Calcium lanthanum sulfide transparent ceramic powder, preparation method and application thereof

Abstract

This invention relates to the field of ceramic materials technology, and more particularly to a transparent lanthanum calcium sulfide ceramic powder, its preparation method, and its applications. The preparation method includes the following steps: placing CaS powder and La2S3 powder in a sealed quartz container, mixing the raw materials uniformly by ultrasonic rotation, performing high-temperature shaking sintering under vacuum, then slowly cooling to room temperature, and grinding to obtain CaLa2S4 powder. The CaLa2S4 powder preparation method provided by this invention can largely avoid the problem of sulfur loss, does not use toxic and dangerous gases such as hydrogen sulfide or carbon disulfide, and is safe, efficient, simple to operate, and has low raw material costs. It is suitable for industrial mass production and is expected to promote the further development of infrared transparent ceramic application technology.

Description

Technical Field

[0001] This invention relates to the field of infrared transparent ceramic materials technology, and in particular to a lanthanum calcium sulfide transparent ceramic powder, its preparation method, and its application. Background Technology

[0002] Infrared windows are crucial components of infrared optoelectronic systems, located at the very front of the system. They serve to transmit target signals, maintain aerodynamic shape, and protect internal precision optoelectronic components. In modern integrated warfare, high-performance infrared optoelectronic systems have become indispensable keys to victory, widely used in various unmanned aerial vehicles (UAVs), fighter jets, air-to-air missiles, and defense and interception systems. However, with technological advancements, countries are demanding faster and farther-range operations for hypersonic vehicles and hypersonic weapons. Infrared optoelectronic system window materials, especially long-wave infrared window materials, are insufficient to meet these development goals, primarily due to a lack of suitable materials and fabrication technologies.

[0003] Compared to glass and single-crystal materials, ceramics often possess higher thermal conductivity and strength. Furthermore, they can be sintered from powder, resulting in shorter manufacturing cycles, lower production costs, and easier fabrication of large-size devices according to desired shapes. Lanthanum calcium sulfide (CaLa2S4) is an alkaline earth metal-rare earth sulfide with a cubic crystal structure. It exhibits good transmittance in the wavelength range of 0.5μm to 14μm and a hardness of up to 570 kgf / mm². 2 The Young's modulus is 96 GPa. Due to the unique advantages of CaLa2S4 material in infrared optical transmission, resistance to harsh environments, and resistance to environmental corrosion, CaLa2S4 infrared transparent ceramic has great potential in practical applications such as high-power laser weapons, infrared windows of high-speed aircraft, and high-Mach missile fairings. It is the preferred window material for infrared detection systems of future hypersonic aircraft.

[0004] Powder purification and densification sintering are crucial for achieving good optical properties in CaLa2S4 infrared transparent ceramics. The first step in obtaining ideal CaLa2S4 infrared transparent ceramics is the preparation of pure powder, which must possess the following characteristics: 1) high purity and low impurity content; 2) pure phase and uniform composition; 3) high sintering activity, small particle size, and uniform particle size distribution; 4) regular particle morphology; and 5) good powder dispersibility. In summary, the preparation of transparent ceramics requires the use of ultrapure, fine powder raw materials, the incorporation of as few additives as possible, and the reduction of impurity second phases. Simultaneously, strict control over molding and sintering processes is essential to ensure the full removal of pores and impurities, ultimately achieving a ceramic density close to the theoretical density, thus enabling the preparation of transparent ceramics with high light transmittance.

[0005] Currently, the main methods for preparing CaLa2S4 powder include precursor sulfidation, thermal decomposition, carbonate co-deposition, and solution combustion. These methods are complex and cannot guarantee batch stability, which is not conducive to the industrial production of transparent ceramics. Taking the precursor sulfidation method as an example, La(OH)3 and CaCO3 are dissolved in HNO3, and then (NH4)2CO3 is slowly added while stirring. The resulting precipitate is dried, and the precursor is then added to a tube furnace. CS2 or H2S is used as the sulfiding agent, and CaLa2S4 powder is obtained by high-temperature sulfidation at around 900℃. The precursor method requires long-term sulfidation of the precursor at high temperature, and the sulfidation medium used is CS2 or H2S gas. Although this method can produce CaLa2S4 ceramic powder with high purity, the sulfidation gas used is highly toxic, flammable, and explosive, posing significant safety hazards.

