Preparation method of high-purity magnesium aluminate spinel powder and magnesium aluminate spinel powder

Abstract

The invention relates to a preparation method of high-purity magnesium aluminate spinel powder and the high-purity magnesium aluminate spinel powder. The preparation method comprises the following steps: S1, weighing raw materials in percentage by mass, wherein the raw materials comprise 65-80% of magnesium oxide powder and 20-35% of aluminum powder; s2, adding fluoride accounting for 1-10% of the mass of the raw materials into the raw materials, mixing, stirring and grinding uniformly to obtain a mixture; s3, pressurizing and pressing the mixture into a solid blank; s4, the solid blank is subjected to a calcination reaction for 1-4 h at the temperature of 900-1500 DEG C in a vacuum environment, and a sintered blank is obtained; and S5, cooling the sintered blank to room temperature, and crushing to obtain the high-purity magnesium aluminate spinel powder. The preparation method provided by the invention is based on a low-temperature solid-phase reaction between several raw materials and the fluoride, and by controlling specific reaction parameters, the preparation method is simple, the roasting temperature is low, the dosage of the fluoride is small, and the obtained magnesium aluminate spinel powder is relatively high in phase purity and small and uniform in particle size.

Description

Technical Field

[0001] The present invention relates to the field of inorganic non-metallic materials, and specifically relates to a method for preparing high-purity magnesium aluminate spinel powder and magnesium aluminate spinel powder. Background Art

[0002] Magnesium aluminate spinel transparent ceramics have a relatively wide light transmission band and a high transmittance, and are ideal materials for medium-wave infrared windows. At the same time, they have characteristics such as high melting point, low thermal expansion coefficient, and low thermal conductivity, and have good thermal shock resistance and resistance to alkaline slag erosion. Magnesium aluminate spinel has become an ideal material in the fields of transparent armor, missile fairings, spacecraft windows, solid-state lighting, etc.

[0003] High-purity, small and uniform particle size, and magnesium aluminate spinel raw material powder with good sinterability are important prerequisite conditions for preparing high-quality magnesium aluminate spinel transparent ceramics. Currently, the commonly used methods for preparing magnesium aluminate spinel in the industry are mainly divided into two directions: high-temperature solid-phase sintering and wet low-temperature synthesis. Among them, high-temperature solid-phase sintering is widely used because of its relatively mature process and simple operation, but high-temperature solid-phase sintering has high requirements for sintering temperature, equipment accuracy, etc., and has high energy consumption; while for low-temperature wet method, in order to promote crystal growth and recrystallization and reduce the sintering temperature, etc., more additives need to be used, which inevitably leads to too many impurity atoms in the spinel system and the problem of unsatisfactory purity of the final product.

[0004] In summary, there is an urgent need for a method for producing magnesium aluminate spinel that is simple to operate, economical, and has an ideal purity of the finished product. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a method for preparing high-purity magnesium aluminate spinel powder and magnesium aluminate spinel powder. By preparing magnesium aluminate spinel through low-temperature solid-phase reaction, it is possible to simply and economically synthesize magnesium aluminate spinel powder with high purity, small and uniform particle size.

[0006] The technical solution adopted by the present invention is as follows:

[0007] On the one hand, the present invention provides a method for preparing high-purity magnesium aluminate spinel powder, including the following steps:

[0008] S1. Weigh the raw materials according to mass percentage. The raw materials include 65% - 80% of magnesium oxide powder and 20% - 35% of aluminum powder;

[0009] S2. Add 1% - 10% of fluoride based on the mass of the raw materials, and after mixing, stir and grind evenly to obtain a mixture;

[0010] S3. Press the mixture to form a solid blank;

[0011] S4. Calcinate and react the solid blank at 900 - 1500 °C for 1 - 4 h in a vacuum environment to obtain a sintered blank;

[0012] S5. Naturally cool the sintered blank in the furnace to room temperature, and then pulverize it to obtain the high-purity magnesium aluminate spinel powder.

[0013] In a possible implementation,

[0014] In S3, press the mixture under a pressure of 10 - 100 MPa to form a solid blank.

[0015] In a possible implementation,

[0016] In S3, press the mixture to form a flat cake-shaped solid blank.

[0017] In a possible implementation,

[0018] In S4, during the calcination reaction, the vacuum degree of the vacuum environment is maintained at 5 - 50 Pa.

[0019] In the above possible implementation, further,

[0020] In S4, during the calcination reaction, the vacuum degree of the vacuum environment is maintained at 1 - 10 Pa.

[0021] In a possible implementation,

[0022] The fluoride in S2 is at least one of aluminum fluoride and magnesium fluoride.

[0023] In a possible implementation,

[0024] The magnesium oxide powder weighed in S1 is selected as the first-class light magnesium oxide, and the magnesium oxide content is greater than 95%.

