Lanthanum calcium sulfide transparent ceramic powder and preparation method thereof

Abstract

The invention is suitable for the technical field of ceramic materials, and relates to lanthanum calcium sulfide transparent ceramic powder and a preparation method thereof. Comprising the following steps: weighing nitrate containing La and Ca according to a certain molar ratio, respectively dissolving into deionized water, and uniformly mixing to obtain a solution A; adding a citric acid solution into the solution A, adjusting the pH value with ammonia water, and stirring to obtain a mixed solution; the mixed solution is heated and stirred for a period of time, white transparent sol is formed through hydrolysis and polymerization reaction, and then the sol is placed in a drying box to be dehydrated into dry gel; heating the dried gel at high temperature to obtain lanthanum calcium sulfide precursor powder; and putting the lanthanum-calcium sulfide precursor powder into a tubular furnace, and vulcanizing in a sulfur-containing atmosphere to obtain the lanthanum-calcium sulfide powder. The method has the beneficial effects that the operation steps are simple, and the production cost and the production difficulty are effectively reduced. And gel organic components are removed by means of spontaneous combustion treatment, and the raw material proportion and reaction conditions are accurately controlled, so that the powder purity is greatly improved. In the hydrolysis and polymerization reaction, citric acid complexation is utilized and reaction conditions are strictly controlled, so that the particle size of the powder is uniform, the dispersity is good, and the transparency, the mechanical property and the optical property of the transparent ceramic are improved. Besides, by adjusting parameters such as raw material proportion, solution pH value, reaction temperature and time and the like, the performance of the powder is flexibly regulated and controlled, and diversified requirements on the performance of the lanthanum calcium sulfide ceramic powder in different application scenes are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic powders, and particularly relates to a calcium lanthanum sulfide transparent ceramic powder and a preparation method thereof. Background Art

[0002] Infrared optical materials are the cornerstone for the realization of infrared imaging and guidance technologies. With their unique optical properties, they are widely used in the manufacture of key components such as precision windows, radomes, filters, and prisms. Infrared transparent window materials are important elements in thermal imaging and can collect the energy (heat) naturally radiated by objects. The body temperatures of humans and most animals are around 300K, and the radiation is the largest in the long-wave infrared (LWIR) region of 10μm. Based on this, we began to search for window materials that can transmit LWIR. Currently, known competitive LWIR window materials, such as ZnS, ZnSe, GaAs, single-crystal Ge, and chalcogenide glasses, have good thermal, optical, and mechanical properties. However, ZnS, ZnSe, GaAs, and single-crystal Ge exhibit high thermal conductivity, low hardness, and poor corrosion resistance in harsh environments. Although chalcogenide glasses have excellent infrared transmittance, their low hardness and low softening temperature limit their applications in harsh environments and at high temperatures. With the increasingly in-depth application of infrared technology in multiple important fields such as military reconnaissance, environmental monitoring, medical diagnosis, and astronomical observation, the demand for new IR transparent optical materials with a wide transmission range, high transmittance, low absorption coefficient, and good mechanical and chemical stability is becoming more and more urgent.

[0003] Calcium lanthanum sulfide ceramics are a kind of infrared optical transparent ceramics, which have excellent properties such as isotropy, wide transmission band, high hardness, good rain erosion resistance, and wear resistance, and can be widely used in military facilities such as infrared guidance windows, dome materials, transparent armor, and optoelectronic devices under extreme conditions. As a highly potential transparent ceramic material, the properties of calcium lanthanum sulfide largely depend on the quality of the ceramic powder. The methods for preparing calcium lanthanum sulfide ceramic powders include solid-phase method, co-precipitation method, alkoxide method, wet chemical pyrolysis method, etc. However, these methods have problems such as complex preparation processes, low powder purity, and uneven particle size distribution, which severely limit the application of calcium lanthanum sulfide ceramics in high-performance optical and electronic components and other fields. Therefore, it is necessary to develop a preparation method for high-efficiency and high-quality calcium lanthanum sulfide ceramic powders. Summary of the Invention

[0004] 1. Object of the Invention

[0005] The object of the present invention is to provide a method for simply and efficiently preparing calcium lanthanum sulfide ceramic powders with high purity and uniform particle size to meet the application requirements of transparent ceramic materials in high-performance fields.

