Monodisperse nano calcium carbonate standard substance with uniformity and stability and preparation method of monodisperse nano calcium carbonate standard substance

Abstract

The invention discloses a monodisperse nano calcium carbonate standard substance with uniformity and stability and a preparation method of the monodisperse nano calcium carbonate standard substance, and relates to the technical field of nano calcium carbonate preparation. The method comprises the following technical steps: (1) preparing slurry; (2) pre-sanding treatment; (3) carbonization reaction; (4) sanding treatment; and (5) hydrothermal reaction. Through the steps of pre-sanding treatment, carbonization reaction, sanding treatment, hydrothermal reaction and the like, the nano calcium carbonate has very good particle size distribution, crystalline phase purity and dispersity. The nano calcium carbonate standard substance has an atypical cubic crystal form, the average particle size is 110-130 nm, crystal grain distribution is uniform, D50 is 0.110-0.140 [mu] m, and the crystal phase is a single calcite phase. And the material shows excellent uniformity and long-term stability in a water phase. The preparation method has the outstanding advantages of cheap and easily available raw materials, no need of adding any organic additive, simple and efficient process and the like, and is suitable for standardized production and practical application.

Description

Technical Field

[0001] This invention relates to the field of nano-calcium carbonate preparation technology, specifically to a monodisperse nano-calcium carbonate standard substance with both uniformity and stability, and its preparation method. Background Technology

[0002] Calcium carbonate, as an inorganic non-metallic mineral powder, possesses excellent properties such as non-toxicity, good biocompatibility, biodegradability, low production cost, high specific surface area, and high porosity, making it one of the most widely used and consumed powder materials. Due to its unique optoelectronic properties, electronic-grade nano-calcium carbonate has become an indispensable key material in the electronics and information industry, widely used in piezoelectric ceramics, ceramic capacitors, integrated circuit boards, microwave dielectric devices, and other fields. It not only serves as a filler and insulating material, enhancing the strength and hardness of seals, but also helps reduce production costs and improve product processing performance. For example, in ceramic capacitors, nano-calcium carbonate can act as a barium titanate refiner, inhibiting excessive grain growth and reducing voltage effects; as a coating material for vacuum electronic devices, it can generate high-intensity emission currents at high temperatures (e.g., 750℃), thereby significantly extending the service life and reliability of oxide cathodes.

[0003] Currently, the preparation of electronic-grade nano-calcium carbonate still faces key technological bottlenecks, hindering the further promotion and application of the material. The main issues are significant shortcomings in batch consistency and long-term stability of high-purity nano-calcium carbonate. Different batches exhibit large fluctuations in particle size distribution, dispersibility, and morphology, with some batches even failing to meet the requirements of high-precision applications. Specifically, this manifests as easy particle agglomeration, a wide particle size distribution range, uneven morphology, and poor dispersion stability in application systems. These defects severely impact the material's application in electronic components and high-performance composite materials.

[0004] The aforementioned problems mainly stem from two factors: first, the production process fluctuates greatly, making precise control difficult; second, there is a lack of standard materials suitable for current technological levels and possessing good uniformity and stability, serving as a reference for quality control. Currently, the synthesis methods for nano-calcium carbonate mainly include grinding and precipitation. Grinding primarily involves prolonged, high-speed mechanical processing of heavy calcium carbonate or coarse calcium carbonate powder to obtain fine-particle products. However, this method suffers from drawbacks such as easy introduction of impurities, high energy consumption, and low efficiency, and it is difficult to achieve precise control over particle morphology and size. Precipitation methods mainly include carbonation and metathesis. Carbonation uses calcium hydroxide and carbon dioxide as raw materials to synthesize calcium carbonate through a gas-liquid-solid three-phase reaction, offering advantages such as low cost, readily available raw materials, and high product purity. However, it still faces challenges in precisely controlling the morphology, size, and crystal form of the product. Metathesis involves the reaction of compounds containing calcium ions and carbonate ions in the liquid phase to generate calcium carbonate, with a wide range of applications, but it suffers from slow reaction rates, low product purity, and high production costs.

