A method for simultaneous calcination preparation of graphene-coated type II anhydrous gypsum

Abstract

This invention provides a method for the simultaneous calcination preparation of graphene-coated type II anhydrous gypsum, comprising the following steps: S1: Mixing gypsum dihydrate and water at a mass ratio of 1:0.3 to 1:0.8, and stirring to obtain a dispersed slurry; S2: Adding an organic carbon source to the slurry, continuously stirring to ensure uniform adsorption onto the surface of the gypsum dihydrate particles, filtering and separating the slurry to obtain adsorbed gypsum dihydrate particles and filtrate; S3: Drying the gypsum dihydrate particles obtained in S2, then calcining, and cooling to obtain graphene-coated type II anhydrous gypsum. The preparation method of this invention achieves the preparation of type II anhydrous gypsum and in-situ growth and modification of graphene, reduces the cost of graphene preparation, effectively solves the problem of poor dispersion of graphene in gypsum, significantly increases the graphene content, and broadens the application of type II anhydrous gypsum in self-leveling materials for underfloor heating backfill and energy storage materials.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a method for the simultaneous calcination preparation of graphene-coated type II anhydrous gypsum. Background Technology

[0002] Gypsum has a long history. As an ancient cementitious material, it is valued for its high strength, thermal insulation, sound absorption, fire resistance, and good biocompatibility, as well as its relatively lightweight properties. Furthermore, from a carbon emission perspective, gypsum is only one-third the carbon footprint of cement, making it a typical low-carbon cementitious material.

[0003] Currently, the call for energy conservation and carbon reduction is growing louder, making the development prospects of low-carbon cementitious materials increasingly promising. Therefore, gypsum cementitious materials are a key development area. From a resource utilization perspective, the main method for preparing gypsum cementitious materials is using industrial by-product gypsum. There are currently two main approaches to using industrial by-product gypsum to prepare cementitious materials: one is to use low-temperature calcination or autoclaving to prepare β-type or α-type hemihydrate gypsum; the other is to use high-temperature calcination to prepare type II anhydrous gypsum. High-temperature calcination not only removes organic matter and harmful impurities such as soluble phosphorus and fluorine from industrial by-product gypsum, but also produces type II anhydrous gypsum with higher later-stage strength and better water resistance, making it an important direction for the resource utilization of industrial by-product gypsum.

[0004] However, the existing high-temperature calcination preparation method of Type II anhydrous gypsum has some drawbacks. First, Type II anhydrous gypsum has a slow early hydration rate, low strength, and limited function. Moreover, it is currently only used in a small amount of self-leveling gypsum. Therefore, how to improve the early hydration activity and comprehensive performance of Type II anhydrous gypsum and broaden its application range is an urgent problem for the industry to solve. Summary of the Invention

[0005] This invention provides a method for the simultaneous calcination preparation of graphene-coated type II anhydrous gypsum.

[0006] The technical solution adopted in this invention is as follows:

[0007] S1: Mix gypsum dihydrate and water at a mass ratio of 1:0.3 to 1:0.8, and stir to obtain a uniformly dispersed slurry;

[0008] S2: Add the organic carbon source to the slurry and stir continuously to make it uniformly adsorbed on the surface of the gypsum dihydrate particles. Filter the slurry to separate the adsorbed gypsum dihydrate particles and filtrate.

[0009] S3: The dihydrate gypsum particles obtained in S2 are dried, then calcined, and cooled to obtain graphene-coated type II anhydrous gypsum.

[0010] Furthermore, during the S1 process, a magnetic stirrer is used to stir for 2 to 5 minutes.

[0011] Furthermore, the dihydrate gypsum described in S1 is one of natural dihydrate gypsum, desulfurized gypsum, phosphogypsum, titanium gypsum, citric acid gypsum, and industrial by-product dihydrate gypsum, which can increase the selectivity and economy of dihydrate gypsum.

[0012] Furthermore, the stirring time in S2 is 0.5 to 4 hours, and the organic carbon source accounts for 1% to 10% of the dry mass of gypsum dihydrate, which can increase the organic carbon source and adsorption stability, ensuring that saturated adsorption can be formed.

[0013] Furthermore, the stirring process can form a calcium-rich double layer on the particle surface.