[0006] 2. Technical Solution

[0007] A production method for preparing calcium lanthanum sulfide powder, a transparent ceramic material, includes the following steps:

[0008] S1: Raw material preparation:

[0009] Weigh lanthanum (La) and calcium (Ca) nitrates as raw materials respectively, dissolve them in deionized water according to a certain molar ratio, and control the molar concentration of metal ions to prepare solution A.

[0010] S2: Adding complexing agent and adjusting pH value:

[0011] Add citric acid solution to the prepared solution A, and then adjust the pH value of the mixture with ammonia water. In this mixture, the total molar number of metal ions to citric acid is 1:1.2 - 3.

[0012] S3: Forming sol and gel:

[0013] Heat and stir the mixture. During this process, the solution undergoes hydrolysis and polymerization reactions to form a white transparent sol. Place the sol liquid in an oven at a certain temperature, and through the dehydration process, the sol gradually turns into a dry gel.

[0014] S4: Obtaining precursor powder through self - combustion treatment:

[0015] Put the obtained dry gel into a muffle furnace, keep it at a certain temperature for a period of time for self - combustion treatment. After the self - combustion treatment, a white powder - like sub - micron - level powder product can be obtained, and this product is the calcium lanthanum sulfide precursor powder.

[0016] S5: Obtaining powder through sulfidation treatment

[0017] Place the obtained calcium lanthanum sulfide precursor powder in a tube furnace, and under a sulfur - containing atmosphere, after high - temperature sulfidation for a period of time, the obtained powder is the calcium lanthanum sulfide powder.

[0018] Further, the nitrates of La and Ca in the first step are lanthanum nitrate hexahydrate and calcium nitrate tetrahydrate respectively, the molar ratio is La / Ca = 2.0 - 10.0, and the molar concentration of metal ions is 0.1 - 0.4 mol / L.

[0019] Further, in the second step, the ratio of the total molar number of metal ions to citric acid is 1:1.2 - 3, and the pH of the solution is 1 - 5.

[0020] Further, in the third step, the mixture is heated for 2 - 6 hours to obtain a transparent colloid, the drying temperature of the oven is 60 - 90 °C, and the drying duration is 6 - 24 h.

[0021] Further, in the fourth step, the temperature of the muffle furnace is 500 - 900 °C, and the holding time is 0.5 - 3 h.

[0022] Further, the sulfur-containing atmosphere in the fifth step is hydrogen sulfide, carbon disulfide, a mixed gas of hydrogen sulfide and hydrogen, a mixed gas of hydrogen sulfide and nitrogen, and a mixed gas of carbon disulfide and nitrogen. The sulfidation time is 1-9 h, and the sulfidation temperature is 800-1300 °C.

[0023] Advantages of the present invention:

[0024] (1) Simple process: The preparation method of the present invention has simple and clear steps. Compared with traditional methods, it reduces complex process flows and cumbersome operation links, and reduces production costs and production difficulties. (2) High powder purity: Through spontaneous combustion treatment, organic components in the gel can be effectively removed, avoiding the influence of impurities on the powder purity. At the same time, accurately controlling the ratio of raw materials and reaction conditions further ensures the high purity of the product.

[0025] (3) Good particle size uniformity: During the hydrolysis and polymerization reactions, through the complexing action of citric acid and strictly controlled reaction conditions, the generated nano-powder has uniform particle size and good dispersibility. Such powders with uniform particle size are of great significance for the preparation of high-quality transparent ceramic materials, and can improve the transparency, mechanical properties, optical properties, etc. of the ceramics.

[0026] (4) Strong controllability: By adjusting parameters such as the ratio of raw materials, solution pH value, reaction temperature and time, the performance of the powder can be flexibly regulated, so as to meet the diverse requirements for the performance of lanthanum calcium sulfide ceramic powder under different application scenarios. Description of the drawings

[0027] Figure 1 It is the XRD pattern of the lanthanum calcium sulfide powder in Example 1 of the present invention.