[0025] In a possible implementation,

[0026] In S5, gently pulverize the sintered blank that has been naturally cooled to room temperature in the furnace to obtain the high-purity magnesium aluminate spinel powder.

[0027] In the second aspect, the present invention provides a high-purity magnesium aluminate spinel powder, which is obtained by the above preparation method; wherein the content of the magnesium aluminate spinel phase reaches more than 95%, and the contents of the alumina and magnesium oxide phases are less than 5%.

[0028] The above technical solution provided by this application has at least the following technical effects or advantages:

[0029] The preparation method provided by this application is based on the low-temperature solid-phase reaction between several raw materials and fluoride. By controlling specific reaction parameters, the preparation method is simple, the calcination temperature is low, the dosage of fluoride is small, and the obtained magnesium aluminate spinel powder has a relatively high phase purity, reaching 97%, and the particle size is small and uniform. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments of this application or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1 It is the X-ray diffraction pattern of the magnesium aluminate spinel powder prepared in Example 1 of this application;

[0032] Figure 2 It is the scanning electron microscope image of the magnesium aluminate spinel powder prepared in Example 1 of this application;

[0033] Figure 3 It is the distribution diagram of the elemental composition of the magnesium aluminate spinel powder prepared in Example 1 of this application, that is Figure 2 The partial enlarged view of area A in. Detailed Embodiments

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0035] Example 1

[0036] This example provides a preparation method for high-purity magnesium aluminate spinel powder, including the following steps:

[0037] S1. Weigh the following raw materials by mass percentage: 75.5% of magnesium oxide powder and 24.5% of aluminum powder; in this example, the magnesium oxide is specifically selected as the first-class product of light magnesium oxide, and its magnesium oxide content is greater than 95%;

[0038] S2. Weigh 3% of the total mass of the raw materials in S1 of fluoride; in this example, the fluoride is specifically selected as aluminum fluoride;

[0039] S3. Mix the raw materials weighed in S1 and the fluoride weighed in S2 evenly to obtain a mixture;

[0040] S4. Under a pressure of 20 MPa, the mixture in S3 is pelletized to obtain flat cake-shaped pellets as solid embryos. Compacting the mixture into flat cake-shaped pellets is convenient for applying pressure on the one hand, which is beneficial to fully compact the mixture, and on the other hand, it is conducive to the full and uniform conduction of temperature to the inside and outside of the solid embryo during the subsequent sintering process, thereby improving the sintering effect.

[0041] S5. The cake-shaped pellets are placed in a vacuum furnace. After evacuating to 5 Pa, they are heated to 1200 °C and calcined for 2 hours while maintaining the vacuum degree within the range of 5 - 50 Pa to obtain sintered embryos.

[0042] S6. The sintered embryos obtained in S5 are cooled to room temperature. At this time, the cake-shaped sintered embryos have become loose, and the high-purity magnesium aluminate spinel powder can be obtained by gently crumbling them.

[0043] The process method adopted in this embodiment is simple and the sintering temperature is low. Nanoscale magnesium aluminate spinel powder can be obtained under low-vacuum conditions. After testing, the content of the magnesium aluminate spinel phase in the prepared powder reaches more than 95%, and the contents of the alumina and magnesia phases are less than 5%.

[0044] The high-purity magnesium aluminate spinel powder is prepared by the preparation method provided in this embodiment. The obtained magnesium aluminate spinel powder is characterized, and its X-ray diffraction pattern is measured as follows Figure 1 As shown, the peaks corresponding to the magnesium aluminate spinel are narrow and high, indicating that the generated magnesium aluminate spinel has good crystallization. The peaks of the magnesia phase are very small, and the peaks of metallic aluminum and fluoride are not visible, indicating that there is a trace amount of magnesia remaining in the product, while the metallic aluminum and fluoride have been consumed. After calculation, the content of magnesium aluminate spinel is greater than 97%, that is, the product is high-purity magnesium aluminate spinel powder.

[0045] The high-purity magnesium aluminate spinel powder provided in this embodiment is characterized by SEM, and its scanning electron micrograph is as Figure 2 shown;

[0046] For the A area (as shown in Figure 2 ) in the SEM image of the high-purity magnesium aluminate spinel powder provided in this embodiment, local magnification is performed to analyze the elemental composition distribution; the result is as Figure 3 shown.

