A bifunctional gypsum admixture based on plant polyphenols-nanoparticles and its preparation method

Abstract

The present invention belongs to the technical field of building material additives. In particular, it relates to a bifunctional gypsum additive based on plant polyphenols - nanoparticles and a preparation method thereof. In the present invention, plant polyphenols are added to a metal oxide nanoparticle dispersion liquid, the pH is adjusted, and after reaction, filtration, washing, and drying are carried out to obtain the bifunctional gypsum additive. The gypsum additive provided by the present invention can delay the setting time of gypsum, increase the plasticity time of the gypsum slurry. After introducing 10 - 50% of this additive based on the mass of gypsum, the initial setting time of gypsum is extended to 20 - 80 min. Meanwhile, high - efficiency shielding of X - rays by gypsum can be realized, and the problem that metal oxide nanoparticles cannot be uniformly and stably loaded onto gypsum crystals is solved at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of building material admixtures, and particularly to a bifunctional gypsum admixture based on plant polyphenols-nanoparticles and a preparation method thereof. Background Art

[0002] X-rays are widely used in fields such as medical imaging, radiotherapy, and non-destructive inspection. However, the widespread application of X-rays has brought a series of safety problems, posing higher requirements for the performance of protective materials. Currently, commonly used shielding materials such as lead plates and lead-containing organic glass have excellent shielding performance for X-rays. However, lead materials have the disadvantages of high density, high toxicity, and low strength, and there is also a problem of poor absorption of X-rays with energies between 40 - 90 keV. Therefore, it is urgent to develop new materials with X-ray shielding performance to reduce the safety hazards brought by X-rays.

[0003] The mechanism of shielding X-rays is achieved by the photoelectric effect and Compton effect of ray photons with matter. Among them, the photoelectric effect refers to the elastic collision of ray photons with the extranuclear electrons of matter, causing most of the energy of the photons to be absorbed by the electrons. The Compton effect refers to the inelastic collision of ray photons with higher energy with electrons, causing most of the energy of the photons to be transferred to the electrons. Due to their high atomic numbers and special optical, electrical, and magnetic properties, rare earth elements have a high probability of occurring photoelectric effect and Compton effect with ray photons, thus having excellent shielding performance for X-rays. Therefore, preparing new materials containing rare earth elements with high atomic numbers is expected to achieve efficient shielding of X-rays.

[0004] Building gypsum is a commonly used inorganic building material and is widely used due to its advantages such as light weight, high strength, and low production cost. However, its short setting time (5 - 10 min) greatly limits the plasticity and transportation efficiency of gypsum itself. And simply doping rare earth elements into gypsum can improve the X-ray shielding performance of gypsum-based materials, but it will further accelerate the setting of gypsum, which is more unfavorable for the subsequent processing and application of gypsum-based materials.

[0005] In summary, how to endow gypsum with high X-ray shielding performance and improve its processability is an urgent problem to be solved. Summary of the Invention

[0006] The purpose of the present invention is to provide a bifunctional gypsum admixture based on plant polyphenols-nanoparticles and a preparation method thereof to solve the problems existing in the above-mentioned prior art.

[0007] To achieve the above purpose, the present invention provides the following solutions:

[0008] One of the technical solutions of the present invention: Provide a preparation method of a bifunctional gypsum admixture based on plant polyphenols-nanoparticles, and the steps include:

[0009] Add plant polyphenols to the metal oxide nanoparticle dispersion, adjust the pH to 7.5 - 8.0, and after the reaction, filter, wash, and dry to obtain the bifunctional gypsum admixture.

[0010] Furthermore, the metal oxide nanoparticles in the metal oxide nanoparticle dispersion include at least one of erbium oxide nanoparticles, bismuth oxide nanoparticles, tungsten oxide nanoparticles, lanthanum oxide nanoparticles, tin oxide nanoparticles, and cesium oxide nanoparticles.

[0011] Preferably, the particle size of the metal oxide nanoparticles is 50 - 200 nm.

[0012] Furthermore, the concentration of the metal oxide nanoparticles in the metal oxide nanoparticle dispersion is 5 - 10 wt%.

[0013] Furthermore, the metal oxide nanoparticle dispersion is prepared by dispersing metal oxide nanoparticles in water.