[0028] Figure 2 It is the SEM image of the lanthanum calcium sulfide precursor in Example 1 of the present invention.

[0029] Figure 3 It is the SEM image of the lanthanum calcium sulfide powder in Example 1 of the present invention.

[0030] Figure 4 It is the EDS pattern of the lanthanum calcium sulfide powder in Example 1 of the present invention. Detailed implementation manners

[0031] The present invention will be further described below through specific examples in combination with, but it should not be understood as a limitation to the protection scope of the present invention. Those skilled in the art make some non-essential changes and adjustments based on the content of the above invention, which all belong to the protection scope of the present invention.

[0032] The following are specific examples of the present invention:

[0033] Example 1

[0034] (1) Accurately weigh 2.3 mol of lanthanum nitrate hexahydrate and 1 mol of calcium nitrate tetrahydrate. After mixing them, dissolve them in an appropriate amount of deionized water to make the molar concentration of metal ions reach 0.1 mol / L, obtaining a mixed solution A.

[0035] (2) Add 3.96 mol of citric acid solution to solution A, and then slowly adjust the pH value of the mixed solution to 2 with ammonia water. In this mixed solution, ensure that the total molar number of metal ions to citric acid is 1:1.2.

[0036] (3) Stir the mixed solution on a heating and stirring device at an appropriate speed for 2 hours to cause hydrolysis and polymerization reactions to form a white transparent sol. Subsequently, place the sol in an oven at 90 °C until dehydration forms a dry gel.

[0037] (4) Put the dry gel into a muffle furnace, keep it at 800 °C for 1 hour, and then conduct self-ignition treatment to obtain a white powdery lanthanum calcium sulfide precursor.

[0038] (5) Put the obtained precursor powder into a tube furnace, keep it at 1250 °C for 4 hours under a H2S gas stream to obtain a yellow powdery lanthanum calcium sulfide powder.

[0039] Lanthanum oxide and calcium oxide were obtained before sulfidation. It can be seen from Figure 1 the XRD pattern that lanthanum calcium sulfide powder was obtained after sulfidation at 1250 °C for 4 h. Figure 2 This is the SEM image of the precursor powder obtained in Example 1 of the present invention. It can be seen from Figure 3 it that the lanthanum calcium sulfide powder obtained in the present invention has small and uniform particle sizes, which is beneficial for preparing ceramics with excellent properties. It can be seen from Figure 4 the EDS pattern that La, Ca, and S elements are evenly distributed, and La and S elements are the main elements.

[0040] Example 2

[0041] (1) Accurately weigh 2.3 mol of lanthanum nitrate hexahydrate and 1 mol of calcium nitrate tetrahydrate. After mixing them, dissolve them in an appropriate amount of deionized water to make the molar concentration of metal ions reach 0.1 mol / L, obtaining a mixed solution A.

[0042] (2) Add 4.95 mol of citric acid solution to solution A, and then adjust the pH value of the mixed solution to 2 with ammonia water, where the total molar number of metal ions to citric acid is 1:1.5.

[0043] (3) Heat and stir the mixed solution for 4 hours. After a white transparent sol is formed, place it in a drying oven at 90 °C for dehydration to obtain a dry gel.

[0044] (4) Put the dry gel into a muffle furnace, carry out spontaneous combustion treatment after holding at 800 °C for 1 hour to obtain a calcium lanthanum sulfide precursor.

[0045] (5) Put the obtained precursor powder into a tube furnace, hold at 1250 °C for 4 hours under a H2S gas flow to obtain a yellow powder of calcium lanthanum sulfide powder.

[0046] Example 3

[0047] (1) Accurately weigh 2.7 mol of lanthanum nitrate hexahydrate and 1 mol of calcium nitrate tetrahydrate. After mixing them, dissolve them in an appropriate amount of deionized water to make the molar concentration of metal ions reach 0.2 mol / L to obtain a mixed solution A.

