Single Crystal Metal Nanorods by Thermomechanical Nanomolding

制作非常小的东西是非常困难的。 想想纳米级设备——这些设备的尺寸比人类头发的宽度还要小（人类的头发大约有 80,000 纳米宽）？需要大量生产，如何才能做到？ 该项目支持通过称为纳米成型的制造工艺大规模制造纳米级设备和系统的纳米结构的研究。 任何规模的成型都会将柔软的液态材料放入模具中进行固化。 尽管晶体金属在纳米和量子器件中具有广泛的潜在应用，但目前不适合纳米成型。 然而，能源、环境和信息等技术取决于有效、精确和多功能的金属纳米加工。 最近，解决金属有限纳米成型性的一个潜在解决方案是热机械纳米成型，它已被用来制造比其直径长一千倍的金和铜纳米棒。 该工艺基于原子扩散，几乎可以对所有金属和合金进行纳米成型。 该项目探索纳米成型工艺及其可扩展性，并确定不同类别金属和合金的纳米成型性。 从技术上讲，制造各种金属和合金的非常大表面积的纳米结构（例如高纵横比单晶纳米棒）的能力影响了多种技术，例如催化、光伏、等离激元以及用于植入物和传感器的可调谐材料细胞相互作用。 因此，这项研究的结果有利于国民健康、繁荣和国防，从而对美国经济和社会产生广泛影响。该项目让学生接触最先进的纳米制造技术，从而有助于培养下一代科学家和工程师。该项目研究热机械纳米成型工艺，以在大面积上形成一系列高纵横比金属纳米棒。 它研究基于原子扩散的变形作为基本机制。 该研究涉及确定各种金属和合金（例如FCC和BCC金属以及固溶体和金属间合金）的纳米级可塑性的加工参数，例如时间、温度和压力。 金属纳米棒阵列的特征在于其长度和宏观尺寸上的长度均匀性。 此外，晶体取向和潜在晶界被确定为加工条件和模具直径的函数，以探索形成具有优选取向的单晶纳米棒的可能性。 对热机械纳米成型的理论理解用于探索新颖的纳米制造方法。 其中包括通过使用具有混溶和不混溶金属组合的多层原料为纳米成型增加额外维度的潜力。 这使得在最小尺寸上改变、控制和操纵一根纳米棒内的晶体结构和成分成为可能。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Making very small things is very hard to do. Think of nanoscale devices ??these are devices that are smaller in size than the width of a human hair (a human hair is about 80,000 nanometers wide) ? that need to be manufactured in large numbers, how can it be done?. This project supports research in the mass manufacture of nanostructures for nanoscale devices and systems though a manufacturing process known as nanomolding. Molding, at any scale, places a soft, liquid-like state of a material into a mold to solidify. Crystalline metals, despite their wide range of potential applications in nano and quantum devices, are currently unsuited for nanomolding. However, technologies such as energy, environment, and information hinge on the effective, precise, and versatile nanofabrication of metals. A recent, potential solution to the limited nanomoldability of metals is thermomechanical nanomolding and it has been used to fabricate gold and copper nanorods that are up to a thousand times longer than their diameter. The process, based on atomic diffusion, enables nanomolding with essentially all metals and alloys. This project explores the nanomolding process and its scalability and determines nanomoldability of different classes of metals and alloys. Technologically, the ability to fabricate very large surface area nanostructures, such as, high aspect ratio single crystal nanorods, of a broad range of metals and alloys impacts several technologies, for example, catalysis, photovoltaics, plasmonics, and tunable material cell interaction for implants and sensors. Therefore, results from this research benefits national health, prosperity, and defense, and hence, have a broad impact on U.S. economy and society. This project exposes students to state-of-the-art nanofabrication techniques, thus contributing to the training of the next generation of scientists and engineers.This project investigates the thermomechanical nanomolding process to form an array of high aspect ratio metallic nanorods over a large area. It studies deformation based on atomic diffusion as the underlying mechanism. The research involves determining processing parameters, such as time, temperature and pressure, on the nano-scale moldability of various metals and alloys, such as FCC and BCC metals and solid-solution and intermetallic alloys. Metal nanorod arrays are characterized in terms of their length and length uniformity over macroscopic dimensions. Furthermore, crystallographic orientation and potential grain boundaries are identified as a function of processing conditions and mold diameter to explore possibilities of the formation of single crystal nanorods with preferred orientation. A theoretical understanding of thermomechanical nanomolding is used to explore novel nanofabrication methods. These include the potential to add an additional dimension to nanomolding by using a multi-layered feedstock with combinations of miscible and immiscible metals. This allows for the possibility of varying, controlling, and manipulating the crystal structure and composition within one nanorod over the smallest dimensions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.