A method for preparing graphene nanocavitation microspheres

Abstract

The application discloses a preparation method of graphene nanocavitation microspheres, and comprises the following steps: phase change microcapsule preparation: dissolving paraffin and an emulsifier in an aqueous solvent, stirring under constant temperature and rotating speed for a certain time to form a stable oil-in-water emulsion, and the precipitate after centrifugation at room temperature is the paraffin microcapsule; graphene aqueous suspension preparation: dispersing graphene in a tetrahydrofuran solution and mixing with degassed water, removing the tetrahydrofuran by solvent evaporation after reaction for a certain time at a certain temperature; graphene nanocavitation microsphere preparation: mixing the paraffin microcapsule and the graphene solution, performing suction filtration after sufficient stirring, so that the graphene nanosheet is wrapped on the surface of the paraffin microcapsule, and finally drying at 60 DEG C; the paraffin capsule is removed by being heated and melted as a sacrifice layer; the graphene nanocavitation microsphere has the characteristics of high adsorption capacity and wide spectrum while having a fast adsorption rate for various metal ions and soluble organic matters.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new materials, and particularly relates to a preparation method of graphene nanocavitation microspheres. BACKGROUND

[0002] Graphene is a two-dimensional sheet material with a honeycomb structure of hexagonal cells, which is composed of sp 2 hybridized carbon atoms. The sp 2 hybridization of graphene causes the p orbitals of the carbon atoms to form a large π bond in a side-by-side manner. Electrons can move freely within this large π bond, and experiments have shown that the in-plane carrier mobility of graphene can reach 1.5*10 4 cm 2 / (V s), which is about 100 times that of single-crystal silicon. The fascinating properties of graphene have attracted widespread attention from researchers, and how to prepare graphene has become a key issue. Although the micromechanical exfoliation method adopted by Geim can obtain high-quality single-layer graphene, this method has a very low yield, which limits its application. In recent years, many new graphene preparation methods have emerged, including epitaxial growth, chemical vapor deposition (CVD), liquid-phase exfoliation, chemical oxidation-reduction, and electrochemical exfoliation. Graphene itself has unique mechanical, electrical, thermal, and optical properties, and not only can it be directly assembled into new materials, but also can be combined with other materials to prepare nanocomposites. However, the graphene prepared by conventional methods is often in the form of an aqueous solution, and the presence of water brings additional costs and inconvenience to the storage, transportation, and use of graphene. In addition, the conventional drying process often causes the graphene to form stacks, which fundamentally damages its solubility and greatly hinders the large-scale use of graphene. Introducing a microsphere structure into the graphene sheet can effectively reduce the stacking of graphene sheets, which is a feasible solution to realize the drying and then dissolving of graphene.

[0003] Phase change materials (PCM) are substances that change their physical state and provide latent heat as a function of temperature. The process of changing from a solid to a liquid or from a liquid to a solid is called phase change. Phase change materials can be divided into organic and inorganic phase change materials and can also be divided into hydrated phase change materials and waxy phase change materials. The most common phase change material is water, which changes from a liquid to a solid (freezing) when the temperature is as low as 0°C. When the temperature is higher than 0°C, water changes from a solid to a liquid (melting). A large amount of cold energy is absorbed and stored during the freezing process, while a large amount of heat energy is absorbed during the melting process. The larger the amount (volume) of ice, the longer the melting process takes. Phase change materials have the ability to change their physical state within a certain temperature range. For example, in the case of solid-liquid phase change, when heated to the melting temperature, a phase change from solid to liquid occurs. During the melting process, the phase change material absorbs and stores a large amount of latent heat. When the phase change material cools down, the stored heat is released to the environment within a certain temperature range, and the reverse phase change from liquid to solid occurs. In these two phase change processes, the energy stored or released is called phase change heat. When the physical state changes, the temperature of the material itself remains almost constant before the phase change is completed, forming a wide temperature platform. Although the temperature does not change, the latent heat absorbed or released is quite large. Classification of phase change materials Phase change materials mainly include inorganic PCM, organic PCM and composite PCM. Among them, inorganic PCM mainly includes crystalline hydrated salt, molten salt, metal or alloy; organic PCM mainly includes paraffin, acetic acid and other organic substances; in recent years, composite phase change heat storage materials have emerged, which can effectively overcome the shortcomings of single inorganic or organic phase change heat storage materials, improve the application effect of phase change materials and expand their application range.

[0004] Graphene prepared by conventional methods is often in the form of an aqueous solution, and the presence of water brings additional costs and inconvenience to the storage, transportation and use of graphene. In addition, the conventional drying process often causes graphene to form stacks, which fundamentally damages its solubility and greatly hinders the large-scale use of graphene. The present application provides a preparation method of graphene nanocavitation microspheres to solve the above problems. SUMMARY

[0005] In order to overcome the defects in the prior art, the present application provides a preparation method of graphene nanocavitation microspheres. The design of the microsphere structure maintains the original physicochemical properties of graphene, avoids the additional costs and inconvenience caused by graphene agglomeration in storage, transportation and use, greatly expands the application of graphene, and still maintains uniformity and easy dispersion after drying, greatly reducing the reprocessing cost of graphene.

