temperature range, their color intensity is significantly weakened, and they are highly susceptible to the influence of minute fluctuations in the basic composition of the glaze, making it difficult to reproduce the natural and rustic brown tone achieved under high-temperature conditions. Existing low-temperature glaze technologies often tend to introduce strong fluxing components such as lead and boron to promote melting and color development, which raises concerns about environmental protection and safety.

[0003] Therefore, designing a deep, uniform, and stable brown glaze system that can melt smoothly in a relatively low-temperature oxidizing atmosphere under the environmentally friendly premise of no lead or low lead and boron has become an urgent technical problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing dark brown glaze at low temperature. By using manganese slag and chromium oxide, supplemented with titanium dioxide, calcium phosphate and strontium carbonate, a multi-element low-temperature eutectic system of K-Na-Ca-Mg-Fe-Sr-P is formed, which achieves a dark brown color under oxidizing atmosphere and low-temperature firing conditions of 1150-1180℃, thereby saving raw material and energy costs and promoting the development of green environmental protection and circular economy.

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

[0006] This invention provides a method for preparing a dark brown glaze at low temperature. The raw material composition of the dark brown glaze is as follows: 10-20 wt% kaolin, 35-45 wt% quartz, 5-15 wt% albite, 5-15 wt% potassium feldspar, 1-5 wt% titanium dioxide, 2-8 wt% calcium phosphate, 11.2-14.9 wt% manganese slag, 0.5-2 wt% chromium oxide, and 1-5 wt% strontium carbonate; the chemical composition of the manganese slag is 27.98-35% SiO2. The preparation method comprises the following steps: 0.12 wt%, Al₂O₃ 18.36–26.92 wt%, K₂O 0.25–0.74 wt%, Na₂O 0.15–0.98 wt%, MgO 4.73–8.92 wt%, CaO 10.73–15.21 wt%, Fe₂O₃ 5.63–13.48 wt%, MnO 15.36–23.92 wt%, IL 0.73–1.55 wt%.

[0007] (1) After weighing and mixing the raw materials according to the above composition, put them into a ball mill for wet ball milling. After aging, the slurry obtained by sieving is used to obtain glaze slurry.

[0008] (2) The glaze slurry is evenly applied to the surface of the unglazed body and dried to obtain a body with a glaze layer; then, it is sintered in an oxidizing atmosphere at a temperature of 1150-1180℃ for 30-60 minutes to obtain a dark brown glaze; the color value of the dark brown glaze is L=28.7-35.1, a*=+7.5-+9.5, b*=+10.8-+14.2, and the crystal phase composition contains iron-chromium spinel crystal phase and manganese-chromium spinel crystal phase.

[0009] Further, in step (1) of the present invention, ball milling is performed at a mass ratio of material:ball:water = 1:2-3.5:1-1.6, and the ball milling time is 2.5-5 hours. The sieve mesh size is 325 mesh, and the residue is <0.5%; the aging time is 48-72 hours. In step (2), the thickness of the glaze layer is 0.5-1.5 mm.

[0010] The present invention has the following beneficial effects:

[0011] (1) This invention successfully constructed a K-Na-Ca-Mg-Fe-Sr-P multi-element low-temperature eutectic system by ball milling a mixture of kaolin, quartz, potassium feldspar, sodium feldspar, titanium dioxide, calcium phosphate, strontium carbonate, manganese slag, and chromium oxide. This system significantly reduces the melting temperature of the glaze by forming complex eutectic compounds at relatively low temperatures (1150–1180 °C). Among these, Ca, Mg, Fe, Sr, and P ensure that the glaze has good fluidity, spreadability, and surface smoothness.

[0012] (2) This invention abandons the traditional method of forming a brown glaze by changing the valence of coloring ions under a high-temperature (above 1250℃) reducing atmosphere. Instead, under an oxidizing atmosphere (such as air), the iron oxide, manganese oxide, and chromium oxide in the raw materials generate uniform and fine iron-chromium spinel and manganese-chromium spinel crystal phases in a low-temperature eutectic liquid phase environment. These uniform and fine iron-chromium spinel and manganese-chromium spinel crystal phases work together to color the glaze, presenting a full and uniform deep brown tone.

[0013] (3) This invention uses manganese slag, an industrial solid waste, as a raw material. The abundant silicate glass and calcium, magnesium, and other components in the manganese slag help to lower the firing temperature of the glaze and have a high-temperature fluxing effect. At the same time, the manganese and iron elements in the manganese slag combine with the chromium oxide in the raw material to form uniform and fine iron-chromium spinel and manganese-chromium spinel crystal phases, giving the glaze a deep brown color. As an industrial waste, the purchase cost of manganese slag is much lower than that of pure chemical raw materials. The use of manganese slag can not only reduce costs and increase efficiency, but also conform to the concept of a green, low-carbon, and environmentally friendly society. Attached Figure Description

[0014] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings:

[0015] Figure 1 This is a microscopic image of the dark brown glaze obtained in an embodiment of the present invention.

