Nanoscale gear-like hemihydrate gypsum and method for producing the same

Abstract

The application discloses a kind of nanometer gear-like hemihydrate gypsum and preparation method thereof, and relates to the technical field of functional materials.The method comprises the following steps: alcohol is mixed with water to form an alcohol solution, and a crystal regulator is added to the alcohol solution to form a clear transparent solution, wherein the crystal regulator comprises ammonia and ethylenediaminetetraacetic acid disodium salt;Add dihydrate gypsum to the clear transparent solution, uniformly disperse and form a suspension;The suspension is added to a water bath and heated, filtered after reaction under stirring, and the obtained solid is dried to obtain the nanometer gear-like hemihydrate gypsum.The preparation method of the nanometer gear-like hemihydrate gypsum is simple, easy to operate, short production cycle, high yield, low energy consumption, easy to realize industrial production, and the obtained hemihydrate gypsum has a gear-like structure, which can enrich the existing hemihydrate gypsum crystal form.

Description

Technical Field

[0001] This invention relates to the field of functional materials technology, and in particular to a nanoscale gear-shaped hemihydrate gypsum and its preparation method. Background Technology

[0002] Among gypsum products, hemihydrate gypsum is highly favored due to its wide range of applications. The widespread use of hemihydrate gypsum is attributed to its excellent cementing properties, good biocompatibility, and easy biodegradability. It is widely used in building materials, molds, rubber, papermaking, friction materials, and environmental protection materials. Furthermore, its good biocompatibility makes its application in the pharmaceutical field possible.

[0003] High-quality nano-grade hemihydrate gypsum, as a multifunctional material, exhibits broad application potential. For example, nano-grade hemihydrate gypsum, with its high strength and lightweight characteristics, can be used to manufacture high-strength gypsum boards for walls and ceilings; nano-gypsum provides excellent filling properties and surface smoothness in coatings and putties, improving construction results; nano-grade hemihydrate gypsum has good biocompatibility and can be used to prepare biomedical materials, such as bone fillers and drug carriers, promoting bone tissue regeneration and drug release; due to its high precision and high strength, nano-grade hemihydrate gypsum can be used to manufacture high-precision molds, with wide applications in industries such as ceramics and glass.

[0004] Traditional hemihydrate gypsum crystals are typically pentagonal dodecahedral and hexagonal bipyramidal prismatic shapes. However, given the continuously increasing demands for gypsum material performance, particularly for high-strength and high-performance products such as high-quality medical gypsum, existing gypsum materials are no longer sufficient to meet the needs of social and economic development. Therefore, fundamental research on the crystallization laws and particle characteristics of gypsum, as well as research on the preparation technology of high-value-added gypsum products, is of paramount importance for developing gypsum materials with unique morphology, size, and properties. Summary of the Invention

[0005] This invention discloses a nanoscale gear-shaped hemihydrate gypsum and its preparation method, which enriches the crystal form of hemihydrate gypsum and solves the technical problem that existing hemihydrate gypsum materials cannot meet the needs of social and economic development.

[0006] To solve the above problems, the present invention adopts the following technical solution: The first aspect of the present invention provides a method for preparing nanoscale gear-shaped hemihydrate gypsum.

[0007] The preparation method of nanoscale gear-shaped hemihydrate gypsum of the present invention includes the following steps: An alcohol is mixed with water to form an alcohol solution, and a crystallizing agent is added to the alcohol solution to form a clear and transparent solution. The crystallizing agent includes ammonia and disodium ethylenediaminetetraacetate. Add gypsum dihydrate to the clear and transparent solution, disperse it evenly, and form a suspension; The suspension was added to a water bath and heated. After reaction under stirring, the mixture was filtered, and the resulting solid was dried to obtain nano-sized gear-shaped hemihydrate gypsum.

[0008] According to a preferred embodiment, the amount of ammonia added is 10-50 mL / L; the amount of disodium ethylenediaminetetraacetate added is 1-10 g / L.

[0009] According to a preferred embodiment, the alcohol is glycerol, and the volume ratio of the alcohol to water is 16:4-19:1.

