Yttrium red colorant, and preparation method and application thereof

Abstract

The application belongs to the technical field of ceramic colorants, and discloses a yttrium red colorant and a preparation method and application thereof. The preparation method of the yttrium red colorant comprises the following steps: (1) mixing yttrium chloride, aluminum nitrate, chromium chloride and water to obtain a mixed solution; (2) adding lye to the mixed solution to adjust the pH to alkaline to obtain a precipitate; (3) washing and drying the precipitate to obtain yttrium red initial raw material; and (4) mixing the yttrium red initial raw material with a mineralizing agent, and calcining to obtain the yttrium red colorant. In step (2), the pH is adjusted to 8.5-9; and the molar ratio of yttrium chloride, aluminum nitrate and chromium chloride is 1:(0.8-1):(0.07-0.1). The yttrium red colorant prepared by the preparation method maintains good red color effect after high-temperature firing. This is conducive to the application of the yttrium red colorant in the field of ceramics.

Description

Technical Field

[0001] This invention belongs to the field of ceramic pigment technology, and specifically relates to a yttrium red pigment, its preparation method, and its application. Background Technology

[0002] Ceramic pigments are widely used in architectural ceramics, art ceramics, glazes, and body coloring. Yttrium red pigment, used in daily-use porcelain and underglaze decoration, can produce a pure red color, overcoming the shortcomings of other red pigments that are prone to fading at high temperatures.

[0003] In existing technologies, the red coloring effect of ceramic pigments, especially yttrium red pigments, often decreases significantly when fired at temperatures above 1200℃, failing to meet the requirements for vibrant red in high-end ceramic decoration. Current technologies generally employ a simple solid-state mixing and single-firing process, where the raw materials are directly mechanically ground and then fired at high temperatures. However, under high-temperature conditions, some doped ions are prone to valence state changes, and these valence states cannot produce ideal red emission. Simultaneously, due to uneven solid-state reactions, some ions may enter incorrectly coordinated positions in the crystal lattice or form impurity phases. These factors collectively lead to weakened red coloring, a darker hue, or even a brownish tint, severely impacting the application of yttrium red pigments in high-temperature fired ceramics.

[0004] Therefore, there is an urgent need to provide a new method for preparing yttrium red pigment, which can maintain a bright and pure red color effect after firing. Summary of the Invention

[0005] This invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, the object of this invention is to provide a yttrium red pigment, its preparation method, and its applications. The yttrium red pigment prepared by the method of this invention maintains a good red color development effect after high-temperature firing. This is beneficial for the application of yttrium red pigment in the ceramics field.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing yttrium red pigment includes the following steps: (1) Mix yttrium chloride, aluminum nitrate, chromium chloride and water to obtain a mixed solution; (2) Add alkaline solution to the mixed solution to adjust the pH to alkaline and obtain a precipitate; (3) The precipitate is washed and dried to obtain yttrium red initial raw material; (4) The yttrium red initial raw material is mixed with a mineralizing agent and calcined to obtain the yttrium red material; In step (2), the pH is adjusted to 8.5-9; The molar ratio of yttrium chloride, aluminum nitrate, and chromium chloride is 1:(0.8-1):(0.07-0.1).

[0007] Preferably, in step (1), the molar ratio of yttrium chloride, aluminum nitrate, and chromium chloride is 1:1:0.07.

[0008] Preferably, in step (1), the water is deionized water.

[0009] Preferably, in step (1), the ratio of yttrium chloride to water is 1 mol: (1200-1800) mL.

[0010] Preferably, in step (2), the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution. For example, it is a 1-2.5 mol / L sodium hydroxide solution.

[0011] Preferably, in step (2), the pH is adjusted to 8.6-8.8.

[0012] Preferably, in step (2), after adjusting the pH to alkaline, aging is also carried out.

[0013] Preferably, the aging process involves stirring and aging at 45-60°C for 1-2 hours. Aging causes the precipitate particles to become significantly coarser, the flocs to become larger, and the supernatant to become relatively clear and transparent.

[0014] Preferably, in step (3), the washing process is to use deionized water to wash until there are no chloride ions.

[0015] Using silver ions (Ag) + ) and chloride ions (Cl - The reaction produces an insoluble white curd-like precipitate (silver chloride), which is used to determine whether the washing is thorough.