[0014] Furthermore, the organic carbon source mentioned in S2 is soluble glucose, as well as cellulose ether, starch ether, chitosan, or modified natural polysaccharide, which can improve the selectivity of the organic carbon source. Moreover, the unsaturated hydroxyl groups [-OH] and ether bonds [ROR] in the molecular structure of glucose and modified natural polysaccharide can ensure the formation of stable chemical adsorption with calcium ions on the surface of gypsum dihydrate.

[0015] Furthermore, in S3, a vacuum drying oven is used for drying, with a drying time of 12–24 hours and a drying temperature of 40–60°C.

[0016] Furthermore, S3 uses a vacuum tube furnace for high-temperature calcination at a temperature of 600–800°C and a calcination time of 0.5–3 hours. The calcination process is protected by a N2 atmosphere, which can achieve the reduction of organic carbon to generate graphene and the decomposition of gypsum dihydrate to generate type II anhydrous gypsum, while ensuring that graphene grows in situ on the surface of type II anhydrous gypsum.

[0017] A type II anhydrous gypsum particle coated with graphene, wherein the graphene-coated type II anhydrous gypsum has a core-shell structure, with the inner layer being micron-sized anhydrous gypsum and the surface having nano-sized graphene particles grown on it.

[0018] Application of graphene-coated type II anhydrous gypsum particles, wherein the graphene-coated type II anhydrous gypsum is used in underfloor heating backfill self-leveling materials and energy storage materials.

[0019] Beneficial effects

[0020] (1) By regulating and coupling the high-temperature carbonization and reduction process of organic carbon and the high-temperature calcination process of gypsum dihydrate, the preparation of type II anhydrous gypsum and the in-situ growth and modification of graphene are realized simultaneously, and the preparation cost of graphene is reduced. The problem of graphene being difficult to disperse in gypsum is effectively solved, and the graphene content is greatly increased, with the content reaching 0.5% to 5%.

[0021] (2) By growing a layer of graphene in situ on the surface of type II anhydrous gypsum, the graphene acts as a nucleating agent to promote the nucleation and growth of dihydrate gypsum, thus enabling the hydration reaction of type II anhydrous gypsum to proceed in the forward direction and accelerating the hydration process.

[0022] (3) It enhances the hydration activity and mechanical strength of Type II anhydrous gypsum, while giving the material excellent thermal and electrical conductivity, thus broadening the application of Type II anhydrous gypsum in self-leveling materials for underfloor heating backfill and energy storage materials.

[0023] (4) By using graphene to fill the dense microstructure between hydration products, the mechanical strength of the material can be improved. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the preparation process of graphene-coated type II anhydrous gypsum in Example 1 of the present invention.

[0025] Figure 2 This is a SEM image of graphene-coated type II anhydrous gypsum from Example 1 of the present invention.

[0026] Figure 3 This is a TEM image of graphene-coated type II anhydrous gypsum from Example 1 of the present invention. Detailed Implementation

[0027] The following will describe in conjunction with embodiments 1-4 of the present invention and appendices. Figure 1-3 Table 1 further details the technical solutions of this invention, providing a clear and complete description. It is evident that the described embodiments are merely a portion of, and not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0028] The preparation method of this invention mainly includes the following steps: First, gypsum dihydrate and water are mixed in a certain proportion, and then the mixture is stirred evenly in a magnetic stirrer to obtain a uniformly dispersed slurry. Then, an organic carbon source is added to the slurry, and the mixture is stirred continuously to allow the organic carbon source polymer to be uniformly adsorbed onto the surface of the gypsum dihydrate particles. The organic carbon source accounts for 1% to 10% of the dry mass of the gypsum dihydrate. The adsorbed slurry is placed in a vacuum filtration device for filtration and separation to obtain adsorbed gypsum dihydrate particles and filtrate. The filtered gypsum dihydrate particles are placed in a vacuum drying oven for drying. Then, the dried gypsum dihydrate particles are placed in a vacuum tube furnace for high-temperature calcination. After the calcination is completed, the gypsum dihydrate particles are cooled to obtain a graphene-coated type II anhydrous gypsum sample.

[0029] Example 1

[0030] This embodiment proposes a method for the simultaneous calcination preparation of graphene-coated type II anhydrous gypsum, combined with... Figure 1 The flowchart yields the following steps:

[0031] S1: Mix gypsum dihydrate and water at a mass ratio of 1:0.3 and stir with a magnetic stirrer for 5 minutes to obtain a uniformly dispersed slurry;

[0032] S2: Add the organic carbon source, i.e., soluble glucose, to the slurry and stir continuously for 2 hours to allow it to be uniformly adsorbed on the surface of the gypsum dihydrate particles. The organic carbon source accounts for 5% of the dry mass of the gypsum dihydrate. Place the adsorbed slurry into a vacuum filtration device for filtration and separation to obtain the adsorbed gypsum dihydrate particles and filtrate.

