Gadolinium oxysulfide powder based on molten salt method and preparation method of gadolinium oxysulfide powder
By using the molten salt method in the preparation of gadolinium sulfide powder, the synthesis temperature is reduced, and the product defects and high production costs caused by sulfur volatility at high temperature in the existing process are solved, and the preparation of gadolinium sulfide powder with high purity and uniform particles is achieved.
Patent Information
- Application Number
- CN202411651234.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-19
- Publication Date
- 2025-02-28
AI Technical Summary
The existing gadolinium sulfide (Gd2O2S) powder preparation process has problems such as product defects, high production costs, large safety hazards, large particle sizes, and easy agglomeration.
The preparation method based on the molten salt method is adopted, and by adding molten salt during the synthesis process to reduce the synthesis temperature, the resulting Gd2O2S powder has good crystallinity, purity and dispersion.
It realizes the preparation of high-purity, free of impurities and uniform particles of gadolinium oxysulfide powder at lower temperatures, reducing production costs and safety risks, and is suitable for large-scale production.
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Figure CN119528202A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of gadolinium oxysulfide powder preparation, and in particular to a gadolinium oxysulfide powder based on a molten salt method and a preparation method thereof. Background Art
[0002] Gadolinium oxysulfide (Gd2O2S) has the advantages of high density, large bandgap, large X-ray absorption coefficient, high chemical and thermal stability, etc. It can be used as an excellent scintillating material matrix and has a wide range of applications in medical X-ray imaging systems, radiation detection, industrial non-destructive testing and other fields.
[0003] At present, the preparation of Gd2O2S powder mainly adopts high-temperature solid-phase method, which has been applied in industrial production. It usually mixes and grinds raw materials such as gadolinium oxide and sulfur powder, adds a certain amount of flux, and reacts at high temperature (about 1000°C) in a reducing atmosphere. However, this synthesis process still has many shortcomings. For example, sulfur evaporates in large quantities at high temperatures, which not only greatly increases the cost of waste gas treatment, but also produces a large number of defects such as sulfur vacancies in the product Gd2O2S, greatly reducing its optical properties. And it must be synthesized in a reducing atmosphere such as hydrogen, hydrogen sulfide, and carbon monoxide, which not only greatly increases the production and environmental protection costs, but also such reducing gases are flammable, explosive, toxic, and very dangerous. In addition, the Gd2O2S powder synthesized by the high-temperature solid-phase method has problems such as large particle size, easy agglomeration, and easy impurity.
[0004] Therefore, it is urgent to study a method for preparing gadolinium oxysulfide powder with a simple synthesis method and uniform Gd2O2S powder particles. Summary of the invention
[0005] The purpose of the present invention is to provide a gadolinium oxysulfide powder and a preparation method thereof based on a molten salt method in order to overcome the defects of the above-mentioned prior art. By adding molten salt in the resynthesis process, the synthesis temperature is greatly reduced, and the generated Gd2O2S has good crystallinity, high purity, no impurities, and high dispersibility.
[0006] The purpose of the present invention can be achieved by the following technical solutions:
[0007] The present invention provides a method for preparing gadolinium oxysulfide powder based on a molten salt method, comprising the following steps:
[0008] S1: preparing a precursor solution, washing and drying the obtained precipitation product to obtain a precursor powder; the precursor powder is one of Gd2O2CO3, Gd2(SO4)3·8H2O, Gd2(OH)4SO4·xH2O, Gd2(OH)5NO3·xH2O, or the precursor powder is a precursor powder doped with rare earth ions,
[0009] Where x is the number of crystal waters in the chemical formula;
[0010] S2: the precursor powder, sulfur source and molten salt prepared in S1 are mixed evenly and placed in a crucible, and sintered at high temperature under a protective atmosphere to make the mixed powder molten. After sintering is completed, the mixed powder is cooled, washed and dried to obtain gadolinium oxysulfide powder;
[0011] The molten salt is one of Li2CO3 and Na2CO3, Li2CO3 and K2CO3, Li2CO3 and K2CO3, and Na2CO3.
