CN110872487A

Movatterモバイル変換

Info

Publication number: CN110872487A
Application number: CN201811009841.3A
Authority: CN
Inventors: 姜华; 谈笑玲; 郑曙东; 张卫华; 王菊巍
Original assignee: Qinghai University
Current assignee: Qinghai University
Priority date: 2018-08-31
Filing date: 2018-08-31
Publication date: 2020-03-10

Abstract

The invention relates to the field of heat transfer, heat exchange or heat storage materials, in particular to a preparation method of a nitrate/expanded vermiculite-based high-temperature composite phase change material. The method comprises the following steps: 1) placing expanded vermiculite in a crucible, and then dispersing nitrate phase change materials on the surface of the expanded vermiculite; 2) and (2) carrying out heat treatment on the crucible after the nitrate phase change material is dispersed in the step 1) for 2 hours to obtain the expanded vermiculite-based nitrate composite phase change material. The invention has the advantages that the prepared nitrate/expanded vermiculite-based high-temperature composite phase-change material has higher packaging capacity and excellent phase-change cycle reliability, and also has the remarkable advantages of excellent thermal stability, chemical inertness, good compatibility, no toxicity, no corrosiveness, low cost and the like.

Description

Translated fromChinese

一种硝酸盐/膨胀蛭石基高温复合相变材料的制备方法A kind of preparation method of nitrate/expanded vermiculite-based high temperature composite phase change material

技术领域technical field

本发明涉及传热、热交换或储热的材料领域，具体涉及一种硝酸盐/膨胀蛭石基高温复合相变材料的制备方法。The invention relates to the field of materials for heat transfer, heat exchange or heat storage, in particular to a preparation method of a nitrate/expanded vermiculite-based high temperature composite phase change material.

背景技术Background technique

硝酸盐属于高温固-液相变材料，在太阳能集热发电系统有广泛的应用。硝酸盐相变材料在相变过程中存在形态不稳定的缺点，直接利用会对热能存储系统造成一定程度的腐蚀。因此，硝酸盐相变材料应该被加以封装使用，熔融的硝酸盐相变材料在毛细管力和表面张力的作用下有效地限制在封装材料的孔道结构中，从而保持形状稳定性，且免受环境因素的影响和增加传热面积。目前已经报道的封装材料有硅藻土、二氧化硅、SiC陶瓷和膨胀珍珠岩等。封装容量决定了复合相变材料的储热能力，这些封装材料对硝酸盐相变材料封装容量通常较低(～70wt％)，有待通过采用更有前景的封装材料进一步提高，且经历多次相变循环后复合相变材料储热能力发生了显著衰减，不利于长期高效应用。封装材料性质对提高封装能力和循环可靠性起着重要作用，封装材料的尺寸、形状、形态和孔隙特征(孔隙率、孔径分布、比表面积和孔体积)等都会影响复合相变材料的封装容量和相变循环可靠性。Nitrate is a high-temperature solid-liquid phase change material, which is widely used in solar thermal power generation systems. Nitrate phase change materials have the disadvantage of unstable morphology during the phase change process, and direct use will cause a certain degree of corrosion to the thermal energy storage system. Therefore, the nitrate phase change material should be encapsulated for use, and the molten nitrate phase change material is effectively confined in the pore structure of the encapsulation material under the action of capillary force and surface tension, thereby maintaining dimensional stability and protection from the environment. factor and increase the heat transfer area. The encapsulation materials that have been reported so far include diatomite, silica, SiC ceramics and expanded perlite. The encapsulation capacity determines the heat storage capacity of composite phase change materials, which are generally low (~70 wt%) for nitrate phase change materials, which need to be further improved by adopting more promising encapsulation materials and undergo multiple phase changes. The heat storage capacity of the composite phase change material is significantly attenuated after cycling, which is not conducive to long-term high-efficiency applications. The properties of the encapsulation material play an important role in improving the encapsulation capability and cycle reliability. The size, shape, morphology, and pore characteristics (porosity, pore size distribution, specific surface area, and pore volume) of the encapsulation material all affect the encapsulation capacity of the composite phase change material. and phase change cycle reliability.