[0033] S3: The filtered dihydrate gypsum particles were placed in a vacuum drying oven and dried for 24 hours at a temperature of 40°C. The dried dihydrate gypsum particles were then placed in a vacuum tube furnace and calcined at a high temperature of 700°C for 2 hours, under N2 atmosphere protection. After calcination and cooling, graphene-coated type II anhydrous gypsum was obtained.

[0034] Example 2

[0035] This embodiment proposes a method for the simultaneous calcination preparation of graphene-coated type II anhydrous gypsum; combined with Figure 1 The flowchart yields the following steps:

[0036] S1: Mix gypsum dihydrate and water at a mass ratio of 1:0.5 and stir with a magnetic stirrer for 3 minutes to obtain a uniformly dispersed slurry;

[0037] S2: Add the organic carbon source, namely cellulose ether, to the slurry and stir continuously for 4 hours to make it uniformly adsorbed on the surface of the gypsum dihydrate particles. The organic carbon source accounts for 7% of the dry mass of the gypsum dihydrate. The adsorbed slurry is placed in a vacuum filtration device for filtration and separation to obtain the adsorbed gypsum dihydrate particles and filtrate.

[0038] S3: The filtered dihydrate gypsum particles were placed in a vacuum drying oven and dried for 18 hours at a temperature of 50°C. The dried dihydrate gypsum particles were then placed in a vacuum tube furnace and calcined at a high temperature of 750°C for 1 hour, under N2 atmosphere protection. After calcination and cooling, graphene-coated type II anhydrous gypsum was obtained.

[0039] Example 3

[0040] This embodiment proposes a method for the simultaneous calcination preparation of graphene-coated type II anhydrous gypsum; combined with Figure 1 The flowchart yields the following steps:

[0041] S1: Mix gypsum dihydrate and water at a mass ratio of 1:0.6 and stir with a magnetic stirrer for 4 minutes to obtain a uniformly dispersed slurry;

[0042] S2: Add the organic carbon source, i.e. chitosan, to the slurry and stir continuously for 3 hours to make it uniformly adsorbed on the surface of the gypsum dihydrate particles. The organic carbon source accounts for 1% of the dry mass of the gypsum dihydrate. Put the adsorbed slurry into a vacuum filtration device for filtration and separation to obtain the adsorbed gypsum dihydrate particles and filtrate.

[0043] S3: The filtered dihydrate gypsum particles were placed in a vacuum drying oven and dried for 12 hours at a drying temperature of 55°C. The dried dihydrate gypsum particles were then placed in a vacuum tube furnace and calcined at a high temperature of 600°C for 0.5 hours. The process was protected by a N2 atmosphere. After calcination, the particles were cooled to obtain graphene-coated type II anhydrous gypsum.

[0044] Example 4

[0045] This embodiment proposes a method for the simultaneous calcination preparation of graphene-coated type II anhydrous gypsum; combined with Figure 1 The flowchart yields the following steps:

[0046] S1: Mix gypsum dihydrate and water at a mass ratio of 1:0.8 and stir with a magnetic stirrer for 2 minutes to obtain a uniformly dispersed slurry;

[0047] S2: Add the organic carbon source, namely starch ether, to the slurry and stir continuously for 0.5 hours to make it uniformly adsorbed on the surface of the gypsum dihydrate particles. The organic carbon source accounts for 10% of the dry mass of the gypsum dihydrate. Put the adsorbed slurry into a vacuum filtration device for filtration and separation to obtain the adsorbed gypsum dihydrate particles and filtrate.

[0048] S3: The filtered dihydrate gypsum particles were placed in a vacuum drying oven and dried for 16 hours at a temperature of 60°C. The dried dihydrate gypsum particles were then placed in a vacuum tube furnace and calcined at a high temperature of 800°C for 3 hours, under N2 atmosphere protection. After calcination and cooling, graphene-coated type II anhydrous gypsum was obtained.