[0012] Furthermore, in S1, the rare earth ion doped is Tb 3+ , Pr 3+ 、Sm 3+ , Er 3+ 、Ce 3+ 、Eu 3+ 、Nd 3+ 、Ho 3+ 、Tm 3+ One or more of the rare earth ions doped with Gd 3+ The molar ratio is 0.5~1.
[0013] Further, in S2, the sulfur source is thiourea or sulfur powder;
[0014] The molar ratio of the sulfur source to the precursor powder is (2-6):1.
[0015] Further, in S2, the high temperature sintering temperature is 400-900°C, and the holding time is 1-3 hours;
[0016] The material of the crucible is one of alumina, graphite, boron nitride, platinum, and silicon carbide;
[0017] The cleaning process is to use dilute hydrochloric acid to clean until no bubbles are generated, and then use deionized water and anhydrous ethanol to clean in sequence;
[0018] The drying process is drying at 50-80° C., and the drying time is 5-12 hours.
[0019] Furthermore, in S1, the preparation process of the Gd2O2CO3 powder is: ammonium bicarbonate and NH3·H2O are mixed evenly, and Gd(NO3)3 aqueous solution, Ln(NO3)3 aqueous solution, and 30wt.% H2O2 solution are added in sequence, and after the reaction is completed, the precipitate is washed and dried to obtain Gd2O2CO3 precursor powder.
[0020] Further, the molar ratio of the ammonium bicarbonate to NH3·H2O is 1:(0.6-1), and the concentration of the ammonium bicarbonate solution is 3-5 mol / L;
[0021] The molar ratio of Gd(NO3)3 to ammonium bicarbonate is (0.04-0.06):1, and the concentration of the Gd(NO3)3 aqueous solution is 1-1.5 mol / L;
[0022] The concentration of the Ln(NO3)3 solution is 0.5-1 mol / L. 3+ Tb 3+ , Pr 3+ 、Sm 3+ , Er 3+ 、Ce 3+ 、Eu 3+ 、Ho 3+ 、Tm 3+ One of them, Gd 3+ With Ln 3+ The molar ratio is (99.7-99.99):(0.01-0.3);
[0023] The molar ratio of the H2O2 solution to Gd(NO3)3 is 1:(2-4).
[0024] Furthermore, in S1, the preparation process of the precursor Gd2(SO4)3·8H2O powder is: dissolving Gd2O3 in dilute hydrochloric acid, adding excess dilute sulfuric acid and a large amount of ethanol, filtering out the precipitate, washing with ethanol, and drying in the air to obtain the precursor powder Gd2(SO4)3·8H2O.
[0025] Furthermore, the preparation process of the Gd2(OH)4SO4·xH2O or Gd2(OH)5NO3·xH2O powder is as follows: Gd2O3 is dissolved in a dilute sulfuric acid or dilute nitric acid solution to prepare a Gd2(SO4)3 or Gd(NO3)3 aqueous solution with a concentration of 0.1 to 0.5 mol / L, and then ammonium nitrate is added and stirred to obtain a mixed solution;
[0026] Prepare 0.5-1 mol / L NH3·H2O or urea aqueous solution, drop it into the mixed solution and stir it evenly, pour it into a hydrothermal kettle, react at 180°C for 12-24 hours, wash and dry it after cooling, and obtain the precursor powder Gd2(OH)4SO4·xH2O or Gd2(OH)5NO3·xH2O;
[0027] The molar ratio of Gd2(SO4)3 to NH3·H2O is 1:(3-6); the molar ratio of Gd(NO3)3 to urea is 1:(3-6).
[0028] Furthermore, in S2, the protective atmosphere is air, a reducing atmosphere or an inert atmosphere, the reducing atmosphere includes hydrogen, hydrogen sulfide and carbon monoxide, and the inert atmosphere includes nitrogen and argon.
[0029] The present invention also provides a gadolinium oxysulfide powder, wherein the particle size of the gadolinium oxysulfide powder is 400nm-1μm.
