Low-temperature preparation method of NaLa5S8 transparent ceramic powder with high infrared light transmittance

Abstract

The invention relates to a low-temperature preparation method of NaLa5S8 transparent ceramic powder with high infrared light transmittance, which comprises the following steps: preparing a specified sodium halide additive by taking rare earth polysulfide LaS2 powder as a raw material, and mixing the raw material and the additive to prepare a precursor of the NaLa5S8 transparent ceramic powder; and putting the prepared precursor mixture powder into an improved ball milling tank, carrying out mechanochemical reaction in a protective gas environment, and after ball milling is finished and the powder is separated out, obtaining the NaLa5S8 transparent ceramic powder with the cubic phase structure. The problem that the sulfide transparent ceramic powder of rare earth lanthanum is easy to oxidize due to high-temperature vulcanization is solved, and the prepared NaLa5S8 transparent ceramic powder is low in oxygen content and small in particle size.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, specifically relating to a low-temperature preparation method for NaLa5S8 transparent ceramic powder with high infrared light transmittance. Background Technology

[0002] NaLa5S8 is a stable rare-earth lanthanide with a cubic crystal structure. Since the La-S and Na-S bonds have virtually no absorption in the infrared region, this compound theoretically has a range of 1.2–20 nm. μ The NaLa5S8 exhibits excellent transmittance over a wide wavelength range. Rare earth lanthanum sulfides, such as CaLa2S4 and La2S3, generally possess melting points above 2000℃, high mechanical strength, high hardness, good thermal stability, and excellent resistance to rain and sand erosion. Their overall performance is significantly superior to that of the main infrared-transparent materials, ZnS and ZnSe transparent ceramics. The cubic crystal structure of NaLa5S8 polycrystalline material avoids optical anisotropy and birefringence. Therefore, NaLa5S8 can be hot-pressed and sintered to prepare infrared optically transparent polycrystalline ceramics, which are expected to become a new generation of infrared optical window materials for both military and civilian optoelectronic equipment.

[0003] The infrared optical transmittance of rare earth sulfide NaLa5S8 hot-pressed transparent ceramics is closely related to the quality of its powder. Currently, the powders used for preparing lanthanum-based sulfide hot-pressed transparent ceramics are mainly prepared by high-temperature sulfidation. Under high-temperature conditions, H2S or CS2 gas is used as the sulfiding agent to perform long-term sulfidation treatment on different precursor mixtures to obtain lanthanum-based sulfide powders with certain thermodynamic stability. For example, the precursor mixture of lanthanum-based sulfide CaLa2S4 is a mixture of lanthanum oxide or lanthanum carbonate and calcium carbonate (Journal of the American Ceramic Society, 2011, 94(4), pp.1162~1166; Journal of Rare Earths, 2011, 29(4), pp.313-316), and the precursor mixture of La2S3 includes the thermal decomposition products of a mixture of lanthanum oxide and NH4SCN (Materials Transactions, 2009, 50(7), pp.). The preparation methods of lanthanum-based sulfide powders reported in the literature, such as those obtained by hydrothermal methods (Chinese Patent CN108715549A), are complex and costly. The preparation requires high temperatures, such as 800℃~1000℃, and long-term sulfidation of the precursor. Some reports indicate that the sulfidation time can be as long as 48 hours. Therefore, the prepared powder particles are generally large. Furthermore, since rare earth lanthanum is an oxygen-loving element, it is easily oxidized at high temperatures. The prepared powder has a high oxygen content and sulfur oxide impurities, which is not conducive to further sintering to prepare lanthanum-based sulfide transparent ceramics with high infrared transmittance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a low-temperature preparation method for NaLa5S8 transparent ceramic powder with high infrared light transmittance. This method overcomes the complex process of existing rare earth lanthanum sulfide powder preparation technologies, avoids the long-term high-temperature requirements of the process, and enables the preparation of NaLa5S8 transparent ceramic powder with a low oxygen content and ultrafine cubic phase structure at ambient temperature.