[0006] Although significant progress has been made in the preparation of CaLa2S4 powder in recent years, challenges remain, such as complex processes and the inability to guarantee batch stability in particle size and purity control. Therefore, improving the powder preparation process has become one of the technologies that urgently needs to be broken through in the industrial application of CaLa2S4 transparent ceramics. Summary of the Invention

[0007] The present invention provides a solution to at least address one of the problems existing in the related art. To achieve this objective, the present invention is implemented through the following technical solution.

[0008] The first aspect of this invention provides a method for preparing lanthanum calcium sulfide transparent ceramic powder by solid-state reaction. The main mechanism is: high vacuum inhibits the oxidation of raw materials and target phase → ultrasonic rotation promotes uniform mixing of raw materials → high temperature provides diffusion energy → rocking promotes uniform reaction → fine grinding controls particle size. Specifically, it includes the following steps: weighing CaS powder and La2S3 powder directly according to the ratio, vacuum sealing them in a container, then mixing them uniformly by ultrasonic rotation, then sintering them by high temperature rocking, then cooling them to room temperature, and grinding them to obtain CaLa2S4 powder.

[0009] Preferably, the container is a quartz ampoule, used to create a sealed high-vacuum environment to prevent the formation of oxide phases.

[0010] Preferably, the raw material premixing method is rotational ultrasound, which is used to promote contact mixing of the raw materials. Specifically, the quartz ampoule containing the raw materials is placed in a room temperature ultrasonic water bath, the quartz container is rotated 360° at a speed ≤10 rpm, and the mixing time is ≤12h.

[0011] In some preferred embodiments, the heating rate of the high-temperature swaying sintering is 5℃ / min to 20℃ / min, the temperature of the high-temperature swaying sintering is 900℃ to 1200℃, the time is ≥3h, and the swaying speed is ≤20 times / min. The swaying sintering further promotes the contact between raw materials through mechanical collision and tumbling between raw material particles, breaks up local agglomeration, enhances reaction uniformity, and prevents the formation of other non-target phases.

[0012] In some preferred embodiments, the pressure of the vacuum state is ≤3.5×10⁻⁶. -5 Pa.

[0013] In some preferred embodiments, the purity of both CaS powder and La2S3 powder is ≥99.99%, and the particle size is <100μm.

[0014] In some preferred embodiments, the molar mass ratio of the CaS powder to the La2S3 powder is 1:(1-1.02) to prevent the formation of a non-target third phase.

[0015] In some preferred embodiments, the specific steps of the grinding are as follows: the product is ground in an inert gas environment using a high-energy ball mill, wherein the water and oxygen content in the inert gas is controlled to be below 1 ppm.

[0016] In some preferred embodiments, the inert gas is independently one or more of Ar, N2, and He.

[0017] In some preferred embodiments, the high-energy ball milling time is 30 min to 360 min to prevent over-grinding from causing powder agglomeration and loss of powder activity. The ball milling speed is 200 rpm to 800 rpm. Tungsten carbide balls are used for high-energy ball milling, with a ball-to-material mass ratio of (10 to 20):1. The diameter of the tungsten carbide is 5 mm to 12 mm.

[0018] In some preferred embodiments, the purity of the CaLa2S4 powder is ≥99.9%.

[0019] A second aspect of the present invention provides a lanthanum calcium sulfide transparent ceramic powder, which is obtained by the preparation method described above.

[0020] The third aspect of this invention provides an application of lanthanum calcium sulfide transparent ceramic powder in infrared optoelectronic systems.

[0021] The embodiments of the present invention have the following beneficial effects:

[0022] The preparation method provided by this invention can largely avoid the problem of sulfur loss, does not use toxic and dangerous gases such as hydrogen sulfide or carbon disulfide, and is safe, efficient, simple to operate, and has low raw material costs. It is suitable for industrial mass production and is expected to promote the further development of infrared transparent ceramic application technology. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0024] Figure 1 This is a scanning electron microscope (SEM) phase analysis image of the synthesized CaLa2S4 powder in Example 1 of this invention.

[0025] Figure 2 This is an electron microscope image of the CaLa2S4 powder synthesized in Example 2 of the present invention;

[0026] Figure 3 This is a particle size distribution diagram of the CaLa2S4 powder synthesized in Example 3 of the present invention.

[0027] Figure 4 This is an XRD phase analysis diagram of the CaLa2S4 powder synthesized in Comparative Example 1 of this invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details are presented in the various embodiments of the present invention to facilitate a better understanding of this application. However, the technical solutions claimed in this application can be implemented even without these technical details and various changes and modifications based on the following embodiments. The division of the various embodiments below is for ease of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined with and referenced by each other without contradiction.

