Lanthanum calcium sulfide transparent ceramic powder as well as preparation method and application thereof

Abstract

The invention relates to the technical field of ceramic materials, in particular to calcium lanthanum sulfide transparent ceramic powder and a preparation method and application thereof.The preparation method comprises the following steps that CaS powder and La2S3 powder are placed in a sealed quartz container, the raw materials are mixed to be uniform in an ultrasonic rotation mode, high-temperature swing sintering is conducted in a vacuum state, then slow cooling is conducted to the room temperature, and the calcium lanthanum sulfide transparent ceramic powder is obtained. And grinding to obtain the CaLa2S4 powder. According to the preparation method of the CaLa2S4 powder, the problem of sulfur loss can be avoided in a limited mode, toxic and dangerous gas of hydrogen sulfide or carbon disulfide is not used, the preparation method is safe, efficient, easy to operate, low in raw material cost and suitable for industrial batch production, and further development of the infrared transparent ceramic application technology is expected to be promoted.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of infrared transparent ceramic materials, in particular to a lanthanum calcium sulfide transparent ceramic powder and a preparation method and application thereof. BACKGROUND

[0002] An infrared window is an important component of an infrared photoelectric system, is located at the front end of the system, has the functions of transmitting target signals, maintaining aerodynamic shape and protecting internal precise photoelectric components, and in modern comprehensive strength competition, an infrared photoelectric system with excellent performance has become an indispensable winning key and is widely used in various unmanned planes, fighter planes, air-to-air missiles and defense interception systems. With the development of technology, countries put forward faster and farther combat requirements for hypersonic aircraft and hypersonic weapons, and infrared photoelectric system window materials, especially long-wave infrared window materials, are difficult to match the development goal of "faster and farther" of the above aircraft, and the main bottleneck is the lack of available materials and preparation technology.

[0003] Compared with glass and single crystal materials, ceramics often have higher thermal conductivity and strength, can be formed by sintering of powders, have short preparation cycles, low production costs and are easier to prepare large-size devices according to required shapes. Lanthanum calcium sulfide (abbreviated as CaLa2S4) is an alkaline earth metal-rare earth sulfide with a cubic phase crystal structure, has good transmittance in a wavelength range of 0.5-14 microns, and has a hardness of 570 kgf / mm 2 , and a Young's modulus of 96 GPa. Due to the unique advantages of CaLa2S4 materials in infrared optical transmission, endurance to harsh environments and environmental erosion resistance, CaLa2S4 infrared transparent ceramics have great potential in practical applications such as infrared windows of high-power laser weapons, high-speed aircraft and high-Mach missile fairings, and are the preferred window materials for future infrared detection systems of super-speed aircraft.

[0004] The powder purification and densification sintering process is the key to obtaining good optical properties of CaLa2S4 infrared transparent ceramics, and the first step to obtain ideal performance CaLa2S4 infrared transparent ceramics is to prepare pure powder, and the prepared powder has 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 powder particle morphology; and 5) good powder dispersibility. In summary, transparent ceramic preparation needs to use ultra-pure, high-fineness powder raw materials, add as few additives as possible and reduce impurity second phases, and the forming, sintering and other processes are strictly controlled to ensure that pores and impurities are fully discharged, so that the ceramic density is close to the theoretical density, and then high-transmittance transparent ceramics can be prepared.

[0005] Currently, the preparation methods of CaLa2S4 powder mainly include precursor sulfidation method, thermal decomposition method, carbonate co-deposition method, solution combustion method, etc. These methods have complex process and cannot guarantee batch stability, which is not conducive to the industrialized production of transparent ceramics. Taking the precursor sulfidation method as an example, La(OH)3 and CaCO3 are dissolved in HNO3, then (NH4)2CO3 is slowly added and stirred, the obtained precipitate is dried to obtain a precursor, and the precursor is added into a tube furnace, CS2 or H2S is used as a sulfidation agent, and CaLa2S4 powder is obtained by sulfidation at about 900 DEG C. The precursor method needs to sulfidize the precursor at high temperature for a long time, and the sulfidation medium used is CS2 or H2S gas. Although this method can prepare CaLa2S4 ceramic powder with high purity, the use of sulfidation gas is highly toxic, flammable and explosive, which has great safety hazards.

[0006] Although significant progress has been made in the preparation of CaLa2S4 powder in recent years, there are still challenges such as complex process, particle size and purity control, and batch stability cannot be guaranteed. Therefore, improving the powder preparation process has become one of the technologies that need to be broken through to restrict the industrial application of CaLa2S4 transparent ceramics. SUMMARY

[0007] The embodiments of the present application provide a kind of to at least solve one of the problems existing in the related art. To achieve this purpose, the present application is realized by the following technical solutions.