[0016] The process for checking whether the washing is thorough is as follows: (1) During the washing and filtration process, use a clean glass rod or dropper to take about 2-3 mL of the filtrate after the last wash and place it in a clean transparent test tube; (2) Add 2-3 drops of dilute nitric acid (volume fraction of about 10%-20%) to the test tube, and gently shake the test tube to acidify the solution; (3) Add 1-2 drops of 0.1 mol / L silver nitrate solution (or mass fraction of about 1%-2%) to the acidified test solution, observe the changes in the test tube, and see if a white precipitate is produced, so as to determine whether the washing is thorough.

[0017] Preferably, in step (3), the drying temperature is 120-150°C.

[0018] Preferably, in step (3), the drying time is 10-24 hours. For example, 10 hours, 12 hours, 14 hours, 16 hours, or 18 hours.

[0019] Preferably, in step (4), the weight ratio of the initial raw material of yttrium red to the mineralizer is 100:(1-5).

[0020] Preferably, in step (4), the mineralizing agent is lithium fluoride or sodium fluoride.

[0021] Preferably, in step (4), the calcination is carried out by heating from room temperature to 1200-1300°C at a rate of 4-8°C / minute, holding at that temperature for 2-4 hours, and then cooling to room temperature.

[0022] A second aspect of the present invention provides a yttrium red pigment.

[0023] A yttrium red pigment is prepared by the above-described preparation method.

[0024] A third aspect of the present invention provides the application of the above-mentioned yttrium red pigment in the field of ceramics.

[0025] The beneficial effects of this invention are: The preparation method described in this invention (belonging to a liquid-phase method) uses yttrium chloride, aluminum nitrate, and chromium chloride as specific raw materials. By adjusting the pH to 8.5-9, the prepared yttrium red pigment retains its excellent red color after high-temperature firing. This is beneficial for the application of yttrium red pigment in the ceramics field. Attached Figure Description

[0026] Figure 1 The yttrium red pigment prepared in Example 1 of this invention; Figure 2 The yttrium red pigment prepared in Comparative Example 4. Detailed Implementation

[0027] The present invention will be further described in detail below through specific embodiments.

[0028] It should be noted that, unless otherwise specified, the following raw materials can be obtained through conventional commercial channels or prepared using existing technologies.

[0029] Example 1 A method for preparing yttrium red pigment includes the following steps: (1) Raw material preparation: Weigh yttrium chloride, aluminum nitrate and chromium chloride in a molar ratio of 1:1:0.07 and set aside.

[0030] (2) Dissolution: Add yttrium chloride, aluminum nitrate and chromium chloride to 1500 mL of deionized water and stir to dissolve to obtain a mixed solution; (3) pH adjustment: Under stirring conditions, slowly add sodium hydroxide solution (concentration of sodium hydroxide solution is 2.5mol / L) to the mixed solution for 30 minutes to adjust the pH value to 8.5, and continue stirring for 10 minutes to form a precipitate; (4) Washing and filtration: Wash the precipitate with deionized water until there are no chloride ions in the filtrate, and filter to obtain filter cake; (5) Drying: The filter cake was dried at 120°C for 12 hours to obtain the initial raw material of yttrium red; (6) Calcination: The dried yttrium red initial raw material and the mineralizing agent lithium fluoride are mixed evenly in a weight ratio of 100:3. The mixture is heated to 1300°C in a kiln at a heating rate of 5°C / min and held at this temperature for 3 hours. Then it is cooled to room temperature with the furnace and ground to obtain yttrium red material.

[0031] Figure 1 The yttrium red pigment prepared in Example 1 of this invention.

[0032] Yttrium nitrate and chromium nitrate were not selected as raw materials to reduce the nitrogen content in the wastewater, thereby lowering wastewater treatment costs. Aluminum nitrate was chosen because aluminum chloride undergoes explosive hydrolysis upon contact with water, which is detrimental to safe production. Furthermore, the chloride system forms loose flocs during co-precipitation, significantly improving filtration and washing efficiency and effectively avoiding the problems of difficult filtration and agglomeration caused by viscous, gel-like precipitates in a full nitrate system.

[0033] The purpose of washing until there are no chloride ions is not simply to remove Cl. - Instead, it utilizes the high sensitivity of the AgNO3 test as a convenient method for determining Na+. + The endpoint for washing away soluble impurities is indicated by a scale. Forcibly replacing it with full nitrates not only fails to eliminate the washing step but also renders the process unfeasible due to severe colloid aggregation, filtration difficulties, and raw material deliquescence.

[0034] Example 2 A method for preparing yttrium red pigment includes the following steps: (1) Raw material preparation: Weigh yttrium chloride, aluminum nitrate and chromium chloride in a molar ratio of 1:1:0.07 and set aside.