[0048] (2) Add 3.96 mol of citric acid solution to solution A, and then adjust the pH value of the mixed solution to 4 with ammonia water, where the total molar number of metal ions to citric acid is 1:1.2.

[0049] (3) Heat and stir the mixed solution for 2 hours. After a white transparent sol is formed, place it in a drying oven at 90 °C for dehydration to obtain a dry gel.

[0050] (4) Put the dry gel into a muffle furnace, carry out spontaneous combustion treatment after holding at 800 °C for 1 hour to obtain a calcium lanthanum sulfide precursor.

[0051] (5) Put the obtained precursor powder into a tube furnace, hold at 1250 °C for 4 hours under a H2S gas flow to obtain a yellow powder of calcium lanthanum sulfide powder.

[0052] It can be seen from the above examples that the method of the present invention can stably prepare high-quality calcium lanthanum sulfide ceramic nano-powders, and the process parameters can be adjusted according to actual needs to meet different application requirements.

Claims

1. A calcium lanthanum sulfide transparent ceramic powder and a preparation method thereof, characterized in that, The preparation method includes the following steps: S1: Raw material preparation: Weigh the nitrates of La and Ca as raw materials respectively, dissolve them in deionized water according to a certain molar ratio, and control the molar concentration of metal ions to prepare solution A. S2: Adding complexing agent and adjusting pH value: Add citric acid solution to the prepared solution A, and then adjust the pH value of the mixed solution with ammonia water. In this mixed solution, the ratio of the total molar number of metal ions to citric acid is 1:1.2 - 3. S3: Forming sol and gel: Heat and stir the mixed solution. During this process, the solution undergoes hydrolysis and polymerization reactions to form a white transparent sol. Place the sol liquid in an oven at a certain temperature, and through the dehydration process, the sol gradually turns into a dry gel. S4: Obtaining precursor powder by self - combustion treatment: Put the obtained dry gel into a muffle furnace, keep it at a certain temperature for a period of time for self - combustion treatment. After the self - combustion treatment, a white powder - like nano - powder product can be obtained, and this product is the precursor powder of calcium lanthanum sulfide. S5: Obtaining powder by sulfidation treatment: Place the obtained precursor powder of calcium lanthanum sulfide in a tube furnace. Under a sulfur - containing atmosphere, after high - temperature sulfidation for a period of time, the obtained powder is the calcium lanthanum sulfide powder.

2. The lanthanum calcium sulfide transparent ceramic powder according to claim 1 and its preparation method are characterized in that, As described in the first step, the nitrates of La and Ca containing are lanthanum nitrate hexahydrate and calcium nitrate tetrahydrate respectively, the molar ratio is La / Ca = 2.0 - 10.0, and the molar concentration of metal ions is 0.1 - 0.4 mol / L.

3. A lanthanum calcium sulfide transparent ceramic powder and a preparation method thereof according to claim 1, characterized in that, As described in the second step, the ratio of the total molar number of metal ions to citric acid is 1 - 4:1, and the pH of the solution is 1 - 5.

4. A lanthanum calcium sulfide transparent ceramic powder and a preparation method thereof according to claim 1, characterized in that, As described in the third step, heat the mixture for 2 - 6 hours to obtain a transparent colloid, the drying temperature of the oven is 60 - 90 °C, and the drying time is 6 - 24 h.

5. A lanthanum calcium sulfide transparent ceramic powder and a preparation method thereof according to claim 1, characterized in that, As described in the fourth step, the temperature of the muffle furnace is 500 - 900 °C, and the heat - preservation time is 0.5 - 3 h.

6. The lanthanum calcium sulfide transparent ceramic powder and its preparation method according to claim 1, characterized in that, As described in the fifth step, the sulfur - containing atmosphere is hydrogen sulfide, carbon disulfide, a mixed gas of hydrogen sulfide and hydrogen, a mixed gas of hydrogen sulfide and nitrogen, and a mixed gas of carbon disulfide and nitrogen. The sulfidation time is 1 - 9 h, and the sulfidation temperature is 800 - 1300 °C.

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