[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0031] 1. The present invention synthesizes Gd2O2S powder in air or a reducing atmosphere or an inert atmosphere. Compared with the traditional high-temperature solid-phase synthesis method, the synthesis temperature is greatly reduced from 1000°C to 400°C. The generated Gd2O2S has good crystallinity, high purity, and no impurities. The particle size is as small as 400nm to 1μm and the dispersion is high.
[0032] 2. The present invention can greatly reduce the raw material, environmental protection and safety costs in production, and is conducive to the large-scale production of Gd2O2S powder.
[0033] 3. When the molten salt in the present invention is melted at high temperature, it provides a flux environment for the synthesis of Gd2O2S, and the reactants fully react to generate Gd2O2S. Different from the high-temperature solid-phase method that uses inorganic salts as flux, the molten salt method uses molten salt as flux at high temperature, and the amount of salt used is much larger than the flux in the high-temperature solid-phase method. Compared with the traditional high-temperature solid-phase method, the molten salt method has a large contact area between the reactants, and the liquid molten salt has fluidity, which accelerates the reaction speed and can reduce the activation energy of the reaction, thereby reducing the reaction temperature and reducing the reaction time. When the molten salt is in a molten state, due to its high viscosity, it can weaken the diffusion of gases such as oxygen in the environment, thereby effectively slowing down the oxidation of Gd2O2S, so that the synthesis process can be carried out in an air atmosphere. BRIEF DESCRIPTION OF THE DRAWINGS
[0034] Figure 1 The present invention is a flow chart of a method for preparing gadolinium oxysulfide powder based on a molten salt method;
[0035] Figure 2 Gd2O2S:0.1%Pr prepared in Example 1 3+ X-ray diffraction (XRD) pattern;
[0036] Figure 3 Gd2O2S:0.1%Pr prepared in Example 1 3+ Fluorescence spectrum (PL) at 240nm wavelength;
[0037] Figure 4 Gd2O2S:0.1%Pr prepared in Example 1 3+Surface morphology of
[0038] Figure 5 This is the surface morphology of the Gd2O2S powder obtained by the high temperature solid phase method in Comparative Example 1. DETAILED DESCRIPTION
[0039] The specific implementation methods of the present invention are described in detail below through examples. These examples are implemented on the premise of the scheme described in the present invention, and provide detailed implementation methods and specific operating processes, but the protection scope of the present invention is not limited to the following examples.
[0040] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. Any features such as component models, material names, connection structures, preparation methods, materials, structures or composition ratios not clearly described in this technical solution are deemed to be common technical features disclosed in the prior art.
[0041] Example 1
[0042] This embodiment provides a molten salt method for preparing Pr-doped 3+ The gadolinium oxysulfide phosphor has a chemical formula of Gd2O2S:0.1%Pr 3+ , using Gd2O2CO3:0.1%Pr 3+ Precursor, comprising the following steps:
[0043] S1: Synthesis of Gd2O2CO3:0.1%Pr 3+ Precursor: Dissolve Pr(NO3)3·6H2O in deionized water to prepare a 1 mol / L Pr(NO3)3 aqueous solution;
[0044] At room temperature, ammonium bicarbonate and NH3·H2O in a molar ratio of 1:0.73 are added to deionized water to prepare a 4.45 mol / L ammonium bicarbonate solution; a 1.19 mol / L gadolinium nitrate aqueous solution is added to the solution, wherein the molar ratio of ammonium bicarbonate to gadolinium nitrate is 1:0.048, and then 200 μL of a 1 mol / L Pr(NO3)3 aqueous solution is added, and the mixture is stirred evenly to obtain a mixed solution.
[0045] Add 30wt.% H2O2 to the mixed solution to make the molar ratio of gadolinium nitrate to H2O2 1:3.3. After reacting at room temperature for 5 hours, the mixture was aged for 12 hours to obtain a precipitate. The precipitate was washed with deionized water 3 times, washed with anhydrous ethanol 2 times, and dried at 80°C for 12 hours to obtain a precursor powder Gd2O2CO3:0.1%Pr 3+ .