膨胀蛭石(EVM)作为含水的层状铝硅酸盐矿物，经过高温处理后膨胀，从而形成独特的孔结构、高孔隙率和较大比表面积，提供了较大封装空间，对硝酸盐相变材料具有很强的吸附性能，从而对硝酸盐相变材料保持较高封装容量和相变循环可靠性。膨胀蛭石耐高温、优异热稳定性、化学惰性、良好相容性、无毒性、无腐蚀性，轻质和低成本对制备膨胀蛭石基的硝酸盐复合相变材料具有显著优势。目前膨胀蛭石基硝酸盐复合相变材料制备鲜有报道，因此如何利用简便易行的方法制备它们，从而有效改善目前报道的封装材料对硝酸盐相变材料存在封装容量低和相变循环可靠性差的问题，这具有挑战意义。Expanded vermiculite (EVM), as a water-containing layered aluminosilicate mineral, expands after high temperature treatment, thereby forming a unique pore structure, high porosity and large specific surface area, providing a large encapsulation space, which is not suitable for the nitrate phase. The strong adsorption performance of the change material can maintain high packaging capacity and phase change cycle reliability for the nitrate phase change material. Expanded vermiculite has high temperature resistance, excellent thermal stability, chemical inertness, good compatibility, non-toxicity, non-corrosiveness, light weight and low cost, which have significant advantages for the preparation of expanded vermiculite-based nitrate composite phase change materials. At present, there are few reports on the preparation of expanded vermiculite-based nitrate composite phase change materials. Therefore, how to prepare them by a simple and easy method can effectively improve the currently reported encapsulation materials for nitrate phase change materials, which have low encapsulation capacity and reliable phase change cycle. The problem of poor sex, which is challenging.

发明内容SUMMARY OF THE INVENTION

本发明针对目前硝酸盐相变材料封装的诸多研究工作提出一种硝酸盐/膨胀蛭石基高温复合相变材料的制备方法，有效改善了目前报道的封装材料对硝酸盐相变材料存在封装容量低和相变循环可靠性差的问题，且具有热稳定性好、化学相容性好、无毒性、无腐蚀性，轻质和低成本等优势。The present invention proposes a preparation method of nitrate/expanded vermiculite-based high temperature composite phase change material in view of the current research work on nitrate phase change material encapsulation, which effectively improves the encapsulation capacity of currently reported encapsulation materials for nitrate phase change materials. It has the advantages of good thermal stability, good chemical compatibility, non-toxicity, non-corrosiveness, light weight and low cost.

本发明的具体技术方案如下：The concrete technical scheme of the present invention is as follows:

本发明提供了一种硝酸盐/膨胀蛭石基高温复合相变材料的制备方法，包括以下步骤：The invention provides a preparation method of a nitrate/expanded vermiculite-based high temperature composite phase change material, comprising the following steps:

1)将膨胀蛭石置于坩埚内，然后将硝酸盐相变材料分散在膨胀蛭石表面；1) the expanded vermiculite is placed in the crucible, and then the nitrate phase change material is dispersed on the surface of the expanded vermiculite;

2)将步骤1)分散硝酸盐相变材料后的坩埚热处理2小时，获得形态稳定性较差的膨胀蛭石基硝酸盐复合相变材料。2) Heat-treating the crucible after dispersing the nitrate phase change material in step 1) for 2 hours to obtain an expanded vermiculite-based nitrate composite phase change material with poor morphological stability.

作为优选地，步骤1)中所述膨胀蛭石的加入量为3.00g。As preferably, the added amount of the expanded vermiculite described in step 1) is 3.00g.

作为优选地，步骤1)中所述1)将膨胀蛭石置于嵌套金属网的坩埚内。Preferably, as described in step 1), 1) the expanded vermiculite is placed in a crucible nested with a metal mesh.

作为优选地，步骤1)中所述硝酸盐相变材料粉末包括LiNO₃,NaNO₃和KNO₃一种或几种；其加入量为30.00g。Preferably, the nitrate phase change material powder in step 1) includes one or more of LiNO₃ , NaNO₃ and KNO₃ ; the added amount is 30.00 g.

作为优选的，步骤2)所述将步骤1)分散硝酸盐相变材料后的坩埚放入高温炉中热处理2小时，在毛细管力和表面张力作用下，熔融硝酸盐相变材料浸渍到膨胀蛭石的孔结构中，得到样品；多余的相变材料由于重力流入坩埚底部并与膨胀蛭石分离，冷却至室温。Preferably, in step 2), the crucible after dispersing the nitrate phase change material in step 1) is placed in a high-temperature furnace for heat treatment for 2 hours, and under the action of capillary force and surface tension, the molten nitrate phase change material is immersed into the expanded leech In the pore structure of the stone, the sample was obtained; the excess phase change material flowed into the bottom of the crucible due to gravity and separated from the expanded vermiculite, and cooled to room temperature.

作为优选地，步骤2)中所述热处理的温度为300～380℃。Preferably, the temperature of the heat treatment in step 2) is 300-380°C.

作为优选地，将步骤2)得到的样品再次放入嵌套金属网的坩埚内，然后重复上述步骤2)的热处理过程，直到在金属网的表面上没有观察到泄漏痕迹，获得形态稳定性好的膨胀蛭石基硝酸盐复合相变材料。Preferably, the sample obtained in step 2) is put into the crucible of the nested metal mesh again, and then the heat treatment process of the above step 2) is repeated until no leakage traces are observed on the surface of the metal mesh, and good morphological stability is obtained. The expanded vermiculite-based nitrate composite phase change material.

