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使用的15%和二氧化碳排放的32%。气凝胶是一种低密度、超绝缘的纳米材料，可以大大减少这些数量，但制造成本昂贵。虽然隔热材料市场约为400亿美元，但气凝胶只占不到1%，而化石燃料运输占另外27%的排放量。机械强度高的气凝胶可用作塑料的轻质替代品，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从凝胶中除去液体，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，并抑制产量。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，扩大数量和尺寸，并使材料多样化。除了气凝胶之外，多孔三维纳米材料在许多领域都很普遍;例如，人工组织支架。从这项研究中产生的结果将与其他纳米级材料和结构的制造有关。该工作计划包括开发大学预科STEM课程，并通过在线外联门户网站分发有关纳米技术的公众友好内容。使能技术成果是气凝胶干燥条件下超临界二氧化碳中的传质模型，该模型捕捉了流体成分、压缩性和性质以及材料微观结构和应变的影响。该模型将能够确定流速、温度和压力的调节，选择溶剂，订购孔隙流体交换和配制凝胶，以开发和试验廉价的快速干燥过程，从而最大限度地减少对气凝胶的宏观和纳米级损伤。技术方法包括五项任务。(1)测量作为过程参数的函数的干燥动力学，以帮助模型开发和迭代地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，并开发计量学以监测干燥;（3）测量扩散系数;（4）在凝胶干燥时原位测量凝胶内部的体积应变状态;和（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，并识别用于试验的材料。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.