[0005] First, this invention provides a low-temperature preparation method for NaLa5S8 transparent ceramic powder with high infrared light transmittance, the preparation method comprising the following steps: S1. Mixing compound powder raw materials containing rare earth elements lanthanum source and sodium source to obtain precursor powder, wherein the rare earth element lanthanum source compound is a polysulfide LaS2, and the sodium source compound is one of NaCl, NaBr, and NaI; the amount of lanthanum source compound and sodium source compound added in the precursor powder is calculated according to the following ratio: m:n = 5.0:(1.0~2.5), where m is the amount of substance of lanthanum source compound and n is the amount of substance of sodium source compound; S2. The precursor powder is treated by mechanochemical synthesis: At room temperature, the precursor powder and grinding balls are placed together in a ball mill jar and mechanochemical synthesis is carried out under a protective gas. S3. Separate the solid powder, then clean and vacuum dry it.

[0006] Further, step S2 includes: placing the precursor powder and grinding balls together in a modified ball mill jar at room temperature, and then sealing the ball mill jar lid; first, filling the ball mill jar with protective gas through the air inlet pipe, and then venting the air from the ball mill jar through the air outlet pipe; then closing the air inlet pipe and installing a balloon at the outlet pipe; then rotating the ball mill jar at a speed of not less than 90 rpm for a ball milling time of not more than 96 hours, and carrying out mechanochemical synthesis under protective gas to allow the precursor powder to undergo a solid-state reaction; when the volume of the balloon at the outlet pipe no longer increases or changes, ball milling is stopped after another ball milling for not less than 1 hour.

[0007] Furthermore, the ambient temperature mentioned in step S2 is the atmospheric temperature.

[0008] Furthermore, the amount of grinding balls added in step S2 is: (mass of grinding balls): (mass of precursor powder) = 1:(0.2~3.5); The grinding ball is a hard non-metallic non-oxide ceramic grinding ball, including one of the following materials: silicon nitride, aluminum nitride, boron nitride, silicon carbide, tungsten carbide, zirconium boride, and molybdenum disilicide.

[0009] Furthermore, in step S2, the grinding balls used in the mechanochemical synthesis are a combination of large, medium, and small balls. The diameter of the large balls is 9-12 mm, the diameter of the medium balls is 6-9 mm, and the diameter of the small balls is 2-6 mm. The large balls account for 10-20% of the total mass of the grinding balls, the medium balls account for 20-30% of the total mass of the grinding balls, and the small balls account for 50-70% of the total mass of the grinding balls.

[0010] Furthermore, the improved ball mill jar described in step S2 is equipped with an inlet pipe and an outlet pipe along the rotation axis of the ball mill jar body; the inlet pipe is equipped with a gas valve that allows or stops gas flow; the outlet pipe is equipped with a detachable, pressure-sensitive, and volume-expanding organic polymer balloon; the protective gas described in step S2 refers to at least one or more of argon, nitrogen, and H2S gas mixed in any proportion.

[0011] Further, step S3 includes: opening the lid of the ball mill jar, taking out the grinding balls and powder, separating the grinding balls from the solid powder using a sieve with a mesh size of 90-120 mesh; then washing twice with a cleaning solution, and vacuum drying to obtain rare earth sulfide NaLa5S8 powder.

[0012] Furthermore, the cleaning solution in step S3 is a mixture of deionized water and anhydrous ethanol in a volume ratio of 1:1.

[0013] Furthermore, in the vacuum drying process described in step S3, the vacuum degree is 0.01 Pa to 20 Pa, and the drying temperature is 55°C to 80°C.

[0014] The present invention also provides an application of the rare earth sulfide NaLa5S8 transparent ceramic powder prepared by the preparation method, wherein the rare earth sulfide NaLa5S8 transparent ceramic powder is used in hyperspectral infrared optical transmission materials.

[0015] Beneficial effects The technical solution adopted in this invention utilizes a mechanochemical method to promote the solid-state reaction between rare earth lanthanum polysulfides and specific sodium source compounds. This allows for the preparation of cubic, thermodynamically stable lanthanum-based sulfide NaLa5S8 ultrafine powder for transparent ceramics under ambient temperature and in a closed system. The process involved in this invention effectively avoids the high-temperature conditions and prolonged sulfidation required in traditional methods for preparing lanthanum-based sulfide powders. It also avoids the drawbacks of prolonged high temperatures leading to high oxygen content, high sulfur oxide impurity content, and large particle size in the powder. Furthermore, it avoids the technical problem of easy oxidation of NaLa5S8 powder due to the high oxyphilicity of rare earth lanthanum, which is beneficial for achieving high infrared transmittance in NaLa5S8 transparent ceramics. Simultaneously, the process is simple, low-cost, and suitable for large-scale preparation of NaLa5S8 ultrafine powder, possessing broad technical application prospects. Attached Figure Description