[0014] Furthermore, the plant polyphenols include tannic acid, gallic acid, or catechuic acid.

[0015] Furthermore, the concentration of the plant polyphenols in the reaction system is 0.03 - 0.05 mol / L.

[0016] Furthermore, adjusting the pH to 7.5 - 8.0 is to adjust the pH using PBS buffer.

[0017] Furthermore, the temperature of the reaction is 60 - 80 °C, the time is 5 - 8 h, and the rotation speed during the reaction is 2000 r / min.

[0018] Furthermore, the washing is to wash with water at least twice.

[0019] Furthermore, the drying temperature is 40 - 60 °C, and the time is 8 - 12 h.

[0020] The second technical solution of the present invention: Provide a bifunctional gypsum admixture prepared by the above preparation method.

[0021] The third technical solution of the present invention: Provide an application of the above bifunctional gypsum admixture in the preparation of gypsum.

[0022] The fourth technical solution of the present invention: Provide an X-ray shielding gypsum, by mass percentage, the components include:

[0023] 50 - 90% gypsum powder and 10 - 50% of the above bifunctional gypsum admixture.

[0024] In the present invention, by adding an admixture and introducing metal oxide nanoparticles into the gypsum-based material, when gamma-ray photons penetrate the gypsum, effective collisions occur between the nanoparticles in the gypsum-based material, thereby achieving efficient shielding of gamma rays. At the same time, based on the π-π bond interaction, plant polyphenols are coated on the surface of the metal oxide nanoparticles. There are various intermolecular forces between the nanoparticles coated with plant polyphenols, thereby enhancing the dispersibility and stability of the nanoparticles, solving the problems of uneven dispersion and unstable loading that occur when metal oxide nanoparticles are directly loaded onto the substrate, increasing the probability of effective collisions between gamma-ray photons and nanoparticles, and thus improving the shielding performance of the material. Since when metal oxides are directly doped into gypsum, the setting rate of gypsum will be accelerated, which is not conducive to the subsequent processing and application of gypsum-based materials. There are a large number of phenolic hydroxyl groups in plant polyphenols. By coating the metal oxides, these phenolic hydroxyl groups can form stable complexes with Ca 2+ during the coating of the metal oxides, reducing the concentration of free Ca 2+ , thereby slowing down the crystallization process of CaSO4·2H2O. This complexation effect will slow down the hydration reaction rate of gypsum and prolong the setting time of gypsum.

[0025] The present invention discloses the following technical effects:

[0026] The present invention provides a preparation method of a bifunctional gypsum admixture based on plant polyphenols-nanoparticles. By coating plant polyphenols on the surface of metal oxide nanoparticles, a bifunctional gypsum admixture of plant polyphenols-nanoparticles is obtained. The preparation method is simple, the conditions are mild, it is easy to be applied on a large scale, and it has the characteristics of convenient use, high efficiency and multifunction.

[0027] The gypsum admixture provided by the present invention can delay the setting time of gypsum, increase the plasticity time of gypsum slurry. After introducing this admixture based on 10-50% of the gypsum quality, the initial setting time of gypsum is extended to 20-80 min. At the same time, it can achieve efficient shielding of X-rays by gypsum, and at the same time solve the problem that metal oxide nanoparticles cannot be uniformly and stably loaded onto gypsum crystals. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0029] Figure 1 SEM images of gypsum after adding the admixtures of Example 3 and Example 4 with different proportions;

[0030] Figure 2 In it, a is the Fourier infrared spectrum of erbium oxide nanoparticles before and after modification with tannic acid, b is the X-ray diffraction pattern of erbium oxide nanoparticles before and after modification with tannic acid, c is the TSI value of the nanoparticles dispersed in water for one hour before and after modification, and d is the digital photo of the aqueous dispersion of the nanoparticles after standing for 8 hours before and after modification;

[0031] Figure 3 It is the TEM image of Example 3. Among them, a is BF-TEM and b is HAADF-STEM;

[0032] Figure 4 It is the TEM image of Example 4. Among them, a is BF-TEM and b is HAADF-STEM;

[0033] Figure 5 It is a schematic diagram of the ray shielding efficiency test device;

