阅读说明：本技术 一种具有光热转换功能的石蜡Pickering乳液及其制备方法 (Paraffin Pickering emulsion with photo-thermal conversion function and preparation method thereof ) 是由 车黎明 茹绍青 吴雪娥 陈晓东 于 2020-05-27 设计创作，主要内容包括：一种具有光热转换功能的石蜡Pickering乳液及其制备方法,涉及太阳能光热转换与存储领域。按质量百分比计包括以下组分：石蜡10％～40％,镁-铝层状双金属氢氧化物1％～5％,氧化石墨烯大于0、小于等于0.1％,余量为水；本发明以镁-铝层状双金属氢氧化物和氧化石墨烯代替化学乳化剂,制备一种低过冷度、低黏度、高热导率、高度稳定、具有优异光热转换性能的石蜡Pickering乳液,且制备方法简单。(A paraffin Pickering emulsion with a photo-thermal conversion function and a preparation method thereof relate to the field of solar photo-thermal conversion and storage. The composite material comprises the following components in percentage by mass: 10-40% of paraffin, 1-5% of magnesium-aluminum layered double hydroxide, more than 0 and less than or equal to 0.1% of graphene oxide and the balance of water; according to the invention, the magnesium-aluminum layered double metal hydroxide and the graphene oxide are used for replacing a chemical emulsifier to prepare the paraffin Pickering emulsion with low supercooling degree, low viscosity, high thermal conductivity, high stability and excellent photo-thermal conversion performance, and the preparation method is simple.)

1. The paraffin Pickering emulsion with the photo-thermal conversion function is characterized by comprising the following components in percentage by mass: 10-40% of paraffin, 1-5% of magnesium-aluminum layered double hydroxide, more than 0 and less than or equal to 0.1% of graphene oxide and the balance of water.

2. The paraffin Pickering emulsion with photothermal conversion function as claimed in claim 1, wherein: the content of the magnesium-aluminum layered double hydroxide is 2%.

3. The paraffin Pickering emulsion with photothermal conversion function as claimed in claim 1, wherein: the content of the paraffin is 30%.

4. The paraffin Pickering emulsion with photothermal conversion function as claimed in claim 1, wherein: the paraffin is a solid paraffin having a melting point of <90 ℃.

5. The preparation method of the paraffin Pickering emulsion with the photothermal conversion function as claimed in any one of claims 1 to 4, which is characterized by comprising the following steps:

1) adding magnesium-aluminum layered double hydroxides into water, and dissolving and dispersing to obtain a solution A;

2) adding graphene oxide into the solution A, and dissolving and dispersing to obtain a solution B;

3) and adding paraffin into the solution B, heating to a temperature above the melting point of the paraffin, and stirring and emulsifying after the paraffin is completely melted to obtain the paraffin Pickering emulsion with the photothermal conversion function.

6. The method of claim 5, wherein: in the step 1), deionized water is adopted as the water.

7. The method of claim 5, wherein said dissolving and dispersing comprises the following: firstly stirring to dissolve, and then carrying out ultrasonic dispersion.

Technical Field

The invention relates to the field of solar photo-thermal conversion and storage, in particular to a paraffin Pickering emulsion with a photo-thermal conversion function and a preparation method thereof.

Background

As is well known, solar energy is a clean renewable energy source. The efficient utilization of solar energy is an important means for dealing with energy crisis and controlling environmental pollution. Direct utilization of solar energy includes photothermal conversion, photoelectric conversion, and photocatalysis. Among them, solar photo-thermal conversion is the most efficient way so far.

The paraffin emulsion is a novel fluid with heat transfer and heat storage functions, shows good application prospect in solar photo-thermal conversion, but has the following outstanding problems at present:

first, paraffin emulsions are generally milky white and have poor matting properties and thus low photothermal conversion efficiency (Wang F., ethylene graphite nanoparticles-dispersed paraffin/water emulsion with enhanced thermal-physical properties and photo-thermal properties. Solar energy materials and Cells,2016,147: 101-.

Secondly, there is a pronounced supercooling phenomenon in paraffin emulsions (Delgado M., et al. review on phase change material emulsions and microencapsulated phase change material dispersions: Materials, heat transfer students and applications. Recewable and Sustainable Energy Reviews,2012,16(1): 253-. Supercooling delays paraffin crystallization, so that paraffin is not solidified or is incompletely solidified when being cooled, and the heat storage performance of the paraffin is greatly reduced (Chenlin, and the like).