[0005] Whether prepared by grinding or precipitation, the nano-calcium carbonate powders currently available generally suffer from irregular morphology, wide particle size distribution, severe particle agglomeration, and poor uniformity. Furthermore, existing technologies often rely on organic additives such as surface modifiers, crystallization inhibitors, crystal form control agents, or dispersants to control product morphology and dispersibility. This not only increases the complexity and cost of the production process but may also introduce impurities, affecting the product's application in high-purity fields.

[0006] Therefore, there is a need to develop a method for preparing monodisperse nano-calcium carbonate standard materials with good uniformity and stability in batches without the need for additives, with simple process, strong controllability, and no risk of additives, so as to promote the development of the electronic-grade nano-calcium carbonate industry. Summary of the Invention

[0007] To address the above problems, this invention provides a monodisperse nano-calcium carbonate standard material with both uniformity and stability, and its preparation method. Through steps such as pre-milling, carbonation reaction, milling, and hydrothermal reaction, the prepared nano-calcium carbonate has excellent particle size distribution, crystal phase purity, and dispersibility. Moreover, the material exhibits excellent uniformity and long-term stability in the aqueous phase.

[0008] This invention is achieved through the following technical solution: A method for preparing a monodisperse nano-calcium carbonate standard substance with both homogeneity and stability includes the following steps: (1) Slurry preparation: At room temperature, mix calcium hydroxide with water and stir evenly to prepare calcium hydroxide slurry; (2) Pre-grinding treatment: The calcium hydroxide slurry is pre-grinded at a speed of 1500-2500 r / min for 15-25 min. After the treatment, the pre-grinded calcium hydroxide slurry is obtained. (3) Carbonation reaction under sand milling: Under the sand milling conditions of 1500-2500 r / min, water-soluble inorganic carbonates are gradually added to the pre-sand milled calcium hydroxide slurry and carbonized to pH 7-8. After the carbonation reaction is completed, nano calcium carbonate slurry is obtained. (4) Continue sand milling: continue sand milling the nano calcium carbonate slurry at a speed of 1500-2500 r / min for 10-15 min. After the process is completed, filter, wash, dry and crush in sequence to obtain nano calcium carbonate powder. (5) Hydrothermal reaction: After mixing and stirring the nano-calcium carbonate powder with water, the resulting mixture is transferred to a hydrothermal reactor for hydrothermal reaction. After the reaction is completed, it is cooled to room temperature to obtain a monodisperse nano-calcium carbonate standard substance with both uniformity and stability.

[0009] Further, in step (1), the mass ratio of calcium hydroxide to water is 80-112 g: 1 L.

[0010] Further, in step (1), the concentration of the calcium hydroxide slurry is 1 to 1.5 mol / L.

[0011] Furthermore, in step (3), the water-soluble inorganic carbonate is any one or a combination of two or more of ammonium carbonate, ammonium bicarbonate, and sodium bicarbonate.

[0012] Further, in step (3), the mass ratio of the water-soluble inorganic carbonate to calcium hydroxide is 1 to 1.1:1.

[0013] Further, in step (5), the mass-to-volume ratio of the nano-calcium carbonate powder to water is 0.1-0.15 g: 1 mL.

[0014] Furthermore, in step (5), the temperature of the hydrothermal reaction is 100-120°C and the time is 8-16 hours.

[0015] A monodisperse nano-calcium carbonate standard material with both uniformity and stability is prepared by the method described above.

[0016] Furthermore, the monodisperse nano-calcium carbonate standard material exhibits an atypical cubic crystal form with an average particle size of 110–130 nm and a uniform grain size distribution. 50 The size ranges from 0.110 to 0.140 μm, and the crystal phase is a single calcite phase.