[0034] Figure 6 It is the X-ray shielding efficiency of gypsum added with the admixtures of Examples 1 to 4. Among them, a is Example 1, b is Example 2, c is Example 3, and d is Example 4;

[0035] Figure 7 It is the X-ray shielding efficiency of gypsum added with Example 1 and Comparative Example 1. Among them, a is the addition amount of 10%, b is the addition amount of 30%, and c is the addition amount of 50%;

[0036] Figure 8 It is the X-ray shielding efficiency of gypsum added with Example 3 and Comparative Example 2. Among them, a is the addition amount of 10%, b is the addition amount of 30%, and c is the addition amount of 50%;

[0037] Figure 9 It is the X-ray shielding efficiency of gypsum added with the admixtures of Examples 5 to 8. Among them, a is Example 5, b is Example 6, c is Example 7, and d is Example 8;

[0038] Figure 10 It is the X-ray shielding efficiency of gypsum added with Example 5 and Comparative Example 3. Among them, a is the addition amount of 10%, b is the addition amount of 30%, and c is the addition amount of 50%;

[0039] Figure 11 It is the X-ray shielding efficiency of gypsum added with Example 7 and Comparative Example 4. Among them, a is the addition amount of 10%, b is the addition amount of 30%, and c is the addition amount of 50%. Detailed implementation manners

[0040] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0041] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0042] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0043] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and examples are merely exemplary.

[0044] Regarding "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0045] The raw materials and reagents used in the specific embodiments of the present invention are all commercially available products.

[0046] Example 1

[0047] The preparation steps of the bifunctional gypsum admixture based on plant polyphenol-nanoparticles are as follows:

[0048] S1. Add 10 g of erbium oxide nanoparticles with a particle size of 200 nm into a reaction kettle, then add 50 mL of deionized water, and ultrasonically stir at room temperature for 30 min to obtain an erbium oxide nanoparticle dispersion;

[0049] S2. Add 50 mL of 0.03 mol / L tannic acid solution into the reaction kettle of step S1, and use a phosphate buffer solution to adjust the pH of the reaction system to 8.0, then raise the temperature to 60 °C, stir and react at a speed of 2000 r / min for 5 h. After the reaction is completed, filter, then wash the solid product with deionized water twice to remove the unloaded polyphenol compounds, and finally dry at 60 °C for 12 h to obtain the bifunctional gypsum admixture.

[0050] Example 2

[0051] Compared with Example 1, the difference is only that 50 mL of 0.03 mol / L tannic acid solution is replaced by 50 mL of 0.03 mol / L gallic acid solution.

[0052] Example 3

[0053] Compared with Example 1, the difference is only that the particle size of erbium oxide nanoparticles is 50 nm.

[0054] Example 4

[0055] The preparation steps of the plant polyphenol-nanoparticle-based dual-functional gypsum admixture are as follows:

[0056] S1. Add 10 g of erbium oxide nanoparticles with a particle size of 50 nm to the reaction kettle, then add 50 mL of deionized water, and ultrasonically stir at room temperature for 30 min to obtain an erbium oxide nanoparticle dispersion;

[0057] S2. Add 50 mL of 0.05 mol / L tannic acid solution to the reaction kettle in step S1, and use phosphate buffer to adjust the pH of the reaction system to 8.0, then heat up to 80 °C and stir and react at a speed of 2000 r / min for 8 h. After the reaction is completed, filter, and then wash the solid product twice with deionized water to remove the unloaded polyphenol compounds, and finally dry at 60 °C for 12 h to obtain the dual-functional gypsum admixture.

[0058] Example 5

[0059] Compared with Example 1, the difference is only that erbium oxide nanoparticles are replaced by bismuth oxide nanoparticles.

[0060] Example 6

[0061] Compared with Example 5, the difference is only that 50 mL of 0.03 mol / L tannic acid solution is replaced by 50 mL of 0.03 mol / L gallic acid solution.

[0062] Example 7

[0063] Compared with Example 5, the difference is only that the particle size of bismuth oxide nanoparticles is 50 nm.

[0064] Example 8

[0065] Compared with Example 4, the difference is only that erbium oxide nanoparticles are replaced by bismuth oxide nanoparticles.

