SNM: Low-Cost, Large-Scale Nanomanufacturing of Superinsulating Aerogels and Lightweight, Mechanically-Strong Aerogels

在美国，建筑物的供暖和制冷占能源消耗的15%，二氧化碳排放量的32%。气凝胶是一种低密度、超绝缘的纳米材料，可以显著减少这些数量，但制造成本很高。虽然绝缘市场的规模约为400亿美元，但气凝胶在其中所占份额不到1%。以化石燃料为基础的运输占到了另外27%的排放量。机械坚固的气凝胶可以用作塑料的更轻重量的替代品，以减轻车辆的重量，将燃油效率提高10%。在气凝胶制造过程中，通常使用基于超临界二氧化碳的萃取来去除凝胶中的液体，同时保留凝胶骨架的固体纳米结构。这一过程占制造成本的50%，需要大量的二氧化碳和能源，并扼杀了产能。该研究奖将为开发和试验快速、高效的干燥工艺提供科学基础，以保护气凝胶的骨架。它将降低成本，扩大数量和规模，并使材料多样化。气凝胶以外的多孔性三维纳米材料在许多领域都很普遍，例如人造组织支架。这项研究产生的结果将与其他纳米材料和结构的制造相关。该工作计划包括开发大学前STEM课程，并通过在线推广门户网站分发对公众友好的纳米技术内容。使技术成果成为可能的技术成果是气凝胶干燥条件下超临界二氧化碳的传质模型，该模型捕捉到流体组成、可压缩性和性能的影响，此外还包括材料的微观结构和应变。该模型将能够确定流速、温度和压力的调制，选择溶剂，安排孔隙-流体交换和配制凝胶，以开发和试验廉价、快速的干燥工艺，将对气凝胶的宏观和纳米损害降至最低。技术方法由五项任务组成。(1)测量干燥动力学作为工艺参数的函数，以帮助开发模型并反复改进中试规模的纳米制造；(2)测量超临界二氧化碳-溶剂系统的密度，并开发用于监测干燥的计量学；(3)测量扩散系数；(4)测量凝胶在干燥时的体积应变状态；以及(5)使用小角X射线散射来阐明干燥对应力的影响，并将应力与形态结构变化相关联，并确定用于中试的材料。基本的纳米制造原理将适用于一系列无机、聚合物和复合气凝胶。

Heating and cooling of buildings in the United States accounts for 15 percent of energy use and 32 percent of carbon dioxide emissions. Aerogels are low-density, superinsulating nanomaterials that can dramatically reduce these numbers but are expensive to manufacture. While the insulation market is about $40 billion, aerogels account for less than 1 percent of it. Fossil-fuel-based transportation accounts for another 27 percent of emissions. Mechanically-robust aerogels can be used as lighter weight replacements for plastics to reduce the weight of vehicles, improving fuel efficiency by 10 percent. During aerogel manufacturing, supercritical carbon dioxide-based extraction is commonly utilized to remove liquid from a gel while preserving the solid nanostructure of the gel skeleton. This process accounts for as much as 50 percent of manufacturing costs, requires copious amounts of carbon dioxide and energy and stifles throughput. This research award will provide a scientific foundation to enable development and piloting of fast, efficient drying processes that preserve the skeleton of aerogels. It will enable lower costs, scaling of quantities and dimensions and diversification of materials. Porous three-dimensional nanomaterials other than aerogels are pervasive across many fields; for example, artificial tissue scaffolds. Results generated from this research will be relevant to the manufacture of such other nano-scale materials and structures. The work plan includes development of a pre-college STEM curriculum and distribution of public-friendly content about nanotechnology through an online outreach portal.The enabling technical output is a model of mass transfer in supercritical carbon dioxide under aerogel drying conditions that captures the effects of fluid composition, compressibility and properties and, additionally, material microstructure and strain. This model will enable the determination of modulation of flow rates, temperatures and pressures, select solvents, order pore-fluid exchanges and formulate gels to develop and pilot inexpensive, fast drying processes that minimize macroscopic and nanoscopic damage to aerogels. The technical approach consists of five Tasks. (1) Measure drying kinetics as a function of process parameters to aid in model development and iteratively refine pilot-scale nanomanufacturing; (2) Measure densities of supercritical carbon dioxide-solvent systems and develop metrology to monitor drying; (3) Measure diffusion coefficients; (4) Measure volumetric strain states inside gels in situ as they are dried; and (5) Use small-angle X-ray scattering to elucidate effects of drying on and correlate stresses with morphostructural changes and identify materials for pilot testing. The fundamental nanomanufacturing principles will be applicable to a range of inorganic, polymeric and composite aerogels.