[0049] Combination Figure 2 and Figure 3 As shown, Figure 2 The prepared graphene-coated type II anhydrous gypsum sample exhibits a layered porous structure. The layers are mainly type II anhydrous gypsum particles, while the pores are channels left when water molecules between the layers are released during the calcination of dihydrate gypsum to form anhydrous gypsum. Simultaneously, agglomerated substances are uniformly grown on the surface of the type II anhydrous gypsum particles. These substances are mainly formed by the aggregation of in-situ grown nanoscale graphene. Figure 3 The prepared graphene-coated type II anhydrous gypsum sample exhibits a core-shell structure, with a micron-sized anhydrous gypsum inner layer and nano-sized graphene particles grown on the surface, which effectively verifies the SEM test results. Figure 2 and Figure 3From a, b, c, and d in the figure, it can be seen that the preparation of type II anhydrous gypsum and the in-situ growth and modification of graphene were achieved.

[0050] One hundred parts of graphene-coated type II anhydrous gypsum sample, three parts of potassium sulfate, and five parts of CaO powder were mixed evenly. Then, 45 parts of water were added to adjust the slurry flowability to 180 mm. After casting and natural curing for 1 day and 28 days, the compressive strength, thermal conductivity, and resistivity of the samples were tested, with uncoated type II anhydrous gypsum as the control group. The results are shown in Table 1. It can be concluded that compared with pure type II anhydrous gypsum, the compressive strength of graphene-coated type II anhydrous gypsum increased by 2.44 times and 1.17 times at 1 day and 28 days, respectively, the thermal conductivity increased by 1.85 times, and the resistivity decreased by about four orders of magnitude. These results indicate that in-situ grown graphene can significantly improve the strength, thermal conductivity, and electrical conductivity of type II anhydrous gypsum, and can also increase the hydration rate of type II anhydrous gypsum, with particularly significant improvement in early (1 day) strength.

[0051] Table 1 shows the physical and mechanical properties of graphene-coated type II anhydrous gypsum in Example 1.

[0052]

[0053] The preparation method used in this invention can realize the preparation of type II anhydrous gypsum and the in-situ growth and modification of graphene, and reduce the preparation cost of graphene while increasing the graphene content. In addition, it can accelerate the hydration process, improve the electrical and thermal conductivity of the material, and broaden the application of type II anhydrous gypsum in self-leveling materials for underfloor heating backfill and energy storage materials.

Claims

1. A method for the simultaneous calcination preparation of graphene-coated type II anhydrous gypsum, characterized in that, The specific steps are as follows: S1: Mix gypsum dihydrate and water at a mass ratio of 1:0.3 to 1:0.8, and stir to obtain a dispersion slurry; S2: Add an organic carbon source to the slurry and stir, then filter and separate to obtain adsorbed gypsum dihydrate particles; the organic carbon source is one of soluble glucose, cellulose ether, starch ether, chitosan, and modified natural polysaccharides. S3: The dihydrate gypsum particles obtained in S2 are dried, then calcined, and cooled to obtain graphene-coated type II anhydrous gypsum; the calcination temperature is 600-800℃, the calcination time is 0.5-3h, and the calcination process is protected by N2 atmosphere.

2. The method for simultaneous calcination preparation of graphene-coated type II anhydrous gypsum as described in claim 1, characterized in that, The stirring time in S1 is 2 to 5 minutes.

3. The method for simultaneous calcination preparation of graphene-coated type II anhydrous gypsum as described in claim 1, characterized in that, The stirring time in S2 is 0.5 to 4 hours, and the organic carbon source accounts for 1% to 10% of the dry mass of the gypsum dihydrate.

4. The method for simultaneous calcination preparation of graphene-coated type II anhydrous gypsum as described in claim 1, characterized in that, The filtrate produced during filtration in S2 is returned to the adsorption process for recycling.

5. The method for simultaneous calcination preparation of graphene-coated type II anhydrous gypsum as described in claim 1, characterized in that, The drying time in S3 is 12-24 hours, and the drying temperature is 40-60℃.

6. A graphene-coated type II anhydrous gypsum obtained by any one of the preparation methods described in claims 1-5, characterized in that, The graphene-coated type II anhydrous gypsum has a core-shell structure, with the inner layer being micron-sized anhydrous gypsum and the surface covered with nano-sized graphene particles.

7. The application of graphene-coated type II anhydrous gypsum as described in claim 6, characterized in that, The graphene-coated type II anhydrous gypsum is used in self-leveling materials for underfloor heating backfill and in energy storage materials.

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