[0017] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. This invention, through pre-milling, carbonation reaction, milling, and hydrothermal reaction, achieves nano-calcium carbonate with excellent particle size distribution, crystal phase purity, and dispersibility. This nano-calcium carbonate standard material exhibits an atypical cubic crystal form, with an average particle size of 110–130 nm, uniform grain distribution, and D... 50 The particle size is 0.110–0.140 μm, and the crystal phase is a single calcite phase. Furthermore, this material exhibits excellent homogeneity and long-term stability in aqueous solution. The preparation method of this invention has significant advantages such as readily available and inexpensive raw materials, no need for any organic additives, and a simple and efficient process, making it suitable for standardized production and practical applications.

[0018] 2. This invention employs pre-milling, where mechanical force refines calcium hydroxide raw material particles to the nanoscale. This process not only significantly increases the specific surface area and surface energy of the reactants, thereby lowering the reaction barrier and increasing the reaction rate of subsequent carbonization reactions, but more importantly, it yields highly uniform nanoscale precursors. These refined particles more readily form a uniform supersaturated state in the slurry, promoting the simultaneous and abundant generation of nucleation sites. This effectively shortens the nucleation time and inhibits differential crystal growth, laying the foundation for achieving a narrow particle size distribution and uniform precipitation of the final product.

[0019] 3. In this invention, the carbonization reaction is carried out under continuous sand milling conditions. The strong mechanical force provided by the sand milling effectively prevents the initially generated nano-calcium carbonate from coating unreacted calcium hydroxide, thus preventing the reaction from being hindered and ensuring the completeness and speed of the reaction. Simultaneously, the carbon source continuously and uniformly releases carbon dioxide into the slurry, providing a stable environment for uniform nucleation. The mechanical force in this process also instantly breaks down the initial agglomerates formed due to rapid nucleation, while the low-temperature condensation device of the sand mill removes the heat of reaction. Together, these factors inhibit particle agglomeration from both kinetic and thermodynamic perspectives, ensuring the dispersibility of the product.

[0020] 4. After the carbonization reaction is completed, the present invention continues with a short-term sand milling process. Utilizing the high-frequency collision and shear force between the nano-calcium carbonate slurry and the ultra-fine zirconia grinding balls, any weak soft agglomerates that may have formed during the carbonization process are further dispersed. This post-treatment operation provides the slurry with final homogenization, resulting in a nano-calcium carbonate slurry with better dispersibility and a more concentrated particle distribution, providing an optimal precursor for the next stage of hydrothermal reaction.

[0021] 5. In the hydrothermal reaction of this invention, the nano-calcium carbonate particles undergo a dissolution and recrystallization process. This process effectively repairs lattice defects inside the crystal and irregular surface structures, thereby significantly improving the overall crystallinity. The more complete and stable crystal structure significantly reduces the surface energy and chemical reactivity of the particles. This not only further improves the dispersibility of the nanoparticles in the aqueous phase, but also greatly enhances their environmental stability during long-term storage, ultimately resulting in products with uniformity and stability. Attached Figure Description

[0022] Figure 1 This is a SEM image of the monodisperse nano-calcium carbonate standard material prepared in Example 1.

[0023] Figure 2 The image shows the XRD pattern of the monodisperse nano-calcium carbonate standard material prepared in Example 1.

[0024] Figure 3 The particle size frequency distribution diagram is shown for the monodisperse nano-calcium carbonate standard material prepared in Example 1.

[0025] Figure 4 SEM images showing the uniformity of different packaging samples of the monodisperse nano-calcium carbonate standard material prepared in Example 1.

[0026] Figure 5 The particle size frequency distribution diagram shows the different packaging samples of the monodisperse nano-calcium carbonate standard material prepared in Example 1.

[0027] Figure 6 SEM images showing the stability of monodisperse nano-calcium carbonate standard material prepared in Example 1 at different packaging levels after 0 months, 1 month, 3 months, 5 months, 7 months, and 9 months.

[0028] Figure 7 The particle size frequency distribution of the monodisperse nano-calcium carbonate standard material prepared in Example 1 at different packaging samples after 0 months, 1 month, 3 months, 5 months, 7 months and 9 months is shown. Detailed Implementation

[0029] The present invention will be further described in detail below through embodiments. These embodiments are only used to illustrate the present invention and do not limit the scope of protection of the present invention.