[0016] Figure 1 The X-ray diffraction pattern of the NaLa5S8 powder prepared in Example 1 of this invention; Figure 2 SEM image of NaLa5S8 powder prepared in Example 1; Figure 3 The infrared transmission spectrum of the prepared NaLa5S8 material is shown. Detailed Implementation

[0017] The present invention will be further described below through specific embodiments and in combination, but this should not be construed as a limitation on the scope of protection of the present invention. Any non-essential changes and adjustments made by those skilled in the art based on the above-described invention shall fall within the scope of protection of the present invention.

[0018] The following are specific embodiments of the present invention: Example 1 S1. Thoroughly mix 1244.6g of LaS2 powder and 72.0g of NaCl powder to obtain 1316.6g of precursor powder; S2. Mechanochemical synthesis treatment of precursor powders: According to (grind ball mass):(precursor powder mass) = 1316.5g of silicon nitride grinding balls were weighed at a 1:1.0 ratio, including 263.3g of large balls with a diameter of 12mm, 395.0g of medium balls with a diameter of 7mm, and 658.3g of small balls with a diameter of 3mm. At an ambient temperature of 25℃, the precursor powder obtained in S1 and the grinding balls weighed in S2 were placed together in a modified grinding jar. The grinding jar was equipped with an inlet pipe and an outlet pipe along its rotation axis. The inlet pipe was fitted with a gas valve that allowed or stopped gas flow, and the outlet pipe was fitted with a detachable, pressure-sensitive balloon with volume expansion and contraction capabilities. The grinding jar lid was then sealed. Argon protective gas was introduced into the grinding jar through the inlet pipe, and the air in the grinding jar was vented through the outlet pipe. The inlet pipe was then closed, and a latex polymer balloon was installed at the outlet pipe. The grinding jar was rotated at 90 rpm. After grinding for 42 hours, the volume of the balloon at the outlet pipe no longer changed. After grinding for another hour, the grinding was stopped.

[0019] S3. Separate the solid powder, then wash and vacuum dry it: Open the lid of the ball mill jar, remove the grinding balls and powder, and separate the grinding balls from the solid powder using a sieve with a fineness of 90 mesh; then wash the powder twice with a cleaning solution made of deionized water and anhydrous ethanol in a volume ratio of 1:1, and then dry it under a vacuum of 20 Pa and a temperature of 80 °C to obtain a light yellow-green solid powder, namely rare earth sulfide NaLa5S8 powder.

[0020] Example 2 S1. Thoroughly mix 1462g of LaS2 powder and 370g of NaBr powder, which have been weighed separately, to obtain 1832g of precursor powder. S2. Mechanochemical synthesis treatment of precursor powders: According to (grind ball mass):(precursor powder mass) = 9160g of boron nitride grinding balls were weighed in a 1:0.2 ratio, including 916g of large balls with a diameter of 12mm, 2748g of medium balls with a diameter of 7mm, and 5496g of small balls with a diameter of 2mm. At an ambient temperature of 32℃, the precursor powder obtained in S1 and the grinding balls weighed in S2 were placed together in a modified grinding jar. The grinding jar was equipped with an inlet pipe and an outlet pipe along its rotation axis. The inlet pipe was fitted with a gas valve that allowed or stopped gas flow, and the outlet pipe was fitted with a detachable, pressure-sensitive balloon with volume expansion and contraction capabilities. The grinding jar lid was then sealed. Nitrogen protective gas was introduced into the grinding jar through the inlet pipe, and the air in the grinding jar was vented through the outlet pipe. The inlet pipe was then closed, and a latex polymer balloon was installed at the outlet pipe. The grinding jar was rotated at 180 rpm. After grinding for 19 hours, the volume of the balloon at the outlet pipe no longer changed. After grinding for another hour, the grinding was stopped.

[0021] S3. Separate the solid powder, then wash and vacuum dry it: Open the lid of the ball mill jar, remove the grinding balls and powder, and separate the grinding balls from the solid powder using a sieve with a fineness of 120 mesh. Then, wash the powder twice with a cleaning solution made of deionized water and anhydrous ethanol in a volume ratio of 1:1. After vacuum drying at a vacuum degree of 10 Pa and a temperature of 70 °C, a light yellow-green solid powder, namely rare earth sulfide NaLa5S8 powder, is obtained.