与现有技术相比，本发明的优势在于：Compared with the prior art, the advantages of the present invention are:

本发明利用膨胀蛭石独特的孔结构、高孔隙率和较大比表面积，封装硝酸盐相变材料制备复合相变材料，比目前报道的硝酸盐复合相变材料有更高的封装容量和更优异的相变循环可靠性。封装容量大于84wt％，经历100次相变循环后，潜热下降比例小于2％。本发明优势在于制备的硝酸盐/膨胀蛭石基高温复合相变材料有较高的封装容量和优异的相变循环可靠性，且还具有优异热稳定性、化学惰性、良好相容性、无毒性、无腐蚀性和低成本等显著优势。The invention utilizes the unique pore structure, high porosity and large specific surface area of expanded vermiculite to encapsulate the nitrate phase change material to prepare the composite phase change material, which has higher encapsulation capacity and higher encapsulation capacity than the currently reported nitrate composite phase change material. Excellent phase change cycle reliability. The encapsulation capacity is greater than 84 wt%, and the ratio of latent heat drop is less than 2% after 100 phase transition cycles. The advantage of the invention is that the prepared nitrate/expanded vermiculite-based high temperature composite phase change material has high packaging capacity and excellent phase change cycle reliability, and also has excellent thermal stability, chemical inertness, good compatibility, no Significant advantages such as toxicity, non-corrosiveness and low cost.

附图说明Description of drawings

图1为本发明膨胀蛭石基硝酸盐复合相变材料SEM图；Fig. 1 is the SEM image of expanded vermiculite-based nitrate composite phase change material of the present invention;

图2为本发明膨胀蛭石基硝酸盐复合相变材料在相变循环100次前后的DSC曲线，其中(a)为LiNO₃复合相变材料在相变循环100次前后的DSC曲线，(b)为NaNO₃复合相变材料在相变循环100次前后的DSC曲线，(c)为KNO₃复合相变材料在相变循环100次前后的DSC曲线。Fig. 2 is the DSC curve of the expanded vermiculite-based nitrate composite phase change material of the present invention before and after the phase change cycle 100 times, wherein (a) is the DSC curve_of the LiNO composite phase change material before and after the phase change cycle 100 times, (b) ) is the DSC curve of NaNO3 composite phase change material before and after 100 phase change cycles, (_c ) is the DSC curve of_KNO3 composite phase change material before and after 100 phase change cycles.

具体实施方式Detailed ways

下面结合具体实施例对本发明作进一步说明。The present invention will be further described below in conjunction with specific embodiments.

本发明通过如下的方法制备硝酸盐/膨胀蛭石基高温复合相变材料：The present invention prepares the nitrate/expanded vermiculite-based high temperature composite phase change material by the following method:

1.将3.00g膨胀蛭石置于嵌套金属网的坩埚内，然后将30.00g硝酸盐LiNO₃,NaNO₃和KNO₃相变材料粉末均匀分散在膨胀蛭石表面。1. Place 3.00g of expanded vermiculite in a crucible nested with a metal mesh, then 30.00g of nitrates LiNO₃ , NaNO₃ and KNO₃ phase change material powders are uniformly dispersed on the surface of the expanded vermiculite.

2.将坩埚放入高温炉中热处理2小时(LiNO₃-EVM：300℃；NaNO₃-EVM：350℃；KNO₃-EVM：380℃)，在毛细管力和表面张力作用下，熔融硝酸盐相变材料浸渍到膨胀蛭石的孔结构中。多余的相变材料由于重力流入坩埚底部并与膨胀蛭石分离，冷却至室温。2. Put the crucible into a high temperature furnace for heat treatment for 2 hours (LiNO₃ -EVM: 300°C; NaNO₃ -EVM: 350°C; KNO₃ -EVM: 380°C), under the action of capillary force and surface tension, molten nitrate The phase change material is impregnated into the pore structure of the expanded vermiculite. The excess phase change material flows into the bottom of the crucible by gravity and separates from the expanded vermiculite and cools to room temperature.

将上述样品再次放入嵌套金属网的坩埚内，然后重复上述热处理过程，直到在金属网的表面上没有观察到泄漏痕迹，形态稳定性好的膨胀蛭石基硝酸盐复合相变材料被获得。Put the above sample into the crucible nested with metal mesh again, and then repeat the above heat treatment process until no leakage traces are observed on the surface of the metal mesh, and the expanded vermiculite-based nitrate composite phase change material with good morphological stability is obtained. .