[0029] Example 1

[0030] In an argon-atmospheric glove box, 10.821 g of CaS powder (particle size < 100 μm, purity ≥ 99.99%) and 56.10 g of La2S3 powder (particle size < 100 μm, purity ≥ 99.99%) were weighed and rapidly transferred to a quartz reaction vessel. When the vacuum reached 1 × 10⁻⁶, the reaction was carried out. -5At Pa, the quartz reaction vessel was sealed and placed in an ultrasonic water bath. It was rotated 360° at a speed of 8 rpm for 10 hours. The vessel was then transferred to a swing furnace for solid-state sintering. The solid-state swing sintering regime in the high-temperature furnace was as follows: the temperature was increased from room temperature to 1150°C at a rate of 10°C / min, and the solid-state reaction sintering time was 6 hours. The furnace was then slowly cooled to room temperature. During the solid-state reaction sintering, the furnace body began to swing at a temperature of 550°C, with a swing speed of 2 rpm and a swing angle of 180°.

[0031] The high-energy ball milling conditions are as follows: under a pure nitrogen inert atmosphere, the ball milling time is 300 min, the ball milling speed is 300 rpm, and the ball-to-material mass ratio is 20:1. That is, 826 grams of 15 mm tungsten carbide grinding balls and raw materials are put into a high-energy ball milling jar, sealed and locked, and ball milling is carried out to obtain ultra-pure 99.9% fine powder CaLa2S4.

[0032] Example 2

[0033] In an argon-atmospheric glove box, 12.985 g of CaS powder (particle size < 100 μm, purity ≥ 99.99%) and 36.546 g of La2S3 powder (particle size < 100 μm, purity ≥ 99.99%) were rapidly transferred to a quartz reaction vessel. The reaction was carried out under a vacuum of 2.5 × 10⁻⁶. -5 At Pa, the quartz container was sealed and placed in an ultrasonic water bath for 360° rotation at 9 rpm for 10 hours. The raw materials inside the container were then subjected to solid-state sintering. The solid-state sintering regime in the high-temperature furnace was as follows:

[0034] The temperature was increased from room temperature to 1180℃ at a rate of 8℃ / min, and the solid-phase reaction sintering time was 4h. During sintering, the furnace body started to swing at a temperature of 550℃, with a swing speed of 5 rpm and a swing angle of 180°. After sintering, the container was slowly cooled to room temperature.

[0035] The high-energy ball milling conditions are as follows: under a high-purity nitrogen atmosphere, the ball milling time is 200 min, the ball milling speed is 500 rpm, and the ball-to-material ratio is 11:1, that is, 545 g of 9 mm tungsten carbide grinding balls and raw materials are placed together in a high-energy ball milling jar, sealed and locked, to obtain ultra-pure 99.92% fine powder CaLa2S4.

[0036] Example 3

[0037] In an argon-atmospheric glove box, 8.657 g of CaS powder (particle size < 100 μm, purity ≥ 99.99%) and 67.99 g of La2S3 powder (particle size < 100 μm, purity ≥ 99.99%) were transferred to a quartz reaction vessel. When the vacuum reached 1.5 × 10⁻⁶, -5At Pa, the container was sealed and placed in an ultrasonic water bath. It was rotated 360° at a speed of 5 rpm for 11 hours. Then, the raw materials in the container were sintered in solid phase. The solid phase sintering heating regime was as follows: the temperature was increased from room temperature to 1100°C at a rate of 15°C / min, the swing speed was 18 rpm, the swing angle was 150°, the solid phase reaction sintering time was 7 hours, and then it was slowly cooled to room temperature.

[0038] The high-energy ball milling conditions are as follows: under a high-purity nitrogen atmosphere, the ball milling time is 100 min, the ball milling speed is 400 rpm, and the ball-to-material ratio is 15:1, that is, 500 grams of 10 mm tungsten carbide grinding balls and raw materials are placed together in a high-energy ball milling jar, sealed and locked, to obtain ultra-pure 99.93% fine powder CaLa2S4.

[0039] Comparative Example 1

[0040] In an argon-atmospheric glove box, 8.657 g of CaS powder (particle size < 100 μm, purity ≥ 99.99%) and 44.90 g of La2S3 powder (particle size < 100 μm, purity ≥ 99.99%) were rapidly transferred to a quartz reaction vessel. The reaction was carried out under a vacuum of 2 × 10⁻⁶. -2 At Pa, the reaction vessel was sealed. The quartz container was placed in an ultrasonic water bath and rotated 360° at a speed of 8 rpm. After mixing for 10 hours, the raw materials in the container were sintered in solid phase. The solid phase rocking sintering regime in the high-temperature furnace was as follows: the temperature was increased from room temperature to 1100°C at a rate of 15°C / min, and the solid phase reaction sintering time was 7 hours. Then, it was slowly cooled to room temperature. During the solid phase reaction sintering, the furnace body started to rock at a temperature of 550°C, with a rocking speed of 2 rpm and a rocking angle of 150°.