[0010] According to a preferred embodiment, the dihydrate gypsum is a reaction-synthesized dihydrate gypsum or a natural dihydrate gypsum, and the purity of the dihydrate gypsum is above 99%.

[0011] According to a preferred embodiment, the amount of gypsum dihydrate added is 1-200 g / L.

[0012] According to a preferred embodiment, the temperature of the water bath reaction is 80-100 °C, and the reaction time is 2-10 hours.

[0013] According to a preferred embodiment, when filtering the mixture obtained after the reaction, the filter cake obtained is washed with water and anhydrous ethanol.

[0014] According to a preferred embodiment, the temperature during filtration of the resulting mixture after the reaction is above 80 °C.

[0015] According to a preferred embodiment, the filtered solid is placed in an oven at a temperature of 60-100 °C and dried for 4-24 hours.

[0016] A second aspect of the present invention provides a nanoscale gear-shaped hemihydrate gypsum.

[0017] The nanoscale gear-shaped hemihydrate gypsum of the present invention comprises the following raw materials in the following proportions: Alcohol and water, wherein the volume ratio of alcohol to water is 16:4 to 19:1; A crystallizing agent comprising ammonia and disodium ethylenediaminetetraacetate, wherein in the alcohol solution formed by mixing the alcohol and water, the amount of ammonia added is 10-50 mL / L and the amount of disodium ethylenediaminetetraacetate added is 1-10 g / L; In the alcohol solution formed by mixing alcohol and water, the amount of gypsum dihydrate added is 1-200 g / L. Furthermore, the nano-sized gear-shaped hemihydrate gypsum is prepared using the preparation method of nano-sized gear-shaped hemihydrate gypsum described in any of the technical solutions of this invention.

[0018] The technical solution adopted in this invention can achieve the following beneficial effects: This invention discloses a method for preparing nanoscale gear-shaped hemihydrate gypsum. Using dihydrate gypsum as raw material and a mixture of ammonia and disodium ethylenediaminetetraacetate as a crystal modifier, nanoscale gear-shaped hemihydrate gypsum can be obtained by heating in an alcohol-water solution system via a water bath. Compared with existing technologies, the method provided by this invention has a simple preparation route, convenient operation, short production cycle, high yield, low energy consumption, and is easily scalable for industrial production. Furthermore, the resulting hemihydrate gypsum exhibits a gear-shaped structure, enriching the existing crystal forms of hemihydrate gypsum.

[0019] This invention provides a nanoscale gear-shaped hemihydrate gypsum and its preparation method. The nanoscale gear-shaped hemihydrate gypsum exhibits a gear-shaped crystal structure, possessing a larger specific surface area and higher porosity compared to other forms of hemihydrate gypsum. This results in better adsorption performance, making it suitable as a catalyst carrier or adsorbent. Secondly, the high specific surface area and porosity of the nanoscale gear-shaped hemihydrate gypsum, along with its gear-shaped crystal structure, result in a relatively large crystal surface area. Simultaneously, the crystal contains numerous micropores with high porosity, which facilitates the formation of highly structured structures, such as nanowires and nanotubes, on the crystal surface or within the crystal. Thirdly, the tooth-shaped structure of the nanoscale gear-shaped hemihydrate gypsum is located in the circumferential direction at the center, giving the center high strength. This results in good thermal and mechanical stability, making it less prone to deformation. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a synthetic route diagram of the nanoscale gear-shaped hemihydrate gypsum of this application; Figure 2 This is a low-magnification scanning electron microscope image of the nanoscale gear-shaped hemihydrate gypsum obtained in Example 1; Figure 3 This is a high-magnification scanning electron microscope image of the nanoscale gear-shaped hemihydrate gypsum obtained in Example 1; Figure 4 This is the X-ray powder diffraction pattern of the nanoscale gear-shaped hemihydrate gypsum obtained in Example 1; Figure 5 This is a low-magnification scanning electron microscope image of the nanoscale gear-shaped hemihydrate gypsum obtained in Example 2; Figure 6 This is a high-magnification scanning electron microscope image of the nanoscale gear-shaped hemihydrate gypsum obtained in Example 2; Figure 7 This is the X-ray powder diffraction pattern of the nanoscale gear-shaped hemihydrate gypsum obtained in Example 2; Figure 8 This is a low-magnification scanning electron microscope image of the nanoscale gear-shaped hemihydrate gypsum obtained in Example 3; Figure 9 This is a high-magnification scanning electron microscope image of the nanoscale gear-shaped hemihydrate gypsum obtained in Example 3; Figure 10 This is an X-ray powder diffraction pattern of the nanoscale gear-shaped hemihydrate gypsum obtained in Example 3. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0023] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0024] In related technologies, nano-sized hemihydrate gypsum can be prepared by heating it in an alcohol-water system with a water bath using dihydrate gypsum as raw material and adding a crystal modifier. However, the nano-sized hemihydrate gypsum obtained in these technologies is mostly in the form of short columnar, long rod-shaped, needle-shaped, or plate-shaped structures. Due to the limitations of their structure, the application of hemihydrate gypsum with these structures is restricted.