[0022] Example 3 S1. Thoroughly mix 1462g of LaS2 powder and 410g of NaI powder, which have been weighed separately, to obtain 1872g of precursor powder. S2. Mechanochemical synthesis treatment of precursor powders: Weigh 851g of molybdenum disilicide grinding balls according to a ratio of (grind ball mass):(precursor powder mass) = 1:2.2, including 110g of large balls with a diameter of 9mm, 230g of medium balls with a diameter of 6mm, and 511g of small balls with a diameter of 3mm. At an ambient temperature of 2℃, place the precursor powder obtained in S1 and the grinding balls weighed in S2 together in a modified ball mill jar. The ball mill jar is equipped with an inlet pipe and an outlet pipe along the rotation axis. The inlet pipe is equipped with a gas valve that allows or stops gas flow, and the outlet pipe is equipped with a detachable valve. A pressure-sensitive balloon with volume expansion and contraction function is used; then the ball mill jar lid is sealed; a protective gas with an argon volume percentage of 98% and an H2S volume percentage of 2% is introduced into the ball mill jar through the air inlet pipe, and the air in the ball mill jar is vented out through the air outlet pipe; then the air inlet pipe is closed, and a latex polymer balloon is installed at the outlet pipe; the ball mill jar is rotated at a speed of 160 rpm, and after ball milling for 55 hours, the volume of the balloon at the outlet pipe no longer changes, and ball milling is stopped after another hour.

[0023] S3. Separate the solid powder, then wash and vacuum dry it: Open the lid of the ball mill jar, remove the grinding balls and powder, and separate the grinding balls from the solid powder using a 100-mesh sieve. Then, clean the powder twice with a cleaning solution made of deionized water and anhydrous ethanol in a volume ratio of 1:1. After vacuum drying at a vacuum degree of 0.1 Pa and a temperature of 55℃, a light yellow-green solid powder, namely rare earth sulfide NaLa5S8 powder, is obtained.

[0024] Example 4 S1. Thoroughly mix 1786.8g of LaS2 powder and 154.3g of NaCl powder, which have been weighed separately, to obtain 1941.1g of precursor powder; S2. Mechanochemical synthesis treatment of precursor powders: Weigh 1078.4g of aluminum nitride grinding balls according to a ratio of (grinding ball mass):(precursor powder mass) = 1:1.8. This includes 215g of large balls (11mm diameter), 215g of medium balls (7mm diameter), and 648.4g of small balls (3mm diameter). At an ambient temperature of 29℃, place the precursor powder obtained in S1 and the grinding balls weighed in S2 together in a modified grinding jar. The grinding jar is equipped with an inlet pipe and an outlet pipe along the rotation axis. The inlet pipe is equipped with a gas valve that allows or stops gas flow, and the outlet pipe is equipped with a valve that allows for the loading of… Remove the pressure-sensitive balloon with volume expansion and contraction function; then seal the ball mill jar lid; fill the ball mill jar with a protective gas of 95% nitrogen and 5% H2S by volume through the air inlet pipe, and vent the air from the ball mill jar through the air outlet pipe; then close the air inlet pipe and install the latex polymer balloon at the air outlet pipe outlet; rotate the ball mill jar at a speed of 200 rpm, and after 22 hours of ball milling, the volume of the balloon at the air outlet pipe outlet no longer changes, and stop ball milling after another hour.

[0025] S3. Separate the solid powder, then wash and vacuum dry it: Open the lid of the ball mill jar, remove the grinding balls and powder, and separate the grinding balls from the solid powder using a sieve with a fineness of 92 mesh; then wash the powder twice with a cleaning solution made of deionized water and anhydrous ethanol in a volume ratio of 1:1, and then dry it under a vacuum of 0.1 Pa and a temperature of 70 °C to obtain a light yellow-green solid powder, namely rare earth sulfide NaLa5S8 powder.