[0030] Example 1 A method for preparing a monodisperse nano-calcium carbonate standard substance with both homogeneity and stability includes the following steps: (1) Slurry preparation: At room temperature, mix 222.27g of calcium hydroxide with 2.5L of deionized water and stir evenly to prepare a calcium hydroxide slurry with a concentration of 1.2mol / L; (2) Pre-grinding treatment: The calcium hydroxide slurry was pre-grinded at a speed of 2000 r / min for 20 min. After the treatment, the pre-grinded calcium hydroxide slurry was obtained. (3) Carbonation reaction under sand milling: Under the sand milling treatment condition of 2000 r / min, 230 g of ammonium carbonate was gradually added to the pre-sand milled calcium hydroxide slurry to carbonize to pH 7.5. After the carbonation reaction was completed, nano calcium carbonate slurry was obtained. (4) Continue sand milling: The nano calcium carbonate slurry is sand milled for 10 minutes at a speed of 2000 r / min. After the process is completed, it is filtered, washed, dried and crushed in sequence to obtain nano calcium carbonate powder. (5) Hydrothermal reaction: Mix 5g of nano-calcium carbonate powder with 50mL of deionized water and stir evenly. Transfer the resulting mixture to a hydrothermal reactor and carry out a hydrothermal reaction at 100℃ for 12h. After the reaction is completed, cool to room temperature to obtain a monodisperse nano-calcium carbonate standard substance with both uniformity and stability.

[0031] Example 2 A method for preparing a monodisperse nano-calcium carbonate standard substance with both homogeneity and stability includes the following steps: (1) Slurry preparation: At room temperature, mix 259.32g of calcium hydroxide with 2.5L of deionized water and stir evenly to prepare a calcium hydroxide slurry with a concentration of 1.4mol / L; (2) Pre-grinding treatment: The calcium hydroxide slurry was pre-grinded at a speed of 2000 r / min for 20 min. After the treatment, the pre-grinded calcium hydroxide slurry was obtained. (3) Carbonation reaction under sand milling: Under the sand milling treatment condition of 2000 r / min, 265 g of ammonium carbonate was gradually added to the pre-sand milled calcium hydroxide slurry to carbonize to pH 7.5. After the carbonation reaction was completed, nano calcium carbonate slurry was obtained. (4) Continue sand milling: The nano calcium carbonate slurry is sand milled for 10 minutes at a speed of 2000 r / min. After the process is completed, it is filtered, washed, dried and crushed in sequence to obtain nano calcium carbonate powder. (5) Hydrothermal reaction: Mix 5g of nano-calcium carbonate powder with 50mL of deionized water and stir evenly. Transfer the resulting mixture to a hydrothermal reactor and carry out a hydrothermal reaction at 100℃ for 12h. After the reaction is completed, cool to room temperature to obtain a monodisperse nano-calcium carbonate standard substance with both uniformity and stability.

[0032] Example 3 A method for preparing a monodisperse nano-calcium carbonate standard substance with both homogeneity and stability includes the following steps: (1) Slurry preparation: At room temperature, mix 222.27g of calcium hydroxide with 2.5L of deionized water and stir evenly to prepare a calcium hydroxide slurry with a concentration of 1.2mol / L; (2) Pre-grinding treatment: The calcium hydroxide slurry was pre-grinded at a speed of 2300 r / min for 20 min. After the treatment, the pre-grinded calcium hydroxide slurry was obtained. (3) Carbonation reaction under sand milling: Under the sand milling treatment condition of 2300 r / min, 230 g of ammonium carbonate was gradually added to the pre-sand milled calcium hydroxide slurry to carbonize to pH 7.5. After the carbonation reaction was completed, nano calcium carbonate slurry was obtained. (4) Continue sand milling: The nano calcium carbonate slurry is sand milled for 10 minutes at a speed of 2300 r / min. After the process is completed, it is filtered, washed, dried and crushed in sequence to obtain nano calcium carbonate powder. (5) Hydrothermal reaction: Mix 5g of nano-calcium carbonate powder with 50mL of deionized water and stir evenly. Transfer the resulting mixture to a hydrothermal reactor and carry out a hydrothermal reaction at 100℃ for 12h. After the reaction is completed, cool to room temperature to obtain a monodisperse nano-calcium carbonate standard substance with both uniformity and stability.