[0025] Specifically, short columnar hemihydrate gypsum has a small longitudinal dimension, resulting in a relatively small specific surface area, which is not conducive to achieving high efficiency in adsorption and catalytic reactions. In addition, short columnar hemihydrate gypsum is not suitable as a carrier for drug delivery or for depositing highly structured materials such as nanowires and nanotubes, making it difficult to construct high-performance composite materials.

[0026] Long rod-shaped and needle-shaped hemihydrate gypsum also suffer from relatively small specific surface areas, which is not conducive to achieving high efficiency in adsorption and catalytic reactions. In addition, long rod-shaped and needle-shaped hemihydrate gypsum are not suitable as carriers for drug delivery or for depositing highly structured materials such as nanowires and nanotubes, making it difficult to construct high-performance composite materials. Furthermore, the morphology of needle-shaped hemihydrate gypsum is prone to aggregation and accumulation, thereby affecting its application effect.

[0027] Plate-like hemihydrate gypsum has a highly structured characteristic, which can be used to deposit highly structured materials such as nanowires and nanotubes; however, the specific surface area of ​​plate-like hemihydrate gypsum is relatively small, so its efficiency in adsorption and catalytic reactions is relatively low.

[0028] This application provides a nanoscale gear-shaped hemihydrate gypsum and its preparation method. The nanoscale gear-shaped hemihydrate gypsum exhibits a highly structured gear-like crystal facet, possessing a larger specific surface area and higher porosity compared to other forms of hemihydrate gypsum. This results in better adsorption performance, making it suitable as a catalyst carrier or adsorbent. Secondly, the nanoscale gear-shaped hemihydrate gypsum of this application has a high specific surface area and porosity, with a gear-like crystal facet, resulting in a relatively large crystal surface area. Simultaneously, the crystal contains numerous micropores with high porosity. These characteristics facilitate the loading of highly structured structures, such as nanowires and nanotubes, onto the crystal surface or within the crystal. Thirdly, the tooth-like structure of the nanoscale gear-shaped hemihydrate gypsum of this application is located in the circumferential direction at the center, giving the center high strength. This results in good thermal and mechanical stability, making it less prone to deformation.

[0029] The highly structured materials referred to in this application are those with a highly ordered structure and morphology. Such materials typically have certain size and shape limitations, and their structure and morphology can be controlled and adjusted through specific preparation methods. Highly structured materials generally possess the following characteristics: controllable size and shape, high orderliness, large specific surface area, and high porosity.

[0030] Figure 1 A synthetic route diagram for the nanoscale gear-shaped hemihydrate gypsum of this application is shown. Figure 1 As shown, the preparation method of nanoscale gear-shaped hemihydrate gypsum in this application includes the following steps: In some embodiments of this application, a crystallizing agent is provided for preparing nanoscale gear-shaped hemihydrate gypsum. The crystallizing agent comprises ammonia and disodium ethylenediaminetetraacetate. In the solution, the amount of ammonia added is 10-50 mL / L; the amount of disodium ethylenediaminetetraacetate added is 1-10 g / L.

[0031] Step S100: Mix alcohol and water to form an alcohol solution, and add a crystallizing agent to the alcohol solution to form a clear and transparent solution. The crystallizing agent includes ammonia and disodium ethylenediaminetetraacetate.