[0041] The high-energy ball milling conditions are as follows: under a high-purity nitrogen atmosphere, the ball milling time is 10 minutes, the ball milling speed is 400 rpm, and the ball-to-material ratio is 15:1, that is, 815 grams of 10mm tungsten carbide grinding balls and raw materials are placed together in a high-energy ball milling jar, sealed and locked, and ball milling is carried out to obtain CaLa2S4 powder containing the impurity La2O2S. The impurity content is about 1.3wt%, and the purity of CaLa2S4 is reduced to below 98.7%.

[0042] Comparative Example 2

[0043] In an argon-atmospheric glove box, 12.985 g of CaS powder (particle size < 100 μm, purity ≥ 99.99%) and 36.546 g of La2S3 powder (particle size < 100 μm, purity ≥ 99.99%) were rapidly transferred to a quartz reaction vessel. The reaction was carried out under a vacuum of 2.5 × 10⁻⁶. -5At Pa, the quartz container was sealed and placed in an ultrasonic water bath. It was rotated 360° at a speed of 12 rpm for 10 hours. Then, the raw materials in the container were sintered in a solid state. The solid state sintering regime in the high-temperature furnace was as follows: the temperature was increased from room temperature to 1180°C at a rate of 8°C / min, and the solid state reaction sintering time was 4 hours. During sintering, the furnace body started to sway at a temperature of 550°C, with a swaying speed of 5 rpm and a swaying angle of 180°. After sintering, the container was slowly cooled to room temperature.

[0044] The high-energy ball milling conditions are as follows: under a high-purity nitrogen atmosphere, the ball milling time is 200 min, the ball milling speed is 500 rpm, and the ball-to-material ratio is 11:1, that is, 545 g of 9 mm tungsten carbide grinding balls and raw materials are placed together in a high-energy ball milling jar, sealed and locked, to obtain ultra-pure 99.92% fine powder CaLa2S4.

[0045] Compared with Example 2, the increase in ultrasonic rotation speed had no significant impact on the results.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing lanthanum calcium sulfide transparent ceramic powder, characterized in that, The process includes the following steps: CaS powder and La2S3 powder are placed in a sealed quartz container, mixed uniformly by ultrasonic rotation, sintered at high temperature under vacuum, then slowly cooled to room temperature, and ground by high-energy ball milling to obtain CaLa2S4 powder. The heating rate of the high-temperature swaying sintering is 5℃ / min~20℃ / min, the temperature of the high-temperature swaying sintering is 900℃~1200℃, the time is ≥3h, and the swaying speed is ≤20 times / min.

2. The preparation method according to claim 1, characterized in that, The ultrasonic rotation method involves placing a quartz container in a room-temperature ultrasonic water bath, rotating the quartz container 360° at a speed ≤10 rpm, and mixing for ≤12 hours.

3. The preparation method according to claim 1, characterized in that, The pressure under vacuum is ≤3.5×10⁻⁶. -5 Pa.

4. The preparation method according to claim 1, characterized in that, The purity of both CaS powder and La2S3 powder is ≥99.99%, the particle size is <100μm, and the molar mass ratio of the two is 1:(1~1.02).

5. The preparation method according to claim 1, characterized in that, The specific grinding steps are as follows: the product is ground in an inert gas environment using a high-energy ball mill, and the water and oxygen content in the inert gas is controlled to be below 1 ppm.

6. The preparation method according to claim 5, characterized in that, The high-energy ball milling time is 30 min to 360 min, the ball milling speed is 200 rpm to 800 rpm, tungsten carbide balls are used for high-energy ball milling, the ball-to-material mass ratio is (10 to 20): 1, and the diameter of the tungsten carbide is 5 mm to 12 mm.

7. The preparation method according to claim 6, characterized in that, The purity of the CaLa2S4 powder is ≥99.9%.

8. A transparent ceramic powder of lanthanum calcium sulfide, characterized in that, The preparation method according to any one of claims 1-7 is obtained.

9. The application of the lanthanum calcium sulfide transparent ceramic powder according to claim 8 in an infrared optoelectronic system.

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