[0033] Example 4 A method for preparing a monodisperse nano-calcium carbonate standard substance with both homogeneity and stability includes the following steps: (1) Slurry preparation: At room temperature, mix 275.50g of calcium hydroxide with 2.5L of deionized water and stir evenly to prepare a calcium hydroxide slurry with a concentration of 1.49mol / L; (2) Pre-grinding treatment: The calcium hydroxide slurry was pre-grinded at a speed of 2500 r / min for 17 min. After the treatment, the pre-grinded calcium hydroxide slurry was obtained. (3) Carbonization reaction under sand milling: Under the sand milling treatment condition of 2500 r / min, 280 g of ammonium bicarbonate was gradually added to the pre-sand milled calcium hydroxide slurry to carbonize to pH 7.5. After the carbonization reaction was completed, nano calcium carbonate slurry was obtained. (4) Continue sand milling: The nano calcium carbonate slurry is sand milled for 15 minutes at a speed of 2500 r / min. After the process is completed, it is filtered, washed, dried and crushed in sequence to obtain nano calcium carbonate powder. (5) Hydrothermal reaction: 5.5g of nano calcium carbonate powder was mixed with 50mL of deionized water and stirred evenly. The resulting mixture was then transferred to a hydrothermal reactor and subjected to a hydrothermal reaction at 110℃ for 12h. After the reaction was completed, the mixture was cooled to room temperature to obtain a monodisperse nano calcium carbonate standard substance with both uniformity and stability.

[0034] Example 5 A method for preparing a monodisperse nano-calcium carbonate standard substance with both homogeneity and stability includes the following steps: (1) Slurry preparation: At room temperature, mix 250.30g of calcium hydroxide with 2.5L of deionized water and stir evenly to prepare a calcium hydroxide slurry with a concentration of 1.35mol / L; (2) Pre-grinding treatment: The calcium hydroxide slurry was pre-grinded at a speed of 1800 r / min for 25 min. After the treatment, the pre-grinded calcium hydroxide slurry was obtained. (3) Carbonation reaction under sand milling: Under the sand milling treatment condition of 1800 r / min, 255 g of sodium bicarbonate was gradually added to the pre-sand milled calcium hydroxide slurry to carbonize to pH 7.5. After the carbonation reaction was completed, nano calcium carbonate slurry was obtained. (4) Continue sand milling: The nano calcium carbonate slurry is sand milled for 12 minutes at a speed of 1800 r / min. After the process is completed, it is filtered, washed, dried and crushed in sequence to obtain nano calcium carbonate powder. (5) Hydrothermal reaction: 7.5g of nano calcium carbonate powder was mixed with 50mL of deionized water and stirred evenly. The resulting mixture was then transferred to a hydrothermal reactor and subjected to a hydrothermal reaction at 100℃ for 16h. After the reaction was completed, the mixture was cooled to room temperature to obtain a monodisperse nano calcium carbonate standard substance with both uniformity and stability.