[0032] Preferably, the amount of ammonia added is 10-50 mL / L; the amount of disodium ethylenediaminetetraacetate added is 1-10 g / L.

[0033] A mixture of ammonia and disodium ethylenediaminetetraacetate was added to the reaction vessel as a crystal modifier. Ammonia can form a complex with disodium ethylenediaminetetraacetate. The complexation effect of disodium ethylenediaminetetraacetate can inhibit the growth of specific crystal faces of gypsum crystals, thereby promoting the development of crystal morphology and structure.

[0034] Preferably, the alcohol is glycerol, and the volume ratio of alcohol to water is 16:4-19:1. However, it is not limited to this; the alcohol can also be ethylene glycol or other alcohols.

[0035] By mixing alcohol and water to form a reaction solution, it is beneficial to control the solubility and ionic strength of gypsum dihydrate, thereby controlling the morphology and structure of gypsum hemihydrate crystals.

[0036] Step S200: Add gypsum dihydrate to the clear and transparent solution, disperse it evenly, and form a suspension.

[0037] Preferably, the dihydrate gypsum is synthesized through reaction or is natural dihydrate gypsum, with a purity of 99% or higher. The amount of dihydrate gypsum added is 1-200 g / L.

[0038] For example, gypsum dihydrate can be added directly to a clear and transparent solution.

[0039] Step S300: Add the suspension to a water bath and heat it. After reacting under stirring, filter the solution and dry the resulting solid to obtain nano-sized gear-shaped hemihydrate gypsum.

[0040] Preferably, the water bath reaction temperature is 80-100 ℃ and the reaction time is 2-10 hours.

[0041] Preferably, when filtering the mixture obtained after the reaction, the filter cake is washed with water and anhydrous ethanol. More preferably, the temperature during filtration of the mixture obtained after the reaction is higher than 80 °C. Exemplarily, the mixture obtained after the reaction can be filtered immediately after the reaction is completed.

[0042] For example, when washing with water and anhydrous ethanol, the water temperature is above 80°C. The anhydrous ethanol is at room temperature. Washing with hot water removes impurities from the filter cake, while washing with anhydrous ethanol removes water from the filter cake.

[0043] After the reaction is complete, unreacted substances or impurities may remain in the mixture. If the mixture is allowed to cool before filtration, these impurities will begin to crystallize and precipitate, affecting the purity and morphology of the hemihydrate gypsum. Furthermore, hemihydrate gypsum has a metastable crystal structure and tends to transform into stable dihydrate gypsum in aqueous solutions at lower temperatures. The mixture obtained in this application is filtered at a temperature above 80 °C, which avoids the crystallization and precipitation of impurities and the transformation of hemihydrate gypsum into dihydrate gypsum, thus preventing the impact on the purity and morphology of the hemihydrate gypsum.

[0044] Preferably, the filtered solid is dried in an oven at a temperature of 60-100 °C for 4-24 hours.

[0045] This application discloses a method for preparing nanoscale gear-shaped hemihydrate gypsum. Using dihydrate gypsum as raw material and a mixture of ammonia and disodium ethylenediaminetetraacetate as a crystal modifier, nanoscale gear-shaped hemihydrate gypsum can be obtained by heating in an alcohol-water solution system via a water bath. Compared with existing technologies, the method provided in this application has a simple preparation route, convenient operation, short production cycle, high yield, low energy consumption, and is easily scalable for industrial production. Furthermore, the resulting hemihydrate gypsum exhibits a gear-shaped structure, which can enrich the existing crystal forms of hemihydrate gypsum.

[0046] The nano-sized gear-shaped hemihydrate gypsum of this application comprises the following raw materials in the following proportions: Alcohol and water, with a volume ratio of alcohol to water of 16:4 to 19:1; Crystallization agent, which includes ammonia and disodium ethylenediaminetetraacetate. In an alcohol solution formed by mixing alcohol and water, the amount of ammonia added is 10-50 mL / L, and the amount of disodium ethylenediaminetetraacetate added is 1-10 g / L. In an alcohol solution formed by mixing alcohol and water, the amount of gypsum dihydrate added is 1-200 g / L. Furthermore, the nano-sized gear-shaped hemihydrate gypsum is prepared using the preparation method of the nano-sized gear-shaped hemihydrate gypsum according to any one of the technical solutions in this application.