[0006] TECHNICAL SCHEME

[0007] A method for preparing graphene nanocavitation microspheres, comprising the following steps:

[0008] Step 1: Preparation of phase change microcapsules: Dissolve paraffin and emulsifier in the water phase solvent, stir at constant temperature and speed for a certain time to form a stable oil-in-water emulsion, and the precipitate after centrifugation at room temperature is the paraffin microcapsule.

[0009] Step 2: Preparation of graphene aqueous suspension: Disperse graphene in tetrahydrofuran solution and mix with degassed water, react at a certain temperature for a certain time, and then remove tetrahydrofuran by solvent evaporation to obtain a stable graphene solution in water.

[0010] Step 3: Preparation of graphene nanocavitation microspheres: Mix the paraffin microcapsules prepared in step (1) with the graphene solution prepared in step (2), stir thoroughly, and then filter to make the graphene nanosheets wrap around the surface of the paraffin, and finally dry at 60°C. The paraffin capsule is used as a sacrificial layer to remove the paraffin by heating and melting, and the hollow graphene nanocavitation microspheres are obtained.

[0011] Further, the constant temperature and speed in step 1: the temperature is 40-60°C, and the speed is 400-1000 rpm.

[0012] Further, the certain time in step 1 is 1-5h.

[0013] Further, the emulsifier in step 1 is 8.3g sodium dodecyl sulfate, the paraffin is 25g n-eicosane, and the water phase solvent is 250ml formamide solution.

[0014] Further, the paraffin in step 1 is a phase change material, and the optional objects of the phase change material include but are not limited to paraffin and metal (nickel) foam.

[0015] Further, the emulsifier in step 1 includes but is not limited to sodium dodecyl sulfate and formamide.

[0016] Further, the graphene and tetrahydrofuran solution in step 2 are blended at a mass ratio of 0.5 / 100, wherein the graphene is 0.5g, the degassed water is 98g, and the tetrahydrofuran is 1.5g, the preparation temperature is 20-60°C, and the reaction time is 30-120 minutes.

[0017] Further, the graphene nanocavitation microspheres in step 3 are prepared by layer-by-layer assembly of paraffin microcapsules and graphene to form a core-shell structure of graphene microcapsules, and the graphene is coated on the surface of the paraffin microcapsules, and then the paraffin is removed by heating and melting to obtain graphene nanocavitation microspheres.

[0018] Furthermore, the graphene nanocavitation microspheres are prepared from the following components in parts by weight: 0.5-5% graphene, 5-10% paraffin wax, 70-85% degassed water, 1-5% emulsifier, and 1-5% tetrahydrofuran.

[0019] Beneficial effects

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. The microsphere structure design preserves the original physicochemical properties of graphene, while avoiding the additional costs and inconveniences caused by graphene agglomeration in storage, transportation and use, thus greatly expanding the application of graphene.

[0022] 2. Conventional drying processes often cause graphene to stack, fundamentally damaging its solubility and greatly hindering the large-scale use of graphene. The microsphere structure designed in this invention remains uniform and easy to disperse and process after graphene drying, greatly reducing the cost of graphene reprocessing.

[0023] 3. The microsphere structure gives graphene a large specific surface area of ​​200-300m². 2 / g, density is only 30-50mg / cm³ 3 It can be used in fields such as electrochemical energy storage, catalytic materials, solvent adsorption, drug coating and microwave absorption.

[0024] 4. The graphene nanocavitation microspheres of the present invention have great application prospects due to their fast adsorption rate for various metal ions and soluble organic compounds, as well as their broad-spectrum and high adsorption capacity. Attached Figure Description

[0025] Fig. 1 This is a schematic diagram of the structure of the graphene phase change microcapsule of the present invention;

[0026] Fig. 2 A schematic diagram illustrating the preparation mechanism of graphene nanocavitation microspheres;

[0027] Fig. 3 This is a microscopic image of the graphene nanocavitary microspheres under a microscope. Detailed Implementation

[0028] To better illustrate the content of this invention, the following description is provided in conjunction with the accompanying drawings and examples:

[0029] have Figs. 1-3 As shown, this invention discloses a method for preparing graphene nanocavitary microspheres, comprising the following steps:

[0030] Step 1: Preparation of phase change microcapsules: Dissolve paraffin and emulsifier in the water phase solvent, stir at constant temperature and speed for a certain time to form a stable oil-in-water emulsion, and the precipitate after centrifugation at room temperature is the paraffin microcapsule.