[0035] Example 6 A method for preparing a monodisperse nano-calcium carbonate standard substance with both homogeneity and stability includes the following steps: 1) Slurry preparation: At room temperature, mix 200.45g of calcium hydroxide with 2.5L of deionized water and stir evenly to prepare a calcium hydroxide slurry with a concentration of 1.08mol / L; (2) Pre-grinding treatment: The calcium hydroxide slurry was pre-grinded at a speed of 2000 r / min for 22 min. After the treatment, the pre-grinded calcium hydroxide slurry was obtained. (3) Carbonation reaction under sand milling: Under the sand milling treatment condition of 2000 r / min, 150 g of ammonium carbonate and 55 g of ammonium bicarbonate were gradually added to the pre-sand milled calcium hydroxide slurry to carbonize to pH 7.5. After the carbonation reaction was completed, nano calcium carbonate slurry was obtained. (4) Continue sand milling: The nano calcium carbonate slurry is sand milled for 10 minutes at a speed of 2000 r / min. After the process is completed, it is filtered, washed, dried and crushed in sequence to obtain nano calcium carbonate powder. (5) Hydrothermal reaction: 6g of nano calcium carbonate powder was mixed with 50mL of deionized water and stirred evenly. The resulting mixture was then transferred to a hydrothermal reactor and subjected to a hydrothermal reaction at 120℃ for 8h. After the reaction was completed, the mixture was cooled to room temperature to obtain a monodisperse nano calcium carbonate standard substance with both uniformity and stability.

[0036] Comparative Example 1 The preparation method of nano-calcium carbonate described in the journal "Synthesis of homogeneous CaCO3 nano powders with good dispersibility via a novel method" was used as a comparative example. The specific preparation method of nano-calcium carbonate in that journal was as follows: 7.41 g of calcium hydroxide was mixed with 8.80 g of dry ice and reacted by ball milling at room temperature. After filtering the slurry, it was dried in an oven at 60 °C for 24 h to obtain a calcium carbonate precursor. Then, 5.00 g of the precursor was transferred to a 100 mL Teflon Parr reactor, which was filled with solutions of different pH values. After sealing, it was heated at 160 °C for 12 h. The resulting powder was filtered, washed, and dried at 60 °C for 24 h to obtain the final calcium carbonate product.

[0037] The average particle size of the nano-calcium carbonate disclosed in this journal is 130–150 nm. 50 The range is 0.240–0.270 μm.

[0038] Material characterization analysis (I) SEM Analysis The morphology of the monodisperse nano-calcium carbonate standard sample prepared in Example 1 was characterized using field emission scanning electron microscopy (FE-SEM). The characterization results are as follows: Figure 1 , Figure 4 , Figure 6 As shown.

[0039] As shown in Figure 1, the average particle size of the monodisperse nano-calcium carbonate standard material prepared in Example 1 is 110-130 nm, which is smaller than that of the nano-calcium carbonate prepared in Comparative Example 1, and has good uniformity and dispersibility.

[0040] Figure 4 In the image, ai represents SEM images of samples packaged at different depths. Figure 4 It can be seen that in the monodisperse nano-calcium carbonate standard material prepared in Example 1, all sample crystals in different packaging samples showed good crystal shape and uniform dispersion, with an average particle size of about 120 nm and small differences between different samples.

[0041] Figure 6In the diagram, the af plots correspond to the SEM images of the samples at 0 months, 1 month, 3 months, 5 months, 7 months, and 9 months, respectively. (From...) Figure 6 It can be seen that the monodisperse nano-calcium carbonate standard material prepared in Example 1 maintained a uniform dispersion state at all test time points of 0 months, 1 month, 3 months, 5 months, 7 months and 9 months, and showed a cubic structure with uniform size and regular morphology. No obvious agglomerates or coarse particles were observed.

[0042] (II) XRD Analysis The crystal phase structure of the monodisperse nano-calcium carbonate standard sample prepared in Example 1 was characterized and analyzed using X-ray diffraction (XRD). The results are as follows: Figure 2 As shown.

[0043] Depend on Figure 2 It can be seen that the monodisperse nano-calcium carbonate standard material prepared in Example 1 is a typical calcite phase and no other diffraction peaks were observed.

[0044] (III) Particle Size Distribution (PSD) Analysis The particle size distribution (PSD) of the monodisperse nano-calcium carbonate standard sample prepared in Example 1 was characterized and analyzed using a laser particle size analyzer. The results are as follows: Figure 3 , 5 As shown.