[0047] The following is in conjunction with the appendix Figures 2 to 10 Examples 1 to 3 of this application provide a detailed description of the nanoscale gear-shaped hemihydrate gypsum and its preparation method.

[0048] Example 1 The preparation method of nanoscale gear-shaped hemihydrate gypsum in this embodiment includes the following steps: Step S100: Add 95 mL of glycerol and 5 mL of deionized water to a 200 mL beaker, stir and mix thoroughly to form an alcohol solution. Then add 2 mL of ammonia and 0.5 g of disodium ethylenediaminetetraacetate, stir and dissolve thoroughly to form a clear and transparent solution.

[0049] Step S200: Add 10 g of gypsum dihydrate to the clear and transparent solution obtained in step S100, and sonicate until completely dispersed and a suspension is formed.

[0050] Step S300: The suspension obtained in step S200 was placed in a 98 ℃ water bath for 4 h and then filtered directly. The resulting filter cake was then rinsed three times with 98 ℃ deionized water and then rinsed three times with anhydrous ethanol. Finally, the washed filter cake was dried at 90 ℃ for 5 hours to obtain nano-sized gear-shaped hemihydrate gypsum.

[0051] The microstructure and phase structure of the nanoscale gear-shaped hemihydrate gypsum prepared above were measured, and the results were as follows: Figure 2 and Figure 3 The scanning electron microscope image shown is as follows: Figure 4 The X-ray powder diffraction pattern shown.

[0052] Depend on Figure 2 and Figure 3 It can be seen that the material obtained in Example 1 mainly exhibits a nanoscale gear-like structure and has good dispersibility. Figure 4 It can be seen that the composite material has a high degree of crystallinity, and the peak positions of the diffraction peaks coincide with those of the standard X-ray powder diffraction pattern of hemihydrate gypsum (JCPDF NO.81-1848). Therefore, the material obtained in Example 1 is mainly composed of hemihydrate gypsum.

[0053] Example 2 The preparation method of nanoscale gear-shaped hemihydrate gypsum in this embodiment includes the following steps: Step S100: Add 80 mL of glycerol and 20 mL of deionized water to a 200 mL beaker, stir and mix thoroughly to form an alcohol solution. Then add 5 mL of ammonia and 1 g of disodium ethylenediaminetetraacetate, stir and dissolve thoroughly to form a clear and transparent solution.

[0054] Step S200: Add 20 g of gypsum dihydrate to the clear and transparent solution obtained in step S100, and sonicate until completely dispersed and a suspension is formed.

[0055] Step S300: The suspension obtained in step S200 is placed in a water bath at 100 ℃ for 2 h and then filtered directly. The resulting filter cake is then rinsed three times with deionized water at 80 ℃, and then rinsed three times with anhydrous ethanol. Finally, the washed filter cake is dried at 60 ℃ for 24 hours to obtain nano-sized gear-shaped hemihydrate gypsum.

[0056] The microstructure and phase structure of the nanoscale gear-shaped hemihydrate gypsum prepared above were measured, and the results were as follows: Figure 5 and Figure 6 The scanning electron microscope image shown is as follows: Figure 7The X-ray powder diffraction pattern shown.

[0057] Depend on Figure 5 and Figure 6 It can be seen that the material obtained in Example 2 mainly exhibits a nanoscale gear-like structure and has good dispersibility. Figure 7 It can be seen that the composite material has a high degree of crystallinity, and the peak positions of the diffraction peaks coincide with those of the standard X-ray powder diffraction pattern of hemihydrate gypsum (JCPDF NO.81-1848). Therefore, the material obtained in Example 2 is mainly composed of hemihydrate gypsum.

