NIRT: Composition Graded, Epitaxial Oxide Nanostructures: Fabrication and Properties

这项研究是响应主动纳米结构和纳米系统倡议，NSF 06-595，类别NIRT。 它的重点是在分离领域最有前途的发展之一：分子筛或沸石膜技术。很明显，用于大规模工艺的沸石膜技术依赖于可靠的制造，其可以产生大的膜面积，同时实现基本的膜特性：具有低缺陷密度的膜连续性、适当的孔取向和远低于微米范围的小膜厚度。该NIRT团队面临着挑战，在开发此类工艺方面取得飞跃。在过去的十年中，已经确定了某些分子筛材料成核和生长的一套机械原理。这些原理激发了该奖项的实验努力，试图将沸石纳米颗粒的尺寸和形状控制到前所未有的水平，并将这些纳米颗粒用作通过分级纳米制造制成的分子筛薄膜的精确工程构建块。据推测，在密闭环境中的合成将使得能够操纵和控制不期望的聚集步骤，并将最终产生沸石颗粒形状的期望的完美性和尺寸的所需的单分散性。精确成形的纳米颗粒随后将用作构建块，以使用反应性附着形成紧密堆积的、晶体学上对齐的单层。二次生长后，开发的连续膜将进行渗透性能测试，其微观结构和性能将与当前最先进的进行比较。显着的分子筛膜资本和运营成本的好处是预期的成果，拟议的工作。这些改进代表了更广泛使用节能分子筛膜分离技术的重大飞跃。除了能够实现有史以来最薄，因此最具生产力的沸石膜外，所提出的分层膜处理技术可能会影响其他技术，如微电子和传感器。这些潜在用途之一，即，用于微处理器的低k电容器也将被评估。目前，分离占全球能源消耗的15%。预计到2040年，全球商品生产将增加六倍，一切照旧的局面是不可持续的。分离和纯化过程效率的数量级提高是实现可持续全球繁荣的必要步骤。在使用膜的分离领域中最有前途的发展之一是分子筛或沸石膜技术。通过使分子分辨率的分离取代热驱动过程，它可以满足这一效率目标，并正在成为纳米技术和能源研究的一个领域。沸石和其它分子筛是具有能够通过形状和尺寸识别分子的孔的结晶无机骨架。这种能力，沿着它们的热化学稳定性和催化活性，导致它们作为催化剂、吸附剂和离子交换剂在各种各样的应用中使用。将这些材料结合到具有分子分辨率的薄膜器件中的愿望可以追溯到20世纪40年代。然而，自从第一个商业沸石膜以小规模分布式应用为目标（即，大约10平方米的膜组件）变得可用。从那时起，商业化进展一直停滞不前，受到从实验室到商业规模的问题的阻碍。这项研究全面和系统的调查将导致一个可扩展的和经济的制造技术的发展，导致有史以来最薄的沸石膜转化为商业现实的节能分子筛膜的愿景。

This research was received in response to the Active Nanostructures and Nanosystems initiative, NSF 06-595, category NIRT. Its focus is on one of the most promising developments in the field of separations: molecular sieve or zeolite membrane technology. It has become evident that zeolite membrane technology for large scale processes depends on reliable manufacturing that can generate large membrane areas while achieving essential film characteristics: film continuity with low defect density, appropriate pore orientation, and small membrane thickness well under the micrometer range. This NIRT team undertakes the challenge to make the leap forward towards developing such a process.In the last decade, a set of mechanistic principles for the nucleation and growth of certain molecular sieve materials has been identified. These principles motivated the award experimental efforts, which attempt to control size and shape of zeolite nanoparticles to an unprecedented level and use these nanoparticles as precisely engineered building blocks for molecular sieve thin films made by hierarchical nanomanufacturing. It was hypothesized that synthesis in a confined environment will enable manipulation and control of undesirable aggregation steps and will ultimately yield the desirable perfection in zeolite particle shape and the needed monodispersity in size. The precisely shaped nanoparticles will be used subsequently as building blocks to form closed packed, crystallographically aligned, monolayers using reactive attachment. Following secondary growth, the developed continuous films will be tested for permeation properties, and their microstructure and performance will be compared with the current state-of-the-art. Significant molecular sieve membrane capital and operating cost benefits are the expected outcome of the proposed work. These improvements represent a major leap forward for wider use of energy efficient molecular sieve membrane separation technology. In addition to enabling the thinnest, and consequently most productive, zeolite membranes ever made, the proposed hierarchical film processing technology may impact other technologies, like microelectronics and sensors. One of these potential uses, i.e., low-k dielectrics for microprocessors, will also be evaluated. Separations currently represent 15% of global energy consumption. With the global commodity production expected to increase six-fold by 2040, a business as usual scenario is not sustainable. An order of magnitude increase in efficiency of separation and purification processes is a necessary step towards sustainable global prosperity. One of the most promising developments in the field of separations using membranes is that of molecular sieve or zeolite membrane technology. By enabling separations with molecular resolution to replace thermally driven processes, it can meet this efficiency goal and is emerging as an area of nanotechnology and energy research. Zeolites and other molecular sieves are crystalline inorganic frameworks with pores capable of recognizing molecules by shape and size. This ability, along with their thermochemical stability and catalytic activity, has led to their use in a broad variety of applications as catalysts, adsorbents, and ion exchangers. The desire of incorporating these materials in thin film devices with molecular resolution can be traced back in the 1940's. However, it has been only about a decade since the first commercial zeolite membranes targeting small scale distributed applications (i.e., membrane modules of about ten square meters) became available. Since then, commercialization progress has been stagnant, hampered by problems in scale-up from laboratory to commercial scale. This research comprehensive and systematic investigations will lead to the development of a scalable and economic fabrication technique resulting in the thinnest zeolite membranes ever made transforming the vision of energy efficient molecular sieve membranes to a commercial reality.