[0045] Depend on Figure 3 It can be seen that the particle size distribution curves of the monodisperse nano-calcium carbonate standard material samples prepared in Example 1 are highly consistent, both exhibiting a unimodal normal distribution characteristic. 50 The particle size of 119 nm and the average particle size of 110-130 nm correspond to the good dispersibility of the product of the present invention, which is better than that of the calcium carbonate prepared in Comparative Example 1.

[0046] Depend on Figure 5 It can be seen that in the different aliquots of the monodisperse nano-calcium carbonate standard material prepared in Example 1, the particle size is mainly concentrated and uniformly distributed in the range of 80-160 nm. The results show that the average particle size of the samples is stable at around 120 nm, and the difference between different samples is small.

[0047] In addition, the products in Examples 1-6 of this invention all comply with the requirements of JJF 2060-2023 "Development of Submicron and Nanoscale Particle Standard Materials" and the provisions of JJF 1342-2022 "General Requirements for Standard Material Development (Production) Organizations".

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a monodisperse nano-calcium carbonate standard substance with both homogeneity and stability, characterized in that, Includes the following steps: (1) Slurry preparation: At room temperature, mix calcium hydroxide with water and stir evenly to prepare calcium hydroxide slurry; (2) Pre-grinding treatment: The calcium hydroxide slurry is pre-grinded at a speed of 1500-2500 r / min for 15-25 min. After the treatment, the pre-grinded calcium hydroxide slurry is obtained. (3) Carbonation reaction under sand milling: Under the sand milling conditions of 1500-2500 r / min, water-soluble inorganic carbonates are gradually added to the pre-sand milled calcium hydroxide slurry and carbonized to pH 7-8. After the carbonation reaction is completed, nano calcium carbonate slurry is obtained. (4) Continue sand milling: continue sand milling the nano calcium carbonate slurry at a speed of 1500-2500 r / min for 10-15 min. After the process is completed, filter, wash, dry and crush in sequence to obtain nano calcium carbonate powder. (5) Hydrothermal reaction: After mixing and stirring the nano-calcium carbonate powder with water, the resulting mixture is transferred to a hydrothermal reactor for hydrothermal reaction. After the reaction is completed, it is cooled to room temperature to obtain a monodisperse nano-calcium carbonate standard substance with both uniformity and stability.

2. The method for preparing monodisperse nano-calcium carbonate standard material with both uniformity and stability according to claim 1, characterized in that, In step (1), the mass ratio of calcium hydroxide to water is 80-112 g: 1 L.

3. The method for preparing monodisperse nano-calcium carbonate standard material with both uniformity and stability according to claim 2, characterized in that, In step (1), the concentration of the calcium hydroxide slurry is 1 to 1.5 mol / L.

4. The method for preparing monodisperse nano-calcium carbonate standard material with both uniformity and stability according to claim 1, characterized in that, In step (3), the water-soluble inorganic carbonate is any one or a combination of two or more of ammonium carbonate, ammonium bicarbonate, and sodium bicarbonate.

5. The method for preparing monodisperse nano-calcium carbonate standard material with both uniformity and stability according to claim 4, characterized in that, In step (3), the mass ratio of the water-soluble inorganic carbonate to calcium hydroxide is 1 to 1.1:

1.

6. The method for preparing monodisperse nano-calcium carbonate standard material with both uniformity and stability according to claim 1, characterized in that, In step (5), the mass-to-volume ratio of the nano-calcium carbonate powder to water is 0.1-0.15 g: 1 mL.

7. The method for preparing monodisperse nano-calcium carbonate standard material with both uniformity and stability according to claim 1, characterized in that, In step (5), the temperature of the hydrothermal reaction is 100-120°C and the time is 8-16 hours.

8. A monodisperse nano-calcium carbonate standard material with both uniformity and stability, prepared by the preparation method according to any one of claims 1-7.

9. The monodisperse nano-calcium carbonate standard material with both homogeneity and stability according to claim 8, characterized in that, The monodisperse nano-calcium carbonate standard material exhibits atypical cubic crystal form with an average particle size of 110–130 nm and uniform grain size distribution. 50 The size ranges from 0.110 to 0.140 μm, and the crystal phase is a single calcite phase.

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