[0016] Figure 2 This is the EDS elemental distribution spectrum of the dark brown glaze obtained in an embodiment of the present invention. Detailed Implementation

[0017] This invention discloses a method for preparing a dark brown glaze at low temperature. The raw material composition of the dark brown glaze is as follows: 10-20 wt% kaolin, 35-45 wt% quartz, 5-15 wt% albite, 5-15 wt% potassium feldspar, 1-5 wt% titanium dioxide, 2-8 wt% calcium phosphate, 11.2-14.9 wt% manganese slag, 0.5-2 wt% chromium oxide, and 1-5 wt% strontium carbonate. The preparation method comprises the following steps:

[0018] (1) After weighing and mixing the raw materials according to the above composition, put them into a ball mill and perform wet ball milling at a mass ratio of material:ball:water = 1:2~3.5:1~1.6. The ball milling time is 2.5~5h. After passing through a 325 mesh sieve (sieve residue <0.5%), the slurry is aged for 48~72h to obtain glaze slurry.

[0019] (2) Apply the above glaze evenly to the surface of the unglazed body and dry it to obtain a body with a glaze layer (thickness of 0.5 to 1.5 mm); then sinter it in an oxidizing atmosphere at a temperature of 1150 to 1180°C for 30 to 60 minutes to obtain a dark brown glaze.

[0020] The raw material composition of the dark brown glaze in each embodiment is shown in Table 1; the manganese slag comes from Liupanshui City, Guizhou Province; the chemical composition of each raw material is shown in Table 2.

[0021] Table 1. Raw material composition (wt%) of the dark brown glaze in various embodiments of the present invention

[0022]

[0023] Table 2 Chemical composition (wt%) of raw materials used in the embodiments of the present invention

[0024]

[0025] The preparation process parameters for each embodiment are shown in Table 3.

[0026] Table 3. Preparation process parameters of various embodiments of the present invention

[0027]

[0028] Comparative Example 1:

[0029] Using no manganese slag as the first control, four sets of experiments were conducted under the same conditions as in Examples 1, 2, 3, and 4.

[0030] Comparative Example 2:

[0031] Four sets of experiments were conducted with no titanium dioxide added as Comparative Example 2, and the other conditions were the same as in Examples 1, 2, 3, and 4.

[0032] Comparative Example 3:

[0033] Four sets of experiments were conducted with no chromium oxide added as Comparative Example 3, and the remaining conditions were the same as in Examples 1, 2, 3, and 4.

[0034] The glaze color was tested according to the testing method of GB / T 7921-2008. The performance indicators of the glazes obtained in the various embodiments and comparative examples of the present invention are shown in Table 4.

[0035] Table 4. Color values ​​of the glazes obtained in various embodiments and comparative examples of the present invention.

[0036]

[0037] Note: The performance indicators for each comparative example are the average values ​​of the four experimental groups.

[0038] like Figure 1 As shown, the dark brown glaze obtained in this embodiment of the invention exhibits uniform and fine crystalline phases, which were identified as iron-chromium spinel and manganese-chromium spinel crystalline phases through elemental spectrum analysis (see...). Figure 2These uniform and fine iron-chromium spinel and manganese-chromium spinel crystal phases work together to color the glaze, giving it a full and uniform dark brown tone.

Claims

1. A method for preparing a dark brown glaze at low temperature, characterized in that: The raw material composition of the dark brown glaze is 10-20 wt% kaolin, 35-45 wt% quartz, 5-15 wt% albite, 5-15 wt% potassium feldspar, 1-5 wt% titanium dioxide, 2-8 wt% calcium phosphate, 11.2-14.9 wt% manganese slag, 0.5-2 wt% chromium oxide, and 1-5 wt% strontium carbonate; the chemical composition of the manganese slag is 27.98-35.12 wt% SiO2, 18.36-26.92 wt% Al2O3, 0.25-0.74 wt% K2O, 0.15-0.98 wt% Na2O, 4.73-8.92 wt% MgO, 10.73-15.21 wt% CaO, 5.63-13.48 wt% Fe2O3, 15.36-23.92 wt% MnO, and 0.73-1.55 wt% IL; the preparation method includes the following steps: (1) After weighing and mixing the raw materials according to the above composition, put them into a ball mill for wet ball milling. The slurry obtained by sieving is aged to obtain glaze slurry. (2) The glaze slurry is evenly applied to the surface of the unglazed body and dried to obtain a body with a glaze layer; then, it is sintered in an oxidizing atmosphere at a temperature of 1150-1180℃ for 30-60 minutes to obtain a dark brown glaze; the color value of the dark brown glaze is L=28.7-35.1, a*=+7.5-+9.5, b*=+10.8-+14.2, and the crystal phase composition contains iron-chromium spinel crystal phase and manganese-chromium spinel crystal phase.

2. The method for preparing dark brown glaze at low temperature according to claim 1, characterized in that: In step (1), ball milling is performed at a mass ratio of material:ball:water = 1:2 to 3.5:1 to 1.6, and the ball milling time is 2.5 to 5 hours.

3. The method for preparing dark brown glaze at low temperature according to claim 1, characterized in that: In step (1), the sieve mesh size is 325 mesh, the residue is <0.5%, and the aging time is 48-72h.

4. The method for preparing dark brown glaze at low temperature according to claim 1, characterized in that: The thickness of the glaze layer in step (2) is 0.5 to 1.5 mm.

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