Active Thermal Switching of Smart Composite Materials

智能复合材料的主动热开关

• 批准号: 1605354
• 负责人: Alexis Abramson
• 金额: $ 34.64万
• 依托单位: Case Western Reserve University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1605354&HistoricalAwards=false
• 关键词: Active; Thermal; Switching; Smart; Composite

Active Thermal Switching of "Smart" Composite MaterialsAll materials found in nature exhibit an ability to conduct heat defined by their thermal conductivity. Polymers, for example, have a low thermal conductivity, while metals typically possess a high thermal conductivity. This research explores the innovative concept of thermal switching wherein a smart material can be engineered such that its thermal conductivity can be actively controlled. Thermal switching is of interest for use in applications where control of thermal conductivity improves the functionality of a device or system. For example, heating and cooling in buildings, thermal storage, temperature adaptive textiles and thermal management of electronics or solar cells are all applications where intelligent control of heat transfer is required for next generation solutions. The objective of the research is to develop an innovative smart material with a thermal conductivity that can be switched either permanently or temporarily up to three orders of magnitude upon encountering a thermal stimulus. In other words, the material's thermal conductivity may be switched from behaving like a polymer to acting like a metal on demand. The material systems being developed consist of a shape memory polymer matrix and fiber-like fillers that have the ability to intelligently rearrange within the polymer. The goal of this research is to develop an innovative smart material with a thermal conductivity that can be switched either permanently or temporarily by up to three orders of magnitude upon encountering a thermal stimulus with or without the presence of an additional external force. The material system comprises a shape memory polymer as the matrix to control the orientation of nanofiber fillers upon application of a stimulus. The following methods and approaches are being used: 1. Preparation of cellulose nanocrystal, boron nitride and carbon nanofibers. Fibers were chosen as the filler type because during the shape memory polymer contraction/expansion, a high aspect ratio filler is required in order to induce alignment. 2. Fabrication of nanofibers/shape memory polymer composites with the ability to achieve high thermal conductivities when fibers are "switched" into alignment and low thermal conductivities when fiber alignment is reduced. Two key classes of materials are being explored: semi-crystalline crosslinked polymers and cross-linked polymers with a glass transitions temperature above room temperature. In these materials the crystalline regions act as the thermal reversible transitions that fix the material in its strained temporary state. Upon increasing the temperature above the glass transition temperature, the material increases its elasticity, allowing to composite to be stretched and inducing alignment of the fibers. 3. Characterization of the composites to determine degree of dispersion and alignment of fillers using x-ray diffraction techniques. 4. Thermal characterization of the in-plane and through-thickness thermal conductivities of the composites and the axial thermal conductivity of the individual fibers. 5. Theoretical investigations into the thermal conductivity of the individual fibers and composite systems. 6. "Writing" of thermal conduction paths onto composite films and subsequent testing to demonstrate the effectiveness of the thermal switching at the device level.

在自然界中发现的“智能”复合材料材料的主动热开关具有通过导热率定义的热量的能力。例如，聚合物的热导率较低，而金属通常具有较高的导热率。这项研究探讨了热开关的创新概念，其中可以设计出智能材料，从而可以主动控制其导热率。热开关可用于用于控制热导率的应用中，可改善设备或系统的功能。例如，建筑物，热存储，温度自适应纺织品以及电子或太阳能电池的热管理是所有的应用，都是下一代解决方案需要智能控制传热的应用。该研究的目的是开发具有热导率的创新智能材料，在遇到热刺激时，可以永久或暂时切换三个数量级。换句话说，材料的热导率可以从表现像聚合物一样转变为像金属一样的作用。所开发的材料系统由形状内存聚合物矩阵和类似纤维的填充剂组成，它们能够在聚合物内智能重新排列。这项研究的目的是开发具有热导率的创新智能材料，在遇到或不存在额外的外力的情况下，可以永久或临时切换三个数量级。材料系统包含形状存储聚合物作为矩阵，以控制刺激时纳米纤维填充剂的方向。正在使用以下方法和方法：1。制备纤维素纳米晶，硝酸硼和碳纳米纤维的制备。选择纤维作为填充类型，因为在形状内存聚合物收缩/膨胀过程中，需要高纵横比填充物以诱导比对。 2。纳米纤维/形状记忆聚合物复合材料的制造能够在纤维比对降低时将纤维“切换”到对齐和低热导率时，具有高热电导率的能力。正在探索两种关键的材料类别：半晶交联聚合物和交联聚合物，玻璃过渡温度高于室温。在这些材料中，晶体区域是将材料固定在其紧张的临时状态下的热可逆过渡。在将温度提高到玻璃过渡温度以上时，材料会增加其弹性，从而使复合材料被拉伸并诱导纤维对齐。 3。复合材料的表征，以确定使用X射线衍射技术确定填充物的分散程度和对齐。 4。复合材料的平面内和厚度热电导率的热表征以及单个纤维的轴向导热率。 5。对单个纤维和复合系统的导热率的理论研究。 6。将热传导路径的“写入”在复合膜上和随后的测试中，以证明设备级别的热开关的有效性。