[0026] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A low-temperature preparation method for NaLa5S8 transparent ceramic powder with high infrared light transmittance, characterized in that, The preparation method includes the following steps: S1. Mixing compound powder raw materials containing rare earth elements lanthanum source and sodium source to obtain precursor powder, wherein the rare earth element lanthanum source compound is a polysulfide LaS2, and the sodium source compound is one of NaCl, NaBr, and NaI; the amount of lanthanum source compound and sodium source compound added is calculated according to the following ratio: m:n = 5.0:(1.0~2.5), where m is the amount of substance of lanthanum source compound and n is the amount of substance of sodium source compound; S2. The precursor powder is treated by mechanochemical synthesis: At room temperature, the precursor powder and grinding balls are placed together in a ball mill jar and mechanochemical synthesis is carried out under a protective gas. S3. Separate the solid powder, then clean and vacuum dry it.

2. The method for preparing rare earth sulfide NaLa5S8 transparent ceramic powder according to claim 1, characterized in that, Step S2 includes: at room temperature, placing the precursor powder and grinding balls together in a modified ball mill jar, and then sealing the ball mill jar lid; first, filling the ball mill jar with protective gas through the air inlet pipe, and then venting the air from the ball mill jar through the air outlet pipe; then closing the air inlet pipe and installing a balloon at the outlet pipe; then rotating the ball mill jar at a speed of not less than 90 rpm for a ball milling time of not more than 96 hours, and carrying out mechanochemical synthesis under protective gas to allow the precursor powder to undergo a solid-state reaction; when the volume of the balloon at the outlet pipe no longer increases or changes, ball milling is stopped after another 1 hour.

3. The method for preparing rare earth sulfide NaLa5S8 transparent ceramic powder according to claim 2, characterized in that, The ambient temperature mentioned in step S2 is the atmospheric temperature.

4. The method for preparing rare earth sulfide NaLa5S8 transparent ceramic powder according to claim 2, characterized in that, The amount of grinding balls added in step S2 is: (mass of grinding balls): (mass of precursor powder) = 1:(0.2~3.5); The grinding ball is a hard non-metallic non-oxide ceramic grinding ball, including one of the following materials: silicon nitride, aluminum nitride, boron nitride, silicon carbide, tungsten carbide, zirconium boride, and molybdenum disilicide.

5. The method for preparing rare earth sulfide NaLa5S8 transparent ceramic powder according to claim 2, characterized in that, The grinding balls used in the mechanochemical synthesis in step S2 are a combination of large, medium and small balls. The diameter of the large balls is 9-12 mm, the diameter of the medium balls is 6-9 mm, and the diameter of the small balls is 2-6 mm. The large balls account for 10-20% of the total mass of the grinding balls, the medium balls account for 20-30% of the total mass of the grinding balls, and the small balls account for 50-70% of the total mass of the grinding balls.

6. The method for preparing rare earth sulfide NaLa5S8 transparent ceramic powder according to claim 2, characterized in that, The improved ball mill jar described in step S2 is equipped with an inlet pipe and an outlet pipe along the rotation axis of the ball mill jar body; the inlet pipe is equipped with a gas valve that allows or stops gas flow; the outlet pipe is equipped with a detachable, pressure-sensitive, and volume-expanding organic polymer balloon; the protective gas refers to at least one or more of argon, nitrogen, and H2S gas mixed in any proportion.

7. The method for preparing rare earth sulfide NaLa5S8 transparent ceramic powder according to claim 1, characterized in that, Step S3 includes: opening the lid of the ball mill jar, taking out the grinding balls and powder, separating the grinding balls from the solid powder using a sieve with a mesh size of 90-120 mesh, washing twice with a cleaning solution, and vacuum drying to obtain rare earth sulfide NaLa5S8 powder.

8. The method for preparing rare earth sulfide NaLa5S8 transparent ceramic powder according to claim 7, characterized in that, The cleaning solution in step S3 is a mixture of deionized water and anhydrous ethanol in a volume ratio of 1:

1.

9. The method for preparing rare earth sulfide NaLa5S8 transparent ceramic powder according to claim 7, characterized in that, In the vacuum drying process described in step S3, the vacuum degree is 0.01 Pa to 20 Pa, and the drying temperature is 55°C to 80°C.

10. An application of the rare earth sulfide NaLa5S8 transparent ceramic powder prepared by the preparation method described in claims 1-9, characterized in that, The rare earth sulfide NaLa5S8 transparent ceramic powder is used in hyperspectral infrared optical transmission materials.

Images