[0035] (2) Dissolution: Add yttrium chloride, aluminum nitrate and chromium chloride to 1500 mL of deionized water and stir to dissolve to obtain a mixed solution; (3) pH adjustment: Under stirring conditions, slowly add sodium hydroxide solution (concentration of sodium hydroxide solution is 2.5 mol / L) to the mixed solution to adjust the pH value to 9, and continue stirring for 10 minutes to form a precipitate; (4) Washing and filtration: Wash the precipitate with deionized water until there are no chloride ions in the filtrate, and filter to obtain filter cake; (5) Drying: The filter cake was dried at 120°C for 11 hours to obtain the initial raw material of yttrium red; (6) Calcination: The dried yttrium red initial raw material and the mineralizing agent lithium fluoride are mixed evenly in a weight ratio of 100:3.5. The mixture is heated to 1300°C in a kiln at a heating rate of 5°C / min and held at this temperature for 3 hours. Then it is cooled to room temperature with the furnace and ground to obtain yttrium red material.

[0036] Example 3 A method for preparing yttrium red pigment includes the following steps: (1) Raw material preparation: Weigh yttrium chloride, aluminum nitrate and chromium chloride in a molar ratio of 1:0.8:0.1 and set aside.

[0037] (2) Dissolution: Add yttrium chloride, aluminum nitrate and chromium chloride to 1500 mL of deionized water and stir to dissolve to obtain a mixed solution; (3) pH adjustment: Under stirring conditions, slowly add sodium hydroxide solution (concentration of sodium hydroxide solution is 2.5mol / L) to the mixed solution for 30 minutes to adjust the pH value to 8.5, and continue stirring for 10 minutes to form a precipitate; (4) Washing and filtration: Wash the precipitate with deionized water until there are no chloride ions in the filtrate, and filter to obtain filter cake; (5) Drying: The filter cake was dried at 120°C for 12 hours to obtain the initial raw material of yttrium red; (6) Calcination: The dried yttrium red initial raw material and the mineralizing agent lithium fluoride are mixed evenly in a weight ratio of 100:4. The mixture is heated to 1300°C in a kiln at a heating rate of 5°C / min and held at this temperature for 3 hours. Then it is cooled to room temperature with the furnace and ground to obtain yttrium red material.

[0038] Comparative Example 1 Compared with Example 1, the only difference in Comparative Example 1 is that sodium hydroxide solution was not added; the other processes are the same as in Example 1.

[0039] Comparative Example 2 Compared with Example 1, the only difference in Comparative Example 2 is that yttrium chloride is replaced with an equimolar amount of nano-yttrium oxide; the other processes are the same as in Example 1.

[0040] Comparative Example 3 Compared with Example 1, the only difference in Comparative Example 3 is that chromium chloride is replaced with an equimolar amount of nano-chromium oxide; the other processes are the same as in Example 1.

[0041] Comparative Example 4 Comparative Example 4 shows a yttrium red pigment prepared by a solid-state method. The specific preparation process is as follows: Weigh out yttrium chloride, aluminum nitrate, and chromium chloride according to the molar ratio of Y:Al:Cr = 1:1:0.07. First, mix and grind the first two in an agate mortar. Then, add chromium chloride and a small amount of anhydrous ethanol to aid grinding. Continue grinding for 30 minutes until homogeneous. After passing through a 200-mesh sieve, place the mixture into an alumina crucible. In a box-type resistance furnace, heat the mixture to 500℃ at 5℃ / min for 2 hours to pre-decompose nitrates and chlorides. Then, heat the mixture to 1350℃ at the same rate and hold for 4 hours for solid-phase reaction. After cooling in the furnace, remove the mixture and grind it to obtain yttrium red material.

[0042] Figure 2 The yttrium red pigment prepared in Comparative Example 4.

[0043] Comparative Example 5 Compared with Example 1, the only difference in Comparative Example 5 is that in step (2), the pH is adjusted to 10, and the other processes are the same as in Example 1.

[0044] Product effectiveness test 1. The yttrium red pigments prepared in Examples 1-3 and Comparative Examples 1-5 were fired at 1240℃ for 30 minutes. The CIE values ​​of the obtained products were measured according to GB / T 4739-2015 "Method for Determination of Color of Daily-use Ceramic Pigments". The results are shown in Table 1.