[0031] Step 2: Preparation of graphene aqueous suspension: Disperse graphene in tetrahydrofuran solution and mix with degassed water, react at a certain temperature for a certain time, then remove tetrahydrofuran by solvent evaporation to obtain a stable graphene solution in water.

[0032] Step 3: Preparation of graphene nanocavitation microspheres: Mix the paraffin microcapsules prepared in step (1) with the graphene solution prepared in step (2), stir thoroughly, then filter to make the graphene nanosheets wrap around the surface of the paraffin, and finally dry at 60°C. The paraffin capsule is removed by heating and melting as a sacrificial layer to obtain hollow graphene nanocavitation microspheres.

[0033] Further, the constant temperature and speed in step 1: temperature is 40-60°C, speed is 400-1000 rpm.

[0034] Further, the certain time in step 1 is 1-5h.

[0035] Further, the emulsifier in step 1 is 8.3g sodium dodecyl sulfate, the paraffin is 25g n-eicosane, and the water phase solvent is 250ml formamide solution.

[0036] Further, the paraffin in step 1 is a phase change material, and the optional objects of the phase change material include but are not limited to paraffin, metal (nickel) foam.

[0037] Further, the emulsifier in step 1 includes but is not limited to sodium dodecyl sulfate, formamide.

[0038] Further, the graphene and tetrahydrofuran solution in step 2 are blended at a mass ratio of 0.5 / 100, wherein the graphene is 0.5g, the degassed water is 98g, and the tetrahydrofuran is 1.5g, the preparation temperature is 20-60°C, and the reaction time is 30-120 minutes.

[0039] Further, the graphene nanocavitation microspheres in step 3 are prepared by the method of layer-by-layer assembly of paraffin microcapsules and graphene to prepare graphene microcapsules with core-shell structure, and the graphene is coated on the surface of the paraffin microcapsules, and then the paraffin is removed by heating and melting to obtain graphene nanocavitation microspheres.

[0040] Further, the graphene nanocavitation microspheres are prepared from the following components: graphene 0.5-5%, paraffin 5-10%, degassed water 70-85%, emulsifier 1-5%, and tetrahydrofuran 1-5%.

[0041] Specifically, step 1, 8.3 g of sodium dodecyl sulfate (SDS) and 25 g of n-eicosane are added to a 250 ml formamide solution, and a stable oil-in-water emulsion (O / W) is formed by stirring at a constant temperature (45°C) and a rotation speed of 600 rpm for 2.5 h. After centrifugation, paraffin microcapsules with a diameter of 2-10 μm are obtained.

[0042] Step 2, graphene is dispersed in a tetrahydrofuran solution to form a stable dispersion, and then the graphene / tetrahydrofuran solution is added to degassed water to stably disperse graphene in water. Finally, tetrahydrofuran is removed by slow solvent evaporation to obtain a graphene dispersion in water without surfactant.

[0043] Step 3, graphene nanocavitation microspheres are prepared by layer-by-layer assembly of paraffin microcapsules and graphene to form a core-shell structure of graphene microcapsules. Graphene is coated on the surface of the paraffin microcapsules, and then the paraffin is removed by heating and melting to obtain graphene nanocavitation microspheres.

[0044] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto. Although the technical solutions of the present application have been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing examples, or replace some of the technical features with equivalent ones. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing graphene nanocavitation microspheres, characterized in that, The method comprises the following steps: Step 1: Preparation of phase change microcapsules: dissolve paraffin and emulsifier in water phase solvent, the temperature is 40-60 DEG C, the rotating speed is 400-1000 rpm, stirring 1-5 h to form stable oil-in-water emulsion, the precipitate after centrifugation at room temperature is paraffin microcapsule; Step 2: Preparation of graphene aqueous suspension: disperse graphene in tetrahydrofuran solution and mix with degassed water, after reaction at a certain temperature for a certain time, remove tetrahydrofuran by solvent evaporation, and then a stable graphene solution in water is obtained; Step 3: Preparation of graphene nanocavitation microspheres: mix the paraffin microcapsules prepared in step 1 with the graphene solution prepared in step 2, stir thoroughly, then filter, so that the graphene nanosheets are wrapped on the surface of paraffin, finally dry at 60 DEG C, remove the paraffin capsules as the sacrificial layer by heating and melting, and then the hollow graphene nanocavitation microspheres are obtained; In step 1, the emulsifier is 8.3 g of sodium dodecyl sulfate, the paraffin is 25 g of n-eicosane, and the water phase solvent is 250 ml of formamide solution; In step 2, graphene and tetrahydrofuran solution are blended at a mass ratio of 0.5 / 100, wherein the graphene is 0.5 g, the degassed water is 98 g, and the tetrahydrofuran is 1.5 g, the preparation temperature is 20-60 DEG C, and the reaction time is 30-120 minutes.

Images