[0008] The first aspect of the present application provides a method for preparing lanthanum calcium sulfide transparent ceramic powder by solid phase reaction, the main mechanism is that high vacuum inhibits the oxidation of raw materials and target phase→ultrasonic rotation promotes uniform mixing of raw materials→high temperature provides diffusion energy→swing promotes uniform reaction→fine grinding controls particle size, specifically comprising the following steps: CaS powder and La2S3 powder are directly weighed according to the proportion, vacuum sealed in a container, then mixed uniformly by ultrasonic rotation, then high-temperature swing sintering is carried out, then cooled to room temperature, and then ground to obtain CaLa2S4 powder.

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

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

[0011] In some preferred embodiments, the temperature increasing rate of the high-temperature swing sintering is 5-20 DEG C / min, the temperature of the high-temperature swing sintering is 900-1200 DEG C, the time is greater than or equal to 3h, the swing speed is less than or equal to 20 times / min, and the swing sintering promotes the contact between raw materials, breaks local agglomeration, enhances reaction uniformity and prevents the generation of other non-target phases through mechanical collision and turnover between raw material particles.

[0012] In some preferred embodiments, the pressure of the vacuum state is less than or equal to 3.5*10 -5 Pa.

[0013] In some preferred embodiments, the purity of the CaS powder and the La2S3 powder is greater than or equal to 99.99%, and the particle size is less than 100 mu m.

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

[0015] In some preferred embodiments, the grinding is performed by using high-energy ball milling under inert gas conditions, and the water oxygen content in the inert gas is controlled to be less than or equal to 1ppm.

[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 is performed for 30-360 min, the ball milling speed is 200-800 rpm, tungsten carbide balls are used for high-energy ball milling, the ball-to-material mass ratio is (10-20):1, and the diameter of the tungsten carbide is 5-12 mm.

[0018] In some preferred embodiments, the purity of the CaLa2S4 powder is greater than or equal to 99.9%.

[0019] The second aspect of the present application provides a calcium lanthanum sulfide transparent ceramic powder obtained by the above preparation method.

[0020] The third aspect of the present application provides an application of the calcium lanthanum sulfide transparent ceramic powder in an infrared photoelectric system.

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

[0022] The preparation method can avoid the problem of sulfur loss, does not use toxic and dangerous gases such as hydrogen sulfide and carbon disulfide, is safe and efficient, simple to operate, low in raw material cost, suitable for industrialized batch production, and can promote the further development of infrared transparent ceramic application technology. BRIEF DESCRIPTION OF DRAWINGS

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

[0024] Figure 1 The scanning electron microscope phase detection diagram of the CaLa2S4 powder synthesized in the embodiment 1 of the present application;

[0025] Figure 2 The electron microscope photo of the powder of the CaLa2S4 powder synthesized in the embodiment 2 of the present application;

[0026] Figure 3 The particle size distribution diagram of the powder of the CaLa2S4 powder synthesized in the embodiment 3 of the present application.

[0027] Figure 4 The XRD phase detection diagram of the CaLa2S4 powder synthesized in the comparative example 1 of the present application. DETAILED DESCRIPTION

[0028] To make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the embodiments of the present application will be described in detail below with reference to the drawings. However, those skilled in the art can understand that, in the embodiments of the present application, many technical details are proposed in order to make the readers better understand the present application. However, the technical scheme claimed by the present application can be realized even without these technical details and based on various changes and modifications of the following embodiments. The following embodiments are classified for the convenience of description, and should not constitute any limitation on the specific embodiments of the present application, and the embodiments can be combined and referenced with each other without contradiction.

[0029] Embodiment 1

[0030] In an argon atmosphere 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 quickly transferred into a quartz reaction container, and when the vacuum reached 1×10 -5Pa, the quartz reaction vessel is sealed, and the quartz vessel is placed in an ultrasonic water bath for 360° rotation at a rotation speed of 8 rpm for 10 h of mixing time. Then, the vessel is transferred to a rocking furnace for solid phase sintering. The solid phase rocking sintering schedule in the high-temperature furnace is as follows: from room temperature to 1150°C at a rate of 10°C / min, solid phase reaction sintering time of 6 h, and then slowly cooled to room temperature. During the solid phase reaction sintering, the furnace body starts to rock at a temperature of 550°C, the rocking rotation speed is 2 rotations / min, and the rocking angle is 180°.

[0031] The high-energy ball milling conditions are as follows: under a pure nitrogen atmosphere, the ball milling time is 300 min, the ball milling rotation speed is 300 rpm, and the ball-to-material mass ratio is 20:1, i.e., 826 grams of 15 mm tungsten carbide balls are placed in a high-energy ball mill tank together with the raw materials for sealing and locking for ball milling, to obtain ultra-pure 99.9% high-fineness CaLa2S4 powder.