[0058] Example 3 The preparation method of nanoscale gear-shaped hemihydrate gypsum in this embodiment includes the following steps: Step S100: Add 90 mL of glycerol and 10 mL of deionized water to a 200 mL beaker, stir and mix thoroughly to form an alcohol solution. Then add 1 mL of ammonia and 0.1 g of disodium ethylenediaminetetraacetate, stir and dissolve thoroughly to form a clear and transparent solution.

[0059] Step S200: Add 0.1 g of gypsum dihydrate to the clear and transparent solution obtained in step S100, and sonicate until completely dispersed and a suspension is formed.

[0060] Step S300: The suspension obtained in step S200 was placed in an 80 ℃ water bath for 10 h and then filtered directly. The resulting filter cake was then rinsed three times with deionized water at 98 ℃, and then rinsed three times with anhydrous ethanol. Finally, the washed filter cake was dried at 100 ℃ for 4 hours to obtain nano-sized gear-shaped hemihydrate gypsum.

[0061] The microstructure and phase structure of the nanoscale gear-shaped hemihydrate gypsum prepared above were measured, and the results were as follows: Figure 8 and Figure 9 The scanning electron microscope image shown is as follows: Figure 10 The X-ray powder diffraction pattern shown.

[0062] Depend on Figure 8 and Figure 9 It can be seen that the material obtained in Example 3 mainly exhibits a nanoscale gear-like structure and has good dispersibility. Figure 10 It can be seen that the composite material has a high degree of crystallinity, and the peak positions of the diffraction peaks coincide with those of the standard X-ray powder diffraction pattern of hemihydrate gypsum (JCPDF NO.81-1848). Therefore, the material obtained in Example 3 is mainly composed of hemihydrate gypsum.

[0063] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0064] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing nanoscale gear-shaped hemihydrate gypsum, characterized in that, Includes the following steps: An alcohol is mixed with water to form an alcohol solution, and a crystallizing agent is added to the alcohol solution to form a clear and transparent solution. The volume ratio of the alcohol to water is 16:4-19:

1. The crystallizing agent includes ammonia and disodium ethylenediaminetetraacetate, and the amount of ammonia added is 10-50 mL / L, and the amount of disodium ethylenediaminetetraacetate added is 1-10 g / L. Add gypsum dihydrate to the clear and transparent solution, disperse it evenly, and form a suspension; The suspension is added to a water bath and heated. After reaction under stirring, it is filtered. The resulting solid is dried to obtain nano-sized gear-shaped hemihydrate gypsum. The water bath reaction temperature is 80-100 ℃, the reaction time is 2-10 hours, and the temperature of the mixture obtained after the reaction is higher than 80 ℃ when filtered.

2. The method for preparing nanoscale gear-shaped hemihydrate gypsum according to claim 1, characterized in that, The alcohol is glycerol.

3. The method for preparing nanoscale gear-shaped hemihydrate gypsum according to claim 1, characterized in that, The dihydrate gypsum is either synthesized by reaction or natural dihydrate gypsum, and the purity of the dihydrate gypsum is above 99%.

4. The method for preparing nanoscale gear-shaped hemihydrate gypsum according to claim 1, characterized in that, The amount of gypsum dihydrate added is 1-200 g / L.

5. The method for preparing nanoscale gear-shaped hemihydrate gypsum according to claim 1, characterized in that, When filtering the mixture obtained after the reaction, the filter cake is washed with water and anhydrous ethanol.

6. The method for preparing nanoscale gear-shaped hemihydrate gypsum according to claim 1, characterized in that, The filtered solid was dried in an oven at 60-100 ℃ for 4-24 hours.

7. A nanoscale gear-shaped hemihydrate gypsum, characterized in that, The ingredients include the following proportions: Alcohol and water, wherein the volume ratio of alcohol to water is 16:4 to 19:1; A crystallizing agent comprising ammonia and disodium ethylenediaminetetraacetate, wherein in the alcohol solution formed by mixing the alcohol and water, the amount of ammonia added is 10-50 mL / L and the amount of disodium ethylenediaminetetraacetate added is 1-10 g / L; In the alcohol solution formed by mixing alcohol and water, the amount of gypsum dihydrate added is 1-200 g / L. Furthermore, the nano-sized gear-shaped hemihydrate gypsum is prepared using the method described in any one of claims 1 to 6.

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