[0046] S2: Synthesis of Gd2O2S:0.1%Pr in molten salt 3+Powder: weigh 0.233g of precursor powder Gd2O2CO3:0.1%Pr 3+ After being mixed evenly with 0.152g of thiourea, 0.222g of Li2CO3 and 0.318g of Na2CO3, the mixture was placed in an alumina crucible and placed in a muffle furnace. The mixture was heated to 500°C in an air atmosphere and reacted for 3 hours. After cooling, the product was washed with dilute hydrochloric acid until no bubbles were generated, then washed with deionized water until neutral, then washed with anhydrous ethanol for 2 to 3 times, and dried at 80°C for 12 hours to obtain Gd2O2S:0.1%Pr 3+ Powder.
[0047] The Gd2O2S:0.1%Pr prepared in Example 1 3+ The powder was subjected to X-ray diffraction analysis using a D / MAX2500 powder X-ray diffractometer from Rigaku Corporation. The results are as follows: Figure 1 As shown. Figure 1 In the figure, the horizontal axis is 2θ, in degrees; the vertical axis is the diffraction peak intensity. Figure 1 It can be seen that the prepared powder is Gd2O2S with good crystallinity, and no other impurity phases are found, which shows that the synthesis method adopted in Example 1 can successfully prepare pure phase and good crystallinity Gd2O2S.
[0048] Figure 2 Gd2O2S:0.1%Pr prepared in Example 1 3+ Fluorescence spectrum (PL) under 254nm light excitation; the horizontal axis is wavelength, unit: nm; the vertical axis is fluorescence intensity. Figure 2 It can be seen that the prepared Gd2O2CO3:0.1%Pr 3+ The powder can emit 502nm( 3 P1→ 3 H5 transition), 513nm( 3 P0→ 3 H4 transition) fluorescence.
[0049] Figure 3 Gd2O2S:0.1%Pr prepared in Example 1 3+ Surface morphology of gadolinium oxysulfide luminescent powder. The powder particle size is 400nm~1μm, with good dispersion, smooth grain surface and no obvious defects.
[0050] Example 2
[0051] This embodiment provides a method for preparing gadolinium oxysulfide powder based on a molten salt method, using a Gd2(SO4)3·8H2O precursor, comprising the following steps:
[0052] S1: Synthesis of Gd2(SO4)3·8H2O precursor: Dissolve Gd2O3 in dilute hydrochloric acid to prepare a GdCl3 solution with a concentration of 1 mol / L, add dilute sulfuric acid slightly more than the reaction amount to the solution, and then add ethanol to the solution, filter out the precipitate and wash it with ethanol, and dry it in air to obtain the precursor powder Gd2(SO4)3·8H2O precursor.
[0053] S2: Synthesis of Gd2O2S powder in molten salt: The remaining steps are the same as in Example 1.
[0054] Example 3
[0055] This embodiment provides a method for preparing gadolinium oxysulfide powder based on a molten salt method, using a Gd2(OH)4SO4·xH2O precursor, and comprising the following steps:
[0056] S1: Synthesis of precursor Gd2(OH)4SO4·xH2O: Gd2O3 was dissolved in a dilute sulfuric acid solution to prepare a 0.1 mol / L Gd2(SO4)3 aqueous solution, and then ammonium nitrate was added to the prepared Gd2(SO4)3 aqueous solution, and stirred evenly to obtain a mixed solution. At the same time, 1 mol / L NH3·H2O solution was prepared. The prepared NH3·H2O was added dropwise to the mixed solution and stirred evenly, and then poured into the inner tank of the hydrothermal kettle, and then the hydrothermal kettle was placed in a drying oven at 180°C. After high-temperature reaction for 12 hours, the temperature was naturally lowered and cooled. The obtained product was fully washed with deionized water and anhydrous ethanol in turn, and dried at 80°C for 12 hours to obtain the precursor powder Gd2(OH)4SO4·xH2O.
[0057] S2: Synthesis of Gd2O2S powder in molten salt: The remaining steps are the same as in Example 1.