[0047] The product analysis results are shown in Table 1 below:

[0048] Table 1 - Elemental analysis results of magnesium aluminate spinel powder in Example 2

[0049]

[0050] From Figure 2 、 3 and Table 1, it can be seen that: Figure 2The particles are uniform and the particle size is generally below 1μm. Figure 3 The distribution of Mg, Al, and O in the reaction mixture is relatively consistent, indicating that the substance is composed of these three elements. Combined with Table 1, the atomic percentage of the three elements is close to 1:2:4, which is consistent with the atomic ratio of magnesium-aluminum spinel (MgAl2O4). It can be determined that the product obtained by the reaction is magnesium-aluminum spinel. Figure 1 The purity of the magnesium aluminum spinel in the product reaches 97%.

[0051] Example 2

[0052] This embodiment provides a method for preparing high-purity magnesium aluminum spinel powder, comprising the following steps:

[0053] S1. Weigh the raw materials according to the mass percentage of magnesium oxide powder 75% and aluminum powder 25%. In this embodiment, high-quality light magnesium oxide is used, in which the magnesium oxide content is greater than 95%;

[0054] S2, adding 1% fluoride by weight of the raw material, fully mixing, stirring, and grinding to obtain a mixture; in this embodiment, the fluoride is specifically selected from magnesium fluoride;

[0055] S3, forming the mixture into flat cake-shaped pellets; the molding pressure is 10MPa;

[0056] S4, putting the cake-shaped pellets of the pressing number in S3 into a vacuum furnace, and evacuating to a low vacuum state, with the specific vacuum degree maintained at 5Pa;

[0057] S5, maintaining the vacuum degree in the range of 5-50Pa, vacuum baking the cake-shaped pellets in a vacuum furnace to obtain magnesium-aluminum spinel pellets; the temperature during sintering is maintained at 1000°C, the temperature in the vacuum furnace is increased from the initial temperature to the sintering temperature, and then the temperature is maintained for sintering reaction for 4 hours to obtain a sintered blank;

[0058] S6. The sintered blank is naturally cooled to room temperature in the furnace. At this time, the originally compact flat cake-shaped pellets have become loose after sintering with specific processes and process parameters. Magnesium-aluminum spinel powder can be obtained by gently crushing it.

[0059] The high-purity magnesium aluminum spinel powder provided in this embodiment was tested, and the results were similar to those in Example 1.

[0060] Compared with the prior art, the present invention has the following characteristics: simple preparation method, low roasting temperature, small amount of fluoride, high phase purity of the obtained magnesium aluminum spinel powder, up to 97%, and small and uniform particle size.

[0061] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. The above embodiments are only used to illustrate the technical solutions of the present application, rather than limiting the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present application.

Claims

1. A preparation method of high-purity magnesium aluminate spinel powder, characterized in that, It includes the following steps: S1. Weigh the raw materials by mass percentage. The raw materials include 65% - 80% of magnesium oxide powder and 20% - 35% of aluminum powder. S2. Add 1% - 10% of its mass of fluoride to the raw materials, and after mixing, stir and grind evenly to obtain a mixed material. S3. Press the mixed material to form a solid blank. S4. Calcinate and react the solid blank at 900 - 1500 °C for 1 - 4 h in a vacuum environment to obtain a sintered blank. S5. Naturally cool the sintered blank in the furnace to room temperature, and after pulverizing, the high-purity magnesium aluminate spinel powder is obtained.

2. The preparation method of a high-purity magnesium aluminate spinel powder according to claim 1, wherein in S3, the mixed material is pressed to form a solid blank under a pressure of 10 - 100 MPa.

3. The preparation method of a high-purity magnesium aluminate spinel powder according to claim 1, wherein in S3, the mixed material is pressed into a flat cake-shaped solid blank.

4. The preparation method of a high-purity magnesium aluminate spinel powder according to claim 1, wherein in S4, the vacuum degree of the vacuum environment during the calcination reaction is maintained at 5 - 50 Pa.

5. The preparation method of a high-purity magnesium aluminate spinel powder according to claim 4, wherein in S4, the vacuum degree of the vacuum environment during the calcination reaction is maintained at 1 - 10 Pa.

6. The preparation method of a high-purity magnesium aluminate spinel powder according to claim 1, wherein the fluoride in S2 is at least one of aluminum fluoride and magnesium fluoride.

7. The preparation method of a high-purity magnesium aluminate spinel powder according to claim 1, wherein the magnesium oxide powder weighed in S1 selects the first-class product of light magnesium oxide, and the magnesium oxide content is greater than 95%.

8. The preparation method of a high-purity magnesium aluminate spinel powder according to claim 1, wherein in S5, the sintered blank after naturally cooling to room temperature in the furnace is gently crushed to obtain the high-purity magnesium aluminate spinel powder.

9. A high-purity magnesium aluminate spinel powder, characterized in that, It is obtained by the preparation method described in any one of claims 1 - 8; the content of the magnesium aluminate spinel phase in the high-purity magnesium aluminate spinel powder reaches more than 95%, and the contents of the alumina and magnesium oxide phases are less than 5%.

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