实施例1Example 1

将3.00g膨胀蛭石置于嵌套金属网的坩埚内，然后将30.00g硝酸盐(LiNO₃,NaNO₃和KNO₃)相变材料粉末均匀分散在膨胀蛭石表面。将坩埚放入高温炉中热处理2小时(LiNO₃-EVM：300℃；NaNO₃-EVM：350℃；KNO₃-EVM：380℃)，在毛细管力和表面张力作用下，熔融硝酸盐相变材料浸渍到膨胀蛭石的孔结构中。多余的相变材料由于重力流入坩埚底部并与膨胀蛭石分离，冷却至室温。将上述样品再次放入嵌套金属网的坩埚内，然后重复上述热处理过程，直到在金属网的表面上没有观察到泄漏痕迹，形态稳定性好的膨胀蛭石基硝酸盐复合相变材料被获得。3.00 g of expanded vermiculite was placed in a crucible nested with a metal mesh, and then 30.00 g of nitrate (LiNO₃ , NaNO₃ and KNO₃ ) phase change material powders were uniformly dispersed on the surface of the expanded vermiculite. Put the crucible into a high temperature furnace for heat treatment for 2 hours (LiNO₃ -EVM: 300 °C; NaNO₃ -EVM: 350 °C; KNO₃ -EVM: 380 °C), under the action of capillary force and surface tension, the molten nitrate phase changes The material is impregnated into the pore structure of the expanded vermiculite. The excess phase change material flows into the bottom of the crucible by gravity and separates from the expanded vermiculite and cools to room temperature. Put the above sample into the crucible nested with metal mesh again, and then repeat the above heat treatment process until no leakage traces are observed on the surface of the metal mesh, and the expanded vermiculite-based nitrate composite phase change material with good morphological stability is obtained. .

膨胀蛭石对LiNO₃,NaNO₃和KNO₃三种相变材料的封装容量分别为84.6wt.％,85.7wt.％和87.0wt.％，高于目前报道基体的封装容量。膨胀蛭石基硝酸盐复合相变材料的SEM图见图1所示，硝酸盐相变材料被均匀地分布并嵌入到膨胀蛭石的孔道内部空间或表面上，这表明硝酸盐相变材料被有效封装到膨胀蛭石孔道结构中，且孔结构未被完全占据，这有利于防止硝酸盐相变材料发生相变因体积膨胀对封装材料造成破坏。膨胀蛭石基硝酸盐复合相变材料的DSC曲线见图2所示，三种复合相变材料均展示了较高储热能力，且100次相变循环后潜热损失量小于2％，展示了优异的相变循环可靠性。The encapsulation capacities of the expanded vermiculite for the three phase change materials LiNO₃ , NaNO₃ and KNO₃ are 84.6wt.%, 85.7wt.% and 87.0wt.%, respectively, which are higher than those of the currently reported substrates. The SEM image of the expanded vermiculite-based nitrate composite phase change material is shown in Figure 1. The nitrate phase change material is uniformly distributed and embedded in the inner space or surface of the pores of the expanded vermiculite, which indicates that the nitrate phase change material is It is effectively encapsulated into the expanded vermiculite pore structure, and the pore structure is not completely occupied, which is beneficial to prevent the phase change of the nitrate phase change material from causing damage to the encapsulation material due to volume expansion. The DSC curves of the expanded vermiculite-based nitrate composite phase change materials are shown in Figure 2. All three composite phase change materials show high heat storage capacity, and the latent heat loss after 100 phase change cycles is less than 2%, showing that Excellent phase change cycle reliability.

当然，本发明还可以有多种实施例，在不背离本发明精神及其实质的情况下，熟悉本领域的技术人员可根据本发明的公开做出各种相应的改变和变形，但这些相应的改变和变形都应属于本发明的权利要求的保护范围。Of course, the present invention can also have various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the disclosure of the present invention. The changes and deformations should belong to the protection scope of the claims of the present invention.

Claims

1. A preparation method of a nitrate/expanded vermiculite-based high-temperature composite phase-change material comprises the following steps:

1) placing expanded vermiculite in a crucible, and then dispersing nitrate phase change materials on the surface of the expanded vermiculite;

2) and (2) carrying out heat treatment on the crucible after the nitrate phase change material is dispersed in the step 1) for 2 hours to obtain the expanded vermiculite-based nitrate composite phase change material.

2. The method according to claim 1, wherein the amount of exfoliated vermiculite added in step 1) is 3.00 g.

3. The method of claim 1, wherein the nitrate-phase change material in step 1) comprises LiNO₃,NaNO₃And KNO₃One or more of the components; the amount added was 30.00 g.

4. The method according to claim 1, wherein the temperature of the heat treatment in the step 2) is 300 to 380 ℃.

5. The method as claimed in claim 1, wherein the expanded vermiculite-based nitrate composite phase-change material obtained in the step 2) is placed in the crucible again, and then the heat treatment process of the step 2) is repeated to obtain the expanded vermiculite-based nitrate composite phase-change material.