[0058] Example 4
[0059] This embodiment provides a method for preparing gadolinium oxysulfide powder based on a molten salt method, using a Gd2(OH)5NO3·xH2O precursor, and comprising the following steps:
[0060] S1: Synthesis of precursor Gd2(OH)5NO3·xH2O: Dissolve Gd2O3 in dilute nitric acid solution to prepare a 0.1 mol / L Gd(NO3)3 aqueous solution, then add ammonium nitrate to the prepared Gd(NO3)3 aqueous solution, stir evenly, and obtain a mixed solution. At the same time, prepare a 1 mol / L urea solution. Add the prepared urea dropwise to the mixed solution and stir well, pour it into the inner tank of the hydrothermal kettle, and then place the hydrothermal kettle in a drying oven at 180°C. After high-temperature reaction for 12 hours, cool it down naturally. The obtained product is washed with deionized water and anhydrous ethanol in turn, and dried at 80°C for 12 hours to obtain the precursor powder Gd2(OH)5NO3·xH2O.
[0061] S2: Synthesis of Gd2O2S powder in molten salt: The remaining steps are the same as in Example 1.
[0062] Comparative Example 1
[0063] This comparative example adopts a high temperature solid phase method provided in the reference to prepare Gd2O2S powder, comprising the following steps:
[0064] A certain amount of Gd2O3 was dissolved in dilute nitric acid solution to prepare 0.5 mol·L -1 At the same time, add NH3·H2O to adjust the pH value of the solution to 4.82. Prepare 500mL of 0.01mol·L -1 of Gd(NO3)3 solution, dissolve 12g of urea in the Gd(NO3)3 solution and stir until completely dissolved. Heat the mixed solution in a 95°C water bath for 4 hours and age for 2 hours. Then, wash the obtained turbid solution several times with deionized water and anhydrous ethanol, filter, and dry in a vacuum drying oven at 60°C for 12 hours to obtain a precursor powder. The precursor was calcined in a muffle furnace at 1000°C for 2 hours to obtain an intermediate product Gd2O3:Pr, Ce powder. After 0.4531g Gd2O3:Pr, Ce, 0.6625g Na2CO3 and 0.8000g sulfur powder were fully mixed, ground evenly in a mortar, put into a crucible, covered with a lid, and calcined in a furnace at 1000°C for 2 hours to obtain Gd2O2S powder.
[0065] The calcination temperature used in this reaction is high, and the particle size distribution of the prepared Gd2O2S powder is uneven, with a particle size of about 0.5 to 4 μm. Figure 5 shown.
[0066] Reference: Liu H, Shi L, Xie S, et al. Synthesis and characterization of Gd2O2S:Pr 3+ ,Ce 3+ (GOS)scintillation phosphors via a homogeneous precipitation followed by solid-state reaction method[J]. Journal of the Australian CeramicSociety, 2022, 58(2):429-436.
[0067] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.
Claims
1. A method for preparing gadolinium oxysulfide powder based on a molten salt method, characterized in that: The following steps are involved: S1: preparing a precursor solution, washing and drying the obtained precipitation product to obtain a precursor powder; the precursor powder is one of Gd2O2CO3, Gd2(SO4)3·8H2O, Gd2(OH)4SO4·xH2O, Gd2(OH)5NO3·xH2O, or the precursor powder is a precursor powder doped with rare earth ions, Where x is the number of crystal waters in the chemical formula; S2: the precursor powder, sulfur source and molten salt prepared in S1 are mixed evenly and placed in a crucible, and sintered at high temperature under a protective atmosphere to make the mixed powder molten. After sintering is completed, the mixed powder is cooled, washed and dried to obtain gadolinium oxysulfide powder; The molten salt is one of Li2CO3 and Na2CO3, Li2CO3 and K2CO3, Li2CO3 and K2CO3, and Na2CO3.
2. The method for preparing gadolinium oxysulfide powder based on a molten salt method according to claim 1, characterized in that: In S1, the rare earth ion doped is Tb 3+ , Pr 3+ 、Sm 3+ , Er 3+ 、Ce 3+ 、Eu 3+ 、Nd 3+ 、Ho 3+ 、Tm 3+ One or more of the rare earth ions doped with Gd 3+ The molar ratio is 0.5~1.
