Single Crystal Metal Nanorods by Thermomechanical Nanomolding

制造非常小的东西是很难做的。想想纳米设备？这些设备的尺寸比人类头发的宽度还要小(人类头发大约有8万纳米宽)？那些需要大量生产的东西，怎么做呢？该项目支持通过一种称为纳米模压的制造工艺大规模制造用于纳米级设备和系统的纳米结构的研究。成型，在任何规模，将一种柔软的，液体状的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有广泛的潜在应用，但目前还不适合进行纳米模塑。然而，能源、环境和信息等技术依赖于有效、精确和多功能的金属纳米制造。最近，针对金属纳米可成形性有限的一种潜在解决方案是热机械纳米成型，它已被用于制造比直径长达1000倍的金和铜纳米棒。这一过程基于原子扩散，使几乎所有金属和合金的纳米成型成为可能。该项目探索纳米成型过程及其可伸缩性，并确定不同类别金属和合金的纳米可成形性。在技术上，制造非常大的表面积纳米结构的能力，如大长径比单晶纳米棒，广泛的金属和合金，影响到几项技术，例如催化，光伏，等离子体，以及用于植入物和传感器的可调材料细胞相互作用。因此，这项研究的结果有利于国家健康、繁荣和国防，从而对美国经济和社会产生广泛影响。这个项目让学生接触最先进的纳米制造技术，从而为培养下一代科学家和工程师做出贡献。本项目研究热机械纳米模塑过程，以在大范围内形成高深宽比的金属纳米棒阵列。它研究了以原子扩散为基础的变形机制。研究包括确定各种金属和合金的纳米级可成型性的工艺参数，如时间、温度和压力，如面心立方和体心立方金属以及固溶体和金属间化合物合金。金属纳米棒阵列的特征在于它们的长度和宏观尺寸上的长度均匀度。此外，晶体取向和潜在的晶界被确定为工艺条件和模具直径的函数，以探索形成具有择优取向的单晶纳米棒的可能性。通过对热机械纳米模塑的理论理解，探索新的纳米加工方法。其中包括通过使用混合金属和非混合金属组合的多层原料来增加纳米模塑的额外维度的可能性。这使得在一个纳米棒内在最小的维度上改变、控制和操纵晶体结构和成分的可能性成为可能。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.