[0045] Table 1 L 28.3 27.6 27.2 32.7 30.8 31.1 28.5 28.7 a 19.5 20.0 18.8 6.6 10.5 5.7 16.9 11.6 b 10.3 10.4 11.9 9.2 8.9 9.9 10.3 13.4 As can be seen from Table 1, the yttrium red pigment prepared in the embodiments of the present invention still maintains a good red coloring effect after high-temperature firing.

[0046] Compared to Example 1, the slightly higher pH in Example 2 resulted in more complete co-precipitation, and a slight increase in mineralizer promoted crystallization. Cr 3+ The activation efficiency is higher, and the redness is slightly greater than that of Example 1.

[0047] Compared to Example 1, Example 3 has a reduced aluminum content, which prevents some Cr from entering the crystal lattice and may cause segregation; excess Cr is easily oxidized to Cr2. 6+ (Yellowish), brightness decreases, yellowness increases.

[0048] Compared to Example 1, Comparative Example 1 did not include sodium hydroxide solution, resulting in no co-precipitation. The raw materials exhibited severe segregation, producing almost no target crystalline phase, appearing gray with extremely low redness. In Comparative Example 1, due to the absence of sodium hydroxide solution, there was no effective co-precipitation, and only trace amounts of Al were retained during filtration. 3+ / Y 3+ The hydrolyzed flocculants, after calcination, produce a physical mixture of free oxides.

[0049] Compared with Example 1, Comparative Example 2 used nano-yttrium oxide instead of yttrium chloride, which resulted in poor mixing of raw materials, poor reactivity, impure crystal phase, a large amount of residual white oxide, high brightness but significantly low redness.

[0050] Compared to Example 1, Comparative Example 3 used nano-chromium oxide instead of chromium chloride, resulting in Cr 3+ It is difficult to uniformly incorporate into the crystal lattice, there are very few red chromophores, the color is light yellowish-green, and the redness is low.

[0051] Compared to Example 1, the solid-state method used in Comparative Example 4 is limited to micron-level mixing, Cr 3+ Long-distance diffusion is required to enter the crystal lattice, resulting in a large amount of Cr. 3+ Unable to replace Al sites, it segregates at grain boundaries in an inactive aggregate state, failing to form effective red color centers; far less efficient in-situ doping than that achieved by coprecipitation atomic-level mixing, thus its redness (a value) is significantly lower.

[0052] Compared with Example 1, in Comparative Example 5, the excess alkali caused Al to be dissolved, which disrupted the Y / Al stoichiometric ratio, easily generated impurities, and resulted in a yellowish-green color with a sharp decrease in redness and an increase in yellowness.

[0053] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing yttrium red pigment, characterized in that, Includes the following steps: (1) Mix yttrium chloride, aluminum nitrate, chromium chloride and water to obtain a mixed solution; (2) Add alkaline solution to the mixed solution to adjust the pH to alkaline and obtain a precipitate; (3) The precipitate is washed and dried to obtain yttrium red initial raw material; (4) The yttrium red initial raw material is mixed with a mineralizing agent and calcined to obtain the yttrium red material; In step (2), the pH is adjusted to 8.5-9; The molar ratio of yttrium chloride, aluminum nitrate, and chromium chloride is 1:(0.8-1):(0.07-0.1).

2. The method for preparing yttrium red pigment according to claim 1, characterized in that, In step (1), the ratio of yttrium chloride to water is 1 mol: (1200-1800) mL.

3. The method for preparing yttrium red pigment according to claim 1, characterized in that, In step (2), the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution.

4. The method for preparing yttrium red pigment according to claim 1, characterized in that, In step (2), the alkaline solution is a 1-2.5 mol / L sodium hydroxide solution.

5. The method for preparing yttrium red pigment according to claim 1, characterized in that, In step (3), the drying temperature is 120-150℃.

6. The method for preparing yttrium red pigment according to claim 1, characterized in that, In step (4), the weight ratio of the initial raw material of yttrium red to the mineralizer is 100:(1-5).

7. The method for preparing yttrium red pigment according to claim 1, characterized in that, In step (4), the mineralizing agent is lithium fluoride or sodium fluoride.

8. The method for preparing yttrium red pigment according to any one of claims 1-7, characterized in that, In step (4), the calcination is carried out by heating from room temperature to 1200-1300℃ at a rate of 4-8℃ / minute, holding at that temperature for 2-4 hours, and then cooling to room temperature.

9. A yttrium red pigment, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The application of the yttrium red pigment according to claim 9 in the ceramics field.

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