3. The method for preparing gadolinium oxysulfide powder based on a molten salt method according to claim 1, characterized in that: In S2, the sulfur source is thiourea or sulfur powder; The molar ratio of the sulfur source to the precursor powder is (2-6):
1.
4. The method for preparing gadolinium oxysulfide powder based on a molten salt method according to claim 1, characterized in that: In S2, the high temperature sintering temperature is 400-900°C, and the holding time is 1-3 hours; The material of the crucible is one of alumina, graphite, boron nitride, platinum, and silicon carbide; The cleaning process is to use dilute hydrochloric acid to clean until no bubbles are generated, and then use deionized water and anhydrous ethanol to clean in sequence; The drying process is drying at 50-80° C., and the drying time is 5-12 hours.
5. The method for preparing gadolinium oxysulfide powder based on a molten salt method according to claim 1, characterized in that: In S1, the preparation process of the Gd2O2CO3 powder is: ammonium bicarbonate and NH3·H2O are mixed evenly, and Gd(NO3)3 aqueous solution, Ln(NO3)3 aqueous solution, and H2O2 solution with a concentration of 30wt.% are added in sequence. After the reaction is completed, the precipitate is washed and dried to obtain Gd2O2CO3 precursor powder.
6. The method for preparing gadolinium oxysulfide powder based on a molten salt method according to claim 5, characterized in that: The molar ratio of the ammonium bicarbonate to NH3·H2O is 1:(0.6-1), and the concentration of the ammonium bicarbonate solution is 3-5 mol / L; The molar ratio of Gd(NO3)3 to ammonium bicarbonate is (0.04-0.06):1, and the concentration of the Gd(NO3)3 aqueous solution is 1-1.5 mol / L; The concentration of the Ln(NO3)3 solution is 0.5-1 mol / L. 3+ Tb 3+ , Pr 3+ 、Sm 3+ , Er 3+ 、Ce 3+ 、Eu 3+ 、Ho 3+ 、Tm 3+ One of them, Gd 3+ With Ln 3+ The molar ratio is (99.7-99.99):(0.01-0.3); The molar ratio of the H2O2 solution to Gd(NO3)3 is 1:(2-4).
7. The method for preparing gadolinium oxysulfide powder based on a molten salt method according to claim 1, characterized in that: In S1, the preparation process of the precursor Gd2(SO4)3·8H2O powder is as follows: Gd2O3 is dissolved in dilute hydrochloric acid, and excess dilute sulfuric acid and a large amount of ethanol are added, the precipitate is filtered out, washed with ethanol, and dried in air to obtain the precursor powder Gd2(SO4)3·8H2O.
8. The method for preparing gadolinium oxysulfide powder based on a molten salt method according to claim 1, characterized in that: The preparation process of the Gd2(OH)4SO4·xH2O or Gd2(OH)5NO3·xH2O powder is as follows: Gd2O3 is dissolved in a dilute sulfuric acid or dilute nitric acid solution to prepare a Gd2(SO4)3 or Gd(NO3)3 aqueous solution with a concentration of 0.1 to 0.5 mol / L, and then ammonium nitrate is added and stirred to obtain a mixed solution; Prepare 0.5-1 mol / L NH3·H2O or urea aqueous solution, drop it into the mixed solution and stir it evenly, pour it into a hydrothermal kettle, react at 180°C for 12-24 hours, wash and dry it after cooling, and obtain the precursor powder Gd2(OH)4SO4·xH2O or Gd2(OH)5NO3·xH2O; The molar ratio of Gd2(SO4)3 to NH3·H2O is 1:(3-6); the molar ratio of Gd(NO3)3 to urea is 1:(3-6).
9. The method for preparing gadolinium oxysulfide powder based on a molten salt method according to claim 1, characterized in that: In S2, the protective atmosphere is air, a reducing atmosphere or an inert atmosphere, the reducing atmosphere includes hydrogen, hydrogen sulfide and carbon monoxide, and the inert atmosphere includes nitrogen and argon.
10. A gadolinium oxysulfide powder obtained by the preparation method according to any one of claims 1 to 9, characterized in that: The particle size of the gadolinium oxysulfide powder is 400nm to 1μm.