Third, the thermal conductivity of paraffin emulsions is low. The thermal conductivity of the paraffin wax is about 0.2 W.m^-1·K^-1Less than half the thermal conductivity of water, so that the thermal conductivity of paraffin emulsions is lower than that of water (Qu Y., et al. Experimental stuck thermal conductivity of paraffin-based shape-stabilized phase change with hybrid carbon no-additives. renewable Energy,2020,146: 2637-2645). The thermal conductivity of the paraffin emulsion with the solid content of 20 percent is only 60 percent of that of water (Liu Xiaoshi, et al, preparation and convection heat transfer characteristics of graphene oxide/paraffin composite phase-change emulsion, chemical engineering report, 2019,70(3): 1188-1197). Low thermal conductivity is detrimental to heat in paraffin emulsionsDiffuse, thereby forming hot spots on the surface, increasing heat loss.

Fourth, the viscosity of the paraffin emulsion is high. In order to obtain a stable paraffin emulsion, a surfactant is added at the time of preparation. Generally speaking, the more surfactants, the more stable the wax emulsion, but the higher the viscosity (Huang L., Petermann M. an experimental study on biomedical fibers of paraffine/waterphase change emulsion. International Journal of Heat and Mass Transfer 2015,83: 479-. The high viscosity significantly increases the flow resistance of the paraffin emulsion in the pipeline, thereby reducing the energy efficiency ratio of the system.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provides a paraffin Pickering emulsion with a photothermal conversion function and a preparation method thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

a paraffin Pickering emulsion with a photo-thermal conversion function comprises the following components in percentage by mass: 10-40% of paraffin, 1-5% of magnesium-aluminum layered double hydroxides (Mg-Al LDHs), more than 0 and less than or equal to 0.1% of Graphene Oxide (GO), and the balance of water.

The content of the magnesium-aluminum layered double hydroxide is 2%.

The content of the paraffin is 30%.

The paraffin is a solid paraffin having a melting point of <90 ℃.

A preparation method of paraffin Pickering emulsion with a photo-thermal conversion function comprises the following steps:

1) adding Mg-Al LDHs into water, dissolving and dispersing to prepare solution A;

2) adding GO into the solution A, and dissolving and dispersing to obtain a solution B;

3) and adding paraffin into the solution B, heating to a temperature above the melting point of the paraffin, and stirring and emulsifying after the paraffin is completely melted to obtain the paraffin Pickering emulsion with the photothermal conversion function.

In the step 1), deionized water is adopted as the water.

The dissolving dispersion comprises the following: firstly stirring to dissolve, and then carrying out ultrasonic dispersion.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

1. GO can absorb solar radiation to realize photo-thermal conversion;

2. Mg-Al LDHs on the surface of the paraffin droplet is used as a seed crystal to induce the paraffin to perform heterogeneous nucleation and crystallization, so that the supercooling degree of the paraffin Pickering emulsion is reduced;

3. GO is dispersed in water in a nanosheet form, so that the thermal conductivity of the paraffin Pickering emulsion is increased;

4. Mg-Al LDHs form a three-dimensional network structure in water, so that the stability of the paraffin Pickering emulsion is improved, and an emulsifier does not need to be added;

5. GO and Mg-Al LDHs interact, so that the viscosity of the paraffin Pickering emulsion is reduced;

6. the preparation method is simple, has few operation steps, and does not need harsh reaction conditions and the like.

Drawings

FIG. 1 is a photograph of Pickering paraffin emulsions prepared in examples 1-4 (GO content 0.002%, 0.01%, 0.02%, and 0.04%, respectively, from left to right);

FIG. 2 is a temperature rise curve of the Pickering paraffin emulsion prepared in examples 1-4 under the irradiation of standard sunlight intensity (GO content is 0.002%, 0.01%, 0.02% and 0.04%, respectively);

FIG. 3 is a scanning electron microscope image of a Pickering paraffin emulsion prepared in example 4;

FIG. 4 is a DSC curve (GO content is 0.002%, 0.01%, 0.02% and 0.04% respectively) of Pickering paraffin emulsion prepared in examples 1-4;

FIG. 5 is a plot of viscosity versus shear rate for Pickering paraffin emulsions prepared in examples 1-4 (GO content 0.002%, 0.01%, 0.02%, and 0.04%, respectively).

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. All percentages in the examples are by mass, unless otherwise specified.