Vaporization of Nanoparticles in Low Temperature Plasmas

该奖项将支持计算和实验研究，以了解在低温等离子体中合成纳米材料的机制。 低温等离子体（LTP）的高化学反应性-自由相互作用的带电粒子和中性粒子的混合物-为生产新材料提供了巨大的机会。 由于通过与LTP的相互作用将材料加工成新构型的理论极限仍然未知，因此也有机会通过实验发现以意想不到的方式改变材料的新工艺。 LTP在纳米材料制造中的使用是普遍存在的，例如，在生产用于计算机的集成电路或开发先进的蓄电池中。 因此，在低温等离子体中纳米粒子的形成和生长的基础知识对于先进制造工艺的进一步改进至关重要。该项目将探索LTP中以前没有考虑过的新的气溶胶机制。该机制允许生产单分散的纳米颗粒，所述纳米颗粒由目前尚不知道其生产方法的材料组成。 在LTP中，纳米颗粒可以由于离子轰击而蒸发。汽化产生过饱和蒸汽。 过饱和的蒸汽反过来又凝结回等离子体中的粒子上或成核新的团簇。这种在等离子体中蒸发然后冷凝的过程可以导致单分散的尺寸分布。事实上，这种方法可以将多分散的气溶胶转化为具有高质量产率的单分散的气溶胶。强有力的初步证据支持新机制。本项目的目标是：1）开发一个鲁棒的计算模型，该模型结合了新的机制，该模型将是通用的，并适用于许多不同的材料，使用等离子体参数和停留时间作为输入; 2）开发实验控制单分散峰位置的方法; 3）确定将允许质量通量增加同时保持给定的单分散尺寸分布的缩放参数; 4）应用该机理合成含两种或两种以上元素的化合物半导体纳米晶。

This award will support computational and experimental research towards understanding the mechanisms for synthesis of nanomaterials in low temperature plasmas. The high chemical reactivity of low temperature plasmas (LTPs) -- a mix of free interacting charged and neutral particles -- presents a tremendous opportunity for producing novel materials. With the theoretical limits for processing materials into new configurations via interactions with LTPs still unknown, there is also a chance for experimental discovery of novel processes to alter materials in unexpected ways. The use of LTPs in manufacturing of nanomaterials is ubiquitous, for example, in producing integrated circuits used in computers or in developing advanced electricity storage batteries. Fundamental knowledge of the formation and growth of nanoparticles in low temperature plasma is, thus, essential to the further improvement of advanced manufacturing processes. This project will explore a new aerosol mechanism in LTPs that has not been previously considered. The mechanism allows for the production of monodispersed nanoparticles comprised of materials for which production methods are currently not known. In LTPs, nanoparticles can be vaporized as a result of ion bombardment. The vaporization results in a supersaturated vapor. The supersaturated vapor, in turn, condenses back onto particles in the plasma or nucleates new clusters. This process of vaporization in the plasma followed by condensation can result in a monodispersed size distribution. In fact, such a process can transform a polydispersed aerosol into a monodispersed aerosol with high mass yield. Strong preliminary evidence supports the new mechanism. The goals of this project are to 1) develop a robust computational model that incorporates the new mechanism, which will be general and applicable to many different materials using the plasma parameters and residence time as inputs; 2) develop methods to experimentally control the position of the monodispersed peak; 3) identify scaling parameters that would allow the mass throughput to be increased while maintaining a given monodispersed size distribution; and 4) apply the mechanism to synthesize compound semiconductor nanocrystals containing two or more elements.