[0032] Example 2

[0033] In an argon atmosphere 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%) are quickly transferred to a quartz reaction vessel. When the vacuum reaches 2.5×10 -5 Pa, the quartz reaction vessel is sealed, and the quartz vessel is placed in an ultrasonic water bath for 360° rotation at a rotation speed of 8 rpm for 10 h of mixing time. Then, the vessel is transferred to a rocking furnace for solid phase sintering. The solid phase rocking sintering schedule in the high-temperature furnace is as follows: from room temperature to 1150°C at a rate of 10°C / min, solid phase reaction sintering time of 6 h, and then slowly cooled to room temperature. During the solid phase reaction sintering, the furnace body starts to rock at a temperature of 550°C, the rocking rotation speed is 2 rotations / min, and the rocking angle is 180°.

[0034] from room temperature to 1180°C at a rate of 8°C / min, solid phase reaction sintering time of 4 h, and then slowly cooled to room temperature. During the sintering, the furnace body starts to rock at a temperature of 550°C, the rocking rotation speed is 5 rotations / min, and the rocking angle is 180°.

[0035] The high-energy ball milling conditions are as follows: under a pure nitrogen atmosphere, the ball milling time is 300 min, the ball milling rotation speed is 300 rpm, and the ball-to-material mass ratio is 20:1, i.e., 826 grams of 15 mm tungsten carbide balls are placed in a high-energy ball mill tank together with the raw materials for sealing and locking for ball milling, to obtain ultra-pure 99.9% high-fineness CaLa2S4 powder.

[0036] Example 3

[0037] In an argon atmosphere 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%) are quickly transferred to a quartz reaction vessel. When the vacuum reaches 2.5×10 -5Pa, the container is sealed, and the container is placed in an ultrasonic water bath for 360° rotation at a rotation speed of 5 rpm for 11 h. The raw materials in the container are then subjected to solid-phase sintering, with a swing temperature rising program as follows: rising from room temperature to 1100°C at a speed of 15°C / min, swing rotation speed of 18 r / min, swing angle of 150°, solid-phase reaction sintering time of 7 h, and slow cooling to room temperature.

[0038] The high-energy ball milling conditions are as follows: high-purity nitrogen atmosphere, ball milling time of 100 min, ball milling speed of 400 rpm, and ball-to-material mass ratio of 15:1, i.e., 500 g of 10 mm tungsten carbide balls and raw materials are placed in a high-energy ball mill tank for sealing and locking for ball milling, to obtain ultra-pure 99.93% high-fineness CaLa2S4 powder.

[0039] Comparative Example 1

[0040] In an argon atmosphere 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%) are quickly transferred to a quartz reaction container. When the vacuum reaches 2×10 -2 Pa, the container is sealed, and the container is placed in an ultrasonic water bath for 360° rotation at a rotation speed of 5 rpm for 11 h. The raw materials in the container are then subjected to solid-phase sintering, with a swing temperature rising program as follows: rising from room temperature to 1100°C at a speed of 15°C / min, swing rotation speed of 18 r / min, swing angle of 150°, solid-phase reaction sintering time of 7 h, and slow cooling to room temperature.

[0041] The high-energy ball milling conditions are as follows: high-purity nitrogen atmosphere, ball milling time of 100 min, ball milling speed of 400 rpm, and ball-to-material mass ratio of 15:1, i.e., 500 g of 10 mm tungsten carbide balls and raw materials are placed in a high-energy ball mill tank for sealing and locking for ball milling, to obtain ultra-pure 99.93% high-fineness CaLa2S4 powder.

[0042] Comparative Example 2

[0043] In an argon atmosphere 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%) are quickly transferred to a quartz reaction container. When the vacuum reaches 2×10 -5Pa, the quartz container is sealed, and the container is placed in an ultrasonic water bath, rotated at 360°, at a rotation speed of 12 rpm, and mixed for 10 h. Then, the raw materials in the container are solid-phase sintered. The solid-phase swing sintering system in the high-temperature furnace is as follows: the temperature is raised from room temperature to 1180°C at a speed of 8°C / min, and the solid-phase reaction sintering time is 4 h. During sintering, the furnace body starts to swing at a temperature of 550°C, the swing rotation speed is 5 rotations / min, and the swing angle is 180°. After sintering, the container is slowly cooled to room temperature.

[0044] The high-energy ball milling conditions are as follows: the ball milling time is 200 min, the ball milling rotation speed is 500 rpm, and the ball-to-material mass ratio is 11:1, i.e., 545 grams of 9 mm tungsten carbide balls are sealed and locked together with the raw materials in a high-energy ball mill tank for ball milling. In this way, ultra-pure 99.92% high-fineness CaLa2S4 powder is obtained.

[0045] Compared with Example 2, the ultrasonic rotation speed is improved, but the result is not significantly affected.

[0046] Although the embodiments of the present application have been shown and described, it is understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application 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.

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 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.

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

5. 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).

6. 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.

7. The preparation method according to claim 6, 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.

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

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

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

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