[0066] Comparative Example 1

[0067] Using erbium oxide nanoparticles with a particle size of 200 nm as a gypsum admixture.

[0068] Comparative Example 2

[0069] Compared with Example 3, the only difference is that the particle size of the erbium oxide nanoparticles is 500 nm.

[0070] Comparative Example 3

[0071] Compared with Example 5, the only difference is that the reaction temperature is 25 °C and the time is 3 h.

[0072] Comparative Example 4

[0073] Compared with Example 7, the only difference is that the particle size of the bismuth oxide nanoparticles is 500 nm.

[0074] Test Example

[0075] Retarding performance detection of the admixtures prepared in Examples 1 - 8 and Comparative Examples 1 - 4

[0076] The admixtures prepared in Examples 1 - 8 and Comparative Examples 1 - 4 were used in the preparation of X - ray shielding gypsum as follows:

[0077] 10%, 20%, 30%, 40%, and 50% of the admixture (based on the mass of the X - ray shielding gypsum) were respectively dispersed in 30% deionized water (based on the sum of the masses of the gypsum powder and the admixture), and then thoroughly mixed with the gypsum powder to form a gypsum slurry. Subsequently, the slurry was poured into a mold with a diameter of 6 cm and a thickness of 1 cm and waited for complete solidification to obtain gypsum samples. Record the initial setting time of the gypsum slurry and test the compressive strength and X - ray shielding performance of the gypsum samples.

[0078] The preparation method of the blank gypsum sample is as follows:

[0079] An appropriate amount of gypsum powder was taken and poured into 30% deionized water (based on the mass of the gypsum powder), thoroughly mixed to form a gypsum slurry, and then poured into a mold with a diameter of 6 cm and a thickness of 1 cm and waited for complete solidification to obtain a blank gypsum sample.

[0080] In the test example, the X - ray shielding performance of the gypsum material was evaluated by the shielding efficiency, and the calculation method is shown in Equation (1):

[0081]

[0082] Among them, AE is the ray shielding efficiency of the gypsum material, %; D0 is the initial X - ray dose, μGy / s; D π is the remaining X - ray dose after passing through the shielding material, μGy / s.

[0083] The X-ray emission device for testing the shielding performance of the gypsum material is a unidows E dosimeter. The energy range of the effective X-ray photons for testing is 20 - 120 keV. The ray voltage refers to the national standard JJG 393-2003 and the international standard ISO4037-1:1996. The test device is as Figure 5 shown.

[0084] The initial setting time and compressive strength are determined in accordance with GB / T17669.4-1994 "Determination of Physical Properties of Building Gypsum Paste" and GB / T 17669.3-1994 "Determination of Physical Properties of Building Gypsum Paste".

[0085] Table 1 Initial setting time (min) of gypsum under different admixture addition amounts

[0086]

[0087] From the initial setting time data in Table 1, it can be seen that the retarding effect of the gypsum admixture provided by the present invention on gypsum is affected by the addition amount, reaction conditions, nanoparticle particle size, and type of plant polyphenols. Specifically, for Examples 1 - 8, the retarding effect on gypsum increases with the increase of the addition amount, and the initial setting time of gypsum can be extended to 80 min at most. Compared with Example 5, the retarding effect of Comparative Example 3 on gypsum is significantly reduced. This is because the reaction temperature during the preparation of Comparative Example 3 is 25 °C and the reaction time is 3 h, which results in insufficient reaction between the plant polyphenols and the nanoparticles, and only a small amount of plant polyphenols cover the surface of the nanoparticles. In addition, there is also a large gap in the retarding effect between Comparative Example 2 and Example 3, with a maximum difference of 33 min under the same addition amount. The reason is that the nanoparticle particle size used in Comparative Example 2 is 500 nm, while the nanoparticle particle size used in Example 3 is 50 nm. Under the same conditions, smaller-sized nanoparticles are more likely to react with plant polyphenols, and more plant polyphenols can cover the surface. By comparing Example 1 and Example 2, and Example 5 and Example 6, it can be seen that the admixture prepared using tannic acid has better retarding performance than the admixture prepared using gallic acid. This is because tannic acid is a complex phenolic compound with a large molecular structure and contains a large number of phenolic hydroxyl groups, while gallic acid is a simple phenolic acid and is one of the constituent units of tannic acid. It should be noted that the initial setting time of gypsum accelerates with the increase of the addition amount in Comparative Example 1, and it solidifies in 1 minute at the fastest. This is because more crystal nuclei are formed inside the gypsum by the metal oxide nanoparticles, promoting the growth and solidification of gypsum crystals.

[0088] Table 2 Influence of admixture addition amount on compressive strength (MPa)

[0089]

[0090] Table 3 Influence of Additive Dosage on Flexural Strength (MPa)

[0091]

[0092] It can be seen from the compressive strength data in Table 2 and the flexural strength data in Table 3 that the compressive strength of the blank gypsum is 21.7 MPa and the flexural strength is 7.1 MPa. Generally speaking, after adding the additives in Examples 1-8, the compressive strength of the gypsum decreases with the increase of the dosage, but the lowest can still be maintained above 16 MPa, while the flexural strength can be maintained at a relatively high level. Combining the data in Table 1, it can be shown that the additive provided by the present invention not only shows excellent retarding performance for gypsum, but also can ensure that the gypsum has relatively high mechanical strength. It is worth noting that the compressive strength of the gypsum is higher than that of the blank gypsum when the dosage is 10%, and the flexural strength of the gypsum is higher than that of the blank gypsum when the dosages are 10% and 30%. This is because the nanoparticles fill the pores between the gypsum crystals, improve the compactness of the gypsum, and thus enhance the mechanical strength of the gypsum.

[0093] Figure 1 SEM images of gypsum after adding different proportions of the additives in Example 3 and Example 4 are shown in Figure 1 It can be seen that the nanoparticles can fill the micropores in the gypsum matrix, reduce the generation and propagation of microcracks, improve the compactness of the gypsum crystals, and thus increase the mechanical strength. In addition, a strong chemical or physical bond is formed between the nanoparticles and the gypsum crystal interface, enhancing the overall strength of the composite material.

[0094] Figure 2 In is the Fourier infrared spectrum of erbium oxide nanoparticles before and after modification with tannic acid. The vibration peaks corresponding to the functional groups of tannic acid molecules appear in the spectrum after modification. Figure 1 In is the X-ray diffraction of erbium oxide nanoparticles before and after modification with tannic acid. As shown in the figure, before and after modification, the intensity and position of the diffraction peaks corresponding to the nanoparticles do not change significantly, indicating that the tannic acid coating layer is amorphous and does not change the crystal morphology of the nanoparticles after coating. Figure 1 In is the TSI value of the nanoparticles before and after modification after being dispersed in water for one hour. Compared with before modification, the TSI value of the modified nanoparticles in water decreases significantly, indicating that their dispersibility and stability in water are greatly enhanced. Figure 1 In is the digital photo of the aqueous dispersion of the nanoparticles before and after modification after standing for 8 hours. From left to right are Comparative Example 1, Example 3, and Example 4. The framed part in the figure is the supernatant. The unmodified nanoparticles agglomerate and precipitate at the bottom of the bottle, while the modified nanoparticles are still evenly dispersed in water.

[0095] Figure 3TEM images of Example 3, where a is BF-TEM and b is HAADF-STEM; Figure 4 TEM images of Example 4, where a is BF-TEM and b is HAADF-STEM. As Figures 3 - 4 shown, the surfaces of the nanoparticles in Examples 3 and 4 were clearly and uniformly coated with a layer of plant polyphenols. Relatively speaking, due to the higher reaction temperature, longer reaction time, and higher concentration of plant polyphenols used in Example 4, the coating effect of plant polyphenols on the surface of the nanoparticles is better.

[0096] Figure 5 Schematic diagram of the X-ray shielding efficiency test device.

[0097] Figure 6 X-ray shielding efficiencies of gypsum added with the admixtures of Examples 1-4, where a is Example 1, b is Example 2, c is Example 3, and d is Example 4. As can be seen from the figure, the gypsum added with Examples 1 and 2 has excellent ray shielding performance, and the shielding efficiency for X-rays with an energy of 20-80 keV can reach more than 50%. However, the shielding efficiency of Example 2 is slightly lower than that of Example 1 as a whole. In the low energy range of 20-40 keV, the difference between the two is not obvious, about 1-3%. As the ray energy increases, the difference in shielding efficiency between the two gradually increases, with a maximum difference of 8%. The reason for this difference is that the plant polyphenol selected in Example 2 is gallic acid, and the active groups in the gallic acid molecule are far fewer than those in the tannic acid molecule. Therefore, the dispersibility and stability of the nanoparticles coated with gallic acid are poor. The gypsum added with Examples 3 and 4 has a shielding efficiency for X-rays with an energy of 20-80 keV of more than 60%, which is higher than that of Examples 1 and 2. This is because the particle size of the nanoparticles used in Examples 3 and 4 is 50 nm, which is smaller than 200 nm of Examples 1 and 2. When X-ray photons collide with the nanoparticles, the smaller-sized nanoparticles are more likely to have effective collisions, and the number of collisions is also relatively large. Therefore, using smaller-sized nanoparticles can enhance the shielding performance of the material. It should be noted that the shielding efficiency of Example 4 is slightly higher than that of Example 3, because the preparation of Example 4 has a higher reaction temperature and longer reaction time than Example 3, so the surface of the nanoparticles in Example 4 is covered with more plant polyphenols.

[0098] Figure 7The X-ray shielding efficiency of the gypsum added with Example 1 and Comparative Example 1 is shown. Here, a represents an addition amount of 10%, b represents an addition amount of 30%, and c represents an addition amount of 50%. It can be seen from the figure that the shielding performance of the gypsum added with Comparative Example 1 is overall lower than that of the gypsum added with Example 1, and as the addition amount increases, the gap in shielding performance becomes more obvious. For example, in the ray energy range of 80 - 120 keV, when the addition amount is 50%, the shielding efficiency of Example 1 is more than 5% higher than that of Comparative Example 1. The reason for this gap is that the nanoparticles in Comparative Example 1 were not treated at all, and their dispersibility and stability in the gypsum crystals are poor. This further illustrates that the dispersibility and stability of nanoparticles in gypsum crystals are important factors affecting the shielding performance.

[0099] Figure 8 The X-ray shielding efficiency of the gypsum added with Example 3 and Comparative Example 2 is shown. Here, a represents an addition amount of 10%, b represents an addition amount of 30%, and c represents an addition amount of 50%. It can be seen from the figure that generally speaking, the shielding performance of the gypsum added with Comparative Example 2 is lower than that of the gypsum added with Example 3, and as the addition amount increases, the gap in shielding performance is more obvious in the high energy range. In the range of 20 - 60 keV, the shielding efficiency of Example 3 is 1 - 3% higher than that of Comparative Example 2. In the range of 80 - 120 keV, the shielding efficiency of Example 3 is 3 - 5% higher than that of Comparative Example 2. The reason is that the particle size of the nanoparticles in Comparative Example 2 is larger, being 500 nm, while that of Example 3 is 50 nm. This further illustrates that adding nanoparticles with a smaller particle size into gypsum crystals has better shielding performance than adding nanoparticles with a larger particle size.

[0100] Figure 9 The X-ray shielding efficiency of the gypsum added with the admixtures of Examples 5 - 8 is shown. Here, a is Example 5, b is Example 6, c is Example 7, and d is Example 8. It can be seen from the figure that the gypsum added with Example 5 and Example 6 has excellent ray shielding performance, and the shielding efficiency for X-rays with an energy of 20 - 60 keV can reach more than 50%. However, the shielding efficiency of Example 6 is about 3% lower than that of Example 5 overall. This is because the plant polyphenol used in Example 6 is gallic acid, while that used in Example 5 is tannic acid. This further illustrates that the active groups of plant polyphenols affect the dispersibility and stability of nanoparticles, thus affecting the ray shielding performance of the material. The gypsum added with Example 7 and Example 8 has excellent ray shielding performance. The shielding efficiency for X-rays with an energy of 20 - 80 keV can reach more than 40%, and the shielding efficiency for X-rays with an energy of 100 - 120 keV can reach more than 30%. When the addition amount is 50%, the shielding efficiency can reach up to more than 70% at most.

[0101] Figure 10The X-ray shielding efficiency of the gypsum with Example 5 and Comparative Example 3 added is shown. Here, a is the addition amount of 10%, b is the addition amount of 30%, and c is the addition amount of 50%. It can be seen from the figure that the shielding performance of the gypsum with Comparative Example 3 added is lower than that with Example 5 added under the same addition amount and the same ray energy, with the maximum difference being more than 5%. This is because the reaction temperature of Comparative Example 3 is too low and the reaction time is too short, resulting in a large amount of plant polyphenols not covering the surface of the nanoparticles. This further illustrates that the reaction conditions are important factors affecting the performance of this admixture.

[0102] Figure 11 The X-ray shielding efficiency of the gypsum with Example 7 and Comparative Example 4 added is shown. Here, a is the addition amount of 10%, b is the addition amount of 30%, and c is the addition amount of 50%. It can be seen from the figure that the shielding performance of the gypsum with Comparative Example 4 added is lower than that with Example 7 added, and as the addition amount increases, the gap in shielding performance in the high-energy range becomes more obvious, with the maximum difference being more than 7%. This is because the nanoparticle size of Comparative Example 4 is relatively large, being 500 nm, while that of Example 7 is 50 nm. This further illustrates that adding nanoparticles with a smaller particle size to gypsum crystals has better shielding performance than adding nanoparticles with a larger particle size.

[0103] It should be noted that the shielding efficiency of Examples 5 - 8 and Comparative Examples 3 - 4 is not good in the energy range of 40 - 80 keV, and as the ray energy increases, the shielding efficiency drops rapidly. The essence of the Compton effect and the photoelectric effect occurring between the shielding material and X-rays is the interaction between the outer electrons of the nanoparticles and the ray photons. Therefore, the energy magnitudes of the K and L absorption edges of the outer electron layers of elements significantly affect the ray shielding performance of the material, and the shielding effect on rays with energies close to its absorption edge energy is significant. The two absorption edge energies of bismuth element are close to 20 keV and 90 keV, which is quite different from 40 - 80 keV, resulting in poor shielding efficiency of bismuth for X-rays in this energy range.

[0104] The above-described embodiments are only descriptions of the preferred modes of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a dual-functional gypsum admixture based on plant polyphenols-nanoparticles, characterized in that the steps include: Adding plant polyphenols to the metal oxide nanoparticle dispersion, adjusting the pH to 7.5-8.0, filtering, washing and drying after the reaction to obtain the dual-functional gypsum admixture; The metal oxide nanoparticles in the metal oxide nanoparticle dispersion include at least one of erbium oxide nanoparticles, bismuth oxide nanoparticles, tungsten oxide nanoparticles, lanthanum oxide nanoparticles, tin oxide nanoparticles and cesium oxide nanoparticles; The particle size of the metal oxide nanoparticles is 50 to 200 nm; The reaction temperature is 60-80°C, the reaction time is 5-8 hours, and the reaction speed is 2000 r / min.

2. The preparation method according to claim 1, characterized in that The concentration of the metal oxide nanoparticles in the metal oxide nanoparticle dispersion is 5-10 wt %; and / or, The metal oxide nanoparticle dispersion is prepared by dispersing metal oxide nanoparticles in water.

3. The preparation method according to claim 1, characterized in that: The plant polyphenols include tannic acid, gallic acid or catechin acid; and / or, The concentration of the plant polyphenols in the reaction system is 0.03-0.05 mol / L.

4. The preparation method according to claim 1, characterized in that: The pH value is adjusted to 7.5-8.0 by using PBS buffer.

5. The preparation method according to claim 1, characterized in that: The washing is washing with water at least twice; and / or, The drying temperature is 40-60°C and the drying time is 8-12 hours.

6. The dual-functional gypsum admixture obtained by the preparation method as claimed in claim 1.

7. Use of the dual-functional gypsum admixture as claimed in claim 6 in the preparation of gypsum.

8. An X-ray shielding plaster, characterized in that: In terms of mass percentage, the components include: 50-90% gypsum powder and 10-50% of the dual-